Centrum Women Under 50 by Centrum

Biotin deficiency. Oral and injectable biotin prevents and treats biotin deficiency. Details: Biotin up to 10 mg daily has been used to treat and prevent biotin deficiency. Injections of biotin 150 mcg daily for 3-5 days have been used in adults. Biotin deficiency might occur due to different etiologies such as inherited biotinidase deficiency, malnutrition, chronic use of anticonvulsants, pregnancy, and excessive and chronic raw egg consumption (6243,19347). A very small study in newborns aged 1-6 months shows that adding biotin to infant formula safely improves biotin status in formula-fed infants (111365). The validity of these findings is limited by a lack of blinding, no randomization, and the small sample size.

Multiple sclerosis (MS). In spite of contrary reports, high-dose biotin (300 mg daily) does not reduce disability in patients with progressive MS. It also does not seem to be linked to an increased risk for relapse. Details: Although most earlier research suggested benefit, the highest quality evidence shows that high-dose biotin does not improve outcomes in progressive MS (95662,102963,102966,104011). A large multi-centered randomized clinical trial (SPI2) in patients with progressive MS and high disability shows that taking biotin 100 mg three times daily for 15 months does not improve disability, as measured on the expanded disability status scale (EDSS), or 25-foot walking time, when compared with placebo. The SPI2 clinical trial also did not find that biotin increases the rate of relapse (104011), a concern raised in one observational study of high-dose biotin (104000). Also, a large observational study of adults with progressive MS failed to identity an increase in annualized relapse rates in patients that reported taking biotin when compared with controls (105716). Other observational research has also found no effect on the relapse risk (102963,102964). There is some speculation that any increased rate of relapse identified in some high-dose biotin cohorts might be due to detection bias or reduced compliance with disease-modifying therapies.
Seborrheic dermatitis. Oral biotin doesn't seem to improve seborrheic dermatitis of infancy. Details: A clinical trial in infants with seborrheic dermatitis shows that biotin given by mouth does not improve symptoms when compared with placebo (8469).

Alopecia areata. It is unclear if oral biotin is beneficial for alopecia areata. Details: A small clinical study in healthy adults with alopecia areata shows that weekly injections of intramuscular biotin 5 mg/1 mL and dexpanthenol 250 mg/2 mL for 6 weeks reduces hair fall count and transiently increases hair density compared with baseline (111366). The validity of these findings is limited by a lack of a placebo control group, small sample size, and short duration of treatment. It is unclear if the effects are due to biotin, dexpanthenol, or the combination. Another small clinical study in 9-year-old children with alopecia areata shows that taking biotin 20 mg with zinc aspartate 100 mg orally along with topical application of clobetasol propionate 0.025% daily for one year promotes hair regrowth in 33% of children, compared with 0% in the group receiving the steroid deflazacort (6932). It is unclear if these effects are due to biotin, zinc, topical clobetasol, or the combination.
Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). Although there is interest in using oral biotin for ALS, there is insufficient reliable information about the clinical effects of biotin for this condition.
Biotin-thiamine-responsive basal ganglia disease. Adding oral biotin to oral thiamine does not seem to improve most symptoms associated with this condition, although it may slightly speed recovery from acute crisis in children. Details: A small case series in children ages 1-12 years with biotin-thiamine-responsive basal ganglia disease has found that adding biotin 5 mg/kg daily to thiamine 40 mg/kg daily for 30 months is not associated with additional symptomatic improvement in encephalopathy, seizures, dystonia, or other neurologic sequelae when compared with taking only thiamine. However, taking biotin with thiamine is associated with a 1-day reduction in recovery from acute crisis when compared with thiamine alone (95661).
Brittle nails. Low quality clinical studies suggest that oral biotin might improve nail thickness and prevent the splitting of brittle nails. Details: Some small, low quality clinical studies in people with brittle nails shows that taking biotin 2.5 mg orally daily for 1.5 to 15 months increases nail thickness and decreases the splitting of fingernails and toenails in some people when compared with baseline (171,35593). The validity of these findings is limited by the small study sizes and the lack of a comparator group.
Depression. Although there is interest in using oral biotin for mild depression, there is insufficient reliable information about the clinical effects of biotin for this condition.
Diabetes. It is unclear if oral biotin is beneficial for type 2 diabetes. Details: A meta-analysis of randomized controlled trials shows that taking biotin 1.5-15 mg orally daily for 1-3 months does not improve fasting blood glucose or serum insulin levels when compared with placebo. However, the validity of these results is limited by inclusion of subjects with and without diabetes (110044). A very small study in adults with type 2 diabetes also shows that taking biotin 5 mg three times daily for 28 days does not affect glucose or insulin levels when compared to baseline (11579). Biotin has also been studied in combination with other ingredients. Preliminary clinical research shows that a taking a specific supplement containing a combination of biotin 2 mg and chromium picolinate 600 mcg (Diachrome, Nutrition 21) can lower blood glucose and glycated hemoglobin levels in patients with type 2 diabetes who are poorly controlled on oral hypoglycemic drugs (12385,12390,15169). It is unclear if these effects are due to biotin, chromium, or the combination.
Diabetic neuropathy. Although there is interest in using oral and intramuscular biotin for diabetic neuropathy, there is insufficient reliable information about the clinical effects of biotin for this condition.
Muscle cramps. It is unclear if biotin is beneficial for improving muscle cramps in patients undergoing hemodialysis. Details: Patients undergoing hemodialysis are prone to muscle cramps. A small clinical study in patients with hemodialysis-related muscle cramps shows that taking biotin 1 mg in the morning daily for at least one week prevents and reduces severity of muscle cramps when compared to baseline. Cessation of biotin led to recurrence of cramps, and restarting oral biotin led to resolution of cramps during hemodialysis (89475). The validity of these findings is limited by the lack of comparator group. More evidence is needed to rate biotin for these uses.

BORON

Boron deficiency. Oral boron treats and prevents boron deficiency. Details: Taking boron orally is effective for preventing and treating boron deficiency (7135).

Radiation dermatitis. Topical application of sodium pentaborate pentahydrate gel to radiation sites may reduce the risk of dermatitis in patients with breast cancer who are receiving radiotherapy. Details: A small clinical study in patients with breast cancer shows that applying a hydrogel containing sodium pentaborate pentahydrate 3% four times daily during radiotherapy for 5 weeks reduces the risk of moderate to severe dermatitis by 50% when compared with petroleum jelly (Vaseline). However, there is no difference in patient satisfaction (95660). Additionally, a larger clinical trial in patients with breast cancer shows that applying a sodium pentaborate pentahydrate 3% gel to radiation sites 15 minutes before each session for 25 sessions reduces the risk of dermatitis by 90%, erythema by 87%, dry desquamation by 92%, and moist desquamation by 97% when compared with a placebo gel (109557).
Vaginal candidiasis. Boric acid applied intravaginally seems to reduce vaginal candidiasis. Details: Some limited clinical research shows that applying boric acid powder intravaginally 600 mg once or twice daily for up to 3 weeks can treat candidiasis and other vaginal fungal infections, including resistant and chronic infections (15443,15444,15446,15449,15450,15451,15453); however, this research is limited by low study quality. For Candida glabrata yeast infections, which are less prevalent than Candida albicans infections, some evidence shows that intravaginal boric acid capsules are effective in about 65% to 70% of azole-resistant infections; however, boric acid capsules appear to be less effective than intravaginal flucytosine (Ancobon) (15445,15454). For Candida krusei infections, which are rare and resistant to azole antifungal treatment, boric acid capsules also appear to be effective in some cases (15448).

Athletic performance. Oral boron does not seem to improve athletic performance. Details: A small clinical study in male bodybuilders shows that taking boron 2.5 mg daily for 7 weeks does not increase lean body mass, muscle mass, or testosterone levels when compared with placebo (944). Furthermore, the International Society of Sports Nutrition (ISSN) does not recommend boron supplementation as a nutritional ergogenic aid due to a lack of supportive evidence (101009).

Age-related cognitive decline. It is unclear if oral boron is beneficial for age-related cognitive decline. Details: Two very small clinical studies in healthy older adults show that taking boron 3.25 mg daily for up to 49 days orally might improve cognitive function and fine motor skills when compared with lower amounts of boron (943).
Diabetic foot ulcers. It is unclear if topical boron is beneficial for use in diabetic foot ulcers. Details: A large clinical study in adults with diabetic foot ulcers shows that applying boron (sodium pentaborate 3%) gel twice daily for 1 month marginally reduces ulcer severity, measured by the Wagner Classification system at 25 days and 2 months, when compared with control; recurrence and infection rate were also modestly reduced at 2 months (112423). However, it is unclear whether the analysis controlled for systemic antibiotic use among the two groups, which effects the validity of these findings.
Dysmenorrhea. It is unclear if oral boron is beneficial for reducing pain during menstruation. Details: A small clinical study in young females with moderate to severe dysmenorrhea suggests that taking boron tetraborate 10 mg daily, starting two days before and continuing until three days after the start of menstruation for two menstrual cycles, reduces pain levels by 24% and pain duration by 1.5 hours, or 34%. Both pain and pain duration were decreased by only 9% in patients receiving placebo (95428).
Kidney stones (nephrolithiasis). It is unclear if boron is beneficial for medical expulsive therapy after extracorporeal shockwave lithotripsy. Details: A large clinical study in adults undergoing extracorporeal shockwave lithotripsy for kidney stones conducted in Iran shows that taking boron 10 mg twice daily for 2 weeks does not statistically improve the rate of stone expulsion when compared with tamsulosin; however, boron may have fewer side effects (i.e., orthostatic hypotension, headache, nausea, erectile dysfunction) (112414).
Kidney transplant. It is unclear if oral boron is beneficial in patients receiving a kidney transplant. Details: Observational research in kidney transplant recipients has found that higher boron intake, as measured by urinary boron levels, is associated with a lower risk of mortality when compared with lower intake. Patients with 24-hour urinary boron levels in the top tertile had a 49% lower risk of all-cause mortality when compared with those in the lowest tertile; however, there was no association with graft failure (109556). It is unclear if these findings can be generalized to boron supplements.
Obesity. Although there has been interest in using oral boron for obesity, there is insufficient reliable information about the clinical effects of boron for this purpose.
Osteoarthritis. It is unclear if oral boron is beneficial for osteoarthritis symptoms. Details: Small low quality studies in patients with osteoarthritis suggest that taking boron tetraborate 3-6 mg daily for up to 8 weeks might improve pain and other symptoms when compared with a lower intake of boron (941,36870).
Osteoporosis. It is unclear if oral boron is beneficial for osteoporosis. Details: Preliminary clinical research in postmenopausal adults shows that taking boron 3 mg daily does not improve bone density when compared with placebo (36872).
Periodontitis. Small clinical studies suggest that adding topical boric acid to scaling and root planing treatment may be beneficial in periodontitis. Details: A meta-analysis of four small clinical studies in 117 patients with periodontitis shows that using boric acid 0.75% gel or solution in addition to scaling and root planing seems to slightly improve probing pocket depth (PPD) and clinical attachment level (CAL) when compared with placebo or saline control (105690). Another small clinical study in patients with periodontitis shows that using boric acid 0.5% for irrigation in addition to scaling and root planing seems to improve CAL and PPD to a similar degree as using povidone-iodine 0.1% (105691). The available research was conducted in Turkey, Vietnam, and India; it is unknown if these findings are generalizable to other geographic locations.
Tooth extraction. It is unclear if boron is beneficial for use in periodontal healing after impacted third molar surgery. Details: A moderate-sized clinical study in adults 18 to 40 years old shows that using boron 0.1% to 2.5% and chlorhexidine 0.12% mouthwash for 7 days after impacted third molar surgery marginally improves swelling and self-reported pain on day 7, and the higher boron concentrations also improve pain at day 4 when compared with chlorhexidine alone, but does not improve the number of analgesics used or periodontal scores (112379). However, the validity of these results is limited by a lack of statistical adjustment for multiple comparisons which can lead studies to show differences between treatment groups in error (i.e., false positive findings). Additionally, the study period coincides with the expected recovery time (i.e., 2-7 days), making it unclear if any effects are due to the intervention or control. More evidence is needed to rate boron for these uses.

CALCIUM

Dyspepsia. Oral calcium carbonate is approved by the US Food and Drug Administration (FDA) as an antacid. Details: Taking calcium carbonate orally as an antacid is effective for treating dyspepsia (1843). Calcium carbonate has FDA approval as an antacid.
Hyperkalemia. Intravenous calcium gluconate is approved by the US Food and Drug Administration (FDA) for preventing hyperkalemia-induced cardiac abnormalities. Details: Administering calcium gluconate intravenously can reverse electrocardiographic changes and arrhythmias induced by hyperkalemia (12946). Intravenous calcium gluconate is FDA-approved for preventing hyperkalemia-induced cardiac abnormalities.
Hypocalcemia. Oral calcium treats and prevents hypocalcemia. Intravenous calcium is used to treat severe hypocalcemia. Details: Taking calcium orally is effective for treating and preventing hypocalcemia. Intravenous calcium gluconate, acetate, gluceptate, or chloride is effective for severe hypocalcemia or hypocalcemic tetany (12928).
Kidney failure. Oral calcium carbonate or calcium acetate is used as a phosphate binder during kidney failure. Details: Taking calcium carbonate or calcium acetate orally is effective as a phosphate binder. Calcium acetate (PhosLo) appears to control hyperphosphatemia better than sevelamer (Renagel) (12943,12944,38990). Calcium citrate is not recommended for this purpose because it increases aluminum absorption and does not bind phosphate as efficiently as calcium acetate or calcium carbonate (21631). Some clinical research also shows that taking calcium orally reduces blood pressure in patients with kidney failure (975).

Corticosteroid-induced osteoporosis. Oral calcium in combination with vitamin D prevents bone density loss that occurs during long-term treatment with corticosteroids. Details: Taking calcium in combination with vitamin D as adjunctive therapy seems to be effective for reducing bone mineral density loss in people using corticosteroids long-term (982,1046,1830,1831,1832,4462,4463,4464,4465,4466)(4467,12945,38493). One specific product used in clinical research is Oscal (Marion Merrel Dow Inc.), which contains elemental calcium 500 mg per tablet plus vitamin D 125 IU per tablet (982). Another product used is Oscal 250 + D (SmithKline Beecham Healthcare), which contains elemental calcium 250 mg and vitamin D 125 IU per tablet (1046).
Hyperparathyroidism. Oral calcium reduces parathyroid hormone levels in patients with secondary hyperparathyroidism due to kidney failure. Details: Taking calcium orally reduces parathyroid hormone levels in patients with kidney failure and secondary hyperparathyroidism (1827,1828,1829,39174,39425). In elderly women, the combination of calcium and vitamin D reverses secondary hyperparathyroidism and reduces hip fracture risk (8818). Also, population research suggests increased calcium intake from the diet and supplements reduces the risk of primary hyperparathyroidism in women. Supplemental intakes of at least 500 mg/day and dietary intakes of approximately 1100 mg/day are considered to be protective (91353).
Osteoporosis. Adequate calcium intake, from the diet and/or supplements, is recommended for the prevention and treatment of osteoporosis. Details: The Bone Health and Osteoporosis Foundation (BHOF) recommends ensuring adequate calcium intake in line with the recommended dietary allowance (RDA) by age, along with adequate vitamin D intake, for the prevention and treatment of osteoporosis in adults over 50 years of age. Supplementation can be used to augment dietary intake when adequate dietary intake is not feasible (109425). In the US and Canada, foods containing at least 200 mg calcium with less phosphorous content than calcium can be labelled with a health claim regarding the relationship between adequate calcium intake and a reduced risk for osteoporosis (11940,102148). However, calcium supplementation is not recommended specifically for the primary prevention of osteoporosis. The US Preventive Task Force (USPSTF) states that the current evidence is insufficient to assess the balance of benefits and harms of vitamin D and calcium supplementation, alone or in combination, for the primary prevention of fractures in community dwelling adults without osteoporosis (95695). Also, calcium supplements do not seem to be effective for preventing loss of bone mineral density (BMD) during lactation (988), in patients who have had bone marrow transplantation (1817), or in patients who have had renal transplantation (4823,38736,38871). Maximal bone growth occurs in the teenage years, and then BMD in females remains relatively constant until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In males, this occurs several decades later. Bone loss is more pronounced if dietary calcium intake is below the RDA, which is the case for many Americans (2571,2578). One meta-analysis of randomized controlled trials in healthy children 7-14 years old shows that fortifying food with calcium 250-1000 mg daily for up to 24 months modestly improves femoral neck BMD, but not hip or spine BMD. However, the included trials did not supplement vitamin D (107232). During the 5 years immediately after menopause, calcium supplementation has very little effect on bone loss (2569,2570,2575,2576). The rapid loss of estrogen causes a high bone resorption rate, which increases serum calcium levels and therefore decreases intestinal absorption of calcium (2570). After this period, the typical rate of bone loss is 2% per year (2572,2576). Taking calcium 1000-1600 mg daily as carbonate, citrate, lactate gluconate, or citrate malate salt decreases this rate by 0.25% to 1% annually (977,979,981,2569,2571,2572,2575,2576,2578,6850)(38978,38980,39064). The greatest reductions (1% or more) are seen in the first 1-2 years of supplementation when bone remodeling foci can be filled (2569,2576). After this period, the differences in rate of loss between supplemented and non-supplemented females are closer to 0.25% per year (2569,2577). A meta-analysis of clinical evidence suggests that there is no additional benefit after 4 years (38980). Small clinical studies have found that continuous calcium supplementation at an average daily dose of 1050 mg, started after menopause and continued for 1.5-4 years, may reduce fracture rates by 26% when compared with no calcium supplementation. The largest of these studies was conducted in nursing home residents who also received daily vitamin D; the benefits of calcium, specifically, are unclear (39386). Some research also suggests that calcium and vitamin D improves primary prevention of osteoporotic fractures in some older individuals with osteoporosis, particularly the elderly and those who are no longer community dwelling (12930,38875,38849,39026,109471). However, not all research is positive. One large clinical trial in elderly adults with a low-trauma fracture show that taking calcium 1000 mg daily with or without vitamin D 800 IU daily for 2-7 years does not reduce the risk of a second fracture when compared with placebo (13073). Another clinical study shows that taking calcium 1000 mg daily plus vitamin D 800 IU daily does not prevent a second fracture in elderly patients, or prevent a first fracture in elderly patients with other risk factors such as low body weight (less than 58 kg, 127.6 pounds), smoking, family history of hip fracture, or fair or poor self-reported health (12929). Also, some exploratory research suggests that supplements may need to be continued indefinitely; in adults over 68 years of age, any effects of 2 years of calcium supplements on BMD appear to be lost within 2 years after discontinuing supplements (6853). Calcium has additive effects when used with other agents such as vitamin D, estrogens, or calcitonin. Whereas calcium alone generally reduces or prevents loss of BMD, combination with other agents can produce small increases in BMD ranging from 0.3% to 3.3% depending on the combination and dosages used (978,980,1836,2570,2571,2572,2576). However, one meta-analysis in healthy adults shows that fortifying foods with calcium 250-1000 mg daily, in conjunction with vitamin D supplementation, for up to 24 months does not improve BMD when compared with control (107232). The full potential of osteoporosis treatments cannot be realized without adequate calcium intake (2569,2570,2571,2572). Advise patients taking agents such as estrogens, calcitonin, bisphosphonates, or raloxifene (Evista) to ensure that their daily calcium intake meets the RDA. Use supplements if necessary. The usefulness of calcium in preventing osteoporosis in males is not as well-studied. Some observational research has found that calcium 870 mg daily is not associated with changes in BMD and bone loss in males (97201). However, clinical evidence suggests that taking calcium 1000 mg daily for 2 years might improve trabecular or cortical bone mass by 2% to 4% (980,8827,8873). Dietary supplementation with calcium and vitamin D seems to moderately reduce bone loss measured in the femoral neck, spine, and total body, and seems to reduce the incidence of nonvertebral fractures in older patients with osteopenia or low BMD (980).
Premenstrual syndrome (PMS). Adequate calcium intake seems to prevent symptoms of PMS. Details: There seems to be a link between low dietary calcium intake and symptoms of PMS (2004,6847,39007). Taking calcium 1000-1336 mg daily seems to significantly reduce depressed mood, water retention, and pain, especially if daily calcium intake is inadequate (1822,1823,1824,2004,95821). Calcium carbonate 1200 mg daily seems to decrease PMS symptom scores by about 18% when compared with placebo (1822). Increasing dietary calcium intake is also associated with a decreased risk of developing PMS. Consuming an average of 1283 mg of calcium per day from foods is associated with about a 30% lower risk of developing PMS compared with consuming an average of 529 mg daily (13094); however, taking calcium supplements does not appear to be associated with the risk of developing PMS.

Colorectal cancer. Oral calcium seems to be beneficial for preventing colorectal cancer, especially in those with adequate vitamin D levels and normal body mass index (BMI). Details: Population studies have found that increased intake of dietary or supplemental calcium is associated with a reduced risk of colorectal cancer and colorectal adenomas (1047,8820,12120,38951,98898,98899). Clinical trials and meta-analyses of clinical research also show that taking calcium supplements 1.2-2 grams daily for up to 4 years can reduce the risk of colorectal adenoma recurrence by up to 29% (970,12118,12950,15267,34596,38718,39042,95817). However, not all research has been positive. Some meta-analyses of clinical research or observational studies suggest that taking calcium does not reduce the risk of familial adenomatous polyposis or colorectal cancer (34596,39042,39349). Other contradictory research suggests that postmenopausal females who take calcium 1000 mg daily plus vitamin D 400 IU daily do not have a reduced risk of developing colorectal cancer (14290); however, this finding may not be reliable due to the high baseline intake of calcium in study participants. The reason for these conflicting findings is not entirely clear. Vitamin D might be an important factor. People with lower than average vitamin D levels do not seem to get any benefit from calcium supplements (12118). Also, one meta-analysis of previous trials suggests that taking calcium 1200 mg daily reduces the risk of colorectal adenomas in people with a normal BMI, but not in those who are overweight or obese (99715). Despite this conflicting evidence, the US Food and Drug Administration (FDA) approved a qualified health claim in 2005 stating that calcium supplements may reduce the risk of colorectal cancer and colorectal adenomas. However, the FDA has determined that there is little scientific evidence to support this claim (102366).
Fetal bone mineralization. If calcium intakes are low during pregnancy, oral calcium seems to be beneficial for increasing fetal bone density. Details: With low dietary calcium intake (less than 562 mg elemental calcium daily) during pregnancy, calcium supplementation increases fetal bone mineralization and density. However, calcium supplementation does not offer any additional benefit if calcium intakes are adequate (3263,3264).
Hypertension. Oral calcium seems to reduce blood pressure by a small amount. However, it is unclear if this reduction is clinically significant. Details: Many clinical trials and observational studies show that intake of calcium supplements or dietary calcium modestly reduces blood pressure in patients with or without hypertension, usually around 1-2 mmHg. Calcium seems to be more effective for certain subpopulations of patients, such as salt-sensitive people and patients with low baseline dietary calcium intake (945,972,974,976,984,1818,1819,1820,1821,6852)(13138,14406,38803,39063,39094,39221). Also, a meta-analysis of clinical research shows that calcium intake during pregnancy reduces systolic blood pressure in offspring by 1-2 mmHg (38852). However, a large-scale clinical trial in postmenopausal females shows that taking vitamin D (cholecalciferol) 400 IU daily in combination with elemental calcium 1000 mg daily does not lower blood pressure or reduce the risk of developing hypertension (16714). Additionally, a meta-analysis of 8 clinical trials shows that taking calcium in combination with vitamin D for up to 7 years has no effect on blood pressure (98861). The validity of this finding is limited by the poor methodological quality of the included studies. Some observational research suggests that calcium can reduce the risk for hypertension. Population research in females aged 45 years and older suggests that higher intake of calcium from both diet and supplement sources is linked to a lower risk of developing hypertension when compared to lower calcium intake (14265). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim stating that calcium supplements may reduce the risk of hypertension. However, the FDA has concluded that this claim is based on supporting, rather than conclusive, evidence (102367).
Osteomalacia. Oral calcium seems to reverse osteomalacia caused by very low calcium intakes. Details: Osteomalacia is commonly caused by vitamin D deficiency; however, very low calcium intake can also lead to osteomalacia in children and adults. Calcium supplementation can reverse osteomalacia caused by calcium deficiency. Along with appropriate vitamin D supplementation, individuals at risk of osteomalacia need sufficient calcium intake (94819).
Pre-eclampsia. Oral calcium seems to reduce the risk of pre-eclampsia in high risk pregnancies, especially if calcium intakes are low. Details: Although there is some conflicting evidence (971,38756), most clinical research shows that taking calcium orally 1-2 grams daily reduces pregnancy-related hypertension and pre-eclampsia (973,1833,8828,39043,39319,39426,96480). Calcium appears to reduce the risk of pre-eclampsia by about 50% when compared with placebo. One meta-analysis of 19 controlled trials involving over 29,000 pregnancies found that for every 19 females treated with calcium, one episode of pre-eclampsia would be avoided (96480). Calcium appears to have the greatest effect in individuals at high-risk of pre-eclampsia or with low calcium levels, and when taken at greater than or equal to 20 weeks of gestation (15029,38497,96480,99714). In 2005, the US Food and Drug Administration (FDA) approved a qualified health claim regarding the use of calcium supplements to reduce the risk of pregnancy-induced hypertension and pre-eclampsia. However, due to the limited and conflicting research available at that time, the FDA stated that this outcome was highly unlikely. Since then, large, high-quality clinical research has supported this finding. In fact, in 2016 the World Health Organization (WHO) released a recommendation to prescribe oral calcium supplementation 1.5-2 grams daily during pregnancies at high risk of pre-eclampsia if dietary calcium intakes are low, in order to prevent pre-eclampsia (97347).
Rickets. Oral calcium seems to reverse rickets caused by very low calcium intakes. Details: Rickets is commonly caused be vitamin D deficiency; however, very low calcium intake can also lead to rickets. Calcium supplementation can reverse rickets caused by calcium deficiency (94819). A small clinical study in children with nutritional rickets shows that taking calcium 500-2000 mg daily for 24 weeks improves radiographically measured rickets caused by calcium deficiency. Rickets seems to improve more rapidly with calcium 1000 mg compared to calcium 500 mg. However, increasing the calcium dose to 2000 mg daily is not more beneficial than calcium 1000 mg daily (98904).
Tooth retention. Oral calcium with vitamin D seems to help with tooth retention in the elderly population. Details: A clinical trial in the elderly population shows that taking calcium citrate malate 500 mg daily along with vitamin D3 (cholecalciferol) 700 IU daily orally for 3 years reduces the risk of tooth loss by about 52% when compared with placebo (8816).

Breast cancer. Oral calcium does not seem to be beneficial for breast cancer prevention. Details: Although some population research disagrees (15631,39041,95811,107237), most research shows that increased calcium intake is not associated with a reduced risk of breast cancer (15631,16715,98895,107236,107237). Subgroup analyses of population research suggest that calcium intake may reduce the risk of breast cancer in postmenopausal, but not pre-menopausal, adults (15631,107237). Another subgroup analysis in a large meta-analysis of population research also suggests that dietary intake may reduce estrogen receptor(ER)-negative breast cancer, but not ER-positive breast cancer (107236). However, most other research has not evaluated the effects of calcium supplementation or intake on breast cancer subtypes. The best evidence to date, from a large scale clinical trial (Women's Health Initiative), shows that taking vitamin D (cholecalciferol) 400 IU daily plus calcium 1000 mg daily for 7 years after menopause does not reduce the risk of developing invasive breast cancer at the end of the study and 5 years after the end of the intervention (16715,98895).
Fractures. Although oral calcium prevents fractures in osteoporosis, most evidence shows that calcium does NOT prevent factures in people who do not have osteoporosis. See Osteoporosis discussion for more information on the use of calcium for this purpose. Details: The most recent and robust meta-analysis of clinical research shows that calcium supplementation with or without vitamin D is NOT associated with reduced fractures in older adults without osteoporosis (95822). A large-scale study in postmenopausal females aged 50-79 years suggests calcium 1000 mg plus vitamin D 400 IU daily for 7 years only modestly improves bone mineral density (BMD) and does not significantly reduce fracture risk. This lack of effect may have been due to low adherence to the treatment regimen. In those who were 80% adherent, the combination of calcium plus vitamin D reduced the risk of hip fracture by about 29% (14282). Also, some clinical research shows that taking calcium carbonate 1000 mg and vitamin D 400 IU for 5 years does not attenuate loss of height after menopause when compared with placebo (95810). Additional meta-analyses of clinical and observational evidence suggest that calcium supplementation is not associated with a reduced risk of vertebral or nonvertebral fractures, such as hip fractures (38589,38888,98895). Some other research has suggested that calcium in combination with vitamin D reduces fracture risk in older patients without osteoporosis (980,1836,8818,12930,12933,12952,38849,102145,107235); however, this research is confounded by a number of variables, including the presence of hormonal therapy and differing levels of fracture risk at baseline (1836,8818,95822). Conflicting findings on this topic might also be due to genetic differences in patient populations. A population analysis of the Women's Health Initiative study found that, in older females with the lowest genetic susceptibility to low bone mineral density (BMD), taking calcium with vitamin D is associated with a reduction in fracture risk. However, in females with a higher genetic susceptibility to low BMD, there is no association between supplementation and fracture risk. This might be because individuals with a lower susceptibility to low BMD are also more responsive to calcium and vitamin D supplementation (97357). As of April 2018, the U.S. Preventative Services Task Force (USPSTF) concludes that there is insufficient evidence to determine whether supplementing with vitamin D >400 IU daily along with calcium >1000 mg daily is safe and effective for preventing fractures in community dwelling adults without vitamin D deficiency, osteoporosis, or a history of fracture. USPSTF recommends against supplementing with calcium 1000 mg daily or less along with vitamin D 400 IU daily or less for preventing primary fractures in community-dwelling postmenopausal females (95695).
Obesity. Oral calcium does not seem to improve weight loss. Details: Observational research has found that adults and children with low calcium intake are more likely to gain weight, have a higher body mass index (BMI), and be overweight or obese when compared to people with high calcium intake (12124,12125,12126,12127,14265). Additional observational research has found that increasing calcium intake is associated with weight loss in females; the results in males have been conflicting (12127,15602,15603). Despite these findings from observational research and a few small clinical studies (12128,15397,14438,98905), most clinical research has found that increased calcium intake does not increase weight loss (12052,13138,15396,15399,38985,39004,97356). The most recent meta-analysis of 20 clinical studies shows that daily dietary and supplemental calcium intake that meets the dietary reference intake (DRI) of 1000 mg or more daily does not increase weight loss in overweight individuals or patients with obesity when compared with intake below the DRI (95813). An older meta-analysis of 13 clinical trials also shows that increased dietary and supplemental calcium intake does not increase weight loss (15605).
Overall mortality. Oral calcium does not seem to reduce overall mortality. Details: While some population research has found that calcium taken in combination with vitamin D in older females is associated with a lower risk of death (97353), most evidence shows that calcium, with or without vitamin D, has no effect on all-cause mortality (93533,97308).

INEFFECTIVE

Cardiovascular disease (CVD). Oral calcium does not reduce the risk of developing CVD and may actually increase risk in some patients. Details: Clinical research shows that calcium does not decrease CVD risk. Several separate meta-analyses of clinical and population research involving over 50,000 patients show that taking calcium 600-1200 mg daily for up to 7 years does not reduce the risk of CVD-related outcomes, including stroke and myocardial infarction, cardiovascular death, or overall mortality (39018,91350,92994,93533,97308,98902,107231,107233). No association was found between total dietary or supplemental calcium intake with or without vitamin D and the risk of CVD or mortality (91350,93533,97308). In fact, some population and clinical research has found that when calcium is used alone or with vitamin D, there is an INCREASED risk of CVD and coronary heart disease (38077,107233). However, other clinical research disagrees (93533). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of CVD and coronary heart disease by 1.1-1.2 times when compared with control. However, the majority of the included research evaluated postmenopausal females and it is unclear if this finding is applicable to other populations (107233).
Chemotherapy-induced peripheral neuropathy. Intravenous calcium does not prevent nerve pain in patients given oxaliplatin. Oral calcium has not been evaluated for this purpose. Details: While pooled analyses of cohort studies and randomized controlled trials suggest that calcium and magnesium infusion decreases the incidence of oxaliplatin-induced neurotoxicity, a meta-analysis of only randomized controlled trials shows that the infusion has no effect in preventing neurotoxicity (90028,90029,90031). Additionally, clinical trials show that administering calcium gluconate 1 gram with magnesium sulfate 1 gram intravenously immediately before, or before and after, the administration of a single oxaliplatin cycle (90005), or over the entire 6-cycle course of oxaliplatin, does not improve symptoms of neurotoxicity when compared with placebo (96474).
Myocardial infarction (MI). Oral calcium does not prevent MI. When taken in the absence of vitamin D, oral calcium may increase the risk of MI. Details: Population research has found that increased dietary intake of calcium is associated with a decreased risk of MI (91350). However, a 2010 meta-analysis of clinical research shows that taking calcium at a dose of at least 500 mg daily is associated with an approximate 30% INCREASE in the risk of MI in patients over the age of 40. According to this analysis, one additional case of MI will occur for every 69 patients that take calcium for 5 years (17482). A more recent meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years increases the risk of MI by 1.2 times when compared with control. However, the majority of the included research studied postmenopausal females and it is unclear if this finding is applicable to other populations (107233) In contrast, other meta-analyses of clinical research have shown that taking calcium for up to 7 years is NOT associated with an increased risk of MI, including a meta-analysis that only included postmenopausal females (93533,107231). Reasons for these discrepancies are not entirely clear. It may relate to whether calcium is taken as monotherapy or in combination with vitamin D. When taken with vitamin D, which is commonly recommended, calcium supplementation does not appear to be associated with an increased risk of MI in postmenopausal females (93533). Also, the association between calcium supplementation and MI risk may be influenced by the amount of calcium consumed as part of the diet. Supplementation with calcium may be associated with an increased risk of MI in people with dietary calcium intake above 805 mg daily, but not in those with dietary calcium intake below 805 mg daily (17482)

Alcohol use disorder. It is unclear if oral calcium is beneficial for alcohol use disorder. Details: Preliminary clinical research shows that taking calcium carbonate 800 mg and vitamin D 200 IU orally daily for 14 days modestly reduces alcohol craving scores and withdrawal scores when compared with placebo in adults with alcohol dependence that are undergoing withdrawal. Taking calcium carbonate did not reduce the need for diazepam; however, the study may have been inadequately powered to detect a difference between groups (107234).
Atherosclerosis. It is unclear if oral calcium is beneficial for atherosclerosis. Details: A population study has found that taking calcium 1.2 grams daily for 3 years has no effect on carotid intima thickness or carotid atherosclerosis incidence. A total calcium intake (dietary and supplemental) of at least 1794 mg daily in older females may be associated with a decreased risk of carotid atherosclerosis when compared with a total calcium intake below 1010 mg daily (97351).
Autism spectrum disorder. It is unclear if oral calcium during pregnancy is beneficial for reducing the odds of autism spectrum disorder in the offspring. Details: A small observational study found that calcium supplementation during pregnancy is associated with a 52% reduced odds of an autism spectrum disorder in the offspring (98900).
Cancer. Oral calcium alone does not seem to prevent cancer. It is unclear if oral calcium with vitamin D is beneficial for preventing cancer. Details: Taking calcium alone does not seem to significantly reduce the risk of cancer (12118,15629). The role of calcium in cancer prevention when taken along with vitamin D is controversial, as conflicting results exist. One clinical trial shows that healthy postmenopausal females who take supplemental calcium 1400-1500 mg daily plus vitamin D3 (cholecalciferol) 1100 IU daily have a 60% lower relative risk for developing cancer of any type. Approximately 25 postmenopausal females would need to take this combination for 4 years to prevent one occurrence of cancer (15629). However, a more recent clinical study shows that healthy postmenopausal females who take supplemental calcium 1500 mg daily plus vitamin D3 (cholecalciferol) 2000 IU daily do not have a reduced risk of cancer at 4 years (93943). Reasons for the disparate results are not entirely clear. The discrepancies do not appear to be related to baseline vitamin D levels or different study populations. It is possible that, given the 10-year time lapse between the two publications, the discrepancies result from differences in cancer detection capability. Also, since cancer risk was a secondary outcome measure in the earlier study and a primary outcome measure in the more recent study, it is possible that the discrepancies result from differences in statistical methodologies. The effect of vitamin D and calcium on cancer risk in males and younger patients is not known. There is also interest in using calcium for reducing the risk of hematological malignancies. An analysis of the Women's Health Initiative study shows that taking calcium 1000 mg daily in combination with vitamin D3 400 IU for up to 10 years is associated with a 20% reduction in the risk of hematologic malignancies when compared with placebo. However, no effect on hematologic malignancy related mortality was seen (97354).
Depression. It is unclear if oral calcium is beneficial for depression prevention. Details: Population research has found no association between a higher dietary intake of calcium and the risk of depression when compared with a lower dietary intake of calcium (96480).
Diabetes. It is unclear if oral calcium is beneficial for type 2 diabetes prevention. Details: Some population research has found that a higher intake of calcium from diet or supplements, alone or in combination with vitamin D, is associated with a lower risk of developing type 2 diabetes when compared with lower calcium intake (14265,16713,96473). However, population research is often limited by confounding variables. For example, one analysis found that any beneficial effect might be influenced by concomitant magnesium intake (96473). Furthermore, other population research has found that serum calcium levels higher than 9.6 mg/dL are associated with greater risk of developing diabetes in Chinese adults with osteoporosis. This study is limited because it was not determined whether increased serum calcium was due to increased calcium intake or another factor such as parathyroid function (95815).
Dysmenorrhea. It is unclear if oral calcium is beneficial for reducing pain associated with dysmenorrhea. Details: Clinical research shows that taking calcium carbonate 1000 mg with vitamin D 5000 IU daily for three menstrual cycles does not reduce pain when compared with placebo in patients with primary dysmenorrhea (95821). However, calcium carbonate 1000 mg taken alone seems to reduce pain when compared with placebo.
Endometrial cancer. It is unclear if oral calcium is beneficial for endometrial cancer prevention. Details: A meta-analysis of population research suggests that calcium supplements may reduce the risk of endometrial cancer, but dietary calcium does not seem to have any effect (38893).
Fall prevention. It is unclear if oral calcium with vitamin D is beneficial for preventing falls. Details: Research suggests that calcium in combination with vitamin D, but not calcium alone, might prevent falls by decreasing body sway and normalizing systolic blood pressure (6362,11939,39038). Some experts think the combination of calcium and vitamin D may be important (11916). Preliminary clinical research in adults residing in a health care facility shows that taking vitamin D supplements while increasing dietary calcium and protein for 2 years reduces falls by 11% when compared with standard diets. Intervention diets were supplemented with milk, yogurt, and cheese to provide calcium 1142 mg and protein 69 grams daily (107235). There might also be different effects in females compared to males. In one study, females aged 65 years or older who took vitamin D 700 IU plus calcium citrate 500 mg daily over a 3-year period had a 46% lower risk of falling. However, this combination did not decrease falls in males (14291).
Fluorosis. Oral calcium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking calcium orally, in combination with ascorbic acid (vitamin C) and vitamin D, seems to be effective for reducing excessive fluoride levels in children and improving symptoms of fluorosis in children aged 6-12 years (990).
Heart failure. It is unclear if oral calcium in combination with vitamin D is beneficial for preventing heart failure. Details: Based on a secondary analysis of a large-scale clinical trial (Women's Health Initiative), taking calcium 1000 mg with vitamin D 400 IU daily does not reduce the risk of heart failure in the overall population or in individuals at high risk. However, in a subgroup of postmenopausal females without risk factors for heart failure, calcium and vitamin D supplementation might reduce the risk of developing heart failure by about 37% (97307).
Hypercholesterolemia. It is unclear if oral calcium is beneficial for hypercholesterolemia. Details: Some evidence shows that taking calcium carbonate 400 mg three times daily reduces low-density lipoprotein (LDL) cholesterol levels by 4% and increases high-density lipoprotein (HDL) cholesterol levels by 4% after 6 weeks of treatment when used in combination with a low-fat diet (American Heart Association Step 1) (2557). In contrast, a study in females with dyslipidemia shows that taking calcium 800 mg daily for 2 years might INCREASE total cholesterol levels by about 12 mg/dL when compared with placebo. This same study showed an association between calcium supplementation and an increase in total cholesterol levels and carotid intimal thickness in postmenopausal females, but not premenopausal females (97350). A recent meta-analysis of randomized controlled trials which included both healthy patients and patients with dyslipidemia shows that taking calcium 500-2000 mg daily and vitamin D 200-7142 IU daily modestly improves HDL cholesterol and triglyceride levels, but not LDL cholesterol levels, when compared with placebo. Subgroup analyses suggest that calcium and vitamin D supplementation is more effective in patients with dyslipidemia at baseline. It is unclear if this effect is due to calcium, vitamin D, or the combination (107227). However, other research shows that taking a specific supplement containing calcium 600 mg plus vitamin D 200 IU (Caltrate 600 D, Wyeth Consumer Healthcare Inc.) twice daily in combination with calorie restriction does not reduce total or LDL cholesterol levels when compared with placebo (15601).
Lead toxicity. It is unclear if oral calcium is beneficial for reducing blood levels of lead. Details: Lead is mobilized along with calcium from bone during pregnancy and lactation, resulting in increased serum concentrations of lead. One clinical study suggests that calcium supplementation does not significantly decrease these elevated lead concentrations (1586). However, another clinical study suggests that taking calcium reduces blood lead levels by 11% when compared with placebo, with greatest effects observed in those with high baseline levels of lead (38957).
Lyme disease. Although there is interest in using oral calcium for Lyme disease, there is insufficient reliable information about the clinical effects of calcium for this condition.
Metabolic syndrome. It is unclear if oral calcium alone or with vitamin D is beneficial for metabolic syndrome prevention. Details: Population research has found that a higher intake of calcium from diet and supplements alone, or in combination with vitamin D, is associated with a lower risk of developing metabolic syndrome when compared with lower calcium intake (14265,16713).
Nephrotic syndrome. It is unclear if oral calcium with vitamin D is beneficial for preventing nephrotic syndrome. Details: Clinical research shows that taking calcium 500-1000 mg daily for 3 months in combination with vitamin D3 60,000 IU daily or weekly for 4 weeks has no effect on bone mineral density or the risk of relapse in children with steroid-sensitive nephrotic syndrome (97355).
Nonmelanoma skin cancer. It is unclear if oral calcium is beneficial for preventing keratinocyte carcinomas. Details: In middle aged and older adults recently diagnosed with a colorectal adenoma, clinical research shows that taking calcium 1200 mg daily as calcium carbonate for 3-5 years does not reduce the incidence of keratinocyte cancer when compared with placebo over a median of 8 years. A sub-group analysis shows that taking calcium alone or with vitamin D3 1000 IU daily reduced the risk of invasive cutaneous squamous cell carcinoma by a moderate amount, but had no effect on the risk of basal cell carcinoma (104622).
Oral mucositis. When used in combination with fluoride treatments, a calcium phosphate mouth rinse seems to prevent and reduce mucositis-related pain in patients undergoing hematopoietic stem cell transplantation (HSCT). Details: A small clinical study in patients undergoing HSCT shows that using a particular mouth rinse (Caphosol, EUSA Pharma) containing calcium phosphate, in combination with fluoride treatments, reduces days of mucositis, the duration of pain, and the dose and days of morphine used when compared with placebo and fluoride treatment (38611).
Ovarian cancer. It is unclear if oral calcium is beneficial for ovarian cancer prevention. Details: An older meta-analysis of 12 cohort studies found that dietary calcium intake is not associated with a reduced risk of ovarian cancer (38792). However, a more recent pooled analysis of 15 cohort and case-control studies has found that the highest intake of dietary or dairy calcium is associated with a 20% lower risk of ovarian cancer when compared to the lowest intake (97349).
Postpartum depression. It is unclear if oral calcium is beneficial for reducing postpartum depression risk. Details: Preliminary clinical research shows that taking calcium 2 grams daily beginning at 11-21 weeks gestation reduces depression at 12 weeks postpartum when compared with placebo. However, no benefit is seen at 6 weeks postpartum (39447).
Pregnancy-related leg cramps. It is unclear if oral calcium is beneficial for preventing leg cramps during pregnancy. Details: A small clinical study shows that taking calcium 1 gram twice daily (as a mixture of salts) for 2 weeks can reduce pregnancy-related leg cramps during the second half of pregnancy when compared with no treatment (2567).
Prostate cancer. It is unclear if oral calcium is beneficial for prostate cancer prevention. Details: Some clinical research shows that taking calcium 1200 mg daily might decrease the risk of developing prostate cancer (14133). However, some epidemiological research suggests that consuming very high doses of calcium, over 2000 mg daily, might actually increase the risk of developing prostate cancer (14134). Some epidemiological research also suggests that doses greater than 1500 mg daily increase the risk of poorly differentiated, clinically advanced, and fatal prostate cancer (14132). Consumption of dairy products has also been weakly linked to a modest increase in risk of prostate cancer (98894). However, contradictory research suggests that there is no association between dietary intake of calcium and overall risk of prostate cancer (14131,14132,104630).
Stroke. It is unclear if oral calcium is beneficial for stroke prevention. Details: Some population research has found that increasing dietary calcium intake is associated with a decreased risk of ischemic stroke (4822,38678). However, other population research has found that increasing dietary calcium intake is not associated with a decreased risk of stroke (91350). One meta-analysis of high-quality randomized controlled trials shows that taking calcium for 2-7 years does not affect the risk of stroke when compared with control. However, the majority of the included research evaluated postmenopausal females, and it is unclear if this finding is applicable to other populations (107233).
Vertigo. Oral calcium with vitamin D might reduce positional vertigo; the effect of calcium when used alone is unclear. Details: A large clinical study in adults with recurrent benign paroxysmal positional vertigo shows that taking calcium 500 mg and vitamin D 400 IU twice daily for one year reduces annual recurrence of vertigo by 27% when compared with no treatment. The number needed to treat to prevent vertigo was 3.7 (103681). It is unclear if this benefit is due to vitamin D, calcium, or the combination. More evidence is needed to rate calcium for these uses.

CHROMIUM

Chromium deficiency. Oral or parenteral chromium is effective for the treatment and prevention of chromium deficiency. Details: Taking chromium orally is effective for preventing and treating symptoms of chromium deficiency, including hyperglycemia, glycosuria, sudden weight loss, peripheral neuropathy, and confusion (7135).

Diabetes. Oral chromium seems to be modestly beneficial for improving glycemic control in diabetes, especially when used in doses greater than 200 mcg daily and in patients with poorly controlled diabetes. It is unclear if chromium helps to prevent the development of diabetes. Details: Epidemiological research has found that lower toenail chromium levels are associated with an increased risk of diabetes and cardiovascular disease (11908). In 2005, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that chromium picolinate may reduce the risk of type 2 diabetes. However, the FDA has determined that any relationship between chromium picolinate and type 2 diabetes is highly uncertain and is based on limited scientific evidence (102362). Research on the use of chromium for the TREATMENT of type 2 diabetes is conflicting but seems to show modest benefit in some patients. Many small clinical studies show that taking chromium orally decreases fasting blood glucose, postprandial glucose, insulin, and glycated hemoglobin (HbA1C) levels, and increases insulin sensitivity (6867,7137,12390,15169,14440,42628,42638,95097,103745). However, other small clinical studies show that chromium is no better than placebo for improving glycemic indices in patients with diabetes (7060,14325,42679,42707,90059,103746,103749). Some of these studies may not have been adequately powered and some had a high risk of bias. Furthermore, these studies had high heterogeneity related to study population and size, chromium supplementation duration, formulation, and dose, and accepted standards of diabetes care. Multiple meta-analyses pooling results of these small clinical trials also show mixed results (90055,90063,95098,105026,110610). The most recent and comprehensive meta-analyses show that chromium picolinate lowers HbA1C by about 0.6%; while it is unclear if chromium yeast, chromium dinicocysteinate, or chromium with biotin or other natural ingredients are beneficial. Chromium seems to be most beneficial in doses of greater than 200 mcg taken for 12 weeks or longer, and in patients with poorly controlled diabetes with a baseline HbA1C of 8% or greater (90063,105026). There is also speculation that chromium might primarily benefit patients with low chromium levels; however, there has not been an analysis specifically evaluating this population (6867,7058,13725,14325,95098). Some research suggests that chromium might also modestly improve lipid levels in patients with type 2 diabetes (1934,6867,95098). A meta-analysis of randomized clinical trials including patients with type 2 diabetes shows that taking chromium 42-1000 mcg orally daily for 5-26 weeks decreases triglyceride levels by 7 mg/dL and increases high-density lipoprotein cholesterol levels by 2 mg/dL when compared with control. Taking chromium did not affect low-density lipoprotein cholesterol levels. However, the validity of these results is limited by high heterogeneity (110605). In addition, some meta-analyses have failed to demonstrate any effects of chromium on lipid levels (110610). A meta-analysis of randomized clinical trials including patients with type 2 diabetes shows that taking chromium 200-1000 mcg orally daily for 8-25 weeks lowers diastolic blood pressure by 2 mmHg, but not systolic blood pressure or body mass index, when compared with placebo (110607). Preliminary clinical research shows that chromium picolinate might improve metabolic parameters in patients with other forms of diabetes as well. This includes those with type 1 diabetes (1935), diabetes secondary to corticosteroid use (5039,42829), and gestational diabetes (42817).

Hypertension. Meta-analyses of small clinical trials suggest that oral chromium does not lower blood pressure by a clinically meaningful amount. Details: A meta-analysis of randomized clinical trials in adults with different metabolic disorders shows that taking chromium 42-1000 mcg orally daily for 12-24 weeks does not lower systolic or diastolic blood pressure when compared with placebo (110609). A meta-analysis of randomized clinical trials in adults with different chronic disorders shows that taking chromium 42-1000 mcg orally daily for 4-25 weeks lowers systolic and diastolic blood pressure by 3 mmHg and 1 mmHg, respectively, when compared with placebo. However, the validity of this meta-analysis is limited by high heterogeneity (110604). Another meta-analysis of randomized clinical trials including patients with type 2 diabetes shows that taking chromium 200-1000 mcg orally daily for 8-25 weeks lowers diastolic blood pressure by 2 mmHg, but not systolic blood pressure, when compared with placebo (110607). In addition, the validity of these results is limited by inclusion of patients with and without hypertension at baseline (110604,110607,110609).
Impaired glucose tolerance (Prediabetes). Oral chromium does not seem to improve glycemic indices in patients with prediabetes. Details: Some clinical research shows that adults with impaired glucose tolerance do not have improved glycemic parameters or insulin sensitivity after taking chromium picolinate 500-1000 mcg daily for up to 6 months when compared with placebo (13053,42670). Likewise, a small clinical study in elderly patients with impaired glucose tolerance shows that chromium supplements do not improve glucose tolerance or triglyceride or cholesterol levels when compared with placebo (13722). Finally, a preliminary clinical study in overweight or obese adults with prediabetes shows that taking two capsules of a combination product containing chromium, cinnamon, and carnosine (Glycabiane, PiLeJe) daily for 4 months decreases fasting plasma glucose by approximately 4 mg/dL when compared with placebo, but does not improve fasting plasma insulin, measures of insulin sensitivity or resistance, or glycated hemoglobin (HbA1C) (94234). The small effect on fasting plasma glucose is clinically insignificant and may be due to the other ingredients in this product.
Schizophrenia. Oral chromium does not seem to improve psychological measures in patients with schizophrenia. Details: Clinical research in patients with schizophrenia shows that taking chromium polynicotinate 400 mcg daily for 3 months does not affect weight or mental status when compared with placebo (42613).

Antiretroviral-induced insulin resistance. It is unclear if oral chromium is beneficial for preventing antiretroviral-induced insulin resistance. Details: Preliminary clinical research in HIV patients treated with highly active antiretroviral therapy (HAART) shows that taking chromium nicotinate 200 mcg or chromium picolinate 1000 mcg daily for 8-16 weeks may help decrease insulin resistance and increase glucose disposal when compared to baseline (42630,42662). The validity of this finding is limited by the lack of a control group.
Athletic performance. It is unclear if chromium enhances athletic performance, although some research suggests that it may improve body composition when used in conjunction with exercise. Details: One large clinical study shows taking chromium 400 mcg daily, in conjunction with resistance training, can increase weight loss, body fat loss, and lean body mass when compared with placebo and resistance training (6868). However, other, very small clinical studies show that adding chromium picolinate or chromium chloride 177-400 mcg daily to a weight-training program does not improve body composition when compared with weight-training alone (6860,6861,6862,42747). These studies may not have been adequately powered to detect a difference in outcomes.
Atypical depression. It is unclear if oral chromium is beneficial in patients with atypical depression. Details: Preliminary clinical research in patients with atypical depression shows that taking chromium picolinate 400 mcg daily for 2 weeks followed by 600 mcg daily for an additional 6 weeks improves response and remission rates when compared with placebo (10309). However, other clinical research shows that taking elemental chromium 400 mcg in the form of chromium picolinate daily for 2 weeks followed by 600 mcg daily for an additional 6 weeks does not improve most symptoms of atypical depression, although appetite and sexual drive may improve, when compared with placebo (42600).
Beta blocker-induced dyslipidemia. It is unclear if oral chromium is beneficial in patients with dyslipidemia due to beta-blocker use. Details: One small clinical study in patients who take beta-blockers shows that taking glucose tolerance factor (GTF)-chromium 600 mcg daily for 2 months increases high-density lipoprotein (HDL) cholesterol levels by 16%, but does not affect other lipid parameters, when compared with placebo (5040).
Binge eating disorder. It is unclear if oral chromium is beneficial in patients with binge eating disorder. Details: One small clinical study in overweight adults with binge eating disorder shows that taking chromium picolinate 600 or 1000 mcg by mouth daily for 6 months does not affect binge eating frequency, body weight, or depressive symptoms when compared with placebo (90057).
Bipolar disorder. It is unclear if oral chromium is beneficial in patients with treatment-resistant bipolar disorder. Details: Preliminary clinical research in patients with treatment-resistant, rapid-cycling bipolar disorder shows that taking chromium chloride (Hypo-A Chrom, Hypo-A GmbH) 600-800 mcg daily for up to 2 years can decrease the frequency of affective episodes by approximately three episodes annually when compared to baseline (42618). The validity of this finding is limited by the lack of a control group.
Cognitive impairment. It is unclear if oral chromium prevents cognitive impairment. Details: Some clinical research shows that taking chromium picolinate standardized to contain elemental chromium 1000 mcg daily for 12 weeks does not improve memory or depression in elderly patients with mild cognitive impairment when compared with placebo. However, results from neuroimaging scans suggest that chromium increases the activity of certain regions of the brain during memory tasks when compared with placebo (42666).
Hyperlipidemia. Small clinical studies suggest that oral chromium may modestly reduce lipid levels in patients with hyperlipidemia. Details: One small clinical study in patients with atherosclerotic disease shows that taking chromium 250 mcg as chromium chloride daily for 7-16 months decreases triglycerides and increases high-density lipoprotein (HDL) cholesterol, but not other lipid parameters, when compared with placebo (7060). Other small clinical studies in adults with hyperlipidemia show that taking chromium picolinate 200 mcg daily for 6 weeks, chromium polynicotinate 200 mcg twice daily, or brewer's yeast containing 48 mcg elemental chromium daily for 6-8 weeks decrease total and low-density lipoprotein (LDL) cholesterol when compared to baseline (37178,42585,42710). The validity of this finding is limited by the lack of comparison with a control group. A meta-analysis of small heterogeneous clinical studies in patients mostly without hyperlipidemia shows that taking chromium orally does not affect lipid levels when compared with placebo (105029). A meta-analysis of randomized clinical trials including patients with type 2 diabetes shows that taking chromium 42-1000 mcg orally daily for 5-26 weeks modestly improves triglyceride and HDL cholesterol levels, but not LDL cholesterol levels, when compared with control. However, the validity of these results is limited by high heterogeneity and inclusion of patients with and without hyperlipidemia (110605). In addition, some meta-analyses have failed to demonstrate any effects of chromium on lipid levels in adults with diabetes (110610). Limited research has tested high-dose chromium in children. One small clinical study in children with hypercholesterolemia shows that taking chromium polynicotinate 400-600 mcg with glucomannan 1000-1500 mg twice daily for 8 weeks reduces total and LDL cholesterol when compared to baseline (90061). It is unclear if this effect is due to chromium, glucomannan, or the combination. Finally, chromium does not seem to reduce lipid levels in people without hyperlipidemia.
Hypoglycemia. It is unclear if oral chromium helps to reverse or prevent hypoglycemia. Details: One very small clinical study in patients with reactive hypoglycemia shows that taking chromium chloride 200 mcg daily for 3 months increases blood glucose levels and improves insulin binding and hypoglycemic symptoms following an oral glucose load (6859). Another small clinical study in patients with symptomatic hypoglycemia shows that taking chromium yeast (Biochrome, Pharma-Nord) 125 mcg daily for 3 months improves symptoms, including chilliness, trembling, and disorientation, when compared with baseline (42711). The validity of this finding is limited by the lack of a control group.
Metabolic syndrome. It is unclear if oral chromium is beneficial in patients with metabolic syndrome. Details: One small clinical study in patients with metabolic syndrome shows that taking a particular chromium picolinate product (Chromax, Nutrition 21) 500 mcg twice daily for 16 weeks does not affect weight, waist circumference, insulin sensitivity, glycated hemoglobin (HbA1C), or lipid levels when compared with placebo (42654).
Myocardial infarction (MI). It is unclear if oral chromium helps to prevent MI. Details: Epidemiological research has found that low toenail chromium concentrations are associated with an increased risk of MI (13728). However, toenail chromium concentrations might not be a reliable predictor of body stores of chromium. There is also no reliable research showing that chromium supplements can prevent MI.
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral chromium slows NAFLD progression. Details: One small clinical study in patients with NAFLD shows that taking chromium picolinate 200 mcg two times daily after meals for 12 weeks does not affect liver enzyme levels or body weight when compared with placebo (105027).
Obesity. Although some research suggests that oral chromium may increase weight loss, this increase in weight loss is not likely to be considered clinically relevant. Details: Meta-analyses of clinical studies in overweight or obese adults show that taking chromium picolinate 200-1000 mcg daily for 12-16 weeks might result in a cumulative weight loss of about 0.5-1 kg when compared with placebo (90062,90065). However, this small reduction in weight is unlikely to be considered clinically significant. Furthermore, certain small clinical studies in healthy, overweight or obese adults and children show that taking oral chromium 200-1000 mcg daily for 6-24 weeks does not reduce weight when compared with control (6860,13727,17224,42680). Some of these studies may not have been adequately powered to detect a smaller effect. A meta-analysis of randomized clinical trials including patients with type 2 diabetes shows that taking chromium 200-1000 mcg orally daily for 8-25 weeks does not lower body mass index when compared with placebo. However, the validity of these results is limited by inclusion of patients with and without obesity at baseline (110607).
Polycystic ovary syndrome (PCOS). It is unclear if oral chromium improves symptoms of PCOS. Details: One small clinical study in patients with PCOS shows that taking chromium picolinate 1000 mcg daily for 6 months along with diet and exercise counseling decreases body mass index and improves rates of ovulation and regular menstruation when compared with placebo (95094). Also, some clinical research shows that taking chromium picolinate (21st Century HealthCare, Inc. or Nature Made) 200 mcg daily orally for 8 weeks increases insulin sensitivity when compared with placebo (95095,98687). However, other preliminary clinical research shows that taking chromium picolinate 200 mcg daily for 4 months does not affect insulin sensitivity or improve ovulation rates (42603). Although chromium picolinate at doses of less than 1000 mcg might have very small effects on fasting glucose, these doses do not seem to have clinically beneficial effects on fasting glucose, pregnancy rate, or testosterone levels (95094,95095,98687). A lower dose of chromium has also been studied in combination with carnitine. One small clinical study in overweight adults with PCOS shows that taking chromium picolinate 200 mcg daily with carnitine 1000 mg daily for 12 weeks modestly reduces fasting blood glucose, insulin resistance, and body weight, and slightly increases insulin sensitivity, when compared with placebo (103747). However, it is unclear if this benefit is clinically significant. Additionally, it is unclear if these effects are due to chromium, carnitine, or the combination. Carnitine has demonstrated clinical benefit when used alone in PCOS.
Turner syndrome. It is unclear if oral chromium is beneficial in patients with this condition. Details: A small clinical study shows that taking brewer's yeast 30 grams containing chromium 50 mcg daily for 8 weeks might improve abnormalities in glucose and lipid metabolism when compared with baseline in patients with Turner syndrome, a genetic disorder that has a high incidence of diabetes (13729). The validity of this finding is limited by the lack of a comparator group. More evidence is needed to rate chromium for these uses.

COPPER

Copper deficiency. Oral or intravenous copper is beneficial for treatment of copper deficiency. Details: Taking copper orally or intravenously is effective for treating copper deficiency and anemia due to copper deficiency. Copper deficiency is rare. It is seen most commonly in people receiving prolonged parenteral nutrition (7135). Oral cupric sulfate has been used in doses up to 0.1 mg/kg daily (7135). Copper 1-2 mg per day in parenteral nutrition solution has also been used (505).

Alzheimer disease. Oral copper does not seem to be beneficial for Alzheimer disease. Details: Preliminary clinical research shows that taking copper orotate dihydrate, providing 8 mg of elemental copper, daily for 12 months does not improve scores on evaluation scales for Alzheimer disease when compared with placebo (45949). There is also some concern that copper could have detrimental effects. Observational research has found that people with Alzheimer disease have higher levels of copper in their blood than people without the disease (95917); the clinical significance of this finding is unclear.

Acne. Oral copper has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a specific combination product containing copper (NicAzel, Elorac Inc.) 1-4 tablets daily for 8 weeks reduces inflammatory lesions in patients with inflammatory acne when compared with baseline. Other ingredients in this product include nicotinamide, azelaic acid, zinc, pyridoxine, and folic acid; specific quantities are not known (90800). The validity of this finding is limited by the lack of a comparator group.
Brain tumor. It is unclear if oral copper is beneficial for use in glioblastoma. Details: A moderate-sized open-label clinical study in adults with first recurrence of glioblastoma receiving alkylating chemotherapy shows that taking elemental copper 2.5 mg with disulfiram 400 mg daily for 6 months does not improve survival but does result in significantly more adverse effects (e.g., elevated liver enzymes) when compared with control. The trial was stopped early due to safety concerns (112376).
Cardiovascular disease (CVD). Although there is interest in using oral copper for CVD prevention, there is insufficient reliable information about the clinical effects of copper for this purpose.
Chemotherapy-induced acral erythema. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 acral erythema (112377). However, the interpretation of these findings is limited by the lack of a control group.
Chemotherapy-induced anemia. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months does not appear to reduce the incidence of grades 3 and 4 anemia (112377). However, the interpretation of these findings is limited by the lack of a control group.
Chemotherapy-induced diarrhea. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 diarrhea (112377). However, the interpretation of these findings is limited by the lack of a control group.
Chemotherapy-induced leukopenia. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months does not appear to reduce the incidence of grades 3 and 4 neutropenia or febrile neutropenia (112377). However, the interpretation of these findings is limited by the lack of a control group.
Chemotherapy-induced nausea and vomiting (CINV). Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 vomiting (112377). However, the interpretation of these findings is limited by the lack of a control group.
Chronic venous insufficiency (CVI). It is unclear if compression stockings containing copper are beneficial for lipodermatosclerosis in patients with CVI. Details: Preliminary clinical research shows that using compression stockings impregnated with copper for 8 weeks does not improve overall symptoms of lipodermatosclerosis secondary to chronic venous disease when compared with using a compression stocking without copper. However, the affected surface area may be reduced by approximately 16% by 2 weeks when copper-impregnated compression stockings are used (101809).
Dental plaque. It is unclear if rinsing the mouth with copper is beneficial for reducing dental plaque. Details: Preliminary clinical research shows that rinsing the mouth with a solution of copper 1.1 mmol/L for 4 days decreases plaque accumulation when compared with a placebo solution (46006).
Diarrhea. Oral copper has only been evaluated in combination with zinc; its effect when used alone is unclear. Details: Preliminary clinical research in children 6 months to 5 years of age presenting to a hospital in India with acute watery or bloody diarrhea shows that taking a solution providing zinc 2 mg/kg and copper 0.2 mg/kg orally daily for 2 weeks does not reduce the duration of diarrhea, the weight of stool, or the need for rehydration when compared with placebo (87166). It also does not seem to reduce the recurrence of diarrhea or improve weight gain over the next 3 months (95540).
Oral mucositis. Oral copper has only been evaluated in combination with resveratrol; its effect when used alone is unclear. Details: A small clinical study in adults with advanced gastric cancers receiving docetaxel-based chemotherapy suggests that taking copper (Chelated Copper, JR Carlson Laboratories, LLC) with resveratrol three times daily for up to 6 months may reduce the incidence of grades 3 and 4 oral mucositis (112377). However, the interpretation of these findings is limited by the lack of a control group.
Osteoarthritis. Although there is interest in using topical copper for osteoarthritis, there is insufficient reliable information about the clinical effects of copper for this condition.
Osteoporosis. Oral copper has only been evaluated in combination with other minerals; its effect when used alone is unclear. Details: Preliminary clinical research in postmenopausal adults shows that taking copper 2.5 mg in combination with zinc 15 mg, manganese 5 mg, and calcium 1000 mg daily for 2 years can slow bone loss when compared with taking either calcium or the trace minerals alone (1994).
Postoperative infection. It is unclear if copper-impregnated wound dressings are beneficial for the prevention of postoperative infection. Details: Preliminary clinical research shows that using a wound dressing impregnated with copper oxide 3% by weight reduces the incidence of a surgical site infection in the 30-day period following a caesarean section by 39%, but does not reduce length of hospital stay or readmission rate, when compared with a non-copper wound dressing. Eight patients would need to be treated with the copper-impregnated dressing to prevent one infection (105363). This study is limited by the use of a telephone questionnaire to assess the suspicion of infection.
Systemic lupus erythematosus (SLE). It is unclear if oral copper is beneficial for improving symptoms of SLE. Details: Copper status does not appear to be associated with the risk of SLE (101810). Additionally, one small clinical study shows that taking copper 3 mg daily, alone or in combination with fish oil, for 24 weeks does not affect symptoms of SLE when compared with placebo (12953).
Tinea pedis. Although there is interest in using topical copper for tinea pedis, there is insufficient reliable information about the clinical effects of copper for this condition.
Wound healing. It is unclear if topical copper sulfate can improve the healing of umbilical granuloma. Details: A small clinical study in children 1-3 months of age with treatment-naïve umbilical granuloma shows that a single application of copper sulfate to the affected site results in complete resolution in 70% of patients, compared with 90% of patients receiving topical sodium chloride twice daily for 5 days. Some patients who received a second application of copper sulfate experienced full healing; however, it is unclear if this was due to the treatment or natural resolution (109403). More evidence is needed to rate copper for these uses.

FOLIC ACID

Folate deficiency. Oral or intravenous folic acid is effective for the prevention or treatment of folate deficiency. Details: Administering folic acid orally or parenterally improves and prevents folate deficiency (505,8739). Clinical research shows that supplementation with folic acid 100 mcg to 5 mg daily during pregnancy decreases the risk of developing megaloblastic anemia by up to 79% (91307).

Kidney failure. Taking folic acid orally reduces homocysteine levels in people with kidney failure who are on hemodialysis. Details: Over 85% of people with kidney failure have hyperhomocysteinemia. Treatment of hyperhomocysteinemia in kidney failure is often more difficult than with normal kidney function (1489,3324,7289,9413,9414,9416). The reasons for this are not fully understood; renal uptake and metabolism of homocysteine may be reduced in severe kidney failure, and hemodialysis may contribute to vitamin deficiencies (6884,9414,9417). Folic acid 0.8-15 mg daily or 3 times weekly is generally used, but the degree of homocysteine reduction varies between 12% to 50%, and normal homocysteine levels (less than 12 µmol/L) cannot always be achieved. Adding vitamin B12 400-1000 mcg daily and vitamin B6 20-50 mg daily produces an additional reduction in homocysteine (1489,6884,7289,7881,9322,9413,9414,9415,9416,9417). Folic acid doses greater than 15 mg daily do not seem to provide additional benefit. Also, doses of 30-60 mg might cause a rebound in homocysteine levels when treatment is stopped (9219). Despite the homocysteine-lowering effect of folic acid in kidney failure, the most robust meta-analysis of 11 clinical trials suggests that folic acid supplementation does not seem to reduce the risk of cardiovascular events (50527). A smaller meta-analysis of 7 clinical trials that used a different primary composite outcome suggests that folic acid might reduce the risk of cardiovascular events by 15% when compared with control (91311). There has also been interest in using a reduced form of folic acid, L-5-methyltetrahydrofolate (L-5-MTHF). One study in patients on hemodialysis suggests that taking L-5-MTHF 17 mg daily for 12 weeks might lower homocysteine levels to a greater extent than an equimolar 15 mg of folic acid (104908). Another clinical trial in patients on hemodialysis suggests that giving intravenous L-5-MTHF 50 mg three times weekly is associated with an increased survival of about 36 months, compared with about 26 months with folic acid 5 mg daily. There was no difference in homocysteine reduction between groups (104909). These results should be interpreted with caution because they have not been replicated, and there was no placebo control. Furthermore, survival may have been affected by the availability of kidney transplants.
Hyperhomocysteinemia. Oral folic acid, taken alone or in combination with other B vitamins, lowers homocysteine levels in most patients. However, it is unclear if this has cardiovascular benefits. Details: Taking folic acid orally 0.4-5 mg daily lowers fasting homocysteine levels by 20% to 30% in people with normal to moderately elevated homocysteine levels at baseline. Folic acid 0.8-1 mg daily seems to provide maximal reduction (9307,9400,9401,9405,9408,11337,11338,50145). Doses above 1 mg daily do not seem to add benefit (9307), except in some people with certain gene mutations that cause homocysteine levels of 20 µmol/L or higher (9408). The higher the initial homocysteine levels, the lower the folic acid dose needed to attain maximum homocysteine reduction (9307). The effects of folic acid supplementation on homocysteine concentrations appear to be greater in females than males (50145). Adding vitamin B6 25-250 mg or vitamin B12 500 mcg seems to further reduce homocysteine levels (1489,9400,9405,9406,9408,107136). Some experts recommend routine use of vitamin B12 in homocysteine-lowering regimens to avoid the risk of neuropathy in people with undetected vitamin B12 deficiency (9405). Increasing folic acid intake with supplements or folate-fortified cereal products is more effective for reducing homocysteine levels than increasing intake of folate-rich foods (6367). Fortification of cereals and flour with 140 mcg folic acid per 100 grams reduces the mean homocysteine level in the general population by about 7% (7881,9404,9407). Elevated homocysteine levels are considered by some to be an independent risk factor for atherosclerosis progression, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, ischemic stroke, and other vascular complications (3886,3887,6236,7725,9314,9318,50509). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). Although folic acid lowers homocysteine levels, it is not yet known whether this reduces the risk of vascular disease. One meta-analysis shows that taking folic acid can reduce the risk of stroke by about 10% in patients with cardiovascular disease (CVD); the reduction is greatest in patients for whom homocysteine levels are lowered by at least 25% (96157). A meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation, including folic acid, reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136). However other research does not agree. Meta-analyses of clinical research show that folic acid does not prevent CVD or coronary heart disease, in spite of lowering homocysteine by up to 55%, when individuals with normal or high levels of homocysteine are considered (50539,96147,97619). Furthermore, most research shows that folic acid supplementation, alone or in combination with vitamin B6 and vitamin B12, does not improve endothelial function or improve secondary prevention of cardiovascular events such as myocardial infarction in people with existing CVD despite a homocysteine-lowering effect (9313,11337,11387,13482,50437,97619). Some research even suggests an increase in CVD risk concurrent with homocysteine lowering (13482). Large randomized controlled trials are needed to confirm or refute these findings. Some researchers hypothesize that different genetic profiles might explain some of these conflicting results. For instance, individuals with a homozygous 677TT MTHFR genotype typically have increased homocysteine levels. However, a meta-analysis suggests that treatment with folic acid does not reduce the risk of ischemic heart disease despite reducing homocysteine levels in individuals with 677TT MTHFR (50456). It has also been theorized that a reduced form of folic acid, 5-methyltetrahydrofolate (5-MTHF) might work better in these individuals. Although [6RS]-5-MTHF has been shown to lower homocysteine levels (104915), studies assessing its cardiovascular benefits are lacking.
Methotrexate toxicity. Oral folic acid reduces the severity of methotrexate toxicity. Details: Oral folic acid reduces methotrexate toxicity symptoms, such as nausea and vomiting, in the treatment of rheumatoid arthritis (RA) and psoriasis (768,2162,2163,2164,4492,4493,4494,9369,9419). Folic acid also seems to reduce methotrexate-induced hepatic side effects by approximately 36% (50320). Some research shows that a low, 0.8 mg weekly dose of folic acid is equally effective to a higher dose of 5 mg weekly for the prevention of methotrexate toxicity (102388).
Neural tube birth defects. Oral folic acid helps to prevent neural tube birth defects in newborns. Details: Clinical practice guidelines recommend that anyone capable of becoming pregnant take folic acid 400 mcg daily from fortified foods or supplements to prevent neural tube birth defects in infants. Folic acid 600 mcg daily is advised during pregnancy (94811,96146). This recommendation is based on research showing that a higher intake of folic acid from food and supplements during pregnancy reduces the primary incidence of neural tube birth defects by 41% to 69% (3325,9309,50344,50403,50468,95156). Individuals with a history of children with neural tube birth defects usually take a higher dose of folic acid 4000 mcg daily starting one month before and continuing for up to 3 months after conception (96146). Evidence shows that, when used for secondary prevention, folic acid supplementation reduces the incidence of neural tube defects by 66% to 87% (21235,50263,50344,50403,95156). In the US, foods containing at least 60 mcg of folic acid can be labeled with a health claim stating that healthful diets with adequate folic acid intake may reduce the risk of having a child with a brain or spinal cord defect (102369).

Cognitive impairment. Taking folic acid alone, with other B vitamins or with docosahexaenoic acid (DHA), might improve thinking and memory skills in older patients with cognitive impairment. Details: One clinical trial in patients aged 65 years and older with mild cognitive impairment (MCI) shows that taking folic acid 400 mcg daily for 2 years increases IQ scores when compared with placebo (100952). Two small, low-quality clinical studies in patients aged 70-90 years with cognitive impairment and low folate levels or folate deficiency shows that taking folic acid 5 or 15 mg daily for up to 63 days improves cognitive function, including measures such as memory and attention, when compared with placebo or baseline (50301,104911). Folic acid also appears to be beneficial when used in combination with other B vitamins or with DHA. A clinical trial in patients aged 70 years and older with MCI shows that taking folic acid 800 mcg, vitamin B6 20 mg, and vitamin B12 500 mcg daily for 2 years mitigates decline in executive function and, in patients with high baseline homocysteine levels, improves cognition and memory when compared with placebo (50480). Taking folic acid 800 mcg with or without DHA 800 mg daily for 6 months modestly improves cognition, as measured on the full-scale intelligence quotient, when compared with placebo (103978,109196). However, this benefit is no longer present at 6 months after treatment discontinuation (109196).
Depression. Oral folic acid seems to modestly reduce depression severity when added to conventional antidepressant therapy. It is unclear if folic acid can reduce the prevalence of depression or the risk for suicide. Details: Observational studies suggest that depression is correlated with low folate status, particularly in females (50105,50127,50243). Taking folic acid 0.2-15 mg daily for up to 6 months with conventional antidepressants seems to improve treatment response in patients with major depressive disorder (3657,10884,10887,50566,109190). One meta-analysis shows that taking L-methylfolate or folic acid as an adjunct to treatment with conventional antidepressants modestly reduces depression severity when compared with placebo and conventional antidepressants. The response and remission rates were improved by 36% and 39%, respectively (109190). However, limited clinical research suggests that folic acid is not effective as a replacement for conventional antidepressant therapy (10886). Also, a small clinical study in adolescents at high familial risk for mood disorders suggests that taking folic acid 2.5 mg daily for up to 36 months does not prevent mood disorders when compared with placebo. However, in the patients that were eventually diagnosed with depression, the time of onset was delayed from 5 months to 15.5 months in the group using folic acid when compared with placebo (91313). Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that folic acid is not currently recommended as monotherapy treatment for unipolar depression (110318). Observational research has also evaluated the association between folic acid supplementation and suicidal events in patients with or without depression. One within-person cohort study, in which only 12% of patients were diagnosed with depression, has found that filling a folic acid prescription of 0.4-5 mg daily, either alone or as part of a multivitamin, is associated with a reduced risk for suicidal events during the following months when compared with months without a prescription (109201). It is unclear what percentage of these patients, if any, had folate deficiency at baseline.
Hypertension. Oral folic acid seems to modestly reduce hypertension. Details: A meta-analysis of clinical research shows that taking folic acid 5-10 mg daily for at least 6 weeks reduces systolic blood pressure by 2mmHg and improves flow-mediated dilation by 1.6% in hypertensive individuals (50364). Some research has evaluated folic acid in hypertensive patients when used with antihypertensive drugs. Results show that taking folic acid 400-800 mcg in combination with enalapril 10 mg daily for about 4.5 years does not improve blood pressure when compared with enalapril alone (50302,96158). However, in hypertensive patients with heavy proteinuria, this combination seems to reduce the risk of all-cause mortality by about 41% when compared with enalapril alone (96158).
Phenytoin-induced gingival hyperplasia. Topical folic acid seems to reduce gingival hyperplasia due to phenytoin. The effect of oral folic acid is unclear. Details: Applying folic acid topically seems to inhibit gingival hyperplasia secondary to phenytoin therapy (2151). However, taking folic acid orally does not seem to improve gingival hyperplasia secondary to phenytoin therapy in adults (2150,2151,2152), although some evidence suggests that taking folic acid 500 mcg daily reduces the risk of phenytoin-induced gingival hyperplasia by 33% in children when compared with placebo (50463).
Stroke. Although some clinical research has shown that oral folate reduces stroke risk by a small amount, more research is needed to determine who is most likely to benefit. Most individual clinical trials show that folic acid seems to reduce stroke risk only in regions without food-fortification policies. Details: Multiple clinical studies have shown that folic acid supplementation reduces the risk of stroke by 10% to 25% in regions WITHOUT established policies mandating folic acid fortification of grain products (50240,50485,50525,50539,91325,96154,96157,96159,97308). The effect appears to be greatest when folic acid is taken in low doses (usually 0.8 mg daily or lower) (50525,96157,96159), in regions with a low prevalence of statin use (50525,96159), in patients with high cholesterol levels at baseline (96152), in patients who achieve homocysteine reduction of at least 20% (50407,96157), and in patients with the lowest folate levels at baseline (96154,96157). There is also some evidence that the effect of folic acid on stroke risk is greatest in patients with low baseline levels of vitamin B12 (96159). In 2001, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Most research shows that folic acid supplementation does not reduce the risk of stroke in regions WITH established policies mandating folic acid fortification (50240,50485,50525,50539,96157,96159,97308). However, there is some evidence that folic acid may reduce the risk of stroke in patients from regions with folic acid fortification who have recently had a stroke or transient ischemic attack and are not using antiplatelet drugs (90379). Meta-analyses of clinical research have been conducted. However, possible confounding due to the presence or absence of folic acid fortification is unclear. A meta-analysis of the available research in adults with existing CVD shows that folic acid supplementation at a daily dose of less than 2 mg reduces the risk for stroke by about 10% (102386). Also, a meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation, including folic acid, reduces the relative risk of stroke by 10% when compared with placebo (97619). In patients with a history of stroke, a meta-analysis shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136). It is unclear if folic acid reduces the stroke risk in patients with impaired kidney function. Some research shows that taking folic acid in combination with high doses of vitamin B12 (cyanocobalamin) does not reduce the risk of stroke in these patients (11387,96150). However, there is concern that the lack of benefit may have been due to the decline in kidney function from high doses of cyanocobalamin (96150). Additional research is needed to determine if folic acid supplementation is beneficial in patients with impaired kidney function when used with other forms of vitamin B12 such as methylcobalamin or hydroxycobalamin.
Vitiligo. Oral folic acid seems to improve vitiligo symptoms. Details: Taking folic acid orally seems to improve symptoms of vitiligo (2153,2154). This finding is supported by a meta-analysis of observational research which shows that patients with vitiligo have higher serum homocysteine levels when compared with patients without vitiligo (100951).

Anemia. Adding oral folic acid to oral iron therapy does not seem to improve hematologic parameters in patients with anemia. Details: In postpartum patients with anemia, clinical research shows that taking iron as ferrous fumarate 600 mg and folic acid 1 mg daily is no more effective than iron alone for improving hemoglobin status (91319). Also, clinical research in non-pregnant menstruating females shows that taking folic acid 0.4 mg daily or 2.8 mg once weekly for 16 weeks with iron 60 mg daily does not reduce anemia or improve iron status when compared with iron alone (109193). During pregnancy, clinical research shows that folic acid supplementation does not decrease the risk of pre-delivery anemia or low hemoglobin levels (91307).
Age-related cognitive decline. Oral folic acid does not seem to prevent cognitive decline in healthy elderly adults. Details: Most clinical research shows that taking folic acid, alone or in combination with other B vitamins, does not improve cognitive function, including memory, language, or executive function, in elderly adults with age-related cognitive decline (50318,50412,50510). In fact, a large-scale observational study in the US has found that people over 65 years of age who consume large amounts of folic acid (median of 742 mcg daily) have cognitive decline at a rate twice as fast as those consuming smaller amounts (median of 186 mcg daily) (13068). While most research on folic acid for age-related cognitive decline lacks positive findings, many of the studies are small, short-term (<1 year), underpowered to detect significant differences, and not specific to patients with high homocysteine levels. Population research has found that high homocysteine levels are associated with decreased cognition in older adults, suggesting that using folic acid to lower homocysteine levels might mitigate cognitive decline in these patients (50094). Two long-term clinical trials examining the effects of folic acid in elderly adults with high homocysteine levels show mixed results. A large-scale clinical trial of patients aged 50-70 years from the Netherlands who have high homocysteine levels shows that taking folic acid 800 mcg daily for 3 years increases memory, information processing, and other measures of cognitive function when compared with placebo (15271). However, another large-scale clinical trial of patients aged 65 years and older from the Netherlands who have high homocysteine levels shows that taking folic acid 400 mcg and vitamin B12 500 mcg daily for 2 years lowers homocysteine levels, but does not appear to improve overall measures of cognitive function, when compared with placebo (90392). The reasons for the discrepant findings in these two studies are not clear but might relate to differences in the dose of folic acid, duration of treatment, and age of patients included.
Cataracts. Oral folic acid does not seem to reduce cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or with risk factors for CVD shows that taking folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of developing cataracts. Furthermore, the risk of cataract extraction was increased by 28% in these patients (96149).
Diarrhea. Oral folic acid does not seem to reduce the risk of diarrhea, and might even increase the incidence of diarrhea in children. Details: In children aged 6-30 months at risk of malnourishment, clinical research shows that taking a nutritional supplement (Nutriset Ltd) enriched in folic acid 75-150 mcg, with or without vitamin B12 0.9-1.8 mcg, daily for 6 months does not reduce the incidence of diarrhea when compared with placebo. Enrichment with folic acid, with or without vitamin B12, actually seems to increase the likelihood of having more episodes of both persistent diarrhea and diarrhea lasting over 3 days (90391).
Fall prevention. Oral folic acid does not seem to reduce the risk of falls. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg daily, for 2 years, does not prevent falls when compared with placebo in elderly individuals also taking vitamin D (96148).
Fetal and premature infant mortality. Oral vitamin B12 does not seem prevent mortality in premature infants. Details: Clinical research shows that supplementation with folic acid during pregnancy does not decrease the risk of miscarriage, stillbirth, or neonatal death (91307,96156).
Leukemia. Oral vitamin B12 does not seem to reduce the risk for pediatric acute lymphoblastic leukemia. Details: A meta-analysis of results from two case-control studies has found that increased folate intake during pregnancy is not associated with a reduced risk of childhood acute lymphoblastic leukemia (50247).
Male infertility. Oral folic acid does not seem to improve sperm parameters or pregnancy rates in males with infertility. Details: Some small clinical studies show that taking folic acid, alone or with zinc, increases sperm count in males with idiopathic infertility or in males with a grade III varicocele (9334,90194). However, another small study in males with asthenozoospermia shows that taking folic acid 5 mg, selenium 200 mcg, and vitamin E 400 IU daily for 3 months does not improve sperm parameters when compared with placebo (104907). Furthermore, there seems to be no improvement in clinical outcomes. One large, high-quality clinical study in males with idiopathic infertility shows that taking folic acid 5 mg with zinc 30 mg daily for 6 months does not improve sperm morphology, pregnancy rate, or live birth rate when compared with placebo (102085). Folic acid has also been evaluated in combination with other ingredients. A retrospective study in males with or without varicocele-related infertility suggests that taking a specific combination product containing folic acid 0.2 mg, vitamin C, zinc, L-carnitine fumarate, acetyl-L-carnitine, coenzyme Q10, selenium, and vitamin B12 (Proxeed Plus, Sigma-Tau) twice daily for 6 months is associated with improvements in sperm count, sperm concentration, and sperm motility when compared to baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles (111296). The validity of this study is limited by the lack of a comparator group.
Osteoporosis. Oral folic acid does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in elderly adults or adults with a history of cerebrovascular disease shows that taking vitamin B12 500 mcg and folic acid 0.4-2 mg, with or without vitamin B6 25 mg, daily for 2-3 years does not seem to reduce the risk for osteoporotic fractures when compared with placebo (90377,90393). A 5-7 year follow-up of this research has also found no benefit (103981).
Physical performance. Oral folic acid does not seem to improve physical performance in older adults. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg daily for 2 years, does not improve hand strength or improve performance such as walking when compared with placebo in elderly individuals also taking vitamin D (96148).
Pre-eclampsia. Oral folic acid does not seem to prevent pre-eclampsia in pregnant patients. Details: While the effect of low-dose prenatal folic acid is unclear, high-dose folic acid does not seem to reduce the risk of pre-eclampsia. Some population research has found that low-dose folic acid is associated with a 22% reduced odds of pre-eclampsia, while other research has found no association (91308,99370,99372,110447). A large clinical trial evaluating high-dose folic acid in pregnancies at risk for pre-eclampsia shows that taking 4 mg daily, starting at 8-16 weeks of gestation and continuing until delivery, does not reduce the risk of pre-eclampsia when compared with placebo (103929). A secondary analysis of this study in twin pregnancies has also found no benefit with high-dose folic acid supplementation (103977).
Respiratory tract infections. Oral folic acid does not seem to prevent respiratory tract infections. Details: Clinical research in children aged 6-30 months at risk of malnourishment shows that taking a nutritional supplement (Nutriset Ltd) enriched in folic acid 75-150 mcg, with or without vitamin B12 0.9-1.8 mcg, daily for 6 months does not reduce the incidence of lower respiratory infections when compared with a supplement not enriched with folic acid and vitamin B12 (90391).

Colorectal adenoma. Oral folic acid does not prevent colorectal adenomas. Details: Although some population research and one clinical study has found that high folate intake is associated with reduced colorectal adenoma risk (2142,2143,91303), most clinical research does not support this finding. Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily for up to 9.2 years, does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389). Other clinical research suggests that taking folic acid does not reduce the occurrence or recurrence of adenomas or incidence of advanced adenomas (34596,50241,50265,50369,50394,50449,50522). Furthermore, treatment with folic acid for more than 3 years seems to be associated with an increased risk of advanced adenomatous lesions (50378).
Fragile X syndrome. Oral folic acid does not improve symptoms in children with fragile X syndrome. Details: Clinical research shows that taking folic acid orally does not improve symptoms of fragile X syndrome (2155,2156,2157,2158,2159,2160,50575).
Preterm labor. Oral folic acid does not seem to reduce the risk of preterm birth. Details: Meta-analyses of clinical research show that supplementation with folic acid 200 mcg to 5 mg during pregnancy does not decrease the risk of preterm birth (91307,96155). An observational study in patients with and without epilepsy found that folic acid supplementation during pregnancy was associated with a lower odds of preterm birth in patients receiving antiseizure medications; however, no link between folic acid and preterm labor was reported in patients without epilepsy or in those with epilepsy not receiving antiseizure medications (110447).

Abdominal wall defects. It is unclear if oral folic acid helps to prevent abdominal wall defects in newborns. Details: Observational research in a population in northern China has found that taking folic acid supplements until the end of the first trimester modestly reduces the risk of abdominal wall defects and the risk of omphalocele, specifically, in the newborn when compared with not taking folic acid. However, this association was not found in a population in southern China (109191). These differing outcomes may be related to the lower dietary folate intakes in northern China.
Acne. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing folic acid, vitamin B6, nicotinamide, azelaic acid, zinc, and copper for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared with baseline (90800).
Age-related macular degeneration (AMD). Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking folic acid 2.5 mg, vitamin B6 50 mg, and vitamin B12 1 mg daily reduces the risk of developing AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to folic acid, other ingredients, or the combination.
Age-related testosterone deficiency. Folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in males with overweight or obesity, mild erectile dysfunction, and normal to low androgen levels shows that taking a combination product containing folic acid 400 mcg, alpha-lipoic acid, myo-inositol, and apple (Sinopol Forte) increases testosterone, luteinizing hormone, and measures of erectile dysfunction but not follicle-stimulating hormone or sperm parameters when compared to baseline (111674). The validity of these effects is limited by the small sample size and the lack of a comparator group, and it is unclear if these effects are due to folic acid, other ingredients, or the combination.
Alzheimer disease. It is unclear if oral folic acid reduces the risk of developing this condition. Details: Low levels of folate and high levels of homocysteine have been linked to a greater risk of Alzheimer disease (50094). Also, some observational studies have found that higher intake of folate from the diet and supplements in elderly adults is associated with a reduced risk of developing Alzheimer disease when compared with lower intake (13165,15270). One small clinical trial in patients with Alzheimer disease who are taking cholinesterase inhibitors shows that taking folic acid 1 mg daily for 6 months increases the likelihood of treatment response, classified as global improvement in behavioral and/or functional status with no decline in mental status scores, by 78% to 87% when compared with placebo (50246). Also, preliminary clinical research in patients with probable Alzheimer disease who are not consuming a folate-fortified diet shows that taking vitamin B12 50 mcg daily plus folic acid 1.2 mg daily for 6 months modestly improves some measures of cognitive performance and decreases levels of homocysteine when compared with placebo (107150). However, not all research agrees. Clinical research in patients with probable Alzheimer disease using routine medications shows that taking folic acid 5 mg, vitamin B12 1 mg, and vitamin B6 25 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo (50319). However, all patients in this study were also consuming a folate-fortified diet.
Angioplasty. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that folic acid 1 mg, vitamin B12 400 mcg, and pyridoxine 10 mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6, and vitamin B12 followed by oral administration of folic acid 1.2 mg, vitamin B6 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151).
Atopic dermatitis (eczema). It is unclear if oral folic acid during pregnancy reduces the risk of eczema in the child. Details: Observational research has found that consuming both iron and folic acid supplements during pregnancy is associated with a four-fold reduced risk for developing atopic dermatitis in the child. However, use of either iron or folic acid supplementation alone is not associated with an effect on the child's risk for atopic dermatitis (102387).
Autism spectrum disorder. It is unclear if oral folic acid intake during pregnancy reduces the risk of autism spectrum disorder in the child. Details: A meta-analysis of population research has found that consumption of folic acid of at least 400 mcg daily from both diet and supplements during pregnancy is associated with a 45% reduced risk of autism in the child at 2-15 years of age. Also, supplementation with folic acid during the prenatal to early period of pregnancy is associated with an approximate 43% reduced risk of autism in the child. This association did not differ between countries with or without a folate fortification program (109198). An individual population study has also found that prenatal folic acid supplementation initiated the first day of the last menstrual period before conception is associated with a 39% reduced odds of autism in the child at age 3.3-10.2 years when compared to pregnancies without folic acid supplementation (91324).
Beta-thalassemia. There is limited evidence on the oral use of folic acid for beta-thalassemia minor. Details: Patients with beta-thalassemia minor may experience decreased muscle strength and increased bone or muscle pain. A small clinical study in children with this condition shows that taking folic acid 1 mg, with or without L-carnitine 50 mg/kg, daily for 3 months reduces bone pain by 64% to 84% and increases the number of stairs climbed by 2- to 5-fold when compared with baseline (90631). The validity of this finding is limited by the lack of a control group.
Bipolar disorder. It is unclear if adding oral folic acid to conventional bipolar therapy further improves symptoms. Details: Some clinical evidence suggests that folic acid does not improve the antidepressant effects of lithium in patients with bipolar disorder (50566). However, other clinical evidence suggests that taking folic acid in combination with valproate during the acute phase of mania improves the effects of valproate (50357).
Breast cancer. It is unclear if oral folic acid reduces breast cancer risk. Details: Some older population research suggests that increased intake or levels of folic acid alone does not affect the risk of breast cancer or breast cancer-related mortality (50218,50224). However, in a specific group of women who also consume high amounts of dietary methionine, cyanocobalamin (vitamin B12), or pyridoxine (vitamin B6), dietary intake of folate is associated with a reduced risk of breast cancer (9328,50224). Also, more recent population research has found that folic acid plus folate dietary intakes between 153-400 mcg are associated with a reduced risk of breast cancer. This risk is further reduced in those who drink relatively large amounts of alcohol (90794). Folate intakes greater than 400 mcg daily do not appear to be protective against breast cancer (90794).
Cancer. It is unclear if oral folic acid prevents cancer. Details: A large cohort study of children born to mothers with epilepsy on antiseizure medications suggests that prenatal folic acid exposure of 1 mg daily or more, at an average of 4.3 mg daily, is associated with a 2.7-fold greater risk of pediatric cancer when compared with children born to mothers with epilepsy but without prenatal exposure to high-dose folic acid. Additionally, this risk is not present in children of mothers without epilepsy taking high-dose folate (112103). It is unclear how maternal epilepsy, antiseizure medications, and folate interact to increase the risk of pediatric cancers. However, in the absence of clear guidelines, mothers with epilepsy should take no more than 4 mg of folic acid daily (112101,112102).
Cardiovascular disease (CVD). Although oral folic acid does not seem to prevent most CVD events, some research suggests that increased dietary folic acid might lower the risk of stroke and CVD-related mortality in patients at high risk for CVD. Details: In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Meta-analyses of available research show that folic acid might lower the risk of stroke in patients with CVD (97619,102386,107136). Some clinical research shows that taking folic acid reduces the risk of CVD by 15% in patients with kidney failure or chronic kidney disease (50444,91311). However, most research shows that folic acid supplementation, alone or in combination with vitamin B6 and vitamin B12, does not improve endothelial function or reduce the risk of death or CVD events in patients with existing hyperhomocysteinemia, coronary heart disease, CVD, kidney disease, or prior stroke, despite having a homocysteine-lowering effect (9313,9322,11337,11387,13482,50437) (50512,50527,96154,96147,97619,102386). Some population research has evaluated adults at high risk for CVD. This research has found that dietary folate intake of at least 382 mcg daily is associated with a modest reduction in CVD-related mortality and possibly all-cause mortality. Consuming folic acid as a component of fortified food in doses of more than 251 mcg daily is associated with a modest reduction in CVD-related mortality. Conversely, folic acid supplementation is associated with a higher risk of CVD and overall mortality, and there is a J-shaped association between folate intake, serum folate levels, and red blood cell folate levels, with both CVD-related and all-cause mortality (109199).
Cervical cancer. It is unclear if oral folic acid prevents cervical cancer. Details: Epidemiological evidence has found that increasing folate intake from dietary and supplement sources, along with thiamine, riboflavin, and vitamin B12, might decrease the risk of precancerous cervical lesions (11074).
Child development. It is unclear if oral folic acid supplementation during pregnancy improves child development. Details: Clinical research in Northern Ireland shows that taking folic acid 400 mcg daily starting in the 14th week of gestation and continuing until the end of pregnancy improves word reasoning in the child at 7 years of age when compared with placebo. When compared with a historical cohort from Britain, folic acid supplementation was associated with an increase in full scale IQ, verbal IQ, performance IQ, and general language at 7 years of age (102385). At age 11, benefits in word reasoning were no longer significant. However, there were modest benefits in some measures of processing speed when compared with placebo. Verbal comprehension was modestly improved in females, but not males (109192). Observational research in pregnant individuals and their children in Spain has found that taking less than 400 mcg of folic acid daily during pregnancy is associated with lower mental alertness scores in children at ages 7-9 years when compared with folic acid 400-999 mcg daily, while taking folic acid 1000 mcg or more daily during pregnancy was associated with improvements in some measures of working memory in the children. However, no relationship between folic acid dosing and most other measures of cognitive function was identified (110449).
Chronic fatigue syndrome (CFS). Although there is interest in using oral or injectable folic acid for CFS, there is insufficient reliable information about the clinical effects of folic acid for this condition.
Chronic kidney disease (CKD). While adding oral folic acid to enalapril might slow CKD progression, adding folic acid to high-dose vitamin B12 does not seem to be beneficial. Details: Clinical research in adults with hypertension and CKD shows that taking enalapril with folic acid 800 mcg for a median of 4.4 years reduces the risk of worsening kidney function by 21% and slows the rate of kidney function decline by 44% when compared with enalapril alone (96153). However, clinical research does not support the use of folic acid in patients with CKD when used in combination with high-dose vitamin B12 (cyanocobalamin). Vitamin B12 might increase the risk of negative outcomes (50253,50409,96150). More research is needed to determine the benefits of folic acid when used alone.
Colorectal cancer. It is unclear if oral folic acid prevents colorectal cancer. Details: Although the majority of population research suggests that taking folic acid orally from dietary and supplemental sources reduces the risk of colorectal cancer (505,2140,2144,2145,2250,6271,9325,9326,50109,50427,50450)(91306,91323,96160,109188,110450), clinical evidence in general is not supportive. Most clinical research and meta-analyses of clinical trials suggest that taking folic acid from dietary or supplemental sources does not reduce the risk of colorectal cancer (2141,34596,50394). The reason for this discrepancy is unclear. Some observational research suggests that an inverse association between folate intake and risk of colorectal cancer was not apparent until at least 12 years after baseline folate intake was determined (109188). A meta-analysis of observational studies suggests that the benefits of folic acid supplementation on colorectal cancer risk might be limited to patients with moderate to high alcohol consumption (110450). Other clinical evidence suggests that the beneficial effect of folic acid may be limited to colon, but not rectal, cancer (21501). Furthermore, the beneficial effect for colon cancer may be limited to only certain subtypes. For instance, females with folate intake of at least 400 mcg daily seem to have a 46% reduction in the risk of p53-overexpressing colon cancer, but not p53-negative tumors, when compared with those who consume less than 200 mcg daily (21300). Also, the source of folic acid may influence its effects. Some observational research suggests that dietary folate, but not folic acid supplementation, reduces the risk of colon cancer (21501).
Congenital heart disease. It is unclear if oral folic acid prevents congenital heart disease. Details: The exact cause of congenital heart disease is unknown but is thought to be a combination of genetic and environmental factors. Population research has found that supplementation with folic acid or folic acid-containing prenatal vitamins during pregnancy is associated with up to a 40% lower risk of congenital heart defects in newborns (99373).
Dementia. It is unclear if oral folic acid is beneficial for the prevention or treatment of dementia. Details: While some preliminary research shows that folic acid might aid in the prevention and treatment of Alzheimer disease (13165,15270,50246,90374), two small clinical trials show that taking folic acid 15-20 mg daily for 10-12 weeks does not seem to improve cognitive function or the severity of dementia in patients with various forms of dementia, including vascular dementia, Lewy body dementia, probable Alzheimer disease, or dementia due to other causes (50062,50597).
Diabetes. Small clinical studies suggest that oral folic acid does not improve glycemic control. Details: Meta-analyses of small clinical trials in patients with type 2 diabetes show that folic acid does not reduce glycated hemoglobin (HbA1C) when compared with placebo (50528,109197). Another small clinical study in patients with diabetes who are stabilized on metformin and/or a sulfonylurea shows that taking folic acid 5 mg daily for 8 weeks does not affect HbA1C when compared with placebo (104917). The validity of this study is limited by its small size and lack of blinding. Conversely, a meta-analysis of clinical research shows that taking folate modestly reduces fasting blood glucose and insulin levels, as well as measures of insulin resistance, when compared with placebo or no intervention (109197). There was no clear relationship between these changes and the dose or duration of folate. However, the studies included in this analysis evaluated multiple patient populations; the effect of folate in patients with diabetes, specifically, is unclear. Beyond glycemic control, some research has assessed the impact of dietary folate intake on cardiovascular risk in patients with diabetes. An observational study in Chinese adults with type 2 diabetes has found that dietary intake of folate in the highest quartile is associated with 68% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with folate intake in the lowest quartile (110452). Folic acid has also been evaluated in gestational diabetes. A meta-analysis of 20 studies shows that serum and red blood cell (RBC) folate levels are higher in patients with gestational diabetes than without gestational diabetes. Subgroup analysis suggests that patients with gestational diabetes have higher serum and RBC folate levels in the second trimester than in those without gestational diabetes, while RBC folate levels in patients with gestational diabetes were higher in the first trimester than those without gestational diabetes. Overall, higher serum folate levels are associated with a slight increase in the odds of gestational diabetes when compared with lower serum folate levels (112107).
Diabetic neuropathy. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with diabetic neuropathy shows that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate), for 24 weeks does not improve neural dysfunction based on vibration perception, but does seem to improve total neuropathy symptoms, when compared with placebo. These symptoms, which include both sensation and pain, decreased by 25% with the B vitamin combination, compared with only 15% in those taking placebo (90375).
Epilepsy. It is unclear if oral folic acid reduces seizure frequency. Details: A meta-analysis of preliminary clinical research shows that taking folic acid does not reduce seizure frequency in patients with epilepsy (50124). However, there is some speculation that folate deficiency might be linked to increased seizure frequency. A preliminary clinical study in folate-deficient children with epilepsy shows that taking folic acid 5 mg daily for 3 months reduces seizure frequency when compared to baseline, but not when compared with a control group that is not deficient in folate (99371).
Erectile dysfunction (ED). Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in males with mild erectile dysfunction, overweight or obesity, and normal to low androgen levels shows that taking a combination product containing folic acid 400 mcg, alpha-lipoic acid, myo-inositol, and apple (Sinopol Forte, Laborest) improves measures of erectile dysfunction when compared to baseline (111674). The validity of these effects is limited by the small sample size and the lack of a comparator group, and it is unclear if these effects are due to folic acid, other ingredients, or the combination.
Esophageal cancer. Higher dietary folate intake is associated with a lower risk of esophageal cancer. Details: One meta-analysis of observational research has found that higher levels of dietary folate are associated with a 34% lower risk of esophageal squamous cell carcinoma and a 50% lower risk of esophageal adenocarcinoma when compared with low levels of dietary folate (50208). Another meta-analysis of observational research has found that consuming high amounts of folate is associated with a 36% decrease in the odds of esophageal cancer when compared with lower dietary folate intake (100950).
Fenofibrate (Tricor)-induced hyperhomocysteinemia. Folic acid seems to attenuate increases in homocysteine in people taking fenofibrate. Details: A small open-label clinical trial in patients taking fenofibrate shows that adding folic acid 10 mg every other day might reduce elevated plasma homocysteine levels by up to 59% when compared with taking fenofibrate alone (9321).
Gastric cancer. It is unclear if oral folic acid reduces gastric cancer risk. Details: Observational research has found that taking folic acid reduces the risk of gastric cardia adenocarcinoma by 17% and the risk of noncardia gastric cancer by 33%, but does not reduce the risk of gastric cancer overall (50208). Also, a meta-analysis of 13 small clinical studies in patients with gastric precancerous conditions shows that taking folic acid 20-30 mg daily for 3-6 months improves gastric mucosal atrophy and intestinal metaplasia but does not seem to improve symptoms when compared with a control (110448). Whether these findings are associated with a lower risk of gastric cancer is unclear.
Gout. It is unclear if oral folic acid reduces the risk for gout. Details: An observational study has found that increased dietary folate intake is associated with a lower incidence of gout (50454).
Head and neck cancer. It is unclear if oral folic acid is beneficial for head and neck cancer prevention. Details: Population research has found that the highest intake of dietary folate is associated with a 50% reduced risk of head and neck cancer when compared with the lowest intake of folate. Each 100 mcg increase per day seems to reduce the risk by about 4% (96151).
Hearing loss. It is unclear if oral folic acid prevents hearing loss. Details: Low levels of serum folate seem to be a risk factor for sudden sensorineural hearing loss in adults (21283). Observational research in females has found that serum folate levels in the lowest quintile are associated with a 19% increased risk for hearing loss when compared with levels in the second quintile. Also, folate levels in the highest quintile are associated with a 12% lower risk of hearing loss when compared with the second quintile (109807). A clinical study in older adults from the Netherlands shows that taking folic acid 800 mcg daily for 3 years slows the decline of age-related low-threshold hearing loss when compared with placebo (15163). However, at the time of this study, folate enrichment of foods was not allowed in the Netherlands. As a result, baseline folate levels in this study population were about 50% lower than in the US population. The effect of folic acid supplementation in people with higher baseline folate levels is unclear.
Infertility. It is unclear if oral 5-methyltetrahydrofolate (5-MTHF) in combination with vitamin B6 and vitamin B12 is more beneficial than folic acid alone for increasing pregnancy rate in females undergoing assisted reproductive technology (ART). Details: Retrospective research from Italy suggests that taking 5-MTHF 400 mcg, vitamin B12 5 mcg, and vitamin B6 3 mg daily results in clinical pregnancy and live birth rates of approximately 60% and 49%, respectively, compared with 45% and 35% of those taking folic acid 400 mcg daily. A sub-analysis suggests that beneficial effects on pregnancy rates are limited to individuals aged less than 40 years (109189). The findings from this study are limited by its retrospective design. Also, it is unclear if these findings are generalizable to countries with folate fortification.
Kidney failure. It is unclear if oral folic acid is beneficial in patients with kidney failure. Details: Because hemodialysis removes folate from the body, there is concern that folate deficiency may cause complications in patients with kidney failure receiving hemodialysis. Observational research in Taiwanese patients with kidney failure undergoing hemodialysis has found that taking folic acid 5 mg daily for an average of 5.8 years is associated with a 31% lower risk of arteriovenous access thrombosis when compared with folic acid 5 mg weekly. However, daily folic acid supplementation was not linked to a lower risk of cardiovascular events, cancer, or mortality when compared with weekly folic acid (110120). Oral folic acid has also been evaluated in combination with other ingredients. A small, low-quality clinical study in adults with kidney failure undergoing regular hemodialysis shows that taking oral folic acid 30 mg daily with thiamine 90 mg daily for 96 weeks reduces overall mortality by 67% and improves cognitive scores by 31% when compared with no intervention (107724). It is unclear if these findings are due to folic acid, thiamine, or the combination.
Lometrexol toxicity. While oral folic acid might reduce lometrexol toxicity, intravenous folic acid does not seem to help. Details: In a phase I trial, intravenous folic acid 5-25 mg administered 1 hour or 3 hours prior to lometrexol 15-30 mg/m2 every 3 weeks does not seem to reduce cumulative lometrexol toxicity (2161). However, in a phase II study, taking oral folic acid 3 mg/m2 daily in addition to lometrexol 10 mg/m2 weekly seems to attenuate cumulative toxicity and improve its tolerability in cancer patients (104948).
Low birth weight. It is unclear if oral folic acid supplementation during pregnancy reduces the risk of a low birth weight. Details: Clinical research shows that supplementation with folic acid 200 mcg to 5 mg daily during pregnancy increases mean birth weight when compared with placebo (91307). Furthermore, some population research has found that pre- or peri-conception folic acid supplementation, usually 400 mcg daily, is associated with a reduced risk of a child born small-for-gestational age. However post-conception folic acid supplementation is not associated with reduced risk (91304,103983). An observational study in pregnant Chinese patients found that supplementation with folic acid is associated with a 20% lower odds of low birth weight when compared with no supplementation. This association was observed when folic acid was used both before conception and during pregnancy for at least 24 weeks or during pregnancy only for at least 12 weeks. Increased dietary folate intake was not linked to a lower risk of low-birth-weight infants (110446). However, other observational research has found no association between folic acid supplementation during pregnancy and the risk for small-for-gestational age births (110447).
Lung cancer. It is unclear if oral folic acid reduces lung cancer risk. Details: There does not appear to be a relationship between deficiency of folate and lung cancer (9454). However, consuming at least 130.4 mcg of folate per 1000 kcal daily seems to reduce the risk of lung cancer by 40% in former smokers when compared to those with lower dietary folate intake (50065).
Melanoma. It is unclear if oral folic acid reduces melanoma risk. Details: Population research has found that folic acid supplementation of 2-2.5 mg daily in combination with vitamin B6 and vitamin B12 is linked with a 53% reduced risk of melanoma (91312).
Metabolic syndrome. Although there is interest in using oral folic acid for metabolic syndrome, there is insufficient reliable information about the clinical effects of folic acid for this condition.
Nitrate tolerance. It is unclear if oral folic acid helps to prevent the development of tolerance to treatment with nitroglycerin. Details: Some clinical evidence suggests that taking folic acid 1 mg daily for 1 week does not prevent the development of nitroglycerin-induced endothelial dysfunction or tolerance in healthy individuals (50442). However, other research suggests that taking folic acid 10 mg daily for 1 week prevents nitric oxide synthase dysfunction caused by continuous nitroglycerin (9316).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral folic acid is beneficial for NAFLD. Details: A cross-sectional analysis suggests that adults with NAFLD have lower levels of serum folate and its major component 5-MTHF when compared with healthy controls. Additionally, adults with NAFLD seem to consume less supplementary and dietary folate when compared with healthy controls. Overall, serum folate levels are negatively associated with the risk of NAFLD, and inadequate folate intake is associated with an increased risk of NAFLD (112104).
Oral clefts. It is unclear if oral folic acid reduces the risk of oral clefts in infants. Details: Observational research has found that maternal folic acid supplementation is associated with an up to 49% reduced risk of cleft lip with or without cleft palate (50220,104921). Furthermore, a large clinical trial in pregnancies at-risk for oral cleft suggests that taking a higher dose of folic acid 4 mg from pre-conception until the end of the first trimester results in a similar oral cleft recurrence rate of 2.5%, compared with a 2.9% recurrence with a lower dose of folic acid (400 mcg). Both doses demonstrate a lower incidence of oral clefts when compared with historical rates of 6.3% (91322). Although there is speculation that genetic markers of folate status impact the effect of folic acid on orofacial cleft incidence, the current data do not show a relationship (104921).
Overall mortality. It is unclear if oral folic acid reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of folic acid in the highest quintile is associated with a 14% to 23% lower risk of all-cause mortality and a 41% to 47% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary folic acid intake (110451).
Pancreatic cancer. It is unclear if oral folic acid reduces pancreatic cancer risk. Details: Consuming greater than 280 mcg daily of dietary folate is associated with a decreased risk of exocrine pancreatic cancer (9327). A meta-analysis of case-control and cohort studies suggests that consuming higher amounts of dietary folate reduces the risk of pancreatic cancer by 51% compared to low levels of dietary folate (50208). However, another meta-analysis of prospective cohort studies suggests that folate/folic acid intake does not significantly affect the overall risk of pancreatic cancer (50499). The contradictory results may be associated with the form of intake or may be related to the gender of the participants. A meta-analysis of clinical research shows that dietary folate, but not folic acid, significantly reduces the risk of pancreatic cancer (50387). Also, one meta-analysis of observational studies has found that high dietary folate decreases the risk of pancreatic cancer in females, but not males (50387).
Peripheral neuropathy. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows taking a combination of folic acid 400 mcg, vitamin B12 3 mcg, and uridine monophosphate 50 mg daily (Keltican) for 60 days reduces pain associated with peripheral neuropathy. Use of this product reduces pain intensity by approximately 44%, with loss of burning pain in approximately 50% of patients, strong tingling or pricking in approximately 57% of patients, strong pain attacks in 92% of patients, and numbness in 90% of patients when compared with baseline. Radiating pain and the use of concomitant medications are also reduced (90384). The validity of this finding is limited by the lack of a comparator group. Furthermore, it is unclear if the benefits are due to folic acid, other ingredients, or the combination.
Pharyngeal cancer. It is unclear if oral folic acid reduces pharyngeal cancer risk. Details: Population research has found that intake of folic acid and folate from natural, fortified, and supplemented sources, may protect against oropharyngeal cancer. Intake of at least 258-816 mcg total folate/folic acid reduces the odds by 35% when compared with intakes of less than 344 mcg. Furthermore, folate/folic acid may be more beneficial for oral cancer versus pharyngeal cancer and in heavy alcohol users versus non users or light users (91302).
Polycystic ovary syndrome (PCOS). It is unclear if oral folic acid is beneficial for PCOS. Details: One clinical study in overweight or obese patients with PCOS shows that taking folate 1 mg or 5 mg daily for 8 weeks modestly reduces levels of homocysteine, as well as insulin resistance, when compared with placebo. However, only the 5 mg dose modestly reduces insulin, total cholesterol, and low-density lipoprotein (LDL) cholesterol levels. Neither dose appears to affect fasting plasma glucose, high-density lipoprotein (HDL) cholesterol, or triglyceride levels when compared with placebo (109200). Other clinical research in patients with PCOS taking metformin shows that taking folate 400 mcg daily for 6 months does not affect glycemic parameters, plasma lipid levels, or hormone levels when compared with placebo (109194). The reasons for discrepancies between studies are unclear but may relate to patient characteristics. One study included only overweight or obese individuals with at least two of the three PCOS criteria, whereas the other study limited enrollment to patients in any weight category but with all three PCOS criteria (109194,109200).
Pregnancy-induced hypertension. It is unclear if oral folic acid reduces the risk of hypertension during pregnancy. Details: Population research has found that taking folic acid during pregnancy is not associated with a reduced risk of gestational hypertension (91308,99370,99372).
Restless legs syndrome (RLS). Although there is interest in using oral folic acid for RLS, there is insufficient reliable information about the clinical effects of folic acid for this condition.
Schizophrenia. Oral folic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination of folic acid 2 mg and vitamin B12 400 mcg daily for 16 weeks improves negative symptoms when compared with placebo in patients with schizophrenia who have persistent symptoms and a specific genetic variant of the folate transporter gene FOLHI. This variant normally results in reduced folate absorption. However, in patients without this genetic variant, folate is not beneficial with respect to negative symptom improvement (90387).
Sickle cell disease. Oral folic acid has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B12 4.2-6 mcg, folic acid 700 mcg, and vitamin B6 4.2-6 mg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
Suicidal ideation. It is unclear if oral folic acid reduces the risk of suicidal ideation or suicide attempts. Details: One observational study has evaluated the association between folic acid supplementation and suicidal events in patients with various underlying conditions, including 12% with depression, 15% with anxiety, and 46% with pain. This within-person cohort study found that filling a prescription for folic acid 0.4-5 mg daily, either alone or as part of a multivitamin, is associated with a 44% reduced rate of suicidal events during the months after the prescription when compared with the months without the prescription. For the 48% of patients who received folic acid 1 mg daily, each additional month of taking the prescription was associated with a 5% decrease in suicidal events (109201). Prospective clinical research is needed to confirm any benefits of folic acid and to determine whether baseline folate deficiency plays a role in these outcomes. More evidence is needed to rate folic acid for these uses.

IODINE

Iodine deficiency. Oral iodine supplements, including iodized salt, are effective for improving iodine status and reducing goiter size in adults and children. Iodine supplementation is also recommended during pregnancy in areas at risk for iodine deficiency. Details: Iodine deficiency is associated with several adverse outcomes. The earliest clinical symptom of iodine deficiency is low circulating thyroid hormone and thyroid stimulating hormone (TSH), followed by thyroid goiter (7135,16747,91398). Iodine deficiency and subsequent hypothyroidism can lead to anovulation, infertility, autoimmune thyroiditis, and gestational hypertension. Iodine deficiency is also associated with increased risk of thyroid cancer (16747). Clinical research shows that taking iodine supplements, including iodized salt, improves iodine status and reduces goiter size in adults with iodine deficiency (16747,55919,103071). Studies also show that taking iodine supplementation, including iodized salt, in areas of endemic iodine deficiency, reduces goiter size in children (16747,55919). When taken during pregnancy for iodine deficiency, iodine supplements and iodized salt reduce both maternal and newborn thyroid size and thyroglobulin; however, the effect on maternal TSH is inconsistent (91399,103070). Although some clinical studies and one analysis show that perinatal use of iodine has no effect on the incidence of thyroid disorders during pregnancy (91399,97240,97241), one analysis shows that iodine supplementation reduces the risk of postpartum hyperthyroidism by 68% when compared with placebo (97240). Taking iodine supplementation before 12 weeks' gestation appears to be more effective than when taken later in pregnancy. Perinatal iodine supplementation has no effect on preterm birth rate (97240,97241). Evidence is limited to females with mild-moderate iodine deficiency; the routine use of iodine supplementation during pregnancy has not been extensively studied. For example, the effect of perinatal supplementation on newborn neurocognitive development is conflicting and the evidence is generally low quality (55976,97241,105880,108706). Despite the limited evidence, iodine supplementation is recommended in areas at risk of deficiency.
Radiation exposure. Oral potassium iodide prevents thyroid uptake of radioactive iodine. However, it does not protect against other sources of radiation. Details: Taking potassium iodide is effective for preventing the uptake of radioactive iodine by the thyroid (7517,7518). Doses of potassium iodide protect for about 24 hours. Therefore, it should be taken daily until the risk of radiation exposure no longer exists (17575,17576).

Conjunctivitis. Ophthalmic povidone-iodine solution seems to reduce the risk of conjunctivitis in infants. It may also improve the resolution of acute conjunctivitis in adults. It is unclear if it is beneficial in patients with adenoviral conjunctivitis. Details: A meta-analysis of low-quality clinical trials shows that povidone-iodine solutions are more effective than silver nitrate for preventing neonatal conjunctivitis. However, povidone-iodine solutions are not more effective than erythromycin or chloramphenicol (56084). Povidone-iodine in combination with dexamethasone also seems to be helpful in adults. A clinical trial in patients with acute viral conjunctivitis shows that applying povidone-iodine 0.6% with dexamethasone 0.1% four times daily for 4 days improves clinical symptoms and eradiation of viral counts when compared with placebo control (103075). A small clinical study in adults with adenoviral conjunctivitis shows that administering 4-5 drops of a povidone-iodine 5% eye drop solution within 4 days of symptom onset decreases viral load, mucoid discharge, and bulbar edema and redness on day 4 of a 21-day follow-up period, but at no other time points, when compared with a single dose of artificial tears (108705). Due to the single-dose nature of this study, the effects of continued administration are unclear.
Diabetic foot ulcers. Topical iodine seems to help with the management of diabetic foot ulcer wounds. Details: A small clinical study in patients with diabetic foot ulcers shows that topically applying cadexomer iodine ointment (Iodosorb) for 12 weeks seems to improve healing to a similar degree as using standard treatment with gentamicin solution, streptokinase, and/or dry saline gauze (2200).
Endometritis. Topical application of iodine prior to cesarean delivery seems to reduce the risk of endometritis. Details: A meta-analysis of eight clinical trials shows that vaginally applying povidone-iodine 1% to 10% solution immediately before cesarean delivery reduces the risk of post-cesarean endometritis by 62% when compared with saline or no cleaning. It also reduces postoperative fever by 13% and wound infection by 23% (99794). These findings are consistent with other meta-analyses (56080,103076). There seems to be no difference in benefit whether povidone-iodine 1%, 5%, or 10% is used. A network meta-analysis of clinical studies in patients having cesarean delivery suggests that povidone-iodine is no better at preventing endometritis than using chlorhexidine or metronidazole; however, there may not have been sufficient power to detect a difference (103076).
Fibrocystic breast disease. Oral iodine seems to reduce breast pain in patients with fibrocystic breast disease. Details: Preliminary clinical research in patients with fibrocystic breast disease shows that taking sodium iodide, protein bound iodide, or molecular iodine for 6 months or longer improves mastalgia and reduces breast nodules when compared with baseline or control. Molecular iodine in doses of 70-90 mcg/kg appears to be more effective and better tolerated than the other forms (2197). Another clinical study in patients with cyclic mastalgia due to fibrocystic breast disease shows that taking tablets containing molecular iodine 3000-6000 mcg daily for 5 months reduces pain, tenderness, and nodularity in patients with cyclic mastalgia when compared with placebo. However, a lower dose of 1500 mcg daily does not appear to be beneficial (55960).
Oral mucositis. Rinsing the mouth with a povidone-iodine solution may prevent oral mucositis from radiochemotherapy. Details: Small clinical studies in patients receiving radiation and chemotherapy for cancer shows that using an oral povidone-iodine rinse seems to reduce the risk for oral mucositis when compared with using sterile water (2198,2199).
Periodontitis. Rinsing with povidone-iodine solution in addition to scaling and root planing seems to be modestly beneficial in patients with periodontitis. Details: A meta-analysis of mostly small clinical studies in patients with chronic periodontitis suggests that rinsing with povidone-iodine 0.1% to 10% during scaling and root planing modestly reduces the periodontal pocket depth when compared with rinsing with water or saline solution (56072).
Postoperative infection. Povidone-iodine antisepsis prevents postoperative infection when compared with inactive controls such as normal saline and water. However, it is unclear how it compares to active controls such as chlorhexidine; practice guidelines are conflicting. Details: A meta-analysis of clinical research shows that intraoperative application of povidone-iodine reduces the risk of surgical site infection by approximately 40% when compared with saline or no irrigation (56088). However, research comparing povidone-iodine with other antiseptics such as chlorhexidine is conflicting, as are official guidelines for surgical antisepsis. Many of these discrepancies seem to be related to the presence or absence of alcohol in the preparation. A meta-analysis of clinical research comparing aqueous or alcohol-based povidone-iodine shows that using alcohol-based chlorhexidine for skin antisepsis is more effective for preventing postoperative surgical site infections and may be associated with a lower overall positive culture rate. However, since evidence for both aqueous and alcohol-based solutions of povidone-iodine were included in this study, it is unclear if this may have affected outcomes (108710). The National Institute for Health and Care Excellence (NICE) Guideline recommends chlorhexidine solution as the first choice for preparing the skin for surgery, with povidone-iodine solution as a second-line option. The antiseptic solutions are recommended to be alcohol-based as long as the surgical site is not near a mucous membrane (105906). The World Health Organization (WHO) guidelines also recommend alcohol-based chlorhexidine solutions over either alcohol-based or aqueous povidone-iodine for preventing surgical site infections. However, some experts have expressed concern that these recommendations are based on faulty evidence, as some studies used povidone-iodine preparations with lower alcohol amounts than their comparator groups (105898). In fact, the guideline from the Centers for Disease Control and Prevention (CDC) does not differentiate between povidone-iodine and chlorhexidine antiseptic solutions as long as they are alcohol-based (105905).
Thyroid storm. Oral iodine is recommended as an adjunct to standard treatment for thyroid storm. Details: The American Thyroid Association (ATA) and the American Association of Clinical Endocrinologists (AACE) recommend a multimodality approach for treating thyroid storm that includes taking five drops of a saturated solution of potassium iodine every 6 hours (15,92699).
Thyroid nodules. Combining oral iodine with thyroxine seems to improve the resolution of thyroid nodules. Details: A clinical study in patients with benign nodular thyroid disease and possible iodine deficiency shows that taking iodized salt 200 mcg daily in addition to thyroxine 1.5 mcg/kg daily after surgery seems to reduce the size of the thyroid remnant by 40%, compared with a 10% reduction in patients given thyroxine alone (55927). Also, one large clinical trial in patients with nodular goiter shows that taking potassium iodide 150 mcg daily in combination with levothyroxine 50-100 mcg daily for 12 months reduces nodule volume by about 17%, compared with 7% in the group using levothyroxine alone (91392).
Venous leg ulcers. Topical cadexomer iodine seems to improve the healing of venous leg ulcers; however, it is unclear if applying povidone-iodine is beneficial. Details: A meta-analysis of four small clinical studies in patients with venous leg ulcers shows that applying cadexomer iodine results in complete healing of ulcers in 33% of patients after 4-12 weeks, compared with only 15% of patients receiving standard care alone. However, use of cadexomer iodine was associated with more adverse effects than standard care. Furthermore, preliminary clinical research shows that applying cadexomer iodine is comparable to hydrocolloid dressing, paraffin gauze dressing, dextranomer, and silver-impregnated dressings for improving the rate of complete healing. A meta-analysis of preliminary clinical research show that povidone-iodine has comparable healing rates when compared with amoxicillin, hydrocolloid dressings, and moist or foam dressings (99798). These findings were consistent with an older version of this meta-analysis (56076).

Catheter-related infections. Topical povidone-iodine seems to be less effective than chlorhexidine for preventing infections from intravascular catheters. Furthermore, it does not seem to reduce the risk of catheter-related urinary tract infections. Details: One meta-analysis of clinical research shows that topical application of povidone-iodine reduces the risk of bloodstream infections when applied at the insertion site of hemodialysis central venous catheters (55883). However, disinfecting catheter insertion sites using povidone-iodine seems to be less effective for preventing blood stream infections in patients receiving central venous, pulmonary artery, or peripheral artery catheters when compared with chlorhexidine solutions (55883,55916). In addition, periurethral cleansing with povidone-iodine 10% prior to bladder catheterization, as well as bladder irrigation with povidone-iodine 2% prior to urinary catheter removal, does not seem to reduce the risk of urinary tract infections when compared with placebo (56058,56126).
Prematurity. Maternal iodine supplementation does not seem to impact neurological development in premature infants. Details: A meta-analysis of two clinical trials in premature infants shows that adding iodine to enteral or parenteral feeds does not improve mental, visual, or auditory development or reduce the risk of death when compared with no iodine supplementation (99797).

Chyluria. It is unclear if topical iodine is beneficial in patients with chyluria. Details: A small clinical study in patients with chyluria suggests that using povidone-iodine 0.2% solution as a sclerosant in renal pelvic instillation sclerotherapy (RPIS) may be as effective as using silver nitrate 1% (55970).
Corneal ulceration. It is unclear if topical iodine is beneficial in patients with corneal ulceration. Details: Preliminary clinical research shows that administering povidone-iodine 2.5% eye drops every two hours for two weeks in addition to standard antibiotic therapy does not reduce visual impairment in patients with corneal ulcers when compared with standard antibiotic therapy alone (55971).
Coronavirus disease 2019 (COVID-19). It is unclear if rinsing with a povidone-iodine mouthwash and using a povidone-iodine nasal spray and ointment can reduce the spread of COVID-19. Details: A small clinical study in adults with PCR-confirmed COVID-19 shows that orally swishing and gargling 25 mL of povidone-iodine (PI) 1% solution, then, into each nostril, spraying 2.5 mL of PI 1% solution and applying one dab of PI 10% ointment, and repeating this 4 times daily for 5 days does not seem to alter the quantity of viral RNA over time when compared with control (105877). The validity of this finding is limited because all study participants achieved negative viral titers on the third day of the study.
Cutaneous sporotrichosis. It is unclear if topical iodine is beneficial in patients with cutaneous sporotrichosis; research is conflicting. Details: Anecdotal reports and case series suggest that taking saturated solution of potassium iodide (SSKI) orally is effective for most patients when used alone or in combination with another antifungal, including terbinafine or itraconazole (17562,17563,17564,17565,17566,17567,17568,17569,17570,17571) (17572,17573). In one non-controlled clinical study, treatment with SSKI, starting with 3 drops (150 mg potassium iodide) daily and titrating up, resulted in symptom resolution in about 90% of patients after about 33 days of treatment (17561). However, some patients are not able to take SSKI due to intolerable side effects (17561,17572).
Hyperthyroidism. It is unclear if oral potassium iodide is beneficial for patients with Graves' disease undergoing total thyroidectomy. Details: A retrospective study in patients with Graves' disease undergoing total thyroidectomy shows that preoperative administration of saturated solution of potassium iodide (SSKI) 5% does not reduce the rate of postoperative complications, such as transient or permanent hypoparathyroidism, transient recurrent laryngeal nerve (RLN) palsy, definitive RLN palsy, and cervical hematoma, when compared with no preoperative administration (108707).
Infant development. It is unclear if maternal iodine supplementation impacts neurological development in infants. Details: Three-year follow-up data from a clinical study in infants and breastfeeding females shows that maternal supplementation of iodine 150 mcg daily improves child cognitive scores, but does not affect language or motor scores, when compared with placebo. Supplementation with a higher dose of 300 mcg daily yielded similar cognitive, language, and motor scores as the 150 mcg dose (108706). This finding aligns with the daily recommended dietary allowance (RDA) of 290 mcg during lactation, which is sometimes achieved by augmenting the diet with a 150-mcg iodine supplement (7135).
Postoperative bleeding. It is unclear if topical iodine is beneficial in patients with postoperative bleeding. Details: A small clinical study suggests that irrigating extraction sockets with povidone-iodine 1% stops bleeding in a greater number of patients following tooth extraction when compared with a saline solution (56011).
Rhinosinusitis. It is unclear if topical iodine is beneficial in patients with rhinosinusitis. Details: A small prospective cohort study in patients with recalcitrant chronic rhinosinusitis has found that using a povidone-iodine 0.08% nasal rinse every other day for 7 weeks in addition to standard therapy improves symptoms and reduces signs of infection when compared with baseline (103074). However, one small clinical study in patients with a history of sinus surgery and acute exacerbations of chronic sinusitis shows that receiving povidone-iodine nasal irrigations twice daily for 30 days is no different than irrigations with mupirocin or normal saline for improving nasal symptoms. However, mupirocin tended to reduce bacteria count to a greater extent than the povidone-iodine solution (105878). This finding is limited due to small study size and potential lack of power to detect differences between groups.
Thyroid cancer. It is unclear if dietary iodine is associated with complications in patients with papillary thyroid cancer. Details: A retrospective study in patients in China with papillary thyroid cancer has found that dietary intake of iodine resulting in serum concentrations greater than 90 mcg/L is associated with a 75% increased risk of cervical lymph node metastases when compared with concentrations less than 45 mcg/L (108708). Actual dietary intake of iodine was not reported, limiting the validity of this finding.
Ventilator-associated pneumonia (VAP). It is unclear if oral iodine rinse is beneficial for the prevention of VAP. Details: A small clinical study in patients with severe head trauma suggests that regularly rinsing the throat with 20 mL of povidone-iodine 10% solution decreases the risk for VAP when compared with using a saline rinse (56003).
Wound healing. It is unclear if topical iodine is beneficial for wound healing. Details: A meta-analysis of clinical research shows that topical iodine, as cadexomer iodine or povidone-iodine, is superior to non-antiseptic dressings and some antiseptic agents, such as silver sulfadiazine, for reducing wound size. However, iodine seems to be less effective than local antibiotics such as rifamycin (56083). More evidence is needed to rate iodine for these uses.

IRON

Anemia of chronic disease. Oral and intravenous iron in combination with erythropoiesis-stimulating agents (ESAs) are effective for treating anemia of chronic disease. Details: Iron supplementation with ESAs is effective for treating anemia associated with chronic kidney disease (CKD) or chemotherapy. During therapy with ESAs, iron levels should be monitored and supplementation provided as needed to ensure that the response is not limited by lack of iron for erythropoiesis (1087,1091,20110,20111,110192). Research shows that intravenous iron appears to be more effective than oral supplements for this purpose (20112,20113). In patients with CKD, intravenous iron at total doses from 2232 mg over 6 months to 1020 mg over one week increases hemoglobin levels more than oral doses of 4-6 mg/kg daily or 325 mg daily for up to 6 months (20112). Some research has evaluated the effect of intravenous or oral iron in patients not treated with ESAs. In patients with cancer or CKD, oral iron supplements have been shown to improve iron status (110184,110192). However, overall benefits of iron alone remain unclear in treated or untreated patients with cancer and more research is needed to rule out an increase in mortality and to determine any effect on blood transfusion requirements (110192). Preliminary clinical research shows that children aged 6 months to 10 years with HIV and anemia who take elemental iron 3 mg/kg daily along with a multivitamin for 3 months have a 41% lower chance of having persistent anemia at 3 months when compared with multivitamins alone (95432).
Iron deficiency anemia. Oral and intravenous iron are effective for treating or preventing iron deficiency anemia. The benefits of iron supplementation in people with iron deficiency without anemia are unclear. Details: Oral iron supplements, mainly as ferrous sulfate, are effective for treating and preventing iron deficiency anemia in adults, children, and infants (1089,7135,17495,17496,17497,103806,20114,20115,91183,96621)(104680,104681,112601). Other forms are also effective, including sodium iron ethylenediaminetetra-acetate (NaFeEDTA), iron(III)-hydroxide polymaltose complex (IPC), iron protein succinylate, iron bisglycinate, and lactoferrin with iron (20117,20118,110189). Treatment with iron supplements should increase hemoglobin levels by 1 gram/dL every 2-3 weeks. However, even after hemoglobin has normalized, it may take up to 4 months for iron stores to be replenished (17497). Historically, treatment of iron deficiency anemia with oral iron supplements has typically consisted of a daily dosing regimen, often taken in divided doses to reduce adverse effects. In more recent years, however, intermittent iron supplementation (1-3 doses/week) has become preferred for some patients, particularly those with mild anemia, due to better absorption and a possible reduction in side effects compared to daily dosing. One small clinical study shows that taking ferrous sulfate 60 mg on alternate days in single doses improves iron absorption when compared to once daily dosing (96630). Another small clinical study in females with iron-deficiency anemia shows that fractional iron absorption is 40% to 50% higher with alternate-day dosing compared with daily dosing. Furthermore, total iron absorption was shown to be similar for alternate day dosing of elemental iron 200 mg compared with daily dosing of 100 mg, but the incidence of gastrointestinal adverse effects may be lower for the alternate day dosing regimen (101514). A meta-analysis of 25 clinical trials, including 10,996 menstruating females with or without pre-existing iron deficiency and/or anemia, shows that intermittent iron reduces the risk of anemia and increases hemoglobin and serum ferritin when compared with placebo or no intervention. This meta-analysis did not identify differences in the risk of anemia, hemoglobin, or serum ferritin between intermittent and daily iron supplementation. However, it did show that females receiving intermittent dosing had a 59% reduction in the risk for adverse effects. The validity of these findings is limited by significant heterogeneity in the enrolled populations and selected dosing strategies, including frequency of intermittent dosing, total weekly dose, and duration of follow-up. In addition, the subgroup analyses performed by baseline anemia, hemoglobin, and serum ferritin, as well as duration of follow-up, showed differing overall conclusions when comparing intermittent and daily iron supplementation. While intermittent dosing appears to be beneficial when compared with daily dosing for some patients with iron deficiency anemia, intermittent dosing may be less effective than daily iron supplementation in some patients (103806). For patients with severe anemia, twice daily dosing may be preferred to alternate day dosing due to faster response. A small clinical study in patients with iron deficiency anemia shows that taking ferrous sulfate 200 mg twice daily is more effective at increasing hemoglobin levels by 3 weeks when compared with ferrous sulfate 400 mg taken on alternate days in single doses (102864). Intermittent iron supplementation has also been investigated in children. A meta-analysis of clinical research in children and adolescents with or without pre-existing iron deficiency and/or anemia shows that taking iron supplements 1-2 times weekly is similarly effective as 3-7 times weekly for decreasing iron deficiency and iron deficiency anemia. However, ferritin and hemoglobin levels increased to a greater extent with 3-7 times weekly supplementation (112601). Blood transfusion may be required for some patients with severe iron deficiency anemia who have symptoms such as dyspnea and fatigue (17497). Intravenous iron should be considered in patients who cannot tolerate oral iron or in patients with chronic bleeding or intestinal malabsorption (17497). Guidelines from the British Society of Gastroenterology recommend treatment with iron while awaiting investigations to rule out gastrointestinal issues in adults in the absence of an alternative explanation. The guidelines recommend ferrous sulfate, fumarate, or gluconate as one tablet daily. If adverse effects occur, intake can be reduced to once every other day, or alternative oral or parenteral sources of iron can be used. Parenteral sources should be used if oral sources are contraindicated or ineffective. Treatment should be monitored and continued after hemoglobin levels are normalized (110193). Iron supplementation may also be beneficial in patients with iron deficiency without anemia, which can cause fatigue and reduced well-being, although guidelines are lacking. A meta-analysis of randomized controlled trials in adults with iron deficiency but not anemia shows that supplemental iron improves iron stores and hemoglobin levels. In addition, iron moderately reduces self-reported fatigue, but not physical capacity, when compared with placebo. Oral ferrous sulfate was used in most studies included in the analysis; however, intravenous or intramuscular iron were also used (104684).
Pregnancy-related iron deficiency. Oral iron is effective for preventing pregnancy-related iron deficiency. Details: Clinical research shows that taking iron orally at an average daily dose of 20-225 mg of elemental iron increases maternal hemoglobin levels by up to 1 gram/dL when compared with placebo and reduces the risk of maternal anemia by 62% to 100% (20122,20123,20124,110180,110188). Some clinicians may recommend alternating days of iron administration to reduce gastrointestinal adverse effects. A pooled analysis shows that taking iron supplements on alternating days during pregnancy maintains adequate iron intake and reduces gastrointestinal adverse effects when compared with taking iron daily (96625). Various forms of oral iron seem to be equally effective for raising hemoglobin levels (110185,110188). However, in patients with anemia during pregnancy, a meta-analysis of clinical research shows that intravenous iron sucrose and ferric carboxymaltose were more effective than oral ferrous sulfate for improving hemoglobin levels (110185).

Breath-holding attacks. Oral iron seems to be effective for reducing the frequency of breath-holding attacks in children with iron deficiency. Details: The incidence of breath-holding attacks is increased in children with iron deficiency or iron deficiency anemia. Most research shows that oral supplementation with ferrous sulfate 3-6 mg/kg daily for 4-16 weeks reduces the frequency of breath-holding attacks in children aged 1-72 months (20128,104682,104683). The best evidence comes from a meta-analysis of one randomized controlled trial and 11 observational single arm studies (104682). In this analysis, approximately 84% of children experienced at least a 50% decreased frequency of breath-holding attacks (104682). Some preliminary clinical research also shows that administering intramuscular iron reduces the frequency of breath-holding attacks and increases remission in children with iron deficiency anemia (20128).
Cognitive function. Oral iron seems to be effective for improving cognitive function in children and adolescents with iron deficiency. Details: Taking iron orally seems to improve cognitive function in iron-deficient children and adolescents (20121,112600). For example, ferrous sulfate 650 mg twice daily for 8 weeks improved verbal learning and memory in non-anemic iron-deficient adolescent females (1095). Ferrous sulfate 50 mg twice weekly for 16 weeks appeared to improve attention measures in adolescent females with possible anemia (91186). Iron also appears to reverse developmental and learning deficits caused by iron-deficiency in anemic infants (1104). Some clinical research is focused on children and adolescents from low- and middle-income countries. In children aged 5-19 years with or without iron-deficiency anemia, a meta-analysis of clinical research shows that iron supplementation for 3-8 months dose-dependently improves measured intelligence by a modest amount. However, there was no effect on other measures of cognition, including attention or memory (110181). Another meta-analysis of clinical research in school age children shows that taking iron for 2-12 months modestly improves intelligence, attention, and memory, but not educational achievement, when compared with placebo or no intervention. However, sub-analyses show that any benefits are limited to children with anemia (112600).
Heart failure. Intravenous iron seems to be effective for improving recovery in patients with heart failure and iron deficiency. It is unclear if oral iron is effective. Details: Iron deficiency is common in patients with heart failure (17499,112597,112598,112599). Individual clinical trials and meta-analyses of clinical research in patients with heart failure show that administering intravenous iron, as ferric carboxymaltose, iron dextran, iron isomaltoside, or iron sucrose, for at least 12 weeks modestly improves quality of life, increases exercise capacity, and reduces hospitalizations when compared with placebo or standard care. However, there was no effect on all-cause mortality or cardiovascular mortality (17498,91179,110176,110187,112597,112598,112599). Some individual clinical trials have used intravenous ferric carboxymaltose 200 mg or iron sucrose 200 mg in patients with mild or moderate heart failure and iron deficiency (17498,91179). Guidelines from the British Society of Gastroenterology suggest that treatment with parenteral iron improves symptoms and quality of life in patients with functional iron deficiency related to CHF (110193). Limited research has investigated the effect of oral iron in this population. A small meta-analysis of clinical research shows with low certainty that taking iron orally has beneficial effects on serum ferritin and left ventricular ejection fraction (110178). Most research shows that taking oral iron does not improve hemoglobin levels, quality of life, or exercise capacity when compared with placebo (100970,110178). However, one small clinical trial shows that taking oral iron modestly improves iron status and overall symptoms and increases the 6-minute walking distance by about 46 meters, compared with a reduction of only 14 meters in those taking placebo (110183). Some doses used in individual clinical studies have included iron polysaccharide 150 mg twice daily for 16 weeks and ferrous sulfate 200 mg three times daily for 12 weeks (100970,110183).
Restless legs syndrome (RLS). Oral and intravenous iron seem to be beneficial for RLS. The American Academy of Neurology recommends a combination of oral ferrous sulfate and vitamin C or intravenous ferric carboxymaltose for patients with RLS. Details: RLS is commonly associated with iron deficiency anemia. Some clinical research shows that taking iron in the form of ferrous sulfate 325 mg twice daily for 12 weeks reduces RLS symptoms comparably to pramipexole. Symptoms such as leg discomfort, need to move, and sleep disturbances improved considerably in about half of the patients taking either treatment (91181). Additional clinical research shows that taking ferrous sulfate 325 mg twice daily along with vitamin C 100 mg twice daily for 12 weeks reduces symptoms of RLS when compared with vitamin C alone in patients with RLS and low-normal serum ferritin levels (94189). Based on these results, clinical practice guidelines by the American Academy of Neurology report that taking this combination of oral ferrous sulfate and vitamin C is likely to improve symptoms in patients with RLS and low-normal serum ferritin (93587). Intravenous iron may also reduce symptoms of RLS. Clinical practice guidelines by the American Academy of Neurology report that two doses of intravenous ferric carboxymaltose 500 mg given 5 days apart are likely to improve symptoms and quality of life within 28 days in patients with moderate to severe RLS, regardless of serum ferritin levels. Intravenous iron sucrose has also been evaluated in patients with RLS, but there is currently insufficient available evidence to support or refute the use of this form of iron for treating RLS (93587).

Athletic performance. Oral iron does not seem to improve athletic performance. Details: A meta-analysis of clinical research in adults of childbearing age shows that iron supplementation improves some exercise performance measures, such as maximal oxygen uptake capacity, but not others, such as time until exhaustion and energy consumption, when compared with control (91184). Another meta-analysis of clinical research in patients with iron deficiency without anemia shows that iron supplementation improves subjective measures of fatigue, but does not improve exercise time to exhaustion or other measures of physical capacity (104684). A small clinical study in healthy children shows that taking iron supplements or consuming food providing iron 30-200 mg daily for 1-2 months improves running performance when compared with placebo. This was demonstrated by reductions of heart rate of 6.6 to 8 beats per minute during the running exercise. One preliminary study included in this analysis also showed that iron supplementation improved treadmill endurance time (20140).
Child growth. Oral iron does not seem to be beneficial for child growth. Details: Meta-analyses of mainly preliminary clinical research show that oral iron supplementation, at doses averaging 2-80 mg or 1-10 mg/kg elemental iron daily for up to 52 weeks, does not increase growth rate in children (20131,20132,20133,95434).
Preterm labor. Oral iron does not seem to prevent preterm labor and may actually increase the risk in malaria-endemic regions. Details: A meta-analysis of results from five clinical studies shows that maternal intake of iron as ferrous sulfate 20-60 mg daily for 14-26 weeks starting in the second trimester of pregnancy does not affect the length of gestation or increase birthweight of the infant (95434). In females from a malaria-endemic area who have never been pregnant before, another clinical study shows that taking ferrous gluconate 60 mg and folic acid 2.8 mg weekly, starting before conception and continuing to the first antenatal visit, may more than double the risk of preterm birth, defined as a delivery under 37 weeks gestation, when compared with folic acid alone (100969). Some research suggests that the adverse outcome in this latter study may be explained by a rise in hepcidin levels in pregnant patients with malaria. Hepcidin is a hormone that regulates iron absorption and distribution, and malaria can upregulate hepcidin. High levels of hepcidin can decrease iron absorption, stimulate inflammatory processes, and cause progesterone withdrawal, leading to preterm labor (102863).

ACE inhibitor-induced cough. It is unclear if oral iron is beneficial in patients with this condition. Details: A small clinical trial shows that taking ferrous sulfate 256 mg daily reduces or eliminates cough induced by ACE inhibitors such as captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil, Zestril), and others, when compared with placebo (7307).
Androgenic alopecia. Oral iron has only been evaluated in combination with other ingredients, its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with androgenic alopecia or telogen effluvium shows that taking one tablet daily of a specific product (GFM Oral, Cantabria Labs), providing an unknown dose of iron in combination with selenium, taurine, cysteine, methionine, and hydrolyzed collagen, along with conventional therapy, consisting primarily of finasteride or minoxidil, for 12 weeks improves hair loss when compared with conventional therapy alone (111636). It is unclear if this effect is due to iron, other ingredients, or the combination.
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral iron is beneficial in children with ADHD. Details: Three small clinical studies in children with ADHD and iron deficiency shows that taking oral iron improves some measures of ADHD after 1-3 months of treatment when compared with baseline or placebo. These studies used ferrous sulfate 5 mg/kg daily, ferrous sulfate 80 mg daily, ferrous fumarate 200 mg daily for children weighing up to 30 kg, or ferrous fumarate 400 mg daily for children weighing more than 30 kg (1093,16013,110191).
Child development. It is unclear if oral iron is beneficial for improving development in non-anemic children. Details: Some observational research has found that iron deficiency in infancy is associated with poor verbal performance and social skills in childhood (102862). It is unknown whether iron supplementation can ameliorate these developmental issues. In non-anemic infants and children, preliminary clinical research shows that iron does not improve cognitive performance; the evidence for the benefits of iron on psychomotor development is conflicting (20129,20130,91315,96616,96626).
Esophageal cancer. It is unclear if oral iron is beneficial for esophageal cancer prevention. Details: Population research has found that taking iron supplements is associated with a 32% lower risk of esophageal adenocarcinoma when compared to never taking iron supplements. However, use of iron supplements is not associated with a lower risk of esophageal squamous cell carcinoma (95435).
Fatigue. It is unclear if oral iron is beneficial in patients with fatigue due to iron deficiency without anemia. Details: A meta-analysis of mainly preliminary clinical research in adults with iron deficiency without anemia shows that iron reduces self-reported fatigue moderately more than placebo (104684). A specific ferrous sulfate supplement (Tardyferon; Pierre Fabre Médicament) providing 80 mg of elemental iron daily for 4-12 weeks was used in two studies included in this analysis (11406,91188).
Inflammatory bowel disease (IBD). In patients with active IBD, intravenous iron may be more beneficial than oral iron due to impaired absorption. However, it may also increase the risk of infection in these patients. Details: Since the absorption of oral iron may be impaired in patients with active symptoms of IBD, guidelines from the British Society of Gastroenterology suggest that treatment with parenteral iron may be needed in patients with IBD who have moderate to severe iron-deficiency anemia (110193). However, a meta-analysis of clinical research in this population shows that administering IV iron, usually as iron sucrose or ferric carboxymaltose, increases the risk of infection by 73% when compared with oral iron or no iron (110186).
Postoperative recovery. It is unclear if intravenous iron is beneficial for recovery following cardiac surgery. Details: A meta-analysis of low- to moderate-quality clinical research in patients with preoperative iron-deficiency anemia shows that treatment with intravenous iron before cardiac surgery does not improve the rate of transfusions or the length of stay in the intensive care unit or hospital when compared with control groups, including placebo, oral iron, or no treatment. Also, a meta-analysis of clinical research shows that intravenous iron does not reduce postoperative mortality rates (110182).
Postpartum depression. Although there has been interest in using iron for postpartum depression, there is insufficient reliable information about the clinical effects of iron for this condition.
Prematurity. Enteral iron seems to be beneficial for some measures of development in preterm infants. Details: A meta-analysis of clinical research in preterm or low birthweight infants fed human milk shows that enteral iron supplementation increases linear growth and reduces the risk of anemia when compared with control groups receiving no iron supplementation. However, there was no effect on serum ferritin, weight, head circumference, cognitive development, risk of infection, or risk of necrotising enterocolitis (110177). Additional clinical research in infants born at 24-28 weeks' gestation shows that a higher average enteral iron dose by 60 days of age is positively associated with cognitive performance at 2 years of corrected age. However, this association was not present for iron doses received at 90 days of age (110190). More evidence is needed to rate iron for these uses.

MAGNESIUM

Bowel preparation. Various magnesium salts are used for cleansing the bowel prior to procedures such as colonoscopy. Details: Various magnesium salts, including citrate, hydroxide, oxide, and sulfate, are ingredients in bowel preparation products available over-the-counter or by prescription only.
Constipation. Magnesium salts are effective when used orally to treat constipation short-term. It is unclear if magnesium is beneficial for chronic idiopathic constipation (CIC). Details: Magnesium citrate, sulfate, and hydroxide salts are commonly used as laxatives. Magnesium citrate 8.75-25 grams has been used; magnesium hydroxide 2.4-4.8 grams, as 30-60 mL of milk of magnesia, has also been used (15). Magnesium sulfate, which seems to have the most potent effect, has been used as 10-30 grams (15,6430). Magnesium salts should only be used for occasional treatment of constipation, and doses should be taken with a full 8-ounce glass of water. There is also interest in using magnesium for symptomatic relief of CIC. A small clinical study in patients with CIC who are not taking chronic medications shows that taking magnesium oxide 1.5 grams in three divided doses daily for 28 days increases spontaneous bowel movements when compared with placebo (104397). It is unknown if magnesium is beneficial for CIC when used long-term.
Dyspepsia. Magnesium salts are effective when used orally as antacids. Details: Magnesium carbonate, hydroxide, oxide, or trisilicate salts are used orally as antacids to reduce symptoms of gastric hyperacidity or gastroesophageal reflux. Magnesium hydroxide has the fastest onset of action. The onset for magnesium carbonate is slower due to its crystal structure. Magnesium trisilicate has the slowest onset and longest duration of action due to poor solubility (6844). Doses used include magnesium hydroxide 400-1200 mg (5-15 mL of milk of magnesia) up to four times daily, or magnesium oxide 800 mg daily (15).
Eclampsia. Magnesium sulfate is considered the drug of choice for control of seizures. Details: Intravenous (IV) and/or intramuscular (IM) magnesium sulfate is considered the agent of choice for seizure prophylaxis during eclampsia by the American College of Obstetricians and Gynecologists (ACOG) (15,12591,12592,61012,61184). Typical doses include 4-6 grams of magnesium sulfate by IV infusion in 250 mL of dextrose 5% or normal saline solution, followed by 4-5 grams of magnesium sulfate IM every 4 hours, or 1-3 grams per hour by continuous IV infusion. Doses should be adjusted according to serum levels and urinary excretion, and should not exceed 30-40 grams of magnesium sulfate daily (15,12591). Meta-analyses of clinical research show that treatment with IV or IM magnesium reduces the risk of seizure recurrence by 33% to 69% when compared with phenytoin, and by 47% to 60% when compared with diazepam (19960,60818,60954,60964,61105). One preliminary clinical study shows that lower doses of IV magnesium sulfate (9 grams loading dose and maintenance of 2.5 grams every 4 hours for 24 hours) are as effective as higher doses (14 grams loading dose and maintenance of 5 grams every 4 hours for 24 hours) for reducing the recurrence of eclamptic seizures (89383). It is generally recommended that treatment be continued for at least 24 hours after the last seizure (15). Oral magnesium has not been evaluated for eclampsia.
Hypomagnesemia. Hypomagnesemia can be effectively treated with oral or parenteral magnesium. Details: Taking magnesium orally or parenterally is helpful for treating and preventing hypomagnesemia associated with alcoholism, cirrhosis of the liver, congestive heart failure (CHF), severe or prolonged diarrhea or vomiting, kidney dysfunction, inflammatory bowel disease (IBD), pancreatitis, malabsorption syndromes, and other conditions (6280,6281,8088,8089). The dose and salt of magnesium for oral replacement therapy should be chosen carefully to avoid causing diarrhea. The gluconate and chloride salts cause less diarrhea, while the oxide salt is more likely to cause diarrhea and should be avoided. Magnesium chloride should also be avoided due to poor solubility which decreases absorption (6430,8099,10664). Orally, magnesium sulfate 3 grams every 6 hours for four doses has been used for hypomagnesemia (15). Parenteral magnesium doses must be individualized according to serum magnesium levels, but a typical starting dose for mild deficiency is 1 gram of magnesium sulfate intramuscularly (IM) every 6 hours for 4 doses (15). For more severe deficiency, 5 grams of magnesium sulfate may be given as an intravenous (IV) infusion in 1 liter of dextrose 5% or normal saline solution over 3 hours (15).
Pre-eclampsia. Magnesium sulfate is considered the drug of choice for seizure prophylaxis in patients with pre-eclampsia. Details: Intravenous (IV) and/or intramuscular (IM) magnesium sulfate is considered the agent of choice for seizure prophylaxis during pre-eclampsia by the American College of Obstetricians and Gynecologists (ACOG) (12591,12592,61012,61184). Some meta-analyses show that IV administration of magnesium sulfate reduces the risk of eclampsia when compared with placebo, phenytoin, or diazepam in patients with pre-eclampsia (19960,60818,60960,60979). A typical initial dose is 4-5 grams of magnesium sulfate by IV infusion in 250 mL of dextrose 5% or normal saline solution, followed by 4-5 grams of magnesium sulfate IM every 4 hours, or 1-3 grams of magnesium sulfate per hour by continuous IV infusion. Doses should be adjusted according to serum levels and urinary excretion, and should not exceed 30-40 grams of magnesium sulfate daily (15,12591). The optimal duration of prophylaxis has not been determined. A meta-analysis suggests that using a shorter duration of 12 hours or less is not associated with an increase in risk of eclamptic seizures when compared with regimens of 24 hours or longer (108732). However, studies are likely underpowered due to the low incidence of eclampsia. Oral magnesium has been evaluated for the prevention of pre-eclampsia in healthy adults, but taking magnesium citrate 300 mg daily, starting at 12-20 weeks' gestation and continuing until delivery, does not reduce the incidence of pre-eclampsia when compared with placebo (103724).

Cerebral palsy. Most evidence shows that antenatal magnesium reduces the risk of cerebral palsy in preterm infants, although there are some inconsistent results. Details: Most clinical studies and meta-analyses show that antenatal magnesium sulfate reduces the risk of cerebral palsy by about 32% and the risk of motor dysfunction by about 45% in preterm infants (60882,60915,60927,60931,61001,97485,103734,103754). The lowest effective dose of magnesium sulfate seems to be 4 grams intravenously, with or without a maintenance dose of 1 gram/hour until birth or for 24 hours. In obese females, a higher dose, based on body weight, may be needed (97485,97495,103734,103754). However, some studies have inconsistent results (8093,19998,98293,98295,112784). Giving females at risk of imminent preterm birth (prior to 32 weeks), intravenous magnesium sulfate 4.5 grams over 20 minutes followed by 1 gram per hour until birth or for 24 hours, in addition to a standard treatment protocol, does not reduce the incidence of cerebral palsy (112784). Oral magnesium has not been evaluated for this purpose.
Seizures. Intravenous magnesium sulfate is used for treating seizures of various etiologies. Details: Intravenous magnesium sulfate may be useful for controlling seizures associated with epilepsy, glomerulonephritis, hypothyroidism, and acute nephritis in children (15). Oral magnesium has not been evaluated for this purpose.
Torsades de pointes. Intravenous magnesium sulfate is the first-line treatment for torsades de pointes after measures to correct precipitating factors have been unsuccessful. Details: Intravenous magnesium sulfate has been used successfully to treat the life-threatening ventricular tachycardia, torsades de pointes (15,6844). The Advanced Cardiac Life Support (ACLS) guidelines of the American Heart Association recommend a dose of 1 to 2 grams diluted in 50-100 mL Dextrose 5% solution given IV over 5-60 minutes, followed by a continuous IV infusion of 0.5-1 gram/hour.

Arrhythmia. Magnesium sulfate is effective for the specific type of ventricular tachycardia known as torsades de pointes, and seems to be helpful for treating other types of arrhythmias. Evidence for the role of oral or intravenous magnesium in preventing postoperative arrhythmias is conflicting. Details: Administering magnesium intravenously or orally may be helpful for treating atrial and ventricular tachycardia and fibrillation, and supraventricular tachycardia (9497,13352,13354,13355,13356,60804,60829,60877,61113,111696). Arrhythmias associated with congestive heart failure have been treated with magnesium sulfate 8 grams infused over 12 hours (9497). For rate control in atrial fibrillation, magnesium sulfate 2.5 grams IV over 20 minutes, followed by 2.5 grams IV over 2 hours has been used (13356). For paroxysmal supraventricular tachycardia, single doses of 1-4 grams of magnesium chloride have been used (13352). For atrial tachycardia, 2 grams of magnesium sulfate in 10 mL of dextrose 5% solution has been given IV over 1-10 minutes, followed by 5-10 grams of magnesium sulfate in 250-500 mL dextrose 5% solution as an IV infusion over 5 hours (13354,13355). Research on the effects of intravenous magnesium for preventing arrhythmias after cardiac surgery is conflicting. Some meta-analyses show that intravenous magnesium reduces the risk of atrial fibrillation, ventricular arrhythmias, or supraventricular arrhythmias following cardiac surgery by 23% to 48% when compared with placebo (60814,60826,60828,60838,61008,61033,61181,97487,97490). Doses of magnesium sulfate used include 30 mg/kg in 500 mL normal saline (97490), or 80-100 mg/kg added to the cardioplegia solution (97487). Also, one small study in adults after CABG surgery suggests that taking magnesium hydroxide 1600 mg orally reduces arrhythmia as effectively as receiving magnesium sulfate 2000 mg intravenously (99315). However, other meta-analyses that only include higher-quality trials show that magnesium supplementation does not reduce the risk of ventricular or supraventricular arrhythmias following cardiac surgery (61010,61024,61031,105081). A meta-analysis of clinical trials of intravenous magnesium for prevention of new-onset atrial fibrillation after non-cardiac surgeries shows that it does not reduce the incidence significantly when compared with placebo (112778). However, there was a high risk of bias in the analysis, and variability in types of surgery, and the salt and dose of magnesium used.
Asthma. Parenteral magnesium sulfate can help to reverse severe acute asthma attacks and reduce the need for hospital admission. Oral or nebulized magnesium, however, does not seem to be beneficial. Details: Overall, a single dose of intravenous magnesium seems to improve pulmonary function in acute asthma exacerbation and reduce the risk of hospitalization, particularly in patients with severe asthma, and those who have failed initial treatment with nebulized albuterol and intravenous corticosteroids (60888,90023,96483,104398,107365). The typical dose used for adults is 2 grams of magnesium sulfate infused over 20 minutes (15). For children, 25-75 mg/kg, to a maximum of 2 grams, infused over 20-30 minutes has been used (15,96483,107365). However, a post-hoc analysis of one large clinical trial (104400) designed to assess nebulized magnesium in children with acute asthma has found that adding IV magnesium to nebulized magnesium is associated with greater odds of hospitalization when compared with no IV magnesium (105919). This post-hoc analysis did not differentiate between precautionary and necessary hospitalizations. Although some clinical research in patients with acute asthma exacerbation shows that nebulized magnesium in combination with albuterol significantly improves airway function when compared with albuterol alone, the benefit is not likely to be clinically relevant (90016). Most evidence, including larger clinical trials, has not shown benefit of adjunct nebulized magnesium for acute asthma in adults or children (60888,90002,96484,104400,105920). Oral magnesium also does not seem to be beneficial. A meta-analysis of small clinical trials in children and adults with asthma shows that taking magnesium supplements orally does not improve lung function or reduce bronchodilator use when compared with control (104404).
Colorectal cancer. Increasing dietary magnesium intake seems to lower the risk of colon cancer but not rectal cancer. Details: Epidemiological research shows that increased dietary magnesium intake is associated with a reduced risk of colon cancer, but the risk of rectal cancer is not affected (89387,90017,90027,101355).
Diabetes. Low dietary magnesium may increase the risk of developing type 2 diabetes, but evidence on the use of supplements for treating type 2 diabetes is conflicting. Details: Higher dietary magnesium intake is associated with lower fasting insulin concentrations and a reduced risk of developing type 2 diabetes in adults and obese children (13369,15548,96473,97486,98294,103736,105918,106920). In people with existing type 2 diabetes, hypomagnesemia is found in 25% to 38% of patients, especially in those with poorly controlled diabetes (1172). Population research in adults with type 2 diabetes also shows that a dietary magnesium intake of less than 250 mg daily is associated with a 56% higher risk of mortality. Preliminary subgroup analyses suggest that the risk of mortality is higher in those with glycated hemoglobin (HbA1C) levels above 7% (110051). A meta-analysis of small, heterogeneous clinical studies in adults with type 2 diabetes suggests that magnesium may modestly reduce HbA1C in patients with hypomagnesemia, but not in patients with normal magnesium levels, when compared with control (105075). Individual clinical studies using magnesium supplements in patients with type 2 diabetes or insulin resistance have shown mixed results. Some research suggests magnesium supplements can decrease fasting blood glucose and improve insulin sensitivity, as well as reduce the risk of developing diabetes in high-risk patients (10664,12582,13376,60854,99313,106920), but other research shows no effect (1171,1172,13379,13380,112780). Discrepancies in these findings might reflect differences in magnesium salts and doses used, or differences in baseline magnesium status in study subjects.
Hypercholesterolemia. Magnesium may help improve lipid levels by a small amount in people with this condition. Details: There is some evidence that taking magnesium oxide 1 gram orally daily for 6 weeks can produce small decreases in low-density lipoprotein (LDL) and total cholesterol levels, and small increases in high-density lipoprotein (HDL) levels in patients with hypercholesterolemia. However, magnesium does not seem to improve lipoprotein (a) levels (1193). Magnesium may also lower triglycerides in people with hypertriglyceridemia (97494).
Metabolic syndrome. Low dietary and serum levels of magnesium seem to be associated with the development of metabolic syndrome. Details: Higher magnesium intake from diet and supplements is associated with a 27% lower risk of developing metabolic syndrome in healthy females (13371) and a 31% lower risk in healthy young adults (14304). Additional epidemiological research suggests that people with low serum magnesium levels are 6-7 times more likely to have metabolic syndrome than people with normal magnesium levels (13372). In a population analysis of over 6000 individuals without metabolic syndrome at baseline, the risk of developing this condition over a 6-year follow-up period was reduced by 16% in the highest quintile of dietary magnesium intake (median intake 371 mg daily) when compared with the lowest quintile (median intake 203 mg daily). Some, but not all, research suggests that the hazard ratio for metabolic syndrome in relation to magnesium intake may be U-shaped, with higher risk at intakes below about 150 mg daily and above 600 mg daily (108963). A combination of magnesium 20 mEq daily and potassium 40 mEq daily (magnesium potassium citrate) taken orally for 16 weeks reverses metabolic side effects of chlorthalidone, such as increased fasting plasma glucose and hypokalemia, more effectively than potassium chloride 40 mEq daily alone (112932).
Osteoporosis. Increased dietary and supplemental magnesium intake seems to increase bone mineral density and decrease bone loss in postmenopausal patients. Details: Preliminary clinical research shows that taking magnesium hydroxide orally, 300-1800 mg daily for 6 months, then 600 mg daily for 18 months, or magnesium citrate orally 1830 mg daily for 30 days, might reduce bone loss and bone turnover in postmenopausal patients with osteoporosis (9104,60928). Some epidemiological research also suggests that magnesium intake is related to increased bone mineral density (12501,12502,12503,12504,90014), although not all studies have found an association (12505,98286).
Postoperative pain. Injectable magnesium has been used with promising results for reducing pain postoperatively. Details: Intravenous magnesium sulfate, 5-50 mg/kg bolus followed by a continuous infusion of 6 mg/kg or 500 mg hourly during surgery, seems to reduce the 24-hour postoperative use of intravenous morphine by 24% when compared with placebo (19968). Adding intravenous magnesium sulfate 3.7-5.5 grams to patient-controlled analgesia for 24 hours after surgery has also been used (19968). Meta-analyses also support that adjunctive intravenous and intrathecal administration of magnesium improves pain relief and sensory nerve block, and decreases the need for other analgesics, when compared with control (89390,90012,90015,98287,103728); however, it appears to be less effective than dexmedetomidine (105082). A moderate-sized clinical study in patients undergoing total knee arthroplasty in China shows that adding magnesium sulfate 2.5 mg/mL to the periarticular infiltration analgesia (PIA) cocktail reduces pain scores, limits the use of postoperative morphine, prolongs analgesia, and reduces markers of inflammation when compared with the usual PIA cocktail (111181). Administering magnesium intravenously also seems to be helpful for pain control after hysterectomy. A 3-gram IV bolus of magnesium sulfate followed by an infusion of 0.5 grams per hour for 20 hours has been used. Lower doses were not effective (6848). In males undergoing laparoscopic radical resection for gastrointestinal cancer, administering intravenous magnesium intraoperatively, as a loading dose of 40 mg/kg followed by 15 mg/kg/hour through the end of surgery, reduces postoperative catheter-related bladder discomfort and analgesic requirements, when compared with placebo (112783). However, intravenous magnesium might not alleviate postoperative pain in children. Two small clinical studies show that administering a magnesium intravenous infusion does not reduce pain when compared with saline in children after tonsillectomy or after elective strabismus surgery (98282,105077).
Premenstrual syndrome (PMS). Taking magnesium orally seems to relieve symptoms of PMS. Details: There is some evidence that magnesium supplementation can improve symptoms, including mood changes and fluid retention, in some patients with PMS (1187,1188,6847). Doses used include magnesium oxide 333 mg daily for 2 menstrual cycles, or magnesium pyrrolidone carboxylic acid equivalent to 360 mg elemental magnesium three times daily, from the 15th day of the menstrual cycle until onset of menstrual flow (1187,1188). Taking magnesium orally in a dose of 360 mg (elemental magnesium) three times daily for 2 months seems to prevent premenstrual migraine (1186,6847). A combination of magnesium 200 mg daily plus vitamin B6 50 mg daily seems to reduce anxiety-related premenstrual symptoms, including nervous tension, mood swings, irritability, and anxiety, when compared with placebo (8555).
Vasospastic angina. Intravenous magnesium seems to prevent coronary spasm in patients with this condition. Details: Clinical research shows that administration of intravenous magnesium sulfate 65 mg/kg infused over 20 minutes dilates coronary arteries and suppresses acetylcholine-induced coronary spasms when compared with infusion of a dextrose solution in patients with vasospastic angina (8091).

Altitude sickness. Taking magnesium citrate orally does not seem to reduce acute altitude sickness risk. Details: Clinical research shows that taking magnesium citrate 1200 mg daily orally in three divided doses, beginning 3 days prior to mountain ascent and continuing until mountain descent, does not reduce the risk of acute altitude sickness when compared with placebo (60801).
Athletic performance. Taking magnesium orally does not seem to improve energy or endurance during athletic activity. Details: Most evidence suggests that taking magnesium orally doesn't increase energy and endurance during athletic activity. Magnesium oxide, aspartate, and orotate salts don't seem to improve exercise performance when used alone or in combination with potassium (2825,2826,2828,2829,2830,60751).
Bronchiolitis. Intravenous or nebulized magnesium is not beneficial in infants with this condition. Details: Clinical research shows that administering a single IV dose of magnesium sulfate 100 mg/kg to infants with acute bronchiolitis does not improve, and may actually worsen, symptoms when compared with placebo (97482). A clinical study in infants with moderate to severe bronchiolitis shows that adding nebulized magnesium sulfate 40 mg/kg to nebulized epinephrine does not reduce hospital stay or the need for ventilator or oxygen support when compared with epinephrine alone (99317). Oral magnesium has not been evaluated for this use.
Chemotherapy-induced peripheral neuropathy. Research on the effects of intravenous infusions of magnesium and calcium for preventing oxaliplatin neurotoxicity are inconsistent, but higher quality studies seem to show no benefit. Details: Pooled analyses of cohort studies and clinical trials show that calcium and magnesium infusions can decrease the incidence of severe oxaliplatin-induced neurotoxicity (90028,90029,90031). However, when only clinical trials are considered, the infusions do not appear to be helpful (90005,90029,90031,96474,96479).
Complex regional pain syndrome. Intravenous magnesium is not beneficial in complex regional pain syndrome type 1. Details: Clinical research shows that receiving magnesium sulfate 70 mg/kg intravenously at the rate of 25 mL/hour for 4 hours each day for 5 days does not improve pain or level of impairment when compared with placebo in patients with chronic complex regional pain syndrome type 1 (89395).
Emergence delirium. The majority of small clinical studies in adults and children undergoing various surgeries suggest that intravenous (IV) magnesium doesn't reduce the risk of emergence delirium. Details: A small clinical study in adults undergoing surgery for endovascular aortic aneurysm repair shows that administering IV magnesium 30 mg/kg as a loading dose, followed by a 10 mg/kg/hour infusion for the duration of surgery, does not improve agitation or delirium scores when compared with administering saline (111182). Similarly, a small clinical study in children ages 2-5 years undergoing elective strabismus surgery shows that administering IV magnesium during anesthesia does not seem to prevent the occurrence of emergence delirium when compared with administering saline (105077). In a meta-analysis of 8 clinical trials in children aged 2-16 years undergoing general anesthesia for oral or ophthalmic surgery, giving IV magnesium as a 30 mg/kg loading dose followed by a 10 mg/kg/hour infusion, or as a single dose of 15-30 mg/kg, does not reduce emergence delirium scores, and may actually prolong emergence times (108729). However, there is some conflicting evidence. In patients undergoing radical mastectomy, giving intraoperative magnesium sulfate 30mg/kg over 1 hour, followed by 10 mg/kg/hour until the end of surgery, reduces emergence agitation (odds ratio 0.26) when compared with placebo (112781).
Menopausal symptoms. Oral magnesium oxide does not seem to be beneficial for menopausal hot flashes. Details: A small, low quality study in postmenopausal patients with a history of breast cancer shows that taking magnesium oxide 400-800 mg orally daily reduces hot flashes when compared with baseline (102454). However, a larger, higher quality clinical study using magnesium oxide 800-1200 mg daily did not show any benefit when compared with placebo (98290).
Muscle cramps. Oral magnesium does not seem to improve muscle cramp frequency or intensity. Details: Meta-analyses of small clinical trials show that magnesium supplementation for 3-6 weeks does not decrease the frequency or intensity of skeletal muscle cramps, whether the cramps are idiopathic or due to liver cirrhosis or pregnancy, when compared with placebo (90022,104395).
Sickle cell disease. Intravenous magnesium does not add any benefit to standard therapy for sickle cell disease in children. Details: Clinical research shows that giving magnesium sulfate 40-100 mg/kg (maximum of 2 grams per dose) intravenously every hour for 6-8 doses as an adjunct to standard therapy does not decrease hospital stay, pain, or opioid use, or improve quality of life, when compared with standard therapy and placebo in children with sickle cell disease (89399,98283,101356). Oral magnesium has not been evaluated for this purpose.
Stillbirth. Magnesium administered during pregnancy does not reduce stillbirth risk. Details: A meta-analysis of clinical research shows that magnesium supplementation does not significantly decrease the risk of stillbirths when administered during pregnancy (60925,60978).
Tetanus. Intravenous magnesium sulfate does not seem to improve outcomes in patients with this condition. Details: A meta-analysis of clinical research shows that intravenous magnesium sulfate does not reduce mortality when compared with placebo or diazepam in patients with tetanus (61020). While some research shows that magnesium reduces the duration of hospitalization and the need for ventilation when compared with diazepam (61170), magnesium does not seem to improve these outcomes when compared with placebo (60860).
Traumatic brain injury (TBI). Magnesium does not improve clinical outcomes in patients with moderate to severe TBI. Its effect in patients with concussions is unclear. Details: A meta-analysis of four clinical trials shows that treatment with magnesium does not significantly improve neurological outcomes or reduce the risk of mortality when compared with placebo in patients with moderate to severe TBI (60905). A small observational cohort study in adolescents with concussions has found that adding oral magnesium 400 mg twice daily for 5 days to standard treatment with acetaminophen and ondansetron is associated with a trend toward reduced symptom severity when compared with standard treatment alone (104401). The validity of this study is limited by its observational nature and small cohort size.

Alcohol use disorder. Intravenous magnesium does not seem to help reduce symptoms of alcohol withdrawal but may reduce the duration of alcoholic delirium. Details: Preliminary clinical research shows that administration of four intramuscular injections of magnesium sulfate 2 grams at 6-hour intervals does not reduce symptoms of alcohol withdrawal when compared with saline (61063). A small observational study in patients with alcoholic delirium has found that administering magnesium sulfate IV 50 mg/kg every 8 hours, in addition to usual sedation, is associated with a reduction of delirium by approximately 2 days, or 4 days when given every 12 hours in addition to dexmedetomidine, when compared with usual sedation alone (111180). However, half of patients had hypomagnesemia at baseline; it is unclear if effects would be similar for patients with normal magnesium levels. Oral magnesium has not been evaluated for this purpose.
Allergic rhinitis (hay fever). Although there has been interest in using oral magnesium for allergic rhinitis, there is insufficient reliable information about the clinical effects of magnesium for this purpose.
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral magnesium is beneficial in children with ADHD. Details: Children with ADHD seem to have lower magnesium levels in their blood and hair (9969,100262,100263). A small clinical study in children aged 7-12 years with ADHD and magnesium deficiency shows that taking magnesium aspartate and lactate 6 mg/kg daily for 6 months might improve hyperactivity and magnesium levels when compared with control (1189). Another small clinical study in children with ADHD but without magnesium deficiency shows that taking magnesium 6 mg/kg daily along with vitamin D 50,000 IU weekly for 8 weeks may modestly improve emotional problems, but not inattention or hyperactivity, as measured on the strength and difficulties questionnaire (SDQ), when compared with placebo (105914).
Back pain. It is unclear if oral or intravenous magnesium is beneficial for acute or chronic back pain in adults. Details: One open-label clinical study in adults with acute low-back pain shows that taking magnesium 365 mg once daily in addition to taking etodolac 400 mg twice daily for 10 days does not further reduce pain when compared with taking etodolac alone (105913). Magnesium has also been tried for chronic back pain. A small clinical study in patients with chronic low-back pain shows that receiving magnesium sulfate 1 gram in 250 mL normal saline intravenously every 4 hours for 2 weeks, followed by magnesium gluconate 100 mg and magnesium oxide 400 mg by mouth daily for 4 weeks, reduces pain severity when compared with placebo (90035). It is unclear if oral magnesium used alone is beneficial.
Bariatric surgery complications. It is unclear if oral magnesium supplementation improves metabolic parameters after bariatric surgery. Details: A retrospective study of over 3000 post-bariatric surgery patients suggests that those who take oral magnesium supplements providing 100-450 mg elemental magnesium daily may have improved metabolic parameters over 4 years of follow-up. When patients taking magnesium supplements were compared with those not taking supplements, 11% and 18% had type 2 diabetes, respectively, 30% and 42% had hypertension, respectively, and 16% and 23% had elevated low-density lipoprotein (LDL) cholesterol levels, respectively. For patients with hypomagnesemia at baseline, supplementation seemed to result in greater benefits (108968).
Bipolar disorder. Taking magnesium orally might improve manic symptoms in some people with bipolar disorder; however, it is unclear how it compares to current standard of care. Details: One preliminary clinical study shows that magnesium 40 mEq daily (Magnesiocard) for 32 weeks has similar effects to lithium in up to 50% of patients treated for rapid cycling bipolar affective disorder (61022). Another preliminary clinical study shows that magnesium oxide 375 mg orally daily plus verapamil 80 mg taken four times daily reduces manic symptoms more effectively than verapamil alone in patients with mania (60742).
Cancer-related neuropathic pain. It is unclear if intravenous magnesium is beneficial for this condition. Details: Single 500 mg to 1 gram doses of magnesium sulfate seem to relieve neuropathic pain for up to four hours when compared to baseline (6846). The validity of this finding is limited by the lack of a comparator group.
Chemotherapy-induced leukopenia. It is unclear if oral magnesium is beneficial in pediatric patients at risk for cisplatin-induced febrile neutropenia. Details: A small clinical study in children with solid tumors aged 9 years and older shows that taking magnesium 250 mg daily while receiving cisplatin-based chemotherapy reduces febrile neutropenia by 47% and septic shock by 57% when compared with not receiving magnesium. Results from this study suggest that four pediatric patients need to take oral magnesium to avoid one case of febrile neutropenia (104394).
Cardiac arrest. Intravenous magnesium does not seem to be helpful in cardiac arrest; however, the risk of sudden cardiac death seems to be inversely correlated to higher plasma magnesium levels or dietary intake. It is unclear if magnesium supplementation is associated with similar risk reduction. Details: Administering magnesium intravenously doesn't seem to improve successful resuscitation in people with cardiac arrest (1190). However, higher plasma magnesium levels and higher dietary magnesium intake might reduce the risk of sudden cardiac death, possibly by protecting against fatal ventricular arrhythmias. In the Nurses' Health Study, the risk of sudden cardiac death was 77% lower in females with the highest quartile of plasma magnesium levels when compared with the lowest quartile. Also, the risk was 37% lower in females with the highest quartile of dietary magnesium intake when compared with the lowest quartile (17132).
Cardiovascular disease (CVD). Evidence regarding the effect of dietary magnesium on CVD risk is conflicting. Details: Epidemiological research in some populations shows that increased dietary magnesium intake is associated with decreased mortality due to strokes, coronary heart disease, ischemic heart disease, and heart failure, but other epidemiological research does not show any effect on these risks (89391,90003,90009,90030,90036,103735). Reasons for the discrepancies may be related to serum levels of magnesium at baseline, risk of cardiovascular disease at baseline, use of concomitant medications such as diuretics, or the presence of concomitant conditions such as kidney dysfunction. A population analysis conducted in Denmark has found that magnesium intake from drinking water may be associated with cardiovascular mortality. The overall risk of cardiovascular death and death due to stroke was reduced by 4% in the lowest 3 quintiles of intake when compared with the highest quintile. However, the risk of death due to acute myocardial infarction was increased by 22% in the lowest quintile when compared with the highest (108726). The relevance of these results is unclear, given that the main dietary source of magnesium is food rather than drinking water.
Chronic fatigue syndrome (CFS). Limited evidence suggests that magnesium may help improve CFS symptoms, but this is controversial. Details: In people with low red blood cell magnesium, there is some evidence that intramuscular injections of 1 gram magnesium sulfate given once weekly for 6 weeks might improve CFS symptoms (7556). However, there is additional evidence that most patients with CFS have normal magnesium stores, and measurement of red cell magnesium is a poor indicator of total magnesium stores (7557,8084,8085,8086,8087).
Chronic obstructive pulmonary disease (COPD). Intravenous, but not nebulized, magnesium may be helpful in acute exacerbations of COPD. Details: Administering magnesium sulfate intravenously, 1.2-2.5 grams over 20 minutes, might be helpful for treating acute exacerbations of COPD (1208,6844,103733). Also, giving magnesium sulfate 2 grams intravenously seems to improve exercise capacity when compared with placebo (89384). A meta-analysis of studies using intravenous magnesium sulfate for COPD exacerbations shows that it reduces hospital admission and mean length of stay and improves dyspnea scores when compared with placebo. Based on the relative risk identified in the included studies, seven patients would need to receive intravenous magnesium to prevent one hospitalization. However, intravenous magnesium sulfate does not change the need for non-invasive ventilation and the available research did not evaluate intensive care unit (ICU) admission (108967). Nebulized magnesium has also been evaluated. In patients experiencing a COPD exacerbation, clinical research shows that administering nebulized magnesium sulfate with albuterol three times at 30-minute intervals does not improve pulmonary function as measured by the forced expiratory volume in 1 second (FEV1) when compared with placebo (89393). Also, a meta-analysis of a small number of low-quality studies shows that nebulized magnesium does not reduce hospital admission or the need for ventilatory support, although it might modestly improve dyspnea scores and reduce ICU admissions, when compared with placebo (108967).
Cluster headache. It is unclear if a single intravenous dose of magnesium sulfate is beneficial for cluster headaches. Details: Administering magnesium sulfate intravenously, 1 gram over 5 minutes, seems to improve cluster headaches when compared with baseline(1184). The validity of this finding is limited by the lack of a comparator group.
Cognitive impairment. It is unclear if oral magnesium is beneficial for cognitive impairment. Details: A large observational study in adults with end-stage renal disease on hemodialysis suggests that serum magnesium levels of 20.2-22.3 mg/dL are associated with the lowest odds of mild cognitive impairment, while serum magnesium levels below and above that range of values are associated with increased odds of mild cognitive impairment (111695).
Coronary heart disease (CHD). It is unclear if magnesium supplementation is beneficial for CHD. Details: Clinical research shows that magnesium oxide 800-1200 mg daily for 3 months reduces platelet-dependent thrombosis by 35% when compared with placebo in patients with CHD (60759). It is unclear if this effect improves clinical outcomes. The effect of magnesium supplementation on coronary artery calcium has also been studied. A meta-analysis of 3 clinical studies in 196 patients with chronic kidney disease (CKD) shows that taking magnesium or increasing the concentration of magnesium in dialysate does not improve coronary artery calcification (CAC) scores when compared with standard therapy. However, magnesium reduced carotid intima-media thickness (111179). Similarly, a large clinical study in patients with CKD shows that taking slow-release magnesium hydroxide (Mablet, Denmark) 360 mg twice daily for 12 months does not slow the progression of CAC scores when compared with placebo (111178). This study may not have been adequately powered to detect a difference between groups.
Depression. It is unclear if magnesium is beneficial for the treatment or prevention of depression in adults. Details: Some population research shows that dietary intake of elemental magnesium between 76-360 mg daily is associated with a reduced risk of depression, but there was no association with greater amounts of magnesium, and other population research shows no association at any intake level (96480,98289). For treatment of mild to moderate depression, one preliminary clinical study shows that taking magnesium chloride 2 grams orally daily for 6 weeks reduces depression scores by 56% and anxiety scores by about 52% when compared to baseline (96477). The validity of these findings is limited by the lack of a comparator group. However, a small clinical study in adults with recurrent depression shows that taking magnesium aspartate 120 mg daily for 8 weeks, along with fluoxetine, does not improve depression scores when compared with patients taking fluoxetine and placebo (111185). Similarly, a very small crossover clinical study in adults with mild or moderate treatment-resistant depression shows that administering a single dose of IV magnesium sulfate 4 grams does not improve depression scores when compared with an infusion of 5% dextrose (96481). However, scores were evaluated 24 hours post-infusion which may be too soon to detect improvement. Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that elemental magnesium in doses of 100-400 mg is not recommended for adjunctive or monotherapy use in patients with depression (110318).
Diabetic foot ulcers. Oral magnesium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with grade 3 diabetic foot ulcers shows that taking magnesium oxide 250 mg plus vitamin E 400 IU daily for 12 weeks modestly reduces ulcer size when compared with placebo (101436). It is unclear if this effect is due to magnesium, vitamin E, or the combination.
Exercise-induced muscle soreness. It is unclear if oral magnesium reduces muscle soreness in adults after resistance training. Details: A very small study in healthy adults, ages 19-23, shows that taking magnesium glycinate 350 mg daily for 10 days seems to reduce muscle soreness after bench press exercise when compared with placebo (104399).
Fibromyalgia. It is unclear if oral magnesium is beneficial for this condition. Details: A small clinical study shows that taking magnesium chloride orally 100 mg once daily for one month reduces mild to moderate, but not severe, stress associated with fibromyalgia when compared with placebo. It also reduces pain levels, but not to a clinically significant extent, and it does not affect sleep, fatigue, or quality of life (108964). Another small clinical study shows that taking magnesium citrate 300 mg daily for 8 weeks improves some symptoms of fibromyalgia, such as number of tender points and depression, when compared to baseline (89385). The validity of this finding is limited by the lack of a comparator group. A small clinical study shows that taking a combination of magnesium hydroxide and malic acid (Super Malic tablets) orally decreases fibromyalgia-related pain and tenderness in some patients when compared with placebo (3262). It is unclear if this effect is due to magnesium, malic acid, or the combination.
Fractures. Population research suggests that higher intakes of magnesium may reduce fracture risk. Details: Observational research has found that higher dietary and supplemental magnesium intake is associated with a 34% lower odds of fracture when compared with lower magnesium intake (101395).
Gastric cancer. Population research suggests that higher intakes of magnesium may reduce gastric cancer risk. Details: Observational research has found that higher dietary and supplemental magnesium intake is not associated with a reduced risk for gastric cancer when compared with lower intake (103730).
Hearing loss. Oral magnesium may prevent and improve hearing loss due to environmental factors or loud noises. Details: Clinical research in healthy military recruits shows that taking magnesium aspartate 167 mg daily for 2 months prevents hearing loss from exposure to loud noises during basic military training when compared with placebo (1205). Also, in patients with acute-onset hearing loss that was not caused by environmental factors, taking magnesium aspartate 167 mg daily for 8 weeks seems to improve hearing loss when compared with placebo (60813).
Hypertension. Oral magnesium supplementation may modestly reduce blood pressure, although these changes are not likely to be considered clinically significant. Details: Most research shows that taking oral magnesium supplements in daily doses that are at least as high as the Recommended Dietary Allowance (RDA) for adults and up to 1000 mg daily can lower diastolic blood pressure by about 2 mmHg in adults with or without hypertension (1192,1199,9465,15165,18111,96482). Significantly lower doses do not seem to have this effect (1180,1195,1197,8098). The effect of magnesium on systolic blood pressure is conflicting. One meta-analysis shows that taking magnesium 240-970 mg daily does not lower systolic blood pressure (15165). However, more recent meta-analyses show that taking magnesium 120-970 mg daily can lower systolic blood pressure in a dose-dependent manner by about 2-4 mmHg in patients with or without hypertension (18111,96482). In 2022, the US Food and Drug Administration (FDA) approved a qualified health claim stating that inconsistent and inconclusive evidence suggests that diets with adequate magnesium may reduce the risk of high blood pressure. Products bearing this claim must provide at least 84 mg of magnesium daily, but no more than 350 mg daily (107451).
Hypokalemia. It is unclear if intravenous or oral magnesium is beneficial for hypokalemia in patients with normal magnesium levels. Details: A preliminary retrospective observational study in patients with hypokalemia and unknown serum magnesium levels has found that administering oral or intravenous magnesium is not associated with improved time to normalization of serum potassium levels when compared with no magnesium treatment (110049). However, hypokalemia with concurrent hypomagnesemia can impede potassium repletion and exacerbate hypokalemia-induced rhythm disturbances. Standard of care in patients with hypokalemia and known hypomagnesemia includes prompt treatment with magnesium (110063).
Impaired glucose tolerance (prediabetes). It is unclear if oral magnesium is beneficial for prediabetes. Details: Preliminary clinical research in patients with prediabetes shows that taking magnesium oxide 250 mg orally daily for 12 weeks does not improve fasting blood glucose levels, insulin resistance, or glycated hemoglobin (HbA1C) levels when compared with placebo. Taking magnesium also did not affect blood pressure, body weight, triglyceride levels, or low-density lipoprotein cholesterol levels; however, it did modestly improve high-density lipoprotein cholesterol levels (110053).
Insomnia. Oral magnesium may modestly improve sleep complaints in adults, but evidence is conflicting. Details: A meta-analysis of two small clinical studies in healthy older adults with or without insomnia suggests that taking magnesium reduces the time to fall asleep by an average of 17 minutes when compared with placebo (105917). However, it does not increase the time spent asleep. Also, these findings are limited by imprecision and a high risk of bias. Studies included in the analysis used elemental magnesium 500-729 mg daily (as magnesium oxide) for up to 8 weeks (102458,105917). Another small clinical study in patients with poor sleep quality and low magnesium status shows that taking elemental magnesium 320 mg (as magnesium citrate) in divided doses daily for 7 weeks does not improve sleep quality, as measured by the Pittsburgh Sleep Quality Index (PSQI), when compared with a sodium citrate placebo (102456). A very small crossover clinical study in patients aged 18-40 years without a sleep disorder shows that taking a combination of magnesium 300 mg, L-tryptophan 1000 mg, glycine 3000 mg, tart cherry 220 mg, and theanine 200 mg for 3 days reduces the time to fall asleep by about 24 minutes, increases total time asleep by about 22 minutes, and improves sleep efficiency, but does not improve the total time in bed or wakefulness after falling asleep when compared with cellulose placebo (111184). It is unclear if these effects are due to magnesium, other ingredients, or the combination.
Intraventricular hemorrhage. It is unclear if antenatal intravenous magnesium sulfate can reduce the risk for intraventricular hemorrhage in neonates. Details: A meta-analysis of clinical research in premature infants shows that if the mother received antenatal intravenous magnesium sulfate, the infant had a non-significant trend toward a reduced risk of intraventricular hemorrhage when compared with infants whose mothers received placebo (103727). This analysis may have been insufficiently powered to detect a difference between groups.
Kidney stones (nephrolithiasis). Taking magnesium orally may prevent the recurrence of kidney stones, although evidence is conflicting. Details: Prophylactic treatment with magnesium hydroxide, 200 mg twice daily for one year, followed by 500 mg daily for another year, might decrease the recurrence rate of calcium stone formation (2007). However, magnesium oxide does not seem to benefit patients considered to be recurrent calcium stone formers when compared with placebo, no treatment, or chlorthalidone (8097,38501,61199). Magnesium oxide 300 mg in combination with vitamin B6 10 mg daily seems to decrease urinary oxalate levels in people with hyperoxaluria who have previously had kidney stones (1201), but it is unclear if this effect translates into a reduced incidence of kidney stones.
Liver cancer. Increased dietary magnesium intake is linked with a lower risk of liver cancer. Details: Observational research in retired older Americans has found that higher dietary magnesium intake is associated with a 35% lower risk of liver cancer when compared with lower intake. This association was especially strong in persons who were moderate or heavy alcohol users (105080).
Migraine headache. Oral magnesium may help prevent migraine in some adults and children. Also, intravenous magnesium may help treat migraine in adults, but evidence is conflicting. Details: Small clinical studies in adults with migraine suggest that taking oral high-dose magnesium citrate 600-1830 mg daily in divided doses for up to 3 months seems to modestly reduce the frequency and severity of headaches when compared with baseline or placebo (4891,9498,60902). Limited evidence suggests that adding oral magnesium to conventional treatment may also be beneficial. A clinical study in adults with migraine living in Iran shows that taking magnesium oxide 250 mg twice daily in addition to sodium valproate 200 mg twice daily for 12 weeks modestly reduces severity and duration of migraine, but not migraine frequency, when compared with taking sodium valproate alone (105915). It is unclear if these improvements would be considered clinically significant. In contrast, one small clinical study shows that taking magnesium does not reduce migraine frequency and severity by at least 50% in adults when compared with placebo (10661). For treatment of migraine, some adults with normal magnesium levels respond to intravenous (IV) magnesium sulfate 1 gram over 5 minutes, but most patients who benefit have low magnesium levels at baseline (1185,6844). Effects of IV magnesium in patients with unknown magnesium levels are conflicting. Some preliminary clinical research shows that magnesium 1-2 grams IV alleviates acute migraine for up to 2 hours, but other research has found no benefit (89388,97493,98285). In children, treatment with magnesium oxide orally 15 mg/kg daily in 3 divided doses for up to 16 weeks reduces the frequency and severity of migraine headaches when compared with placebo (10663). However, adding magnesium sulfate 400 mg orally daily to ibuprofen or acetaminophen does not further reduce migraine severity in children (89396).
Myocardial infarction (MI). Research on the effects of intravenous or oral magnesium after myocardial infarction are conflicting. Details: Administering magnesium intravenously doesn't seem to reduce mortality after an acute MI (8999,13357,13358,13359,13360,19990,60872,61082), although there is some conflicting evidence from a meta-analysis of clinical research that shows that intravenous magnesium sulfate may reduce short-term mortality by 55% when compared with placebo (60795,60895). Clinical research with oral magnesium supplementation has found no benefit (1198,6844).
Neonatal encephalopathy. Intravenous magnesium may improve short-term outcomes in neonates with encephalopathy. Details: A meta-analysis of clinical research shows that intravenous magnesium may improve short term outcomes of neonatal encephalopathy (hypoxic ischemic encephalopathy, HIE). However, long term outcomes are not affected (90025).
Nocturnal leg cramps. It is unclear if oral magnesium is helpful for nocturnal leg cramps. Details: Some clinical research in adults with nocturnal leg cramps shows that taking magnesium oxide 865 mg daily at bedtime for 4 weeks does not reduce the frequency of leg cramping episodes when compared with placebo (96478). However, four weeks may be too short a time to see a benefit. In other clinical research, taking oral magnesium oxide monohydrate 226mg daily at bedtime for 60 days reduces the frequency of leg cramps when compared with placebo. This reduction was not seen after 30 days. Magnesium also reduced cramp duration and improved sleep quality, but did not affect pain scores, at 60 days when compared with placebo (106919).
Nonalcoholic fatty liver disease (NAFLD). Oral magnesium hydroxide has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with NAFLD shows that taking magnesium hydroxide 150 mg and L-carnitine 2000 mg daily for 16 weeks does not improve liver stiffness scores when compared with baseline or controls who took placebo for 8 weeks followed by this magnesium and L- carnitine combination for 8 weeks. Taking magnesium and L-carnitine also did not improve levels of aspartate aminotransferase (AST) or alanine transaminase (ALT) when compared to baseline (111177).
Obesity. Evidence on the use of magnesium for weight loss in obese patients is conflicting; any benefit is likely small at best. Details: A meta-analysis of 7 clinical studies in obese patients shows that taking magnesium reduces body mass index (BMI) by 0.3 when compared with control (103723). Another meta-analysis of 7 studies in obese patients shows that while magnesium supplementation does not reduce weight, it reduces waist circumference by 2 cm when compared with placebo (103729). Interestingly, subgroup analyses did not find that the dose of magnesium or baseline magnesium levels impacted effectiveness. One subgroup analysis found that magnesium supplementation lasting 12 weeks or less seemed to be more beneficial for obesity than supplementation lasting longer than 12 weeks (103723).
Overall mortality. It is unclear if oral or IV magnesium reduces the risk of overall mortality. Details: A meta-analysis of heterogeneous observational studies has found that increased dietary magnesium intake, but not supplemental magnesium intake, is associated with a modestly reduced risk of overall mortality (105073). A meta-analysis of 3 small, low-quality clinical studies in ICU patients shows that administering IV magnesium 24-30 mmol or as a target-directed dose for 3 days reduces overall mortality when compared with patients who did not receive magnesium (111290). However, some studies included patients with hypomagnesemia; it is unclear if effects would be similar for patients with normal levels of magnesium.
Osteoarthritis. Population research has not found a link between magnesium intake and osteoarthritis risk. Details: Observational research has found that dietary and supplemental magnesium intake is not associated with the risk of developing osteoarthritis (101395).
Pain (acute). It is unclear if intravenous magnesium is helpful for acute pain associated with kidney dysfunction. Details: Preliminary clinical research in patients with renal colic shows that intravenous (IV) magnesium sulfate, 50 mg/kg infused over 20 minutes, is as effective as IV morphine sulfate 0.1 mg/kg for controlling acute renal pain at 20 minutes after the dose (107367).
Pain (chronic). Population research suggests that higher intakes of magnesium may modestly reduce the risk for chronic pain. Details: A cross-sectional observational study has found that increased magnesium intake is associated with a 7% to 8% reduced risk for chronic pain. The association was found to be stronger in females than in males (103732).
Perioperative anxiety. It is unclear if oral magnesium is beneficial for perioperative anxiety. Details: Preliminary clinical research in adults undergoing open heart surgery shows that taking magnesium oxide 250 mg orally twice daily during hospitalization moderately improves anxiety and depression scores when compared with no magnesium therapy. Magnesium therapy was held for the 2 days immediately following surgery (110054).
Postoperative sore throat. It is unclear if topical magnesium sulfate is beneficial for reducing sore throat pain after endotracheal intubation. Details: Preliminary clinical research in patients undergoing endotracheal intubation for surgery shows that using a gargle containing magnesium sulfate 20% with lidocaine, 20 minutes before anesthesia induction, is less effective for reducing sore throat pain than a gargle containing dexmedetomidine and lidocaine (112779). The study did not include a comparison to lidocaine alone.
Physical performance. Oral magnesium may modestly improve physical performance in otherwise healthy, elderly females. Details: Clinical research in otherwise healthy elderly females shows that taking a magnesium oxide supplement (Easymag, Sanofi-Aventis) 900 mg daily for 12 weeks modestly improves walking speed and chair stand speed in elderly females when compared with no treatment (90026).
Polycystic ovary syndrome (PCOS). It is unclear if oral magnesium is beneficial for improving metabolic indices in patients with PCOS. Details: Two small clinical studies in patients with PCOS show that taking magnesium oxide orally, 250 mg daily for 8 weeks, does not affect insulin resistance, beta-cell function, lipid levels, or insulin sensitivity when compared with placebo (103725,105887). Other clinical research in patients with PCOS shows that taking magnesium oxide orally, 250 mg daily for 10 weeks, improves subjective measures of quality of life, fatigue, and emotional functioning, but not objective measures such as alopecia, abnormal uterine bleeding, or acne, when compared with placebo (108965). A clinical study using a combination of magnesium 250 mg with vitamin E 400 mg daily for 12 weeks shows a modest reduction in insulin resistance, insulin levels, and triglyceride levels, but not other lipid levels, when compared with placebo (100264). It is unclear if these beneficial effects are due to magnesium, vitamin E, or the combination.
Postoperative sleep disturbance. It is unclear if oral magnesium is beneficial for postoperative sleep disturbances. Details: Preliminary clinical research in adults undergoing open heart surgery shows that taking magnesium oxide 250 mg orally twice daily during hospitalization moderately improves sleep scores when compared with no magnesium therapy. Magnesium therapy was held for the 2 days immediately following surgery (110054).
Pregnancy-related leg cramps. It is unclear if oral magnesium reduces leg cramps during pregnancy; evidence is conflicting. Details: One small clinical study in patients with pregnancy-related leg cramps shows that taking magnesium bisglycinate chelate 300 mg daily for 4 weeks reduces the frequency and intensity of leg cramps when compared with placebo (99318). A smaller clinical study in this population shows that taking a specific mixture of magnesium lactate and citrate (Nycoplus Magnesium) providing elemental magnesium 120 mg in the morning and 240 mg in the evening for 3 weeks reduces the frequency of cramps when compared with placebo (1194). However, not all research agrees. One small clinical study using this same supplement and dose for 2 weeks found no benefit when compared with placebo (17463). It is possible that a 2-week duration of treatment is too short to be beneficial. Finally, a meta-analysis of these studies and one other more recent clinical study shows that taking magnesium does not reduce the frequency or improve the resolution of pregnancy-related leg cramps when compared with placebo (105916). This analysis may not have been adequately powered to detect a difference between treatment groups.
Pre-procedural sedation. It is unclear if intravenous magnesium is beneficial when administered in addition to propofol for sedation. Details: A moderate-sized study of adults aged 65-79 years old undergoing endoscopic retrograde cholangiopancreatography (ERCP) shows that administering a single intravenous bolus of magnesium sulfate 40 mg/kg prior to the procedure reduces intraoperative propofol requirements by about 21% and reduces some peri-procedural adverse events including the incidence of respiratory depression and involuntary movement when compared with control. However, there were no differences in recovery time, hemodynamic parameters, or the incidence of hypotension, bradycardia, perioperative nausea or vomiting, lethargy, or arrythmias (111694).
Preterm labor. The use of magnesium sulfate to inhibit uterine contractions in preterm labor (tocolysis) is controversial. However, its use for the purpose of fetal neuroprotection for up to 48 hours is supported by the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine. Details: Magnesium is given intravenously during preterm labor in an effort to improve fetal neurological outcomes. The typical dosage of magnesium sulfate is 4 grams infused IV over 10-30 minutes, followed by a maintenance infusion of 1-4 grams/hour for 48 hours or until birth. Use beyond 5-7 days has been associated with hypocalcemia and bone abnormalities in the fetus (15,12590,12594). Some meta-analyses of clinical research suggest that magnesium sulfate is more effective at delaying delivery by 48 hours when compared with oxytocin receptor blockers, nitrates, beta-mimetics, and/or placebo (20263,61021). Administration of magnesium during preterm labor has been shown to reduce the risk of cerebral palsy and motor dysfunction in the infant (60882,60915,60927,60931,61001,97485,103734,103754).
Pseudoxanthoma elasticum (PXE). It is unclear if oral magnesium is beneficial for PXE. Details: Preliminary clinical research in patients with PXE shows that taking magnesium oxide 800 mg (500 mg of elemental magnesium) twice daily for one year tends to reduce calcification of elastic skin fibers when compared with placebo, but the effect is not statistically significant (101393). This study was limited by small size and insufficient power to detect smaller effects.
Restless legs syndrome (RLS). It is unclear if oral magnesium is beneficial for RLS. Details: Some observational research has found that hypomagnesemia is associated with RLS; however, not all research agrees (8096,9472). Preliminary clinical research in adults with RLS who are beginning treatment with pramipexole shows that also taking magnesium oxide 250 mg orally daily for 2 months moderately improves RLS scores and sleep quality scores when compared with pramipexole and placebo (110052). Other low-quality clinical research in adults with RLS or periodic limb movement during sleep shows that taking magnesium 12.4 mmol orally in the evening for 4-6 weeks decreases movement and increases sleep when compared with baseline (9466). The validity of this finding is limited by the lack of a comparator group.
Sarcopenia. It is unclear if oral magnesium is beneficial for the prevention or treatment of sarcopenia. Details: Population research in older adults has found that lower dietary intake of magnesium is associated with sarcopenia. However, the effect of magnesium supplementation on sarcopenia prevention or treatment has not been evaluated (110055).
Stroke. Increased dietary magnesium may decrease stroke risk, and using a magnesium-containing salt substitute may improve neurological performance post-stroke. However, intravenous magnesium has not demonstrated benefit. Details: Most population research has found that increased dietary intake of magnesium is associated with decreased stroke risk and decreased mortality from stroke (9001,9002,90013,90030,90036,92107,103736). In patients who have had a stroke, a preliminary clinical study shows that using a salt substitute providing the Dietary Reference Intake (DRI) of magnesium and potassium for 6 months improves neurological performance when compared with using regular salt (97491). However, intravenous (IV) magnesium does not seem to be beneficial in patients who have had a stroke. Large prospective clinical trials show that IV magnesium given within 12 hours of acute stroke does not reduce mortality or disability in most patients when compared with placebo. However, one subgroup analysis suggested that IV magnesium might benefit patients with lacunar (non-cortical) stroke (13361,90021). IV magnesium also doesn't seem to reduce cardiovascular complications after acute stroke. A secondary analysis of a clinical trial in patients after ischemic and hemorrhagic stroke shows that giving IV magnesium does not reduce serious cardiac adverse events when compared with placebo (104393). Another secondary analysis of this trial shows that giving IV magnesium prior to arrival at the hospital and within 2 hours of a hemorrhagic stroke does not reduce hematoma volume on hospital arrival, hematoma expansion during hospital admission, or functional outcomes at 3 months (108733).
Subarachnoid hemorrhage. Intravenous magnesium sulfate may reduce the risk of adverse outcomes in people with subarachnoid hemorrhage, but evidence is conflicting. Details: There is mixed evidence regarding the effect of magnesium sulfate in managing aneurysmal subarachnoid hemorrhage. One meta-analysis of clinical research shows that intravenous magnesium sulfate 64-144 mmol/day for 10-18 days reduces the risk of poor outcomes following aneurysmal subarachnoid hemorrhage, including death, vegetative state, or dependency, by 46% when compared with control (60932). Also, meta-analyses of clinical research show that intravenous magnesium reduces the risk of delayed cerebral ischemia by 27% when compared with placebo (60944,89398). However, these results were not confirmed in other meta-analyses (60973,90034).
Thrombocytopenia. It is unclear if intravenous magnesium sulfate is beneficial in patients with thrombotic thrombocytopenic purpura (TTP). Details: Addition of intravenous magnesium sulfate as a 6-gram loading dose followed by 6 grams infused over 24 hours for 3 days, to standard treatment for TTP does not reduce the time to normalization of the platelet count, the incidence of TTP-related organ dysfunction, or the recurrence rate, when compared with standard treatment alone (112777). This study may have been underpowered to detect a difference.
Urinary incontinence. Although there has been interest in using oral magnesium for urinary incontinence, there is insufficient reliable information about the clinical effects of magnesium for this purpose. More evidence is needed to rate magnesium for these uses.

MANGANESE

Manganese deficiency. Oral and intravenous manganese can prevent and treat manganese deficiency. Details: Taking manganese orally or intravenously is effective for preventing or treating manganese deficiency (15). However, the incidence of manganese deficiency is not well documented. Long-term home parenteral nutrition should provide no more than 55 mcg daily of manganese for adults or 1 mcg/kg daily (up to 50 mcg) of manganese for children unless clinically indicated (96416,99302). A clinical trial in children aged 8-14 months who are manganese deficient shows that taking manganese in addition to other vitamins and minerals in a 30 mL beverage six days per week for up to 14 months promotes growth when compared with placebo (19348).

Allergic rhinitis (hay fever). It is unclear if intranasal manganese is beneficial in patients with allergic rhinitis. Details: A small clinical study in patients with chronic allergic rhinitis shows that using an isotonic seawater nasal spray enriched with manganese (Sterimar Mn, Laboratori Baldacci) four puffs daily for 5 months, in addition to standard treatment with oral antihistamines, nasal corticosteroids, and nasal decongestants, reduces the number of acute exacerbations by about three when compared with the standard treatment alone (99416). However, the effect of the manganese in this product is unclear since nasal lavage with a plain saline nasal spray also helps in allergic rhinitis.
Chronic obstructive pulmonary disease (COPD). Intravenous manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients being treated for exacerbation of COPD shows that intravenous supplementation with manganese 0.4 mg, selenium 100 mcg, and zinc 2 mg daily may shorten the number of days spent on mechanical ventilation when compared with placebo (61432). It is unclear if these findings are due to manganese, other ingredients, or the combination.
Metabolic syndrome. It is unclear if oral intake of or environmental exposure to manganese decreases the risk of metabolic syndrome. Details: A meta-analysis of 12 observational studies suggests that increased dietary intake of manganese or higher levels of manganese in the serum, whole blood, or urine are not associated with a lower risk of metabolic syndrome when compared with lower manganese intake or laboratory values (112138).
Obesity. Oral manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in overweight adults shows that taking a specific combination product (7-Keto Naturalean, Enzymatic Therapy, Inc.) containing manganese 500 mcg, 7-oxo-DHEA 100 mg, L-tyrosine 100 mg, asparagus root extract 100 mg, choline bitartrate 50 mg, inositol 50 mg, copper gluconate 500 mcg, and potassium iodide 100 mcg daily for 8 weeks reduces body weight by around 1.5 kg and body mass index (BMI) by around 0.7 kg/m² when compared with placebo (61581).
Osteoarthritis. Oral manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Small clinical studies in patients with osteoarthritis of the knee and lower back show that taking a specific combination product (Cosamin DS, Nutramax Laboratories) containing manganese ascorbate 228-304 mg (about 31-41 mg of elemental manganese), glucosamine hydrochloride 1500-2000 mg, and chondroitin sulfate 1200-1600 mg daily for 4 months improves pain and ability to do activities of daily living when compared with baseline or placebo (4237,7169). The amount of manganese in the Cosamin DS formulation used in this study is considerably higher than the 1 mg of elemental manganese per 1500 mg of glucosamine hydrochloride in the current formulation. Since numerous studies show glucosamine with chondroitin without manganese might be effective for osteoarthritis, it is not possible to draw conclusions about the effects of manganese alone.
Osteoporosis. Oral manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in postmenopausal patients shows that taking manganese 5 mg in combination with elemental calcium 1000 mg, zinc 15 mg, and copper 2.5 mg daily for 2 years reduces spinal bone loss when compared with placebo (1994). Another small clinical study in females with osteopenia shows that taking a specific combination product (Vitrum Osteomag, Unipharm Inc.) containing manganese 1.8 mg, calcium 600 mg, vitamin D (cholecalciferol) 200 IU, magnesium 40 mg, zinc 7.5 mg, copper 1 mg, and boron 250 mcg twice daily for one year improves bone mineral density when compared with no treatment (36840). However, since numerous studies have demonstrated the efficacy of calcium plus vitamin D for osteoporosis, it is not possible to draw conclusions about the effects of manganese alone.
Premenstrual syndrome (PMS). Oral manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in patients with PMS shows that taking manganese 1.0 mg or 5.6 mg in combination with calcium 587 mg or 1336 mg daily for about 24 weeks improves symptoms of PMS including pain, crying, loneliness, anxiety, restlessness, irritability, mood swings, depression, and tension (2004).
Wound healing. Topical manganese has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research has found that applying an alginate dressing containing manganese, calcium, and zinc to chronic wounds for 12 weeks is associated with improved wound healing when compared with previous treatments (61327). It is unclear if these findings are due to manganese, other ingredients, or the combination. More evidence is needed to rate manganese for these uses.

MOLYBDENUM

Molybdenum deficiency. Taking or consuming molybdenum can treat or prevent molybdenum deficiency (7135,16478). However, molybdenum deficiency is very rare.

Esophageal cancer. Population research suggests that low intake of molybdenum might be associated with an increased risk of esophageal cancer (16478,17205). However, it is not known if molybdenum supplements reduce the risk of developing esophageal cancer. More information is needed to rate molybdenum for this use.

NIACIN

Dyslipidemia. Niacin prescription products, in doses of 500 mg or greater, are FDA-approved for primary hyperlipidemia and mixed dyslipidemia. Niacin dietary supplements are generally available in lower doses and have not been shown to improve lipid levels. Details: Prescription niacin is not routinely recommended as second-line therapy for patients who primarily need to decrease low-density lipoprotein (LDL) cholesterol. This is due to results from clinical trials showing no effect on cardiovascular related events or mortality (93346,93354,96208,96211,97308,97477,97336). However, niacin might be considered for patients with mixed hyperlipidemia or patients who need to increase high-density lipoprotein (HDL) cholesterol and lower triglycerides. Niacin might also be effective for isolated hypoalphalipoproteinemia (4817). The most pronounced increases in HDL and decreases in triglycerides occur at 1-1.5 grams daily, and the greatest LDL reduction occurs at 2-3 grams daily. Niacin reduces LDL cholesterol by up to 25%, compared with up to a 55% reduction with statins. High-dose niacin can also decrease triglycerides by 20% to 50%, increase HDL by 13% to 35%, decrease apolipoprotein B levels by 2% to 20%, and decrease lipoprotein(a) levels by 23% (4818,4886,4887,4888,4889,4890,12033,25567,93347,96213). The effects of higher dose extended-release niacin on LDL cholesterol and triglycerides appear to be greater in females than males (25565). Experts recommend maximizing statins first because they have the best evidence for improving cardiovascular outcomes (97477,97336,97337). However, if patients cannot reach their LDL goal with a statin alone or if they cannot tolerate a statin, niacin might be combined with other cholesterol-lowering drugs when diet and single-drug therapy are not adequately effective (8545,25566,93351,94191,97337). Adding low-dose niacin, 50 mg daily, to statin therapy has no additional benefit on lipid levels (8546). Population research in adults without dyslipidemia has also found that higher dietary intake of niacin for 3-10 years is associated with a 29% lower risk of developing dyslipidemia when compared with low dietary niacin intake (110493).
Pellagra. Oral niacin is FDA-approved for the prevention and treatment of pellagra. Details: Population research has found that low consumption of niacin is associated with an increased risk of developing pellagra (25903). Taking niacin 500-1000 mg daily can resolve symptoms of pellagra within a week of treatment initiation (25904). However, niacinamide is sometimes preferred for this indication because it lacks the vasodilating effects of niacin (15,6243).

HIV/AIDS-related dyslipidemia. Oral niacin seems to improve lipid levels in patients with dyslipidemia due to HIV/AIDs. Details: Small clinical trials in HIV patients with dyslipidemia associated with antiretroviral therapy shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated up to 2 grams daily for 14-48 weeks improves total cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride levels when compared to baseline (25570,25902). Other preliminary clinical research in this population shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated to 2 grams daily for up to 2 years improves HDL cholesterol levels, but not total cholesterol or triglyceride levels, when compared with no treatment (25569).
Metabolic syndrome. Oral niacin seems to improve lipid levels in patients with metabolic syndrome. Details: Clinical research shows that taking niacin (Niaspan, Abbott Laboratories) 2 grams daily orally for 16 weeks reduces triglyceride levels by 39 mg/dL and increases high-density lipoprotein (HDL) cholesterol by 5 mg/dL when compared to baseline in patients with metabolic syndrome. These improvements are significant when compared with placebo and are further increased when niacin is taken along with prescription omega-3 ethyl esters (Lovaza, GlaxoSmithKline Pharmaceuticals) 4 grams daily orally (93353). However, niacin does not seem to improve postprandial glucose levels in patients with metabolic syndrome (97333).

INEFFECTIVE

Cardiovascular disease (CVD). Oral niacin does not seem to reduce cardiovascular-related events in patients with or without CVD. Details: Overall, niacin is not recommended for primary or secondary prevention of CVD. Most clinical trials and meta-analyses conducted prior to 2011 showed a reduction in cardiovascular-related events, cardiovascular-related mortality, and all-cause mortality in patients taking niacin alone or in combination with a statin or clofibrate for primary or secondary prevention of CVD (4847,7388,25095,25911,25912,93349). However, recent meta-analyses of these studies and additional moderate-to-high quality research conducted in over 39,000 patients show no effect of niacin on cardiovascular-related events, cardiovascular-related mortality, or overall mortality (93346,93354,96208,96211,97308). Additionally, one meta-analysis shows that patients taking niacin are twice as likely to report side effects when compared with placebo (96211).

Alzheimer disease. It is unclear if oral niacin is beneficial for reducing Alzheimer disease risk. Details: Observational research has found that consuming higher amounts of niacin (17-45 mg daily) from food and supplements is associated with a slower cognitive decline and a lower risk of developing Alzheimer disease when compared with people who consume less niacin (14 mg daily) (12077). It is not known if the risk of Alzheimer disease is reduced by taking a stand-alone niacin supplement.
Atherosclerosis. It is unclear if oral niacin prevents atherosclerosis progression. Details: Preliminary clinical studies show that taking niacin orally, in combination with colestipol for up to 2 years, might modestly reduce progression of atherosclerosis as measured by coronary lesions and carotid arterial intima-media thickness in high-risk males with existing coronary atherosclerosis (25906,25909,25910). However, niacin does not seem to be better than statins. One clinical study in adults with atherosclerosis and peripheral arterial disease shows that taking extended-release niacin 1500 mg, simvastatin 40 mg, and ezetimibe 10 mg daily for 2 years does not reduce atherosclerosis of the superficial femoral artery when compared with simvastatin alone (96208). Niacin has also not been shown to prevent cardiovascular events or mortality (93346,93354,96208,96211,97308).
Athletic performance. It is unclear if oral niacin improves athletic performance. Details: Preliminary clinical research in untrained adult males shows that taking niacin 1000 mg orally once before a cycling test does not improve power, respiratory exchange ratio, or time to exhaustion when compared with placebo. In addition, these measures were significantly worse when compared with taking caffeine 5 mg/kg orally as a single dose (107942). Clinical research in untrained males also shows that taking a supplement containing niacin 40 mg, caffeine 400 mg, capsicum extract 66.7 mg, and black pepper extract 10 mg prior to exercising does not improve strength, time to exhaustion, or maximal oxygen consumption when compared with placebo (37873).
Attention deficit-hyperactivity disorder (ADHD). Although there is interest in using oral niacin for ADHD, there is insufficient reliable information about the clinical effects of niacin for this condition.
Cancer. It is unclear if dietary niacin is beneficial for cancer. Details: Population research in adults with cancer has found that high dietary niacin intake is associated with 49% and 27% lower risk of cancer-related mortality and all-cause mortality when compared with low dietary niacin intake. The same study also found that taking niacin supplements is associated with a lower risk of cancer-related mortality, but not all-cause mortality when compared with not taking niacin supplements (110496).
Cataracts. It is unclear if oral niacin is beneficial for preventing cataracts. Details: Population research has found that high dietary intake of niacin is associated with a reduced risk of nuclear cataracts (6378). However, there is no reliable evidence that niacin supplements reduce the risk of cataracts.
Cholera. It is unclear if oral niacin is beneficial for cholera. Details: One small clinical study in adults with severe cholera shows that taking 1-2 grams niacin orally reduces fluid loss in the stool by 31% to 47% in the first 16 hours when compared with control. The 2 gram dose seemed to result in a greater reduction in fluid loss than the 1 gram dose (4868).
Erectile dysfunction (ED). It is unclear if oral niacin is beneficial in patients with ED and dyslipidemia. Details: Clinical research in patients with erectile dysfunction and dyslipidemia shows that taking extended-release niacin (Niaspan, Abbott Laboratories) titrated to 1.5 grams nightly for a total of 12 weeks significantly improves penetration frequency and the maintenance of an erection after penetration when compared to baseline (25913). The validity of this finding is limited by the lack of a comparator group.
Glaucoma. It is unclear if oral niacin is beneficial for preventing or treating glaucoma. Details: Population research has found that higher dietary intake of niacin is associated with a lower odds of having glaucoma. However, this association was not consistently present when adjusting for confounders. The effects of niacin supplementation on glaucoma have not been evaluated (107942).
Hyperphosphatemia. It is unclear if oral niacin is beneficial for preventing high levels of phosphorus in the blood. Details: Preliminary clinical research in patients on maintenance dialysis who are no longer using phosphate binders shows that taking niacin 375-750 mg daily for 8 weeks reduces serum phosphorus levels by 2.1 mg/dL, increases calcium levels by 0.4 mg/dL, and decreases serum alkaline phosphatase when compared with baseline (25914). However, clinical research in hemodialysis patients with inadequate phosphate control despite using standard phosphate-binding therapy shows that taking niacin at the maximum tolerated dose, up to 1000 mg daily, for 12 weeks, does not decrease serum phosphate levels when compared with placebo (93341). It is possible that this latter study was too small to observe between-group differences in changes in serum phosphate levels.
Hypertension. It is unclear if dietary niacin is beneficial for preventing hypertension. Details: Observational research in Chinese adults found a J-shaped association between dietary niacin intake and development of hypertension, with the lowest risk occurring in those with a daily dietary niacin intake of 14.3-16.7 mg (104934).
Meniere disease. Although there is interest in using oral niacin for Meniere disease, there is insufficient reliable information about the clinical effects of niacin for this condition.
Migraine headache. It is unclear if dietary niacin is beneficial for preventing migraine headaches. Details: Population research in adults has found that high dietary intake of niacin is associated with a 28% lower likelihood of having migraine headaches when compared with low dietary intake of niacin (110495). However, the effect of niacin supplementation on migraines has not been studied.
Motion sickness. Although there is interest in using oral niacin for motion sickness, there is insufficient reliable information about the clinical effects of niacin for this purpose.
Parkinson disease. It is unclear if oral niacin is beneficial for improving Parkinson disease symptoms. Details: Low-quality clinical research in adults with Parkinson disease shows that taking slow-release niacin 250 mg orally daily for 12 months improves Parkinson disease motor scores and fatigue scores by 17% and 26%, respectively, when compared with baseline (107944). However, higher quality clinical research shows that taking niacin 250 mg orally daily for 6 months does not improve Parkinson disease motor scores when compared with placebo (107943).
Retinal vein occlusion. It is unclear if oral niacin is beneficial for improving retinal vein occlusion symptoms. Details: A small case series in patients with chronic retinal vein occlusion shows that taking niacin titrated to 500 mg three times daily for 1 year is associated with reduced central macular thickness and improved visual acuity in over 50% of patients when compared with a control group. The addition of prednisolone eye drops does not alter the outcomes of those taking niacin (96212). The validity of this finding is limited due to the retrospective nature of this study.
Sickle cell disease. It is unclear if oral niacin is beneficial for improving lipid levels in patients with sickle cell disease. Details: A small clinical study in patients with sickle cell disease shows that taking extended-release niacin titrated to 1.5 grams daily for 12 weeks does not improve vascular function or increase high-density lipoprotein (HDL) or apolipoprotein A-I cholesterol levels when compared with placebo (96209).
Schizophrenia. Although there is interest in using oral niacin for schizophrenia, there is insufficient reliable information about the clinical effects of niacin for this condition.
Vertigo. Although there is interest in using oral niacin for vertigo, there is insufficient reliable information about the clinical effects of niacin for this condition. More evidence is needed to rate niacin for these uses.

NICKEL

Nickel deficiency. Oral nickel, taken in trace amounts, prevents nickel deficiency. Details: Taking trace amounts of nickel in a supplement is effective for preventing nickel deficiency (7135).

Iron deficiency anemia. Although there has been interest in using oral nickel to improve iron absorption in patients with iron deficiency anemia, there is insufficient reliable information about the clinical effects of nickel for this purpose.
Osteoporosis. Although there has been interest in using oral nickel for osteoporosis, there is insufficient reliable information about the clinical effects of nickel for this purpose. More evidence is needed to rate nickel for these uses.

Pantothenic acid deficiency. Taking pantothenic acid 5-10 mg daily is effective for treating and preventing pantothenic acid deficiency (15).

Radiation dermatitis. Topical dexpanthenol does not seem to be beneficial for preventing or treating radiation dermatitis. Details: Applying dexpanthenol, an analog of pantothenic acid, twice daily to areas of irradiated skin does not seem to reduce erythema, desquamation, itching, or pain following radiation treatment (7192). Also, applying dexpanthenol 0.5% cream (Bepanthen, Hoffmann LaRoche ) daily during radiation therapy and for 2 weeks after completing radiation therapy is less effective than methylprednisolone aceponate 0.1% cream (Advantan) at reducing radiation-induced skin irritation (67779).

Acne. Oral or topical pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In adults with mild to moderate acne, clinical research shows that taking a specific supplement (Pantothen, Avilan Marketing LLC) providing pantothenic acid 1.1 grams twice daily in addition to other B vitamins for 12 weeks modestly reduces total and non-inflammatory lesion counts when compared with placebo (105188). Also, in adolescents or young adults with mild to moderate acne, preliminary clinical research shows that topical application with a gel containing D-panthenol 4%, hydrogen peroxide 4%, and salicylic acid 0.5% once daily for 60 days modestly reduces acne lesions when compared with baseline (105189). The validity of this finding is limited by the lack of a comparator group.
Alcoholism. Although there is interest in using oral pantothenic acid for improving recovery from alcoholism, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Allergic rhinitis (hay fever). Although there is interest in using oral pantothenic acid for allergic rhinitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Alopecia areata. Pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy adults with diffuse hair loss shows that intramuscular administration of dexpanthenol 250 mg and biotin 5 mg once weekly for 6 weeks reduces hair fall count at weeks 1 and 8, but only increases hair density at week 1, when compared to baseline (111366). The validity of these findings is limited by the study's small size, short duration, and lack of comparator group.
Anxiety. Although there is interest in using oral pantothenic acid for anxiety, there is insufficient reliable information about the clinical effects of pantothenic acid for this purpose.
Asthma. Although there is interest in using oral pantothenic acid for asthma, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Athletic performance. Although there is interest in using oral pantothenic acid to improve athletic performance, there is insufficient reliable information about the clinical effects of pantothenic acid for this purpose.
Attention deficit-hyperactivity disorder (ADHD). Oral pantothenic acid has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some small outdated clinical studies in children diagnosed with hyperkinesis suggest that taking calcium pantothenate 1.2 grams, alone or in combination with niacinamide, ascorbic acid, and pyridoxine, does not improve symptoms of hyperactivity when compared with placebo (3351,9957). It is unclear what effects pantothenic may have, if any, in children with a modern diagnosis of ADHD.
Atopic dermatitis (eczema). It is unclear if topical pantothenic acid is beneficial in infants or children with atopic dermatitis. Details: One preliminary clinical trial in infants and children with stable mild atopic dermatitis shows that topical application of an emollient containing panthenol (Bepanthen, SensiDaily, Bayer Consumer Care AG) for 3 months is as effective as a reference emollient for reducing symptoms and preventing a flare. However, the efficacy of the reference emollient (Stelatopia Emollient Cream, Mustela; Laboratoires Expanscience) is unclear based on available preliminary clinical research (105190).
Autism spectrum disorder. Although there is interest in using oral pantothenic acid for autism spectrum disorder, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Carpal tunnel syndrome. Although there is interest in using oral pantothenic acid for carpal tunnel syndrome, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Chronic fatigue syndrome (CFS). Although there is interest in using oral pantothenic acid for CFS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Conjunctivitis. Although there is interest in using oral or ocular pantothenic acid for conjunctivitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Constipation. It is unclear if oral or intramuscular dexpanthenol is beneficial for constipation. Details: Preliminary clinical research shows that administering dexpanthenol (Bepanthene), an analog of pantothenic acid, 400 mg orally or 500 mg intramuscularly daily for 5 days decreases the time to a bowel movement in patients with chronic or occasional constipation when compared with an oral placebo (67822).
Dandruff. Although there is interest in using oral or topical pantothenic acid for dandruff, is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Depression. Although there is interest in using oral pantothenic acid for depression, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Diaper rash. Although there is interest in using topical pantothenic acid for diaper rash, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Dry eye. Although there is interest in using ocular pantothenic acid for dry eye, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Dry skin. It is unclear if topical dexpanthenol is beneficial for patients with dry skin. Details: A small, open-label study in healthy adults with dry skin shows that cleansing the skin with a dexpanthenol-containing liquid cleanser (DCLC, Bepanthen SensiControl Daily Gentle Body Wash) daily for 4 weeks increases stratum corneum hydration by 17% without affecting skin barrier function, pH, or microbiome when compared to baseline (111262). The validity of these findings is limited by the lack of blinding and a comparator group.
Epilepsy. Although there is interest in using oral pantothenic acid for epilepsy, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Eye trauma. It is unclear if ocular dexpanthenol is beneficial for eye trauma. Details: Some preliminary clinical research shows that using eyedrops containing dexpanthenol 5%, a derivative of pantothenic acid, two drops four times daily for 28 days following surgery for retinal detachment reduces eye pain and discomfort when compared with placebo drops (67783). However, using a specific dexpanthenol 5% ointment (Bepanthen) does not seem to improve corneal epithelial wound healing following phototherapeutic keratectomy when compared with placebo (67801).
Heart failure. Although there is interest in using oral pantothenic acid for heart failure, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Herpes zoster (shingles). Although there is interest in using oral or topical pantothenic acid for shingles, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Insomnia. Although there is interest in using oral pantothenic acid for insomnia, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Laser skin resurfacing. It is unclear if topical dexpanthenol or pantothenic acid can reduce adverse effects after laser skin resurfacing procedures. Details: A preliminary clinical study shows that use of a dexpanthenol-containing ointment (Bepanthen Wound Healing Ointment, Bayer) once daily modestly reduces the diameter of lesions up to 3 days after fractional carbon dioxide laser resurfacing when compared with petroleum jelly (105743). Also, applying a specific cream (Cicaplast Baume B5 cream, L'Oreal) containing panthenol 5%, madecassoside, copper, zinc, and manganese to one side of the face for 28 days reduces decrustation time by approximately one day when compared with a control emollient. Redness and swelling were lower at 3 days, but there was no difference in pain and burning (105742). It is unclear if these effects are due to pantothenic acid, other ingredients, or the combination.
Multiple sclerosis (MS). Although there is interest in using oral pantothenic acid for MS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Muscular dystrophy. Although there is interest in using oral pantothenic acid for muscular dystrophy, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Nipple fissures. Although there is interest in using topical pantothenic acid for nipple fissures, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Obesity. Although there is interest in using oral pantothenic acid for obesity, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Pain (chronic). It is unclear if oral or topical pantothenic acid is beneficial for the management of various forms of chronic pain. Details: Although there is interest in using oral or topical pantothenic acid for various forms of chronic pain, including neuropathy and arthritis, there is limited information available about the clinical effects of pantothenic acid for this purpose. One review of preliminary clinical research found that calcium pantothenate does not reduce symptoms of arthritis in patients with rheumatoid arthritis or osteoarthritis (10433).
Parkinson disease. Although there is interest in using oral pantothenic acid for Parkinson disease, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Poison oak and poison ivy dermatitis. Although there is interest in using topical pantothenic acid for poison ivy dermatitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Postoperative pain. It is unclear if oral pantothenic acid is beneficial for postoperative pain. Details: In post-tonsillectomy patients aged 5-12 years, preliminary clinical research shows that taking pastilles containing dexpanthenol (Bepanthene, Bayer) 100 mg three times daily reduces pain when compared with placebo. Postoperative pain was modestly reduced at 1, 3, 7, and 14 days after surgery (105191).
Postoperative sore throat. It is unclear if pantothenic acid lozenges are beneficial for postoperative sore throat. Details: Preliminary clinical research shows that taking two lozenges containing dexpanthenol, an analog of pantothenic acid, 200 mg 30 minutes prior to general anesthesia reduces the incidence and severity of postoperative sore throat when compared with a benzydamine hydrochloride or placebo spray (67792).
Pregnancy-related leg cramps. Although there is interest in using oral pantothenic acid for pregnancy-related leg cramps, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Premenstrual syndrome (PMS). Although there is interest in using oral pantothenic acid for PMS, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Respiratory tract infections. Although there is interest in using oral pantothenic acid for respiratory tract infections, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Rhinosinusitis. It is unclear if nasal dexpanthenol is beneficial for rhinosinusitis. Details: Preliminary clinical research shows that using a nasal spray (MarPlus) containing dexpanthenol, an analog of pantothenic acid, on the first, second, fourth, and sixth week after endoscopic sinus surgery reduces nasal discharge, but not other symptoms associated with chronic rhinosinusitis, when compared with saline nasal spray (67808).
Skin irritation. It is unclear if topical dexpanthenol is beneficial for preventing or treating skin irritation due to sodium lauryl sulfate. Details: Preliminary clinical research shows that applying dexpanthenol (Bepanthol Handbalsam), an analog of pantothenic acid, twice daily for 26 days does not prevent sodium lauryl sulfate-induced skin irritation (67785). However, dexpanthenol may be effective for treating skin irritation caused by sodium lauryl sulfate. Use of an ointment containing dexpanthenol 1% to 5% twice daily for up to 30 days following skin exposure to sodium lauryl sulfate seems to reduce skin water loss, skin roughness, and skin inflammation when compared to control (67802,67806).
Ulcerative colitis. Although there is interest in using oral or rectal pantothenic acid for ulcerative colitis, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Vertigo. Although there is interest in using oral pantothenic acid for vertigo, there is insufficient reliable information about the clinical effects of pantothenic acid for this condition.
Wound healing. Preliminary clinical research suggests that oral dexpanthenol might be beneficial for wound healing. Details: In post-tonsillectomy patients aged 5-12 years, preliminary clinical research shows that taking pastilles containing dexpanthenol (Bepanthene, Bayer) 100 mg three times daily improves wound healing when compared with placebo. Depending on the type of surgery, wound healing occurred in 2.3-2.9 times as many patients within 7 days of surgery, and in 13% to 35% more patients within 14 days, when compared with placebo (105191). More evidence is needed to rate pantothenic acid for these uses.

Bowel preparation. Oral sodium phosphate is effective for cleansing the colon in preparation for colonoscopy; however, it is unclear whether sodium phosphate is as effective as polyethylene glycol (PEG) solution. Some products are approved by the US Food and Drug Administration (FDA) for this use. However, due to the potential for kidney damage, sodium phosphate is not recommended as first-line therapy. Details: Sodium phosphate tablets (OsmoPrep, Salix Pharmaceuticals; Visicol, Salix Pharmaceuticals) are FDA-approved for cleansing the colon in preparation for colonoscopy. Clinical research shows that using the OsmoPrep formulation can achieve an "excellent" or "good" response rate, which is defined as having 90% of the mucosa visible with only some or little suctioning needed, in 94% to 97% of patients (88133). Similarly, using the specific product Visicol has been shown to achieve an excellent or good response rate in 82% to 86% of patients (94674). Non-FDA-approved sodium phosphate products have also been investigated. One such product (Fleet Phospho-soda, C. B. Fleet Co.) has been shown to achieve adequate bowel cleansing in 23% to 89% of patients (93846,94673). Another sodium phosphate tablet preparation (Clicolon tablets, Korea Pharma Co.) has been shown to achieve adequate bowel cleansing in 63% to 93% of patients (93848,93850,93853). Excellent or good bowel cleansing was found in 98.6% of patients using a 32-tablet regimen of other sodium phosphate tablets (Quiklean, Universal Integrated Corporation) (107008). Reasons for the differences in the percentage of patients who achieve adequate bowel cleansing with the same sodium phosphate product may relate to the method used to analyze bowel cleansing, differences in diet followed during bowel cleansing, and demographic factors (93846,93848,93850,93853). Various preparations (OsmoPrep, Salix Pharmaceuticals; Visicol, Salix Pharmaceuticals; Clicolon tablets, Korea Pharma Co.; Quiklean, Universal Integrated Corporation) have been used which contain 1.102 grams of sodium phosphate monobasic monohydrate and 0.398 grams of sodium phosphate dibasic anhydrous. These products have been taken as 3-4 tablets with 8 ounces of water every 15 minutes for a total of 20 tablets the evening before colonoscopy, and 3-4 tablets with 8 ounces of water every 15 minutes for a total of 12-20 tablets the morning of a colonoscopy (88133,93848,93850,94674,107008). Also, sodium phosphate solution (Fleet Phospho-soda, C. B. Fleet Co.) containing sodium hydrogen phosphate 24.4 grams and disodium phosphate dodecahydrate 10.8 grams has also been used the morning and evening before the procedure (93846). Numerous publications have compared the bowel cleansing activity of sodium phosphate with PEG solution. When given as a split-overnight dosage, sodium phosphate is about as effective as PEG solutions in achieving adequate bowel cleansing. However, when day-before dosage is used, PEG is more effective for bowel cleansing than sodium phosphate (93861,93862,107008). Sodium phosphate and PEG may have different effectiveness depending on the colonic site assessed. When only trials assessing descending colon cleansing are considered, sodium phosphate is found to work similarly to PEG solutions. When only studies assessing ascending colon cleansing are considered, PEG is more effective for bowel cleansing than sodium phosphate (93861). Also, a large clinical trial in outpatients scheduled for non-sedated colonoscopy shows that receiving PEG resulted in an easier insertion and a less painful colonoscopy when compared with receiving sodium phosphate (104473). However, in patients with chronic constipation, sodium phosphate seems to be preferable. A meta-analysis of three small clinical studies in adults with chronic constipation shows that using sodium phosphate has an 87% greater chance of a successful bowel preparation when compared with using PEG (104472). Sodium phosphate is not recommended as first-line therapy for bowel preparation prior to colonoscopy due to the potential for kidney damage (93863,94672). In fact, one sodium phosphate preparation (Fleet Phospho-soda, C. B. Fleet Co.) that was previously approved as an over-the-counter supplement for bowel preparation in the US was withdrawn from the market for this indication in December 2008 due to concerns for phosphate-induced kidney disease (94672). Of the sodium phosphate products that are still approved by the FDA, current guidelines recommend that these products not be used for bowel cleansing in patients with kidney disease, pre-existing electrolyte disturbances, congestive heart failure, cirrhosis, ascites, or inflammatory bowel disease. Guidelines also recommend that caution should be used if these products are prescribed for patients who are elderly, hypertensive, or taking certain classes of drugs (94672). For small bowel preparation for endoscopy, a meta-analysis suggests that sodium phosphate is no more effective than fasting alone (93860).
Hypophosphatemia. Oral or intravenous phosphate salts are effective for the prevention or treatment of hypophosphatemia. Some products are approved by the US Food and Drug Administration (FDA) for this use. Details: Taking sodium or potassium phosphate orally is effective for preventing and treating hypophosphatemia (15). Treating hypophosphatemia with oral phosphates requires monitoring of serum electrolyte levels to determine appropriate dosing (15). The FDA-approved intravenous (IV) product is also used for the correction of hypophosphatemia (8302,8303,88135). FDA-approved intravenous (IV) sodium phosphate or potassium phosphate 15-30 mmol is typically given over 2-12 hours. Higher doses have been used if needed to increase efficacy (8302,8303,88135).

Constipation. Oral or rectal sodium phosphate is approved by the US Food and Drug Administration (FDA) as an ingredient in over-the-counter (OTC) products to treat constipation. Details: Sodium phosphate is an FDA-permitted ingredient of oral and rectal OTC products intended for the treatment of constipation (88107).
Dyspepsia. Oral aluminum phosphate and calcium phosphate are approved by the US Food and Drug Administration (FDA) as ingredients in over-the-counter (OTC) antacids. Details: Aluminum phosphate and calcium phosphate are FDA-permitted ingredients of oral OTC products intended for use as antacids (88107).
Hypercalcemia. Although other treatments are preferred, oral non-calcium phosphate salts are beneficial for treatment of mild to moderate hypercalcemia. Details: Taking phosphate salts (except calcium phosphate) orally is effective for treating mild to moderate hypercalcemia (88144,88145). Treating hypercalcemia with oral phosphates requires monitoring of serum electrolyte levels to determine appropriate dosing (15); other agents are now preferred (6479). Intravenous phosphates should be avoided due to the risk of calcium precipitation in vital organs (metastatic calcification) (15,88144,88145).

Kidney stones (nephrolithiasis). Oral potassium phosphate seems to be beneficial for prevention of kidney stones in individuals with hypercalciuria. Details: Taking potassium phosphate orally may help prevent calcium oxalate kidney stones in patients with hypercalciuria (6470). Clinical research in adults with absorptive hypercalciuria and at high risk for stone formation shows that taking a specific slow-release potassium phosphate product (Uro-Phos-K, Mission Pharmacal), providing phosphate 620 mg orally twice daily for 4 days, reduces urinary calcium excretion by 35% to 40% (2208,2209). Potassium and sodium phosphate salts providing 1200-1500 mg of elemental phosphate daily have been used (2209,6470).

Athletic performance. The evidence is mixed as to whether oral sodium phosphate improves cycling or running performance. Most research suggests that oral calcium phosphate and potassium phosphate are not beneficial. Details: Clinical research shows that taking calcium phosphate or potassium phosphate orally does not improve running or cycling performance (2499,9300,8301). Evidence for the use of sodium phosphate to improve cycling performance is mixed. One very small clinical study shows that taking sodium phosphate as tribasic sodium phosphate dodecahydrate for 6 days before a 10-mile cycling trial increases mean power output by about 10% and decreases the time needed to complete the trial by 3% in trained male cyclists (88150). Other small clinical trials in trained cyclists show that taking the same form of sodium phosphate as 50 mg/kg of fat-free mass in four divided doses daily for 6 days modestly improves work, power output, and peak oxygen uptake and reduces heart rate during high-intensity cycling exercise when compared to baseline (93857,93858,93859,107007). However, conflicting research shows that taking a similar dosage of this form of sodium phosphate does not improve time trial performance, work accomplished relative to energy expenditure, power output, or oxygen uptake in trained cyclists (93855,93856,107007). Sodium phosphate has also been evaluated for improving running performance, with mixed findings. Two small clinical trials in female athletes show that tribasic sodium phosphate dodecahydrate 50 mg/kg of fat-free mass taken in four divided doses daily for 6 days moderately improves repeated sprint times when compared with placebo (93843,93844). However, taking the same dosage does not significantly improve sprint times in male athletes (93849). Also, sodium phosphate does not seem to improve endurance or aerobic capacity in treadmill tests (8301,93854). Reasons for the discrepancies regarding the effects of sodium phosphate on athletic performance are not entirely clear, but likely relate to the very small number of participants in the included trials.
Diabetic ketoacidosis. Potassium phosphate infusion is not recommended as first-line therapy for adults with diabetic ketoacidosis. Details: Clinical research shows that intravenous infusion of potassium phosphate 8.5 mmol/hour (approximately 6 grams of phosphate over 24 hours) along with potassium chloride 12.5 mEq/hour provides no benefit over potassium chloride alone in adults with diabetic ketoacidosis (88149). Guidelines for the treatment of diabetic ketoacidosis in the both the US and UK do not recommend phosphate replacement for most patients. However, it may be considered in specific cases, such as cardiac dysfunction, anemia, respiratory depression, and serum phosphate concentrations below 1 mg/dL (107349,107350A).
Osteoporosis. Calcium phosphate seems to be beneficial for bone density improvement; however, it does not seem to be more beneficial than calcium carbonate. Details: In postmenopausal adults with osteoporosis and low phosphate intakes, taking calcium 1800 mg daily as tricalcium phosphate for 12 months improves lumbar spine and hip densities. However, it is no more effective than taking the same amount of calcium as calcium carbonate (93847). The calcium products were used in combination subcutaneous teriparatide and oral vitamin D (cholecalciferol) 1000 IU daily.
Refeeding syndrome. It is unclear if intravenous potassium phosphate or sodium phosphate is beneficial for prevention of refeeding syndrome. Details: Preliminary clinical research shows that giving intravenous sodium and potassium phosphates, 50 mmol (1.56 grams) phosphate over 24 hours, prevents the refeeding syndrome seen when restarting adequate nutrition after severe malnutrition or starvation when compared with historical controls (88148). More evidence is needed to rate phosphate salts for these uses.

POTASSIUM

Hypokalemia. Oral or intravenous potassium can treat and prevent hypokalemia. Details: Administering potassium orally or intravenously is effective for treating and preventing hypokalemia (15,107970). Oral potassium 20 mEq (780 mg of elemental potassium) is typically taken once daily to prevent hypokalemia (15,95010). Oral potassium 40-100 mEq (1560-3900 mg of elemental potassium) is typically taken in 2-5 divided doses daily to treat hypokalemia (95010). Doses should be limited to 40 mEq (1560 mg of elemental potassium), and the total dose should not exceed 200 mEq (7800 mg of elemental potassium) in 24 hours (95010). Potassium supplementation and route of administration should be individualized based on serum potassium level and patient status (15,107970).

Hypertension. Oral potassium, via dietary intake or supplementation, reduces blood pressure. Details: Population research has found that higher dietary potassium consumption is associated with a lower risk of developing hypertension (1310,8817,69512). Additionally, most clinical research shows that potassium, taken orally as part of the diet or as a supplement, reduces systolic blood pressure by about 3-9.5 mmHg and diastolic blood pressure by about 2-6.4 mmHg in patients with or without hypertension (3385,92104,92106,95624,107974). In most of these studies, daily intake of potassium typically ranged from about 1500-7800 mg, with the most common intake being about 2340-2540 mg daily (92104,95624). However, some research shows that taking potassium does not lower systolic or diastolic blood pressure (69541,69550,107966). Differences in the patient populations, potassium intake, and salt intake could have contributed to the conflicting results. Potassium seems to be more effective for people with hypertension, low potassium levels, high daily sodium intake, and for Black adults (3384,3385,3386,92104,92106). Some research also shows that the greatest blood pressure-lowering effects of potassium occur at doses of about 3900-7800 mg daily (95624). A meta-analysis of clinical trials using a novel computational technique to assess both potassium intake and excretion suggests that the optimal blood pressure reduction occurs when taking about 1500 mg supplemental potassium daily or an overall intake of 4500-6500 mg potassium daily (105448). This analysis is limited by the heterogeneity and short duration of the included trials. There is also interest in utilizing low-sodium, high-potassium food substitutes to treat hypertension. Research shows that using salt substitutes containing 25% to 30% potassium chloride reduces systolic and diastolic blood pressure by 3-4.6 mmHg and 1 mmHg, respectively, when compared with regular table salt (107971,107976). In 2017, the American College of Cardiology and the American Heart Association (ACC/AHA) published guidelines recommending that patients with hypertension consume 3500-5000 mg of potassium daily (95680). This intake of potassium is expected to lower systolic blood pressure by about 4-5 mmHg in patients with hypertension and by about 2 mmHg in normotensive patients (3385). Although potassium supplements and dietary potassium both seem to be beneficial, the guidelines recommend getting potassium from dietary sources, since potassium-rich diets are usually heart-healthy (95680). Additionally, the US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).
Kidney stones (nephrolithiasis). Oral prescription potassium citrate reduces the risk of kidney stone recurrence. It is unclear if non-prescription potassium citrate would be beneficial. Details: The American Urological Association (AUA) recommends potassium citrate therapy for patients with recurrent calcium stones and low urinary citrate, those with recurrent calcium or calcium oxalate stones without current metabolic abnormalities, and those with uric acid or cystine stones. The citrate component reduces urine calcium excretion and increases urine citrate and urine pH, which in turn alleviates crystal growth, formation, and aggregation. Sodium citrate may also be used to prevent stone recurrence; however, due to sodium's propensity to increase urine calcium excretion, potassium citrate remains the preferred salt formulation (107972). It is important to note that potassium citrate supplements are not equivalent to prescription potassium citrate products. Dose and duration of treatment is determined by a healthcare professional and individualized based on a patient's urinary citrate levels (107975,107989). Serum potassium levels should be monitored prior to starting potassium citrate, within 2 weeks of treatment initiation, and every 12 months (107975).

Cardiovascular disease (CVD). Eating foods high in potassium and low in sodium might reduce the risk of cardiovascular disease. It is unclear if taking potassium supplements has the same benefit. Details: Large population studies in adults without prior CVD have found that higher dietary potassium intake is associated with a lower risk of cardiovascular events (109395,109399). One study found that daily potassium intake of about 3300 mg is associated with a 13% reduction in CVD risk when compared with intake of about 1920 mg (109399). The other study found that each additional 1000 mg of daily urinary potassium excretion, which is a marker of dietary intake, is associated with an 18% reduction in CVD risk (109395). Another observational study in over 15,000 adults with history of stroke or hypertension shows that replacing regular table salt with a substitute product containing 75% sodium chloride and 25% potassium chloride for an average of 5 years decreases the rate of stroke, major cardiovascular events, or death (107976). High quality clinical trials are needed to confirm this association. The US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).
Stroke. Eating foods high in potassium and low in sodium might reduce the risk of stroke. It is unclear if taking potassium supplements has the same benefit. Details: Higher dietary intake of potassium seems to be associated with a lower risk of stroke. Population research has found that increasing dietary potassium intake by 1-1.5 grams daily is associated with up to a 20% reduced risk of stroke (92105,92107). Some population research has found that higher supplemental intake of potassium is associated with a 29% reduced risk of ischemic stroke. However, supplemental potassium intake is not found to be associated with a lower risk of hemorrhagic or total stroke (92107). An observational study in over 15,000 adults with history of stroke or hypertension shows that replacing regular table salt with a substitute product containing 75% sodium chloride and 25% potassium chloride for an average of 5 years decreases the rate of stroke, major cardiovascular events, or death (107976). High quality clinical trials are needed to confirm this association. The US Food and Drug Administration (FDA) has determined that foods containing at least 350 mg potassium and that are low in sodium, saturated fat, and cholesterol can state that "diets containing foods that are good sources of potassium and low in sodium may reduce the risk of high blood pressure and stroke" (1310,8817).

Dental hypersensitivity. It is unclear if topical potassium improves dental hypersensitivity. Details: One meta-analysis of clinical research shows that using a dentifrice containing 5% potassium nitrite reduces dentin sensitivity when compared with a dentifrice that does not contain potassium nitrite (69549). Other clinical research published in a systematic review shows that potassium-containing toothpastes might reduce dentin sensitivity more than controls that do not contain potassium. However, these toothpastes might be less effective than other active toothpastes, such as those containing sodium monofluorophosphate, and the effect may result from a placebo effect, since the mechanism of action of potassium is unclear (69456).
Diabetes. It is unclear if increasing dietary potassium reduces the risk of diabetes. Details: A meta-analysis of 7 large population studies has found that consuming dietary potassium 3300-3500 mg daily is associated with a 20% reduction in the risk of diabetes when compared with consumption below 1000 mg daily. Results were similar when studies that measured potassium intake with a dietary questionnaire were analyzed separately from those that measured intake based on urinary potassium excretion (110776). However, the validity of this finding is limited by the heterogeneity of the included studies. Furthermore, despite use of data from various databases, most studies included in the analysis were conducted by the same author.
Impaired glucose tolerance (prediabetes). It is unclear if oral potassium improves glycemic control in prediabetes. Details: A small clinical study in Black patients with prediabetes shows that taking extended-release potassium (Klor-Con M10, Cardinal Health) 40 mEq daily as potassium chloride for 3 months does not improve glucose tolerance when compared with placebo. Although fasting glucose levels were slightly reduced in the potassium group when compared with placebo, both groups experienced a worsening of glucose intolerance, with no change in insulin levels or glycated hemoglobin (98533).
Osteoporosis. Although there is interest in using oral potassium for osteoporosis, there is insufficient reliable information about the clinical effects of potassium for this condition.
Physical performance. It is unclear if oral potassium improves physical performance in older adults. Details: Observational research in older adults has found that decreased dietary potassium intake and increased dietary sodium intake over 5 years is associated with worsened physical performance (105450).
Systemic lupus erythematosus (SLE). It is unclear if oral potassium is beneficial in patients with SLE. Details: Observational research in patients with SLE has found that increased dietary potassium intake is not associated with improvements in disease activity scores or markers of cardiovascular disease, including lipid levels and blood pressure, when compared with low dietary potassium intake. However, higher potassium intake does seem to reduce the odds of having elevated levels of C-reactive protein, a marker of inflammation, in these patients (109397). More evidence is needed to rate potassium for these uses.

RIBOFLAVIN

Ariboflavinosis. Oral riboflavin can treat and prevent low riboflavin levels.

Hyperhomocysteinemia. Oral riboflavin reduces homocysteine levels in individuals with the MTHFR 677 TT genotype. It does not seem to provide benefit in individuals with other genotypes. Details: Population research has found that poor riboflavin status is associated with high homocysteine levels in individuals with the 677 TT genotype for the MTHFR enzyme (71386,71403,71409). Taking riboflavin 1.6 mg daily for 12 weeks reduces homocysteine levels by 22% to 40% in individuals with the 677 TT genotype of MTHFR when compared with pretreatment. However, riboflavin supplementation does not seem to reduce homocysteine levels in individuals with the 677 CC or CT genotypes (71443).
Migraine headache. Oral riboflavin modestly reduces migraine attack frequency and severity in adults. The benefits of oral riboflavin in children are unclear. Details: A meta-analysis of 5 small clinical trials in adults with migraine shows that taking riboflavin 100-400 mg daily, alone or in combination with other natural ingredients, for three months modestly reduces migraine duration, frequency, and pain scores when compared with control (105480). These findings are limited by significant heterogeneity. Most clinical studies compared riboflavin 400 mg daily with placebo, no treatment, or an active control (1396,1397,1398,12387,105480). Limited evidence also suggests that taking riboflavin 400 mg daily might be no different for migraine prevention than certain conventional treatments such as bisoprolol 10 mg, metoprolol 200 mg, propranolol 80 mg, or valproate 500 mg (1396,105480). These findings are limited due to small study size and a lack of power to detect a difference between groups. Limited research has also evaluated riboflavin in children. A network meta-analysis of 3 small clinical trials in children with migraine shows that taking oral riboflavin 100-200 mg daily for 4-12 months does not significantly reduce incidence of migraine when compared with placebo. However, there was a non-significant trend towards reduced migraine frequency. Furthermore, conventional treatments such as propranolol, pregabalin, valproate, and topiramate were not shown to be significantly better than riboflavin for migraine prevention (105484). These findings are limited by small population sizes and insufficient power to detect differences between groups. Although riboflavin 100-200 mg has been used in prospective clinical studies, small observational studies have found some benefit in children taking riboflavin doses as low as 10-40 mg daily and as high as 400 mg daily for 3-4 months (105481,105485). Riboflavin has also been studied in combination with other ingredients, with research suggesting potential benefit. Specifically, riboflavin 400 mg has been combined with magnesium 600 mg and coenzyme Q10 150 mg daily (Dolovent; Linpharma Inc.) (92101), and also with magnesium 300 mg and feverfew 100 mg daily (12389).

Acne. Although there is interest in using oral riboflavin for acne, there is insufficient reliable information about the clinical effects of riboflavin for this purpose.
Alzheimer disease. Although there is interest in using oral riboflavin for Alzheimer disease, there is insufficient reliable information about the clinical effects of riboflavin for this condition.
Cardiovascular disease (CVD). It is unclear if oral riboflavin can prevent mortality due to CVD. Details: Epidemiological research has found that dietary and supplemental riboflavin intake in the highest quartile, around 3.4 mg daily, is associated with a 47% lower risk of CVD mortality when compared with riboflavin intake in the lowest quartile, around 1 mg/day. The reduction in CVD mortality with riboflavin was enhanced by higher folate intake (110727). The validity of this finding is limited by the fact that dietary riboflavin intake was based on 2-day dietary recall.
Carpal tunnel syndrome. Although there is interest in using oral riboflavin for carpal tunnel syndrome, there is insufficient reliable information about the clinical effects of riboflavin for this purpose.
Cataracts. It is unclear if oral riboflavin is beneficial in patients with cataracts. Details: Observational research has found that high dietary intake of riboflavin is associated with a reduced risk of nuclear cataracts and age-related lens opacification (6378,14301). Furthermore, a clinical study in Chinese patients with nutrient deficiencies shows that taking a combination of riboflavin 3 mg plus niacin 40 mg daily also seems to reduce the risk of developing nuclear cataracts when compared with no supplementation (4885). It is unclear if the benefit is due to riboflavin, niacin, or the combination.
Cervical cancer. It is unclear if oral riboflavin helps to prevent cervical cancer. Details: Epidemiological evidence has found that increased riboflavin intake from dietary and supplement sources, along with other B vitamins, is associated with a reduced risk of precancerous cervical lesions (11074).
Colorectal cancer. It is unclear if oral riboflavin reduces colorectal cancer risk. Details: Epidemiological evidence in a Chinese population has found that increased dietary intake of riboflavin is associated with a reduced risk of developing colorectal cancer (105482).
Diabetic neuropathy. Intravenous and oral riboflavin have only been evaluated in combination with other ingredients; riboflavin's effect when used alone is unclear. Details: Clinical research in patients with type 2 diabetes shows that intravenous administration of a specific combination product containing succinic acid, inosine, nicotinamide, and riboflavin (Cytoflavin, Polysan) daily for 10 days followed by an oral formulation of the same product, taken daily for 76 days, reduces symptoms of diabetic neuropathy including paresthesia, numbness, and burning when compared with placebo (110503). It is unclear if these findings are due to riboflavin, other ingredients, or the combination.
Esophageal cancer. It is unclear if oral riboflavin reduces esophageal cancer risk. Details: Population research in Iranian patients has found that low riboflavin status is associated with a two-fold increase in the risk of esophageal cancer (71439). However, not all evidence agrees. Preliminary clinical studies in Chinese individuals with esophageal dysplasia shows that taking riboflavin, alone or in combination with calcium or niacin, for 3-5 years does not seem to reduce the risk of esophageal cancer in patients when compared with baseline or control (4679,63576,71488). Taking riboflavin 200 mg weekly, in combination with retinol 15 mg and zinc 50 mg, also does not seem to be beneficial in this patient population (71501). It is unclear if these findings are generalizable to geographic locations other than China and Iran.
Gastric cancer. It is unclear if oral riboflavin reduces colorectal cancer risk. Details: Low quality clinical research in a Chinese population shows that taking riboflavin in combination with niacin does not appear to reduce the risk of gastric cancer when compared with control (4679).
Hypertension. There is limited evidence on the oral use of riboflavin for reducing blood pressure in patients with the MTHFR 677 TT genotype. Details: A 677 C to T polymorphism on the MTHFR gene has been associated with hypertension. In patients with a confirmed MTHFR 677 TT genotype and premature cardiovascular disease, preliminary clinical research suggests that taking riboflavin 1.6 mg daily for 16 weeks reduces systolic blood pressure (SBP) by 9 mmHg and diastolic blood pressure (DBP) by 6 mmHg when compared with placebo . This decrease in blood pressure is larger than that reported in other trials, which may be due to the fact that only patients with the 677 TT genotype were included. These patients seem to respond to riboflavin therapy more so than patients with 677 CC or 677 CT genotype (92102). Additional clinical research in patients with the 677 TT genotype but without cardiovascular disease shows that taking riboflavin 1.6 mg daily for 16 weeks reduces SBP by 5.6 mmHg but does not reduce DBP (92103). There is also interest in using dietary riboflavin for reducing the onset of hypertension. Some epidemiological evidence in a Chinese population has found that increased dietary intake of riboflavin is associated with a reduced risk of developing hypertension (105483).
Liver cancer. Oral riboflavin has only been evaluated in combination with niacin; its effect when used alone is unclear. Details: Preliminary clinical research in Chinese individuals older than 55 years shows that taking riboflavin in combination with niacin does not seem to prevent liver cancer mortality when compared with control. However, there was a reduced risk of liver cancer mortality in people aged less than 55 years when compared with control (63470).
Lung cancer. Oral riboflavin has only been evaluated in combination with niacin; its effect when used alone is unclear. Details: Preliminary clinical research in Chinese individuals shows that taking riboflavin in combination with niacin does not appear to reduce the risk of lung cancer when compared with control (34539).
Malaria. Oral riboflavin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in children ages 5-14 years living in Gambia and at high risk for malaria exposure suggests that taking riboflavin, in combination with iron, thiamine, and vitamin C, for 3 months does not reduce the frequency or severity of malaria infections when compared with placebo (56730).
Malnutrition. There is limited evidence on the oral use of riboflavin with other ingredients in children at risk for kwashiorkor. Details: A clinical study in Malawian children at risk for kwashiorkor, a severe form of malnutrition, suggests that taking riboflavin, vitamin E, selenium, and N-acetyl cysteine at a dose of three times the recommended dietary allowance does not prevent kwashiorkor, reduce edema, increase physical growth, or reduce infection when compared with placebo (71433).
Mitochondrial myopathies. Although there is interest in using oral riboflavin for mitochondrial myopathies, there is insufficient reliable information about the clinical effects of riboflavin for this condition.
Multiple sclerosis (MS). It is unclear if oral riboflavin slows the progression of MS-related disability. Details: A small clinical study in patients with relapsing-remitting MS or secondary progressive MS who are undergoing treatment with disease-modifying therapies suggests that taking oral riboflavin 10 mg daily for six months is no more effective for improving disability than placebo (91752). The validity of this finding is limited by the small study sample size.
Oral leukoplakia. It is unclear if oral riboflavin prevents or slows progression of oral leukoplakia. Details: Population research in people living in Uzbekistan has found that low blood levels of riboflavin are associated with an increased prevalence of oral leukoplakia (71502). However, clinical evidence in patients with a high occurrence of oral and esophageal cancer who are living in Uzbekistan suggests that taking riboflavin 80 mg weekly for 20 months does not improve the prevalence or progression of oral leukoplakia when compared to baseline (71565). The validity of this finding is limited by the lack of a placebo group and unusual once weekly dosing. Furthermore, it is unclear if these results are generalizable to other geographic locations.
Pre-eclampsia. Although there is interest in using oral riboflavin for pre-eclampsia, there is insufficient reliable information about the clinical effects of riboflavin for this purpose.
Pregnancy-related iron deficiency. It is unclear if oral riboflavin is beneficial in patients with iron deficiency due to pregnancy. Details: Preliminary clinical research in pregnant patients in China suggests that adding riboflavin 1 mg daily to supplemental iron and folic acid does not improve iron status when compared with taking iron and folic acid alone (71480).
Sickle cell disease. It is unclear if oral riboflavin is beneficial in patients with sickle cell disease. Details: One small clinical study in patients with sickle cell disease suggests that taking riboflavin 5 mg twice daily for 8 weeks increases serum iron and transferrin saturation when compared to baseline; however, riboflavin does not seem to improve serum ferritin or circulating hemoglobin levels (71566).
Stroke. Oral riboflavin has only been evaluated in combination with niacin; its effect when used alone is unclear. Details: Preliminary clinical research in Chinese individuals with poor nutritional status who are at risk for stroke suggests that taking riboflavin 5.2 mg daily in combination with niacin 40 mg daily does not reduce the risk of stroke-related mortality (2673). More evidence is needed to rate riboflavin for these uses.

SELENIUM

Selenium deficiency. Oral selenium is effective for the treatment and prevention of selenium deficiency. Details: Selenium supplementation is effective for reversing symptoms of selenium deficiency, as well as for preventing the development of selenium deficiency (4844,90357).

Autoimmune thyroiditis. Oral selenium seems to improve autoimmune thyroiditis in adults but not in children. Details: Clinical research in adults with thyroiditis shows that taking selenium up to 200 mcg daily in combination with levothyroxine reduces thyroid peroxidase antibodies by about 6% to 30% more than placebo after 3-12 months of treatment (9797,17510,17511,17512,17513,17515,17516,97943,104424). Selenium also seems to improve measures of quality of life such as feelings of well-being and mood (17515). Doses under 200 mcg daily might not be as effective (17512); selenomethionine might be more effective than sodium selenite (97943). Some research shows that selenium might be more effective in patients with more severe disease activity and less effective in patients with only moderate disease activity (9797,17513,17515). Also, selenium might not reduce thyroid autoantibodies in patients newly diagnosed with thyroiditis not receiving concurrent levothyroxine (97943). There is no reliable evidence about the effect of selenium on thyroid function or thyroid morphology. Despite positive findings in adults, clinical research in children suggests that taking selenium 50-200 mcg daily for 3-12 months does not significantly improve thyroid peroxidase antibodies, thyroglobulin antibody, or thyroid echogenicity (17514,90362).
Kashin-Beck disease. Selenium seems to help prevent Kashin-Beck disease, but does not improve symptoms in patients with existing disease. Details: A meta-analysis of prospective studies conducted in China shows that adding salt enriched with selenium to the diet of healthy children for up to 4 years reduces the odds of developing Kashin-Beck disease by 84% when compared with the use of iodine salt. Additionally, in children with Kashin-Beck disease, adding salt enriched with selenium to the diet might help heal metaphyseal lesions (97945). However, selenium does not seem to improve symptoms in those with existing disease. A clinical trial in children with Kashin-Beck disease shows that selenium supplementation does not improve joint pain or mobility when compared with placebo (55941).
Pre-eclampsia. Oral selenium might reduce the risk of pre-eclampsia in pregnant patients. Details: A meta-analysis of three low-quality clinical trials in pregnant patients shows that taking selenium 60-100 mcg daily for up to 6 months reduces the risk of pre-eclampsia by 72% when compared with placebo. Additionally, a meta-analysis of population research has found that the risk of pre-eclampsia is higher in pregnant patients with low selenium levels. Selenium levels were about 6.5 mcg/L lower in those who developed pre-eclampsia compared with those who did not (97946).

Asthma. Oral selenium does not seem to improve asthma symptoms. Details: Epidemiological research has found that plasma selenium concentration is not associated with asthma (74422). Also, clinical research in patients with asthma shows that taking selenium 100 mcg daily for 14-24 weeks does not improve symptoms, lung function, use of rescue inhalers, or quality of life when compared with placebo (74490,74387).
Atopic dermatitis (eczema). Oral selenium-enriched yeast does not seem to improve eczema symptoms. Details: A small clinical study in patients with eczema shows that taking selenium-enriched yeast 600 mcg daily for 12 weeks, either alone or in combination with vitamin E 600 IU daily, does not improve symptom severity when compared with placebo (74456).
Bladder cancer. Despite promising initial research, oral selenium does not seem to prevent bladder cancer development or recurrence. Details: In 2009, the US Food and Drug Administration (FDA) approved a qualified health claim regarding selenium and bladder cancer risk based on two small studies. However, the FDA determined that it is highly uncertain that selenium supplements reduce the risk of bladder cancer (102373). Since that time, the available research has not confirmed an association between selenium and bladder cancer risk. Epidemiological research has found that selenium supplementation is not associated with a reduced risk of bladder cancer (97085). Furthermore, a clinical study shows that taking selenium 200 mcg daily with or without vitamin E 400 IU daily for about 7 years does not prevent bladder cancer in older men (90352). Selenium also does not seem to prevent bladder cancer recurrence. A clinical study shows that taking selenium yeast 200 mcg daily for 3 years does not prevent the recurrence of bladder cancer when compared with placebo in patients that had undergone a transurethral resection for non-invasive bladder cancer (97087).
Cardiovascular disease (CVD). Most research shows that oral selenium does not reduce the risk of CVD. Details: Meta-analyses of clinical trials in patients with and without risk factors for CVD show that taking selenium alone or with other supplements for up to 8 years does not reduce the risk of CVD mortality or fatal and non-fatal CVD events (90360,97078). When reported, patients in these studies all had adequate plasma selenium levels at baseline (90360).
Colorectal cancer. Oral selenium does not seem to prevent cancer of the colon and rectum. Details: Epidemiological research has found no association between serum concentrations of selenium and the risk of developing colorectal cancer (74321,97085). Also, meta-analyses of clinical research, as well as individual clinical trials, show that taking selenium 100-200 mcg daily, alone or in combination with other vitamins and minerals, does not reduce the risk of colorectal cancer when compared with control (16707,34676,90361,97092).
Diabetes. Increased intake of selenium, either in the diet or as a supplement, is associated with an increased risk for developing type 2 diabetes. It is unclear if oral selenium is beneficial in patients with type 2 diabetes. Details: Observational research has found that high serum selenium levels, high dietary selenium intake, and selenium supplementation are each linked to an increased risk of developing diabetes (97091,99661). Consuming more than the recommended dietary allowance (RDA) of selenium daily is associated with an increased risk of developing diabetes when compared with consuming less than the RDA (99661). However, the effect of short-term selenium supplementation in patients with diabetes is unclear. Three small clinical trials in patients with type 2 diabetes and various other conditions, such as cardiovascular disease or kidney failure, show that taking selenium (Nature Made) 200 mcg daily for 8-24 weeks does not improve fasting blood glucose. However, taking selenium seems to reduce insulin resistance and improve insulin sensitivity and levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol when compared with placebo (97084,97086,109092). These three studies were included in a meta-analysis of 10 small, mostly moderate-quality clinical studies. This analysis shows that taking selenium 100-200 mcg daily for 4 to 24 weeks improves markers of insulin resistance and reduces serum insulin levels but does not lower fasting blood glucose when compared with placebo. Selenium supplementation did not reduce total or LDL cholesterol or triglycerides but may improve HDL cholesterol (110593). However, the validity of the findings from this meta-analysis is limited by the heterogeneity of the included studies, which enrolled patients with diabetes, gestational diabetes, cardiovascular disease, heart failure, or obesity. Additionally, all studies were conducted in Iran; it is unclear if these findings are generalizable to populations in other geographic locations.
Dyslipidemia. Most research shows that oral selenium supplementation does not improve cholesterol levels. Details: A meta-analysis of 11 clinical studies in adults with dyslipidemia shows that taking selenium 50-300 mcg daily for 8-24 weeks does not increase high-density lipoprotein (HDL) cholesterol levels or decrease total or low-density lipoprotein (LDL) cholesterol levels when compared with placebo. Taking selenium might modestly improve triglyceride levels, but this improvement is unlikely to be considered clinically significant (99662). Another meta-analysis of 21 mostly small, low-quality clinical studies, some of which were included in the prior meta-analysis, shows that taking various forms of selenium may modestly decrease total cholesterol levels, but does not improve triglycerides, LDL, or HDL cholesterol when compared with placebo (110595). However, the validity of the findings from this meta-analysis is limited by the heterogeneity of the included studies, which assessed various selenium dosing regimens and enrolled healthy patients or those with various cardiovascular and non-cardiovascular conditions.
Low birth weight. Oral or intravenous selenium supplementation does not improve outcomes in low birth weight infants. Details: Low selenium levels have been documented in low birth weight infants. However, selenium supplementation, orally or intravenously, does not appear to improve most outcomes in low birth weight infants. Clinical research shows that administering selenium, either as 7-10 mcg/kg daily parenterally or 5 mcg/kg daily orally, does not improve oxygen dependency or reduce the risk of death in low birth weight infants when compared with placebo. However, supplementation decreases the incidence of sepsis by up to 33% (74288,97083).
Lung cancer. Oral selenium does not reduce lung cancer risk in most patients. Details: A meta-analysis of three large clinical trials of over 20,000 patients, including patients with resected stage I non-small-cell lung cancer, shows that taking selenium 200-400 mcg daily for up to 5 years does not reduce the risk of lung cancer when compared with control (92912,97092). A secondary analysis of one of these studies found that selenium supplementation might reduce lung cancer risk in people with selenium levels below 105 ng/mL (9798). Also, a large study in healthy Chinese patients shows no benefit of using selenium in combination with other nutrients for over 5 years when compared with control (34539).
Nonmelanoma skin cancer. Oral selenium does not reduce the risk of nonmelanoma skin cancer and has been linked to increased risk in some patients. Details: Epidemiological research has found that higher selenium intake is not associated with a reduced risk of nonmelanoma skin cancer (97085). Furthermore, clinical research shows that taking selenium orally 200 mcg daily does not reduce the risk of basal cell carcinoma when compared with control (2664,10687). In addition, some evidence shows that daily selenium supplementation might increase the risk of squamous cell carcinoma and total non-melanoma skin cancer (10687).
Prostate cancer. Oral selenium does not seem to reduce prostate cancer risk. Details: Population studies have found that higher serum or toenail selenium levels are associated with a decreased risk of prostate cancer (8734,8735,8736,92911,10263). However, clinical research does not support this finding. A meta-analysis of 5 large clinical trials of over 20,000 patients shows that selenium 200-400 mcg daily for up to 5 years does not reduce the risk of prostate cancer when compared with control (97092). A 7-14 year follow-up study of one of these trials shows there was still no reduction of prostate cancer risk (17688). Selenium has also shown no benefit when used in combination with other supplements. In a large-scale clinical study (SU.VI.MAX), taking selenium 100 mcg in combination with vitamin C, vitamin E, beta-carotene, and zinc did not reduce prostate cancer risk (14135). In 2009, the US Food and Drug Administration (FDA) approved a qualified health claim regarding selenium and prostate cancer risk, stating that it is highly unlikely that selenium supplements reduce the risk of prostate cancer (102373).
Psoriasis. Oral selenium does not seem to reduce psoriasis severity. Details: Clinical research shows that taking selenium-enriched yeast 600 mcg daily for 12 weeks, either alone or in combination with vitamin E 600 IU daily, does not reduce the severity of psoriasis when compared with placebo (74460).
Sepsis. Intravenous selenium does not appear to improve outcomes in septic adults. Details: Earlier meta-analyses of clinical trials in septic adults showed that parenteral administration of selenium, along with routine nutritional interventions, reduces the risk of mortality by 11% to 27% when compared with placebo (90347,92907,92910). However, a more recent meta-analysis, which includes a large, multi-center study of over 1000 cases, shows that parenteral selenium does not reduce mortality in septic adults at 28, 90, or 180 days when compared with placebo (99658). Enteral selenium with other nutrients has been studied for sepsis in children. Clinical research in children shows that taking enteral selenium 40-400 mcg daily with zinc, glutamine, and IV metoclopramide is no more effective than whey protein for reducing time to first episode of nosocomial infection or sepsis in the intensive care unit (ICU). However, the selenium combination treatment might reduce the risk for sepsis in immunocompromised pediatric patients (86095).

Age-related cognitive decline. It is unclear if oral selenium reduces the risk of cognitive decline in older adults. Details: A cross-sectional study in elderly Americans has found that lower blood levels of selenium are associated with a greater risk of poor cognitive scores when compared with higher levels (104426).
Alcohol-related liver disease. Although there is interest in using oral selenium for alcohol-related liver disease, there is insufficient reliable information about the clinical effects of selenium for this condition.
Allergic rhinitis (hay fever). Although there is interest in using oral selenium for allergic rhinitis, there is insufficient reliable information about the clinical effects of selenium for this condition.
Arsenic poisoning. It is unclear if oral selenized yeast is beneficial for patients that were exposed to high levels of arsenic in the environment. Details: A small clinical study in Chinese people environmentally exposed to high concentrations of arsenic shows that taking selenized yeast providing 100-200 mcg of selenium daily for 14 months decreases the concentration of arsenic and symptoms of toxicity when compared with placebo (7831).
Benign prostatic hyperplasia (BPH). Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in men with BPH shows that taking selenium 240 mcg plus silymarin 570 mg daily for 6 months reduces lower urinary tract symptoms when compared with placebo (88155). Another clinical study in men with BPH shows that taking tamsulosin 0.4 mg plus a specific product containing selenium, saw palmetto, and lycopene (Profluss, Ayanda AS) daily for one year improves lower urinary tract symptoms and urodynamic parameters when compared with tamsulosin-alone (90354). It is unclear if these effects are due to selenium, other ingredients, or the combinations.
Burns. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Small clinical studies in patients with burns on 46% of their body surface suggest that taking a combination of copper 2.5-3.1 mg, selenium 315-380 mcg, and zinc 26.2-31.4 mg daily reduces the incidence of hospital-acquired pneumonia, but does not seem to improve wound healing, hospital stay, or mortality, when compared with placebo (6520,74382). Another very small clinical study in burn patients suggests that taking copper 4.5 mg, selenium 190 mcg, and zinc 40 mg daily reduces the duration of hospitalization, but does not have an effect on recovery and wound treatment requirements, when compared with standard dietary doses of these nutrients (74485).
Cancer. Selenium does not seem to reduce the risk of cancer in most people, but it might be beneficial in those with low selenium levels and in men. Details: Meta-analyses of clinical research and several clinical studies show that selenium supplementation does not reduce the incidence of cancer or cancer-related mortality when compared with control (14109,34538,74414,97078,97092). In clinical studies, selenium 100-400 mcg taken daily for 2-7.5 years with or without additional antioxidants did not reduce overall cancer risk (14109,34538,74414). However, most evidence did not assess baseline selenium levels. Other evidence suggests that selenium may have a benefit in men and in people with lower selenium levels. Epidemiological research has found that selenium intake at the recommended daily allowance (RDA) of 55 mcg or higher is associated with decreased cancer incidence and cancer mortality, especially in men (97085,103164). However, this research suggests that cancer risk was also influenced by age, body mass index, and smoking status (103164). Some clinical research also suggests that taking selenium might decrease the risk of cancer, when only men are considered (14109). An older meta-analysis of clinical research suggests that selenium was particularly beneficial in patients with lower baseline levels of selenium and in patients at high risk for cancer (90350). In 2003, the US Food and Drug Administration (FDA) approved a qualified health claim stating that consumption of selenium may produce anticarcinogenic effects and reduce the risk for certain forms of cancer. However, the FDA has determined that the evidence is limited and inconclusive (102374).
Cataracts. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An ancillary clinical study shows that taking selenium 200 mcg daily with or without vitamin E 400 IU daily for around 5.6 years does not reduce the risk of age-related cataracts in men when compared with placebo (92902).
Cervical dysplasia. It is unclear if oral selenized yeast is beneficial for patients with cervical dysplasia of mild severity. Details: A small clinical study in patients with cervical intraepithelial neoplasia grade 1 (CIN1) shows that taking yeast containing selenium 200 mcg daily for 6 months resulted in regression of CIN1 in 88% of participants, compared with regression in only 55% of participants taking placebo (97944).
Chemotherapy-induced nephrotoxicity. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in cancer patients shows that drinking a beverage containing vitamin C, vitamin E, and selenium does not prevent cisplatin-induced nephrotoxicity when compared with a placebo beverage (74340). However, poor compliance to treatment may limit the validity of these findings.
Chronic fatigue syndrome (CFS). Although there is interest in using oral selenium for CFS, there is insufficient reliable information about the clinical effects of selenium for this condition.
Cirrhosis. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with primary biliary cirrhosis shows that taking a combination of selenium, vitamin A, vitamin C, vitamin E, methionine, and coenzyme Q10 for 12 weeks does not improve fatigue or any other disease-related symptoms when compared with placebo (34494).
Cisplatin-associated ototoxicity. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in cancer patients shows that drinking a beverage containing vitamin C, vitamin E, and selenium does not prevent cisplatin-associated hearing loss when compared with placebo beverage (74340). However, poor compliance to treatment may limit the validity of these findings.
Colorectal adenoma. It is unclear if oral selenium prevents recurrence of adenomas in the colon and rectum. Details: A large clinical study in patients with a history of colorectal adenomas shows that taking a specific selenium supplement (SelenoExcell High Selenium Yeast, Cypress Systems) 200 mcg daily for about 33 months does not reduce adenoma recurrence when compared with placebo. However, in a sub-group of patients with advanced adenomas at baseline, selenium seems to reduce risk of recurrence by 18% when compared with placebo (97091). Some research also shows that taking selenium in combination with zinc, and vitamins A, C, and E reduces adenoma recurrence when compared with placebo (92903). It is not clear any benefit is due to selenium, other nutrients, or the combination.
Congestive heart failure (CHF). Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large clinical study in elderly patients with heart failure living in Sweden shows that taking a specific selenium supplement (SelenoPrecise, Pharma Nord) 200 mcg plus a specific coenzyme Q10 supplement (Bio-Quinon, Pharma Nord) 200 mg daily for about 4 years reduces the risk of cardiovascular mortality by about 55% when compared with placebo (92904). The risk reduction seems to be most pronounced in patients with lower selenium levels (97906). Furthermore, at 10- and 12-year follow-ups, cardiovascular mortality in the treatment group continued to be 49% and 41% lower, respectively, when compared with placebo (96546,97466). It is unclear if the benefit can be attributed to selenium, coenzyme Q10, or the combination.
Coronary artery bypass graft (CABG) surgery. It is unclear if oral selenized yeast is beneficial for patients undergoing CABG surgery. Details: A small clinical study in patients undergoing CABG surgery shows that taking selenium 200 mcg daily as selenium yeast for 4 weeks improves glycemic control, lipid levels, and markers of inflammation when compared with placebo (103163). It is not known whether this influences the outcome or complications of CABG surgery.
Critical illness (trauma). Evidence on the use of intravenous selenium in critically ill patients is conflicting. Details: The most recent meta-analysis of 24 clinical trials in critically ill patients shows that intravenous selenium does not improve survival over 6 months, shorten hospital stay, or reduce intensive care unit (ICU) stay, infectious complications, development of acute kidney failure, or duration of mechanical ventilation when compared with control. Also, length of ICU stay was increased by about 4.5-fold in patients receiving selenium in doses of more than 1000 mcg daily (109086). These findings are similar to those of a meta-analysis of 21 randomized controlled trials in critically ill patients from 2016 which shows that intravenous selenium given alone or with other nutrients does not improve mortality, duration of hospital stay, or kidney function when compared with control (97090). However, another recent meta-analysis of 19 clinical trials in critically ill patients shows that intravenous selenium reduces total mortality by 14% and shortens hospital stay by about 2 days when compared with control, without affecting ICU stay, duration of mechanical ventilation, or mortality over 28 days (101345). The reasons for these discrepancies are not clear and do not seem to be completely explained by differences in doses or durations of selenium (109086). Some reasons for the discrepancies might include differing analytic methods used in meta-analyses, as well as variations in forms of selenium, concomitant treatments, and specific patient populations. One sub-analysis shows that, when limited to randomized controlled trials examining the effect of selenium supplementation in patients sustaining traumatic injury, the odds of mortality was reduced by about 26% and duration of ICU and hospital stay were modestly reduced. There was no effect on infectious complications (109090).
Dementia. It is unclear if oral selenium prevents dementia or reduces symptoms. Details: Observational research has found that taking selenium 200 mcg daily for 4 years does not decrease the incidence of dementia in men 60 years or older (93570). However, the follow-up period may not have been long enough to reliably detect the effect of selenium on the development of dementia. Also, the screening method used to detect new cases of dementia may have failed to identify individuals presenting with only the initial symptomatic stages of the disease (93570,93571).
Depression. It is unclear if oral selenium is beneficial for the treatment of prevention of depression. Details: A meta-analysis of observational research has found no difference in serum levels of selenium between patients with or without depression. In addition, serum levels of selenium do not correlate with depression scores (109091). A meta-analysis of clinical research shows that selenium supplementation, usually 100-200 mcg daily, modestly reduces symptoms of depression; however, at least one of the three studies included in this meta-analysis investigated the effects of selenium in patients with postpartum depression, specifically (109091). These meta-analyses are limited by the quality of included research and the small number of available studies.
Diabetic nephropathy. It is unclear if oral selenium alleviates diabetic nephropathy symptoms. Details: A small clinical study in patients with diabetic nephropathy shows that taking selenium (Nature Made) 200 mcg daily for 12 weeks does not improve kidney markers such as blood urea nitrogen or serum creatinine when compared with placebo (97084).
Dilated cardiomyopathy. There is limited evidence on the oral use of selenium in patients with Keshan disease and peripartum cardiomyopathy. Details: Observational research in patients with a specific type of dilated cardiomyopathy called Keshan disease and congestive heart failure has found that selenium supplementation is associated with a 61% decreased risk of cardiac death when compared with no supplementation (101346). A small clinical study in patients with peripartum cardiomyopathy and selenium deficiency shows that taking selenium 200 mcg daily for 3 months does not seem to improve heart failure symptoms or left ventricle systolic function, or prevent death, when compared with no treatment (104420).
Esophageal cancer. Limited research suggests that oral selenium does not reduce esophageal cancer risk. Details: Low quality clinical research suggests that taking selenium supplements alone or with other vitamins does not decrease the risk of esophageal cancer when compared with control (4679,12185).
Gastric cancer. Oral selenium has only been evaluated in combination with other ingredients and in a specific patient population; its effect when used alone and in other populations is unclear. Details: Population research in Chinese patients has found that high levels of selenium are associated with lower risk of gastric cancer and cancer mortality (97948). However, clinical research does not agree. A large clinical study in patients residing in China shows that taking selenium 37.5 mcg in combination with vitamin C 250 mg and vitamin E 100 IU twice daily for about 7.3 years does not reduce the risk of developing gastric cancer or precancerous gastric lesions when compared with placebo. This combination treatment was not associated with reduced gastric cancer incidence or mortality at the 14-year follow-up of this study (14447,51470). Another clinical study in healthy Chinese adults also shows that taking a combination of selenium 50 mcg, vitamin E 30 mg, and beta-carotene 15 mg daily for 5.2 years does not reduce the risk of gastric cancer when compared with control (4679). It is unclear if these findings are generalizable to populations in geographic locations other than China.
Graves' ophthalmopathy. It is unclear if oral selenium is beneficial for Graves' ophthalmopathy. Details: A small clinical trial in adults with Graves' ophthalmopathy shows that taking selenium 100 mcg twice daily for 6 months is modestly beneficial for reducing disease activity, based on signs and symptoms including pain, swelling, and redness, when compared with placebo (109085).
Hepatitis C. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with hepatitis C shows that taking a combination of selenium 200 mcg, vitamin C 500 mcg, and vitamin E 945 IU daily for 6 months does not have an effect on levels of alanine aminotransferase or viral load when compared with placebo (74377).
HIV/AIDS. It is unclear if oral selenium improves outcomes in patients with HIV. Details: Clinical trials in HIV-positive men and women, most receiving anti-retroviral therapy (ART), shows that taking selenium 200 mcg daily for up to 2 years can reduce HIV-1 viral load, increase CD4 cell counts, and lower the risk of hospitalizations when compared with placebo (15266,74314). However, not all research agrees. Two small clinical trials in HIV-positive patients taking ART shows that taking selenium 100-200 mcg daily for 6-12 months does not reduce the risk for opportunistic infections and does not increase CD4 counts when compared with control (7830,104417). Furthermore, selenium does not seem to benefit patients that are not receiving conventional ART. A large clinical study in HIV-infected pregnant patients in Tanzania with poor access to ART shows that taking selenium 200 mcg daily with prenatal vitamins until 6 months after delivery, does not improve progression of HIV nor pregnancy outcomes when compared with no selenium supplementation (74419). Another large clinical study in HIV-infected and ART-naïve patients in Botswana shows that taking selenium 200 mcg daily for 24 months does not slow HIV progression when compared with placebo (92905).
Hypertension. It is unclear if oral selenium improves blood pressure. Some evidence suggests selenium supplementation may slightly increase systolic blood pressure. Details: A meta-analysis of 5 small clinical studies in adults with various health conditions shows that taking selenium or selenium yeast 100-200 mcg/day for 6-12 weeks may increase systolic blood pressure by about 2 mmHg but does not impact diastolic blood pressure when compared with placebo (110595). However, the validity of the findings from this meta-analysis is limited by the heterogeneity of the included studies, which enrolled patients with preeclampsia, gestational diabetes, obesity, or heart failure. Additionally, all studies were conducted in Iran; it is unclear if these findings are generalizable to populations in other geographic locations.
Hyperthyroidism. It is unclear if oral selenium alleviates symptoms in patients with Graves' disease. Details: A small clinical study in patients with Graves' hyperthyroidism shows that taking sodium selenite 300 mcg daily in addition to treatment with methimazole for 24 weeks does not affect symptoms or recurrence rates when compared with placebo plus methimazole (97089). Oral selenium has also been studied in combination with other supplements. A small preliminary clinical trial in patients with newly diagnosed Graves' disease and low levels of selenium and vitamin D shows that taking selenium 100 mcg daily for 180 days along with vitamin D as cholecalciferol 7000 IU weekly for 270 days, in addition to methimazole, modestly reduces levels of serum free thyroxine and improves quality of life when compared with methimazole alone. However, taking selenium and vitamin D did not affect levels of free triiodothyronine or positive thyroid stimulating hormone (TSH) receptor antibody (109049).
Hypothyroidism. It is unclear if oral selenium improves thyroid hormone balance in elderly individuals, pregnant patients, or patients with subclinical hypothyroidism. In patients with iodine deficiency, selenium supplementation may be harmful. Details: Low selenium levels or selenium deficiency seems to reduce conversion of thyroxine (T4) to triiodothyronine (T3). However, clinical research in healthy elderly patients is conflicting. Although one study shows that taking selenium 100 mcg daily for 3 months increases conversion of T4 to T3 when compared with placebo (17508), a larger study shows that taking selenium 100-300 mcg daily for 6 months does not impact conversion of T4 to T3 when compared with placebo (17509). Additionally, taking selenium can worsen hypothyroidism in people with iodine deficiency. People who are iodine- and selenium-deficient should not receive selenium supplements without concomitant iodine. In these individuals, selenium increases conversion of T4 to T3, but the thyroid gland lacks iodine to synthesize more T4 (1664,14563,14564,14565,17508). Selenium does not have a significant effect on thyroid function when iodine intake is adequate (1664,4844). In pregnant patients with hypothyroidism, clinical research shows that taking selenium does not reduce complications such as pre-eclampsia or preterm birth. However, selenium might improve postpartum thyroid function and decrease the risk of postpartum thyroiditis (17507). Also, taking selenium 200 mcg daily during pregnancy seems to reduce the risk of developing postpartum thyroid dysfunction and permanent hypothyroidism by 41% and 42%, respectively, when compared with placebo in euthyroid pregnant patients who are positive for thyroid peroxidase antibodies (74391). Selenium supplementation has also been studied for subclinical hypothyroidism. Clinical research in females aged 18 to 50 years with or at risk for subclinical hypothyroidism in Slovakia shows that taking selenium 83 mcg daily and myo-inositol 600 mg daily for 6 months modestly reduces thyroid stimulating hormone (TSH) and thyroid auto-antibody titers when compared with baseline. Selenium and myo-inositol supplementation also reduced patient-reported hypothyroid symptoms including fatigue, menstrual cycle irregularity, and intolerance to heat or cold (110591). The interpretation of these results is limited by the lack of a control group. In addition, it is unclear if these effects are due to selenium, myo-inositol, or the combination.
Influenza. Although there is interest in using oral selenium for influenza, there is insufficient reliable information about the clinical effects of selenium for this condition.
Kidney failure. It is unclear if oral selenium is beneficial for improving lipid parameters in patients on hemodialysis. Details: Selenium levels may be low in patients undergoing chronic hemodialysis, and supplementation might be needed (1805,11053). However, clinical research in patients on hemodialysis shows that taking selenium daily for 3 months does not improve the lipid profile when compared with taking placebo (109095).
Lichen planus. It is unclear if topical or oral selenium alleviates oral lichen planus symptoms. Details: A small clinical study in patients with oral lichen planus shows that applying a selenium hydrogel (selenomethionine 14 mcg/gram) twice daily for 6 weeks seems to significantly reduce pain at a 12 week follow-up, but not immediately after use, when compared with applying topical corticosteroids and antifungal agents 2-4 times daily. Taking oral selenium 200 mcg twice daily for 6 weeks seems to be no different than the topical corticosteroids and antifungal treatment at both time points (104422).
Liver cancer. It is unclear if oral selenium reduces liver cancer risk. Details: Preliminary clinical research in China suggest that taking selenium 200 mcg daily for 2-5 years can reduce the incidence of liver cancer when compared with control (74389). The benefit of selenium on prevention of liver cancer in Western countries is unknown.
Lymphedema. It is unclear if oral selenium reduces lymphedema complications. Details: Preliminary clinical research in patients with secondary lymphedema after breast cancer surgery shows that taking a sodium selenite solution 1000 mcg daily for 1 week followed by 300 mcg daily for 2 weeks and then 200 mcg daily for a total of 15 weeks might reduce recurrence of erysipelas, a type of bacterial skin infection, when compared with placebo (15334).
Male infertility. It is unclear if oral selenium, used alone or in combination with other antioxidants, improves pregnancy or live birth rates for couples with idiopathic male infertility. Details: Meta-analyses of 2-3 clinical trials show that taking selenium, alone or in combination with other antioxidants, for 12-26 weeks modestly improves sperm count and motility when compared with placebo. However, pregnancy rates and live birth rates were only studied in one clinical trial each, with no statistical evidence of benefit (109094). Studies included in the analysis used selenium 26-200 mcg daily for 12-26 weeks, either alone or in combination with vitamin A 1 mg, vitamin C 10 mg, and vitamin E 15 mg; vitamin E 400 IU and folic acid 5 mg; lycopene 6 mg, vitamin E 400 IU, vitamin C 100 mg, zinc 25 mg, folate 0.5 mg, and garlic 1000 mg; or N-acetyl-cysteine 600 mg (74526,74493,102968,109094).
Mercury toxicity. It is unclear if oral selenium improves clearance of mercury and reduces symptoms of toxicity. Details: A small clinical trial in Chinese adults environmentally exposed to high concentrations of mercury shows that taking selenium-enriched yeast, containing selenium 100 mcg, daily for 3 months increases urinary excretion of mercury when compared with control (90351).
Muscular dystrophy. There is limited evidence on the oral use of selenium in Duchenne muscular dystrophy. Details: Preliminary clinical research suggests that supplementation with sodium selenite 1 mg daily for 6 months does not improve disease activity in patients with muscular dystrophy (74455).
Obesity. It is unclear if oral selenium is beneficial for weight reduction. Details: A small clinical study in adults with obesity shows that taking selenium 240 mcg daily and following a low-calorie diet for 3 months is no different for weight reduction when compared with following a low-calorie diet alone (104416).
Oral mucositis. It is unclear if oral selenium is beneficial for reducing oral mucositis in patients undergoing radiotherapy. Details: A small clinical study in patients with head and neck cancers shows that taking selenium 200 mcg twice daily for the duration of radiation therapy does not seem to reduce the incidence or severity of oral mucositis when compared with placebo (104421). It is unclear if other doses or routes of administration might be beneficial.
Osteoarthritis. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with osteoarthritis shows that taking a specific selenium-containing combination supplement (Selenium-ACE) does not improve most clinical symptoms when compared with placebo (74449).
Ovarian cancer. It is unclear if oral selenium reduces ovarian cancer risk. Details: Epidemiological research has found that there is no association between dietary selenium intake and the risk of developing ovarian cancer (74342).
Overall mortality. Although oral selenium does not seem to reduce overall mortality risk in most patients, it might have benefit in patients with low nutrient intake. Details: Meta-analyses of clinical research show that selenium supplementation, alone or in combination with other micronutrients, does not reduce all-cause mortality when compared with placebo (15305,90360,97078). Selenium might also not be beneficial when used in combination with non-nutrient supplements. An additional large clinical study in elderly patients in Sweden shows that taking selenium 200 mcg daily plus coenzyme Q10 100 mg twice daily for around 5 years does not reduce the risk of all-cause mortality when compared with placebo. The baseline selenium status of these patients is unclear (92904). Despite these results, some evidence suggests that selenium used with other nutrients might have benefit in patients with low nutrient intake. In a large clinical study, selenium in combination with zinc, vitamin C, vitamin E, and beta-carotene lowered all-cause mortality risk in men, but not women, when compared with control (14109). Researchers speculate that this result occurred because men have a lower intake of dietary antioxidants than women. Another large clinical study in Chinese patients with chronically low nutrient intake shows that taking selenium with beta-carotene and vitamin E decreases stroke mortality, cancer mortality, and total mortality when compared with control (2673).
Pancreatic cancer. It is unclear if oral selenium reduces pancreatic cancer risk. Details: Some epidemiological research has found that increased selenium intake is associated with a 34% lower risk of pancreatic cancer (97093). However, other observational research has found no association (101342).
Pancreatitis. Although there is interest in using oral selenium for pancreatitis, there is insufficient reliable information about the clinical effects of selenium for this condition.
Polycystic ovary syndrome (PCOS). It is unclear if oral selenium is beneficial for PCOS. Details: A small clinical study in patients with PCOS shows that taking selenium (Nature Made) 200 mcg daily for 8 weeks results in a significantly higher pregnancy rate of 19%, compared with 3% in those taking placebo. The incidences of alopecia and acne were reduced by 77% and 73%, respectively. There were also modest reductions in hirsutism severity and serum levels of high sensitivity C-reactive protein (hs-CRP) and dehydroepiandrosterone (DHEA); however, there was no effect on other hormone levels (109096). Another small clinical study in patients with PCOS undergoing in vitro fertilization shows that taking selenium yeast 200 mcg daily for 8 weeks improves measures of insulin sensitivity and reduces serum insulin and fasting blood glucose levels when compared with placebo. However, selenium supplementation does not improve the pregnancy rate or lipid parameters (110596). The effect of selenium supplementation on the live birth rate in this population is unclear. Selenium has also been studied in combination with other supplements for patients with PCOS. A small clinical study in adults with PCOS shows that taking selenium 200 mcg daily for 12 weeks, in conjunction with a combination probiotic product, modestly improves subjective scores of depression, anxiety, and stress when compared with placebo. Taking this combination also modestly reduces total testosterone levels and subjective ratings of hirsutism when compared with placebo (99659). It is not clear if these effects are due to selenium, the probiotic, or the combination.
Postpartum depression. It is unclear if oral selenium is beneficial for postpartum depression. Details: A meta-analysis of two observational studies has found that a high selenium intake is associated with a modestly reduced risk of postpartum depression. The effect of selenium supplementation on symptoms of postpartum depression is unclear. One moderate-sized clinical trial included in this publication shows that taking selenium reduces symptoms of postpartum depression (109091).
Pregnancy-induced hypertension. It is unclear if oral selenium reduces the development of hypertension during pregnancy. Details: A small clinical study in pregnant patients shows that drinking a dietary liquid containing selenium 100 mcg daily for 6-8 weeks seems to decrease the incidence of pregnancy-induced hypertension when compared with placebo (74481).
Premature rupture of membranes (PROM). It is unclear if oral selenium during pregnancy prevents PROM. Details: One clinical trial shows that taking selenium 100 mcg daily from the first trimester of pregnancy until delivery significantly reduces the incidence of PROM to 13%, compared to 34% with placebo (109097).
Radiation-induced diarrhea. It is unclear if oral selenium reduces diarrhea in patients receiving radiation therapy for cancer. Details: A small clinical study in patients with cervical or endometrial cancer shows that taking selenium 500 mcg on days of radiation therapy and 300 mcg on days without radiation therapy reduces the incidence of radiation-induced diarrhea to 20.5%, compared to 44.5% in the control group not taking selenium. This benefit appears to be more pronounced in patients receiving a larger (>1302 mL) planning target volume of radiation (90355).
Rheumatoid arthritis (RA). It is unclear if oral selenium, as selenized yeast, reduces RA symptoms. Details: A small clinical study in patients with RA suggests that taking selenized yeast, providing selenium 200 mcg, daily for 90 days does not improve objective measures of RA when compared with placebo. However, there might be small improvements in quality of life measures (9763).
Schizophrenia. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with schizophrenia shows that taking a combination of selenium (Nature Made) 200 mcg and a combination probiotic mixture (LactoCare, Zisttakhmir Company) daily for 12 weeks modestly improves general positive and negative symptoms of schizophrenia, but not positive or negative scores, when compared with placebo. There were also modest improvements in levels of high-sensitivity C-reactive protein (CRP), fasting glucose, insulin resistance, and insulin sensitivity, but not lipid parameters (109087).
Statin-induced myopathy. Small clinical studies suggest that oral selenium may not improve symptoms of myopathy in patients taking statins. Details: Small clinical studies in patients with statin-induced myopathy suggests that taking selenium (SelenoPrecise, Pharma Nord) 200 mcg daily with or without coenzyme Q10 for 3 months does not improve myopathy symptoms when compared with placebo (92908,92909).
Stroke. It is unclear if intravenous selenium improves neurological outcomes following a stroke. Details: A small clinical trial in patients with a recent first ischemic stroke shows that intravenous sodium selenite pentahydrate (Selenase, Biosyn, Arzenitmittel GmbH) 2000 mcg after admission and then 1000 mcg daily for 5 days modestly improves some, but not all, measures of neurological deficits when compared with placebo (109088). Another small clinical trial in patients with a recent ischemic stroke shows that the same intervention improves some neurological outcome measures on day 7 or at an earlier discharge, but benefits were not maintained at 3 months (109093). The effects of oral selenium on neurological outcomes following a stroke have not been investigated.
Succinylcholine-induced myalgia. It is unclear if oral selenium is beneficial for preventing succinylcholine-induced postoperative myalgia. Details: Clinical research in patients receiving succinylcholine for a sinuscopy shows that taking a single dose of selenium 200 mcg 2 hours before anesthesia induction modestly decreases the incidence of postoperative myalgia at 24 hours. In those taking selenium, 95% of patients had no postoperative myalgia, compared with 77.5% of those taking placebo. Postoperative analgesia requirements were also modestly reduced; however, there was no difference in overall pain or the incidence of muscle twitching (109089).
Thyroid cancer. It is unclear if oral selenium reduces the risk of thyroid cancer in most patients. Details: In 2009, the US Food and Drug Administration (FDA) approved a qualified health claim regarding selenium and thyroid cancer risk. This qualified health claim was based on one weak and limited study. The FDA has determined that it is highly uncertain that selenium supplements reduce the risk of thyroid cancer (102373). More recent observational research in postmenopausal individuals using data from the Women's Health Initiative has found that selenium intake at or above the recommended daily allowance from dietary sources or supplements is not associated with a decreased risk of thyroid cancer (110590).
Ulcerative colitis. Oral selenium has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in patients with ulcerative colitis shows that taking a liquid supplement containing a combination of selenium, fish oil, fructo-oligosaccharides, acacia, vitamin E, and vitamin C daily for 6 months does not improve disease activity scores when compared with placebo. However, taking the combination supplement seems to reduce the need for oral prednisone for symptom control (13757). The effect of selenium alone is unclear. More evidence is needed to rate selenium for these uses.

SILICON

Osteoporosis. Higher dietary intakes of silicon in males and premenopausal females seem to be associated with higher bone mineral density (BMD), but it is unclear whether silicon supplements reduce the risk of osteoporosis. Details: Males and premenopausal females who have dietary intakes of silicon of at least 40 mg daily seem to have higher BMD than those with lower intakes. This could reduce the risk of osteoporosis (10470,12425). However, it is unclear if silicon supplements can reduce the risk for osteoporosis. Silicon intake has also been evaluated in postmenopausal females. Clinical and population-based research suggests that higher silicon intake does not seem to benefit postmenopausal females in general, although it may benefit those on hormone replacement therapy (10470,12425,75118,92135). Bone loss in postmenopausal females is primarily due to bone resorption. Silicon seems to affect only bone formation (12425).

Aging skin. It is unclear if oral silicon is beneficial in patients with aging skin. Details: A small preliminary clinical study in healthy volunteers aged 40-60 years shows that taking a specific product (Exsynutriment by Biotec) containing organic silicon 600 mg in hydrolyzed marine collagen once daily, 15 minutes before breakfast, for 90 days improves skin firmness, hydration, and texture, but not wrinkles, brightness, or softness, when compared with placebo (100837).
Alzheimer disease. Although there has been interest in using oral silicon for Alzheimer disease, there is insufficient reliable information about the clinical effects of silicon for this condition.
Androgenic alopecia. Although there has been interest in using oral silicon for androgenic alopecia, there is insufficient reliable information about the clinical effects of silicon for this condition.
Cardiovascular disease (CVD). Although there has been interest in using oral silicon for CVD, there is insufficient reliable information about the clinical effects of silicon for this condition.
Dental peri-implantitis. It is unclear if oral silicon is beneficial in patients with peri-implantitis. Details: A small, preliminary clinical study in patients aged 18-75 with peri-implantitis shows that a specific choline-stabilized orthosilicic acid product (BioSil, Bio Minerals NV) containing silicon 5 mg and choline 100 mg, taken twice daily for 12 months, does not improve markers of inflammation and periodontal disease (i.e. probing pocket depth, bleeding on probing) when compared with placebo (110028). However, this study may not have been adequately powered to detect a difference between groups. More evidence is needed to rate silicon for these uses.

THIAMINE

Thiamine deficiency. Oral thiamine prevents and treats thiamine deficiency syndromes. Details: Thiamine deficiency is treated with oral thiamine 5-30 mg daily as a single dose or in divided daily doses for one month. For severe deficiency, thiamine up to 300 mg daily can be used (15).Thiamine deficiency can occur in people with malabsorption conditions such as alcohol use disorder, cirrhosis, and gastrointestinal diseases; in those with inadequate intake due to anorexia, nausea, and vomiting; and in those with increased requirements, including pregnancy, increased carbohydrate intake, increased physical activity, hyperthyroidism, infection, and liver disease. However, deficiency is rare with these conditions (15). The elderly might also be at increased risk for subclinical thiamine deficiency (11076).
Wernicke-Korsakoff syndrome (WKS). Parenteral thiamine is effective for treating symptoms of WKS. Details: Parenteral administration of thiamine 5-200 mg daily for 2 days decreases the risk of developing WKS and decreases symptoms of WKS in acute alcohol withdrawal. Between 30% and 80% of alcoholics are suspected to have thiamine deficiency (11075). An optimal dose for treating WKS has not been established; however, early research suggests that a 200 mg intramuscular dose may be more effective than lower doses (11075). In contrast, a moderate-sized clinical trial in adults with a history of heavy alcohol use who were asymptomatic or symptomatic for WKS shows that there is no benefit to administering high doses (300 mg 3 times daily) compared with medium (100 mg 3 times daily) or low (100 mg daily) doses of parenteral thiamine on cognitive or neurological functioning (111690). The study may have been inadequately powered to detect a difference between groups.

Dysmenorrhea. Oral thiamine might reduce pain in some patients with dysmenorrhea. Details: A clinical study in adolescent Iranian females with dysmenorrhea shows that taking thiamine 100 mg alone or along with fish oil 500 mg daily for 2 months moderately reduces pain intensity and duration when compared with placebo (89341). Another preliminary clinical study in Indian females 12-21 years of age with moderate to severe primary dysmenorrhea shows that taking thiamine 100 mg daily for 90 days eliminates pain in 87% of participants when compared to baseline (77820). The validity of this finding is limited by the lack of a placebo group. Furthermore, available research was conducted in India and Iran, so it is unclear if these findings are generalizable to other geographic locations.

Coronary artery bypass graft (CABG) surgery. Intravenous thiamine does not seem to improve outcomes after CABG surgery. Details: A small clinical study in adults undergoing CABG surgery with cardiopulmonary bypass shows that giving intravenous thiamine 200 mg immediately prior to surgery and immediately after surgery does not improve clinical outcomes or lactate levels when compared with placebo (97010). Larger doses of thiamine also don't seem to be beneficial. Another small clinical study in patients receiving CABG with cardiopulmonary bypass shows that giving thiamine 600 mg intravenously on the day of surgery, and 400 mg daily for three postoperative days, does not improve postoperative outcomes when compared with placebo (103000).
Heart failure. Most research suggests that oral or intravenous thiamine does not improve outcomes in patients with heart failure. Details: Observational research suggests that having heart failure is associated with 2.5-fold increased odds of having thiamine deficiency, possibly because of diuretic use, intestinal malabsorption, and metabolism changes. However, it is unclear if thiamine supplementation is beneficial. A meta-analysis of 2 small clinical trials in adults with systolic heart failure and unclear thiamine status shows that thiamine 200-300 mg given orally or by IV for 7-28 days improves left ventricular ejection fraction (LVEF) by 3% when compared with control (97012). However, other meta-analyses and clinical studies in adults with heart failure with or without thiamine deficiency show that taking intravenous, intramuscular, or oral thiamine 100-500 mg daily does not improve LVEF fraction, left ventricular end-diastolic volume, dyspnea, mortality, hospitalization, or exercise tolerance when compared with placebo or control (103002,111682,111686,111688).
Mosquito repellent. Oral thiamine does not seem to repel mosquitos. Details: Clinical research in healthy volunteers shows that taking thiamine does not improve mosquito repellency when compared with taking vitamin C as a control (18016).
Sepsis. Intravenous or oral thiamine, alone or in combination with vitamin C and hydrocortisone, does not seem to reduce mortality or prevent organ failure in sepsis or septic shock. Details: Multiple meta-analyses of small clinical studies in patients with septic shock show that intravenous or oral thiamine 100-500 mg 2-3 times daily for 3-7 days is no better than placebo for improving mortality, end-organ damage, number of ventilator-free days, and duration of intensive care unit (ICU) stay (105443,107717,107727,111689). One meta-analysis suggests that administration of thiamine alone increases the risk of mortality in these patients (111689). Subgroup analyses including only higher quality studies also fail to show a benefit of thiamine (107717). Another recent small clinical trial in patients with septic shock shows that receiving the same dose of intravenous thiamine does not increase vasopressor-free days when compared with placebo (105441). Intravenous thiamine 200 mg every 12 hours has also been evaluated in combination with intravenous vitamin C 1.5-2 grams and hydrocortisone 50-200 mg every 6-12 hours for 4-10 days (HAT therapy). While some retrospective research found HAT therapy to be beneficial (100315,102980,111689), high-quality, prospective clinical research has shown no benefit (105447,109956,111689). Meta-analyses in patients with sepsis and septic shock shows that receiving HAT therapy does not improve mortality, kidney injury, number of ventilator-free days, or ICU length of stay when compared with control (102129,104027,104028,104032,102998,105447,109956,111642,111689). Additionally, the meta-analyses suggest that HAT therapy does not reverse shock or improve sequential organ failure assessment (SOFA) scores (109556,111642). However, one meta-analysis found that HAT therapy shortened the duration of vasopressor use when compared with placebo (111642). Long-term follow up from a study in patients with sepsis-induced respiratory and/or cardiovascular dysfunction shows that receiving HAT therapy does not improve cognitive, psychological, or functional status after 6 months and, for immediate memory scores and development of posttraumatic stress disorder, HAT therapy was less beneficial when compared with placebo (111299).

Acute kidney injury (AKI). It is unclear if oral or intravenous thiamine is beneficial for treating or preventing AKI. Details: Observational research in adults admitted to the intensive care unit (ICU) with AKI has found that treatment with thiamine (dose unspecified) within the first 48 hours of admission is associated with 39% lower odds of in-hospital mortality and 28% higher odds of kidney function recovery when compared with patients that did not receive thiamine. Receiving thiamine was also associated with a 0.5-day reduction in ICU length of stay (107719).
Anxiety. Although there is interest in using oral thiamine for anxiety, there is insufficient reliable information about the clinical effects of thiamine for this purpose.
Cardiac arrest. It is unclear if intravenous thiamine reduces the risk of death after resuscitation from cardiac arrest. Details: A small clinical study in adults resuscitated from cardiac arrest shows that receiving intravenous thiamine 100 mg every 8 hours for 7 days does not reduce 28-day mortality when compare with a normal saline placebo (105442).
Cardiovascular disease (CVD). It is unclear if oral thiamine is beneficial for treating or preventing CVD. Details: Population research in Korea has found that insufficient dietary thiamine intake (daily intake of less than 1.22 mg in males or 1.03 mg in females) is associated with a 16% increased odds of developing angina or myocardial infarction when compared with sufficient dietary thiamine. However, the effects of thiamine supplementation on CVD have not been studied (107725).
Cataracts. Small studies suggest that increased dietary thiamine might help prevent cataracts. Details: Observational research has found that a high dietary intake of thiamine 10 mg daily is associated with 40% lower odds of nuclear cataracts (6378). Other population research has found that higher dietary intake of thiamine is associated with a modestly reduced risk of age-related lens opacification (14301).
Cervical cancer. It is unclear if oral thiamine reduces the risk of developing cervical cancer. Details: Epidemiological research has found that increasing intake of thiamine from dietary and supplemental sources, along with folic acid, riboflavin, and vitamin B12, is associated with a lower odds of precancerous cervical lesions (11074).
Child development. It is unclear if supplementing breastfeeding females with oral thiamine improves infant neurocognitive development. Details: Preliminary clinical research shows that supplementing breastfeeding females with oral thiamine, 1.2-10 mg daily for 22 weeks, starting at 2 weeks postpartum, does not improve most cognitive or neurodevelopmental scores in the child when compared with placebo. However, one subgroup analysis suggests that thiamine supplementation may improve language scores (107726).
Cognitive function. Oral thiamine has only been studied in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy, middle-aged adults shows that taking a combination product containing thiamine hydrochloride 50 mg, other group B vitamins, bacopa, and ginkgo daily for 12 weeks does not improve measures of memory, attention, cognition, mood, or stress reactivity when compared with placebo. Subgroup analysis shows a possible benefit of the combination supplementation on measures of attention in those with an optimal diet at baseline (111334). It is unclear if these findings are due to thiamine, other ingredients, or the combination.
Coronavirus disease 2019 (COVID-19). It is unclear if intravenous or oral thiamine improves clinical outcomes in patients hospitalized with COVID-19. Details: A small observational study of adults admitted to the intensive care unit with COVID-19 has found that treatment with intravenous or oral thiamine 100 mg daily for an average of 7 days is associated with a 63% reduction in the odds of death within 30 days when compared with control. However, there was no associated reduction in duration of hospitalization or mechanical ventilation (107721). In addition, a small observational study of adults with encephalopathy that were mechanically ventilated secondary to COVID-19 has found that taking thiamine 500 mg three times daily orally for 5 days improves neurological manifestations, including ophthalmoparesis and ataxia, when compared with baseline. The validity of this study is limited by the lack of a comparator group (107722).
Critical illness (trauma). It is unclear if oral or intravenous thiamine is beneficial in patients with critical illness. Details: A meta-analysis of critically ill patients shows that treatment with oral or intravenous thiamine 100-600 mg daily for up to 7 days does not affect the need for mechanical ventilation, duration of hospital stay, or mortality when compared with control (107727).
Delirium. It is unclear if oral or intravenous thiamine helps to prevent or treat delirium. Details: In critically ill patients, a meta-analysis of clinical research shows that treatment with oral or intravenous thiamine 100-600 mg daily for up to 7 days reduces the odds of developing delirium by 42% when compared with control (107727). However, some observational research in adults with septic shock has found that receiving intravenous thiamine 400 mg daily with vitamin C 6 grams daily, both in divided doses, is not associated with reduced delirium when compared with control (103001). In non-critically ill, hospitalized adults with altered mental status, retrospective, observational research has also found that administration of oral or intravenous thiamine is not associated with improved cognitive function or reduced in-hospital mortality when compared with control (107723). Preliminary clinical research in adults undergoing an allogeneic hematopoietic stem cell transplant also shows that administering thiamine 200 mg three times a day intravenously for 7 days does not prevent delirium or shorten duration of delirium when compared with placebo (107718).
Dementia. It is unclear if oral thiamine is beneficial for the prevention of dementia. Details: Observational research in patients with alcohol use disorder has found that taking thiamine is associated with a 24% to 46% lower risk of developing dementia when compared with not taking thiamine (102999).
Depression. It is unclear if oral thiamine is beneficial in patients with depression. Details: Meta-analyses of population research in adults has found that high dietary consumption of thiamine is associated with a 10% to 31% lower risk of having depression when compared with low dietary consumption of thiamine. However, this research did not evaluate the effects of thiamine supplementation on depression (107133,107725). One small clinical study in adults with major depressive disorder shows that taking thiamine 300 mg daily in conjunction with fluoxetine 20 mg daily leads to greater improvements in depressive symptoms at 6 weeks when compared to fluoxetine with placebo. This benefit was no longer present at 12 weeks. This suggests that thiamine may accelerate improvement in symptoms during initiation of fluoxetine therapy (97013).
Diabetes. It is unclear if oral thiamine is beneficial for type 2 diabetes or gestational diabetes. Details: A meta-analysis of 6 clinical studies in adults with type 2 diabetes shows that taking thiamine 100-300 mg or its derivative benfotiamine 120-900 mg daily for 1-3 months does not reduce glycated hemoglobin (HbA1c), fasting blood glucose, or postprandial blood glucose when compared with placebo (111681). A large, prospective cohort study in adults without type 2 diabetes suggests that the risk of new-onset diabetes is minimized in adults consuming thiamine 0.75-1.10 mg daily from the diet, while lower and higher thiamine intake levels are associated with an increased risk of new-onset diabetes (111685). Thiamine has also been studied for preventing gestational diabetes. A large, prospective cohort study in pregnant adults suggests that higher supplementation with thiamine during the first and second trimesters is associated with a lower risk of gestational diabetes when compared with lower levels of total thiamine intake. However, this effect was not found for dietary intake of thiamine, only supplementation. Additionally, the participants were mostly Han Chinese adults, limiting the generalizability of the findings to other populations (111680).
Diabetic nephropathy. It is unclear if oral thiamine is beneficial for diabetic nephropathy. Details: A small clinical study in patients with early-stage diabetic nephropathy and microalbuminuria shows that taking thiamine 100 mg three times daily for 3 months decreases urinary albumin excretion, but does not affect glomerular filtration rate (GFR), when compared with placebo (16556).
Diabetic neuropathy. Although there is interest in using oral thiamine for diabetic neuropathy, there is insufficient reliable information about the clinical effects of thiamine for this condition.
Dry eye. Oral thiamine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with dry eye suggests that adding unspecified doses of thiamine and mecobalamin to treatment with daily artificial tears and corticosteroid drops might slightly improve overall symptoms when compared with only artificial tears and corticosteroid drops for 1 month. There were no differences between groups at 2 months (105444). This finding is limited due to incomplete reporting and a lack of adjustment for multiple hypothesis testing.
Dyslipidemia. It is unclear if oral thiamine is beneficial for treating or preventing dyslipidemia. Details: A meta-analysis of 3 clinical studies in adults with type 2 diabetes shows that taking thiamine 100-300 mg or its derivative benfotiamine 120-900 mg daily for 1-3 months does not improve low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, or triglycerides when compared with placebo (111681). Observational research in Korea suggests that insufficient dietary thiamine intake (daily intake of less than 1.22 mg in males or 1.03 mg in females) is associated with 10% higher odds of developing dyslipidemia when compared with sufficient dietary thiamine intake. However, the effects of thiamine supplementation on dyslipidemia have not been studied (107725).
Emergence delirium. It is unclear if intravenous thiamine helps to prevent emergence delirium in patients after surgery. Details: One clinical study in adults in the intensive care unit (ICU) after gastrointestinal surgery shows that receiving intravenous thiamine 200 mg daily for 3 days is associated with up to 84% lower odds of emergence delirium on the first two days, but not on the third day, when compared with a normal saline control (105440).
Fatigue. It is unclear if oral thiamine is beneficial in patients with fatigue. Details: A small clinical crossover study in patients with chronic fatigue and inflammatory bowel disease (IBD) shows that taking thiamine 600-1800 mg daily for 20 days reduces fatigue scores when compared with placebo (105438). Taking oral thiamine 300 mg daily for an additional 12 weeks did not seem to affect fatigue scores when compared with placebo. However, an observational follow-up study found that those who self-continued thiamine for an additional 24 weeks after the study ended reported lower fatigue scores when compared with those who did not self-continue thiamine (107720).
Glaucoma. Although there is interest in using oral thiamine for glaucoma, there is insufficient reliable information about the clinical effects of thiamine for this condition.
Herpes zoster (shingles). It is unclear if subcutaneous thiamine is beneficial in patients with shingles. Details: A small clinical trial shows that receiving subcutaneous thiamine 100 mg injections six times weekly for 4 weeks reduces itching by at least 30% in 67% of patients with herpes zoster. However, thiamine does not appear to significantly reduce pain in most patients (90396).
Hypertension. It is unclear if oral thiamine is beneficial in treating or preventing hypertension. Details: Population research in Korea has found that insufficient dietary thiamine intake (daily intake of less than 1.22 mg in males or 1.03 mg in females) is associated with a 5% increased odds of developing hypertension when compared with sufficient dietary thiamine. However, the effects of thiamine supplementation on hypertension have not been studied (107725).
Impaired glucose tolerance (prediabetes). It is unclear if oral thiamine is beneficial in patients with prediabetes. Details: A very small clinical trial in patients with prediabetes shows that taking thiamine 100 mg by mouth three times daily for 6 weeks modestly decreases 2-hour postprandial plasma glucose levels when compared to baseline and decreases fasting blood glucose levels when compared with placebo (91168).
Kidney failure. Oral thiamine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary, low-quality, clinical research in adults with kidney failure undergoing regular hemodialysis shows that taking oral thiamine 90 mg daily with folic acid 30 mg daily for 96 weeks reduces overall mortality by 67% and improves cognitive scores by 31% when compared with no intervention (107724). It is unclear if this effect is due to thiamine, folic acid, or the combination.
Migraine headache. It is unclear if dietary thiamine is beneficial for the prevention or treatment of migraine headache. Details: A large, retrospective, cross-sectional study suggests that higher dietary intake of thiamine is associated with lower odds of severe headache or migraine, especially in females (111684). The validity of these effects is limited by the subjective outcome measures and retrospective study design.
Pneumonia. It is unclear if thiamine is beneficial for patients with pneumonia. Details: A large retrospective cohort study in adults hospitalized with pneumonia and active alcohol use disorder suggests that parenteral administration of thiamine is associated with reduced 14-day mortality and more frequent discharges home, but not a shorter length of stay or fewer ICU transfers, when compared with no thiamine use. Furthermore, parenteral thiamine doses above 200 mg do not appear to improve mortality but may be associated with longer length of stay and less frequent discharges home when compared with low oral doses of thiamine or parenteral thiamine at doses under 200 mg (111679). The validity of these effects is limited by the retrospective study design.
Ventilator-associated pneumonia (VAP). It is unclear if oral or parenteral thiamine is beneficial for patients with VAP. Details: A retrospective study in adults with VAP in the intensive care unit (ICU) suggests that supplementation with intravenous or oral thiamine may be associated with reduced ICU and in-hospital mortality (111683). The validity of these effects is limited by the retrospective study design. More evidence is needed to rate thiamine for these uses.

TIN

Gingivitis. Dentifrices containing various forms of tin have shown some benefit for improving symptoms of gingivitis; most research has evaluated the use of stannous fluoride. Most research shows that dentifrices containing tin as stannous fluoride reduce gingivitis by a small but clinically meaningful amount. One meta-analysis of clinical research shows that stannous fluoride dentifrices modestly reduce gingivitis when compared with placebo or vehicle control when evaluated using the gingival index or modified gingival index (87068). A clinical study in healthy adults with gingivitis shows that a dentifrice containing stannous fluoride 0.454% and stabilized with zinc phosphate (Colgate Total, Colgate-Palmolive Company), applied twice daily for 6 months, reduces gingival inflammation when compared with baseline. However, the validity of these findings is limited by a lack of statistical comparison to sodium monofluorophosphate (106017). Another meta-analysis of 13 trials shows that using a dentifrice containing stannous fluoride is at least as effective as a dentifrice containing triclosan for reducing symptoms of gingivitis, including gingival bleeding (94409). Also, a clinical study in patients with mild to moderate gingivitis shows that a specific stannous fluoride dentifrice (Crest Pro-Health Clinical Gum Protection, Proctor & Gamble) reduces the number of gingival bleeding sites by 74% after 3 months when compared to baseline; this improvement is significant when compared with a control fluoride dentifrice (98566). Research on the use of other forms of tin has also shown benefit. One large meta-analysis of clinical research shows that gluconate chelated stannous fluoride 0.454% dentifrices applied for up to 3 months improve the average number of bleeding sites by 51% when compared with sodium fluoride or sodium monofluorophosphate dentifrice and 31% when compared with triclosan, regardless of baseline disease severity (106014). Another clinical study in healthy adults with gingivitis shows that an amine fluoride dentifrice containing stannous chloride applied twice daily for 12 weeks reduces gingivitis and gingival bleeding when compared with baseline. Stannous chloride seems to be slightly more effective than sodium monofluorophosphate for reducing gingivitis at 12 weeks (101106).

Dental hypersensitivity. Most research shows that tin is beneficial for reducing dental hypersensitivity, although it may not be as effective as other ingredients. Two meta-analyses of clinical research show that topical application of gel or dentifrice containing tin in the form of stannous fluoride 0.4% for up to 8 weeks improves dental hypersensitivity when compared with placebo (28649,98560). However, it seems to take about 2 weeks before improvements occur. This is in contrast to topical fluoride solution 0.717%, which relieves hypersensitivity in approximately 3-5 minutes (28649,98562). Another clinical study in healthy adults with dental hypersensitivity shows that a dentifrice containing anhydrous stannous fluoride 0.454% with sodium fluoride 0.072% applied twice daily for 8 weeks improves sensitivity and tactile threshold scores when compared with baseline. However, stannous fluoride is less effective than sodium monofluorophosphate for improving sensitivity scores (106015). Tin has also been evaluated in endurance athletes, who are at increased risk for dental erosion. A small clinical study shows that a once daily oral hygiene regimen providing stannous fluoride in both a mouth rinse and chitosan-containing dentifrice improves dental erosion in endurance athletes after about 2 years of use when compared with a fluoridated dentifrice. However, dental hypersensitivity and saliva pH were unaffected (106016).

Dental plaque. Overall, using a dentifrice containing tin in the form of stannous fluoride seems to modestly reduce plaque; however, the improvement might not be clinically meaningful. One analysis of clinical research shows that using dentifrices with stannous fluoride reduces plaque by only a small amount when compared with placebo or vehicle control (87068). When compared to other active dentifrices, results from clinical research are conflicting. Some research shows that stannous fluoride dentifrices reduce plaque by a moderate amount when compared with sodium fluoride dentifrices when measured using the Turesky modification of the Quigley & Hein index, but not when measured by the plaque index (28648). A clinical study in healthy adults with gingivitis shows that a dentifrice containing stannous fluoride 0.454% and stabilized with zinc phosphate (Colgate Total, Colgate-Palmolive Company), applied twice daily for 6 months, reduces plaque when compared with baseline. However, the validity of these findings is limited by a lack of statistical comparison to sodium monofluorophosphate (106017). Additional research shows that stannous fluoride dentifrices reduce plaque similarly to triclosan dentifrices according to the Rustogi Modified Navy Plaque Index. However, when measured using the Turesky modification of the Quigly-Hein Plaque Index, triclosan dentifrices seem to reduce plaque more than stannous fluoride (94409). A clinical study in healthy adults with gingivitis shows that an amine fluoride dentifrice containing stannous chloride applied twice daily for 12 weeks is 33% more effective than a sodium monofluorophosphate dentifrice for reducing dental plaque, as measured by the plaque index, when compared with baseline (101106).
Dry mouth. Preliminary clinical research shows that using a specific gel (Enamelon Preventive Treatment Gel, Premier Dental products Co.) containing tin as stannous fluoride 0.4% each evening for 14 days reduces symptoms of dry mouth, with 70% of patients rating the product at least 'good' for improving symptoms such as discomfort, as well as for improving lubrication and moisturization. However, it seems to be less effective than Biotene Oral Balance moisturizing gel, which was rated at least 'good' for the relief of these symptoms by 84% of patients (98565).
Halitosis. A meta-analysis of four clinical studies including 100 patients shows that using a dentifrice containing tin as stannous fluoride 0.4% (Crest Pro-Health) three times over a 28-hour period improves bad breath by 7.7% at 3-4 hours after a single use, 10.6% after two uses and a sleep (morning breath), and 24.5% after a third use that morning, when compared to a control fluoride toothpaste in individuals with halitosis (98561). The long-term effects of this dentifrice on halitosis are unknown. More evidence is needed to rate tin for these uses.

VANADIUM

Vanadium deficiency. Oral vanadium is effective for the prevention of vanadium deficiency. Details: Taking vanadium is effective for preventing vanadium deficiency (7135).

Athletic performance. Although there has been interest in using oral vanadium for improving athletic performance, there is insufficient reliable information about the clinical effects of vanadium for this purpose.
Cancer. Although there has been interest in using oral vanadium for cancer, there is insufficient reliable information about the clinical effects of vanadium for this purpose.
Diabetes. Small clinical studies suggest that high doses of oral vanadium may improve insulin sensitivity in patients with type 2 diabetes; however, these high doses may be unsafe. It is unclear if lower doses of vanadium have the same effects. Details: Five very small clinical studies including fewer than 40 patients with type 2 diabetes show that taking high oral doses of vanadyl sulfate (50-75 mg twice daily; 31-46 mg elemental vanadium daily) for up to 6 weeks can improve hepatic and peripheral insulin sensitivity and might reduce blood glucose levels when compared to baseline (3055,3056,3057,12557,12558). However, prolonged use of these high doses might not be safe (7135). It is not known if lower doses have the same benefit.
Hyperlipidemia. Although there has been interest in using oral vanadium for hyperlipidemia, there is insufficient reliable information about the clinical effects of vanadium for this purpose.
Impaired glucose tolerance (prediabetes). It is unclear if oral vanadium is beneficial in patients with impaired glucose tolerance. Details: A very small clinical study in overweight or obese adults with impaired glucose tolerance shows that taking vanadyl sulfate 50 mg twice daily for 30 days does not improve insulin sensitivity or glucose metabolism when compared with placebo (92819).
Tuberculosis. Although there has been interest in using oral vanadium for tuberculosis, there is insufficient reliable information about the clinical effects of vanadium for this purpose. More evidence is needed to rate vanadium for these uses.

VITAMIN A

Vitamin A deficiency. Oral vitamin A is effective for treatment and prevention of vitamin A deficiency. Details: Clinical and observational research in children shows that taking vitamin A orally is effective for preventing and improving symptoms of vitamin A deficiency, including xerophthalmia, night blindness, and Bitot's spots (82329,82689,82710,90773). Vitamin A deficiency can occur due to abnormal storage and transport of vitamin A in people with abetalipoproteinemia, protein deficiency, diabetes mellitus, hyperthyroidism, fever, liver disease, and cystic fibrosis (7135). However, research suggests that supplementation with vitamin A may not be necessary for most newborns with vitamin A deficiency. An observational study in newborns with vitamin A levels of 0.43-0.59 mcmol/L or >0.59 mcmol/L found that vitamin A levels increased naturally over the first six months of life, regardless of oral vitamin A supplementation. However, in infants with very low vitamin A levels (<0.43 mcmol/L), vitamin A supplementation was associated with significant increases in vitamin A levels at 6 months of age when compared with no supplementation, suggesting that only newborns with very low vitamin A levels should receive oral vitamin A (107298).

Aging skin. Topical vitamin A (retinol) formulations seem to improve symptoms of aging skin, such as wrinkles and mottled pigmentation. Details: The vitamin A analog tretinoin (Renova) is a prescription drug approved by the U.S. Food and Drug Administration for adjunctive use in reducing fine wrinkles, hyperpigmentation, and tactile roughness of aging facial skin (103711). However, this drug is not interchangeable with non-prescription, commercially available vitamin A products, which have not been as extensively evaluated in clinical research. Although research evaluating non-prescription topical vitamin A shows benefit for reducing wrinkles, most studies have been small and used different formulations. One small study in adults over 40 years of age shows that applying a pea size amount of 0.075% retinol cream to the face daily for 26 weeks seems to reduce deep and fine wrinkling when compared with placebo. Applying a lower dose of 0.04% retinol cream for 13 weeks seems to reduce fine wrinkling to a lesser degree, with no effect on deep wrinkles, when compared with placebo cream (104458). Another small clinical study in adults over 80 years of age shows that applying 2 mL of retinol 0.4% lotion to the upper arm up to 3 times weekly for 24 weeks reduces visible wrinkles when compared with placebo (94683). Two small studies in females ages 33 to 65 show that applying retinol 0.15%, 0.3% and 0.5% in liquid crystal formulation once daily to the face for 2-3 months improves skin pigmentation, elasticity, and wrinkles when compared with baseline (103680,104464). The validity of these two studies is limited by the lack of a comparator treatment. Topical vitamin A is frequently combined with other ingredients in commercial formulations; however these combinations have rarely been studied. A small clinical study in adults over 35 years with skin aging shows that applying a cream containing retinol 0.5%, niacinamide, resveratrol, and hexylresorcinol seems to improve wrinkling and skin tone when compared with baseline (104455). Another small preliminary clinical trial in adults ages 35-65 years with periorbital lines and wrinkles shows that applying a cream containing retinol modestly improves dryness, puffiness, redness, and darkness when compared with baseline. The retinol was conjugated with lactic acid, and the cream contained other nutrient and herbal ingredients It was applied around the eyes each evening, sometimes used in combination with another product each morning (109747).
Bronchopulmonary dysplasia. Intramuscular vitamin A may reduce the risk of bronchopulmonary dysplasia (BPD) in very low birth weight infants when given at a dose of 5000 IU three times weekly for 28 days. Lower doses do not seem to be effective. It is unclear if enteral vitamin A is beneficial for BPD. Details: A meta-analysis of 6 clinical trials in premature infants shows that intramuscular administration of vitamin A every other day or three times weekly for 28 days reduces the risk of BPD by around 33% when compared with control (107297). The results from this meta-analysis are primarily driven by a modestly sized clinical trial in very low birth weight infants which shows that intramuscular administration of vitamin A 5000 IU three times weekly for 28 days reduces the risk of BPD by 15% when compared with a sham control (82195). A subgroup analysis of this trial suggests that infants with the lowest BPD risk estimate based on gestational age, birth weight, sex, ethnicity, and oxygen levels 24 hours after birth appear to benefit more from vitamin A therapy than those with higher BPD risk estimates (107296). Previous research in this area utilized a lower dose of only 2000 IU every other day for 28 days, and showed no significant improvement in the rate of BPD (82331,82613). The evaluation of a higher dose was prompted by research noting that the lower doses evaluated in these earlier studies were unable to achieve serum retinol concentrations above 25 mcg/dL, while doses at or above 5000 IU three times weekly could reach this level (82731). Enteral vitamin A has also been investigated. Meta-analyses of two clinical trials show that supplementation with vitamin A at an average of 5,000 IU daily, staring within four days of birth, does not reduce the incidence of BPD when compared with placebo (109750,109753).
Diarrhea. Vitamin A seems to reduce the incidence of diarrhea in young children. However, it is unclear if oral vitamin A while breastfeeding is beneficial for preventing diarrhea in nursing infants. Details: A meta-analysis of clinical research in children up to age 5 shows that vitamin A supplementation reduces the incidence of diarrhea by 15% and mortality related to diarrhea by 12% when compared with control, usually placebo or no supplementation (109755). However, one small clinical trial in breastfeeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of diarrhea in the nursing infants when compared with placebo (107293).
Measles. High-dose oral vitamin A seems to reduce mortality from measles in children under 2 years of age and may also reduce the incidence of measles in children up to 5 years of age. Details: Meta-analyses of clinical research show that taking vitamin A does not reduce mortality in children with measles when all ages and/or doses are considered (82373,82502,95055,109755). However, in children with measles who are less than 2 years of age, taking vitamin A 200,000 IU orally for at least two doses seems to reduce mortality by up to 83% when compared with placebo (82373,82502). Also, taking vitamin A seems to reduce the incidence of measles in children ages 6 months to 5 years (95055,109755).
Night vision. Oral vitamin A as retinyl palmitate seems to reduce night blindness during pregnancy in malnourished patients. Details: Clinical research shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before and during pregnancy reduces pregnancy-related night blindness by 37% in malnourished patients (6154). Some evidence suggests that zinc supplements might potentiate the effects of vitamin A in restoring sight in zinc-deficient pregnant patients affected by night blindness (8630).
Oral leukoplakia. High-dose oral vitamin A seems to reduce oral leukoplakia lesions in patients that chew tobacco and/or betel nut. Details: Clinical research in patients with tobacco and/or betel nut chewing habits shows that taking oral vitamin A 200,000-300,000 IU weekly for 6-12 months seems to result in remission of leukoplakia lesions in over 50% of participants when compared with placebo (34674,82617). However, it is unknown if vitamin A prevents the development of oral cancer from oral leukoplakia lesions.
Overall mortality. In children at risk for vitamin A deficiency, oral vitamin A seems to reduce mortality. However, it does not seem to reduce mortality in healthy adults. Details: Despite previous debate on whether the programs supplying high-dose vitamin A in low- and middle-income countries with prevalent vitamin A deficiency are safe and effective for reducing child mortality, most experts, including World Health Organization, recommend high-dose vitamin A supplementation for those children (95055,95724,97170,109755). In 2010, a meta-analysis of 17 trials involving over 194,000 patients, showed that vitamin A supplementation reduces all-cause mortality by about 24% in children 6 months to 5 years of age (82559). However, some research published after this meta-analysis shows conflicting results (90773,90777). In fact, the largest clinical trial conducted to date (Deworming and Enhanced Vitamin A; DEVTA), which was published after the analysis and involved one million preschool children, suggests that high-dose vitamin A supplementation does not reduce mortality (90773). However, this trial was limited due to under-resourcing and undetermined patient consent and treatment compliance (90773). Furthermore, in 2017, a meta-analysis including the DEVTA trial along with 46 additional studies involving over 1.2 million preschool children, shows that vitamin A supplementation does reduce all-cause mortality by 12% when compared with control (95055). This meta-analysis was updated in 2022 with no additional studies or changes in conclusions (109755). Adult mortality is not reduced by vitamin A supplementation. In fact, some evidence even shows that vitamin A supplementation increases mortality when administered to healthy adult patients or those with a stabilized disease (15305,34622,90775).
Postpartum complications. Oral vitamin A seems to reduce postpartum diarrhea and mortality in malnourished patients. Details: A large clinical study in malnourished pregnant patients in Nepal shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before, during, and after pregnancy reduces the occurrence of blood and mucus in the stool by 93% and the occurrence of diarrhea by up to 90% during the first 6 months postpartum when compared with placebo (2581). Another clinical study in the same population shows that taking vitamin A (as retinyl palmitate) 23,000 IU weekly before and during pregnancy reduces pregnancy-related mortality by 40% when compared with placebo (6153).
Retinitis pigmentosa. Oral vitamin A supplementation in children with retinitis pigmentosa seems to slow retinal function decline. Details: Observational and clinical research in children with retinitis pigmentosa shows that taking an age-adjusted dose of vitamin A, up to a maximum dose of 15,000 IU daily, modestly attenuates the decline in retinal function when compared with control (83,97167,103677).
Ulcerative colitis. Oral vitamin A supplementation in patients with ulcerative colitis seems to improve clinical response and mucosal healing. Details: A clinical study in adults with symptomatic ulcerative colitis despite treatment with 5-aminosalicylic acid shows that taking vitamin A 25,000 IU daily for 2 months reduces disease severity and increases the rate of clinical response and mucosal healing when compared with placebo. The number needed to treat (NNT) for clinical response is 3; the NNT for mucosal healing is 5 (100329).
Wrinkled skin. Topical vitamin A (retinol) formulations seem to improve photodamage and wrinkles. Details: The vitamin A analog tretinoin (Renova) is a prescription drug approved by the U.S. Food and Drug Administration for adjunctive use in reducing fine wrinkles, hyperpigmentation, and tactile roughness of facial skin (103711). This drug is not interchangeable with non-prescription, commercially available vitamin A products, which have not been as extensively evaluated in clinical research. Still, some research in females ages 35-65 with moderately wrinkled and photoaged skin suggests that commercially available retinol formulations might reduce wrinkles and skin roughness similarly to tretinoin. One study used retinol serum starting at a concentration of 0.25% and increased to 1% over 3 months, compared with tretinoin cream 0.025% gradually increased to 0.1% (103671), while another study compared a gradual release tri-retinol 1.1% cream applied daily for 3 months to tretinoin 0.025% cream (104456). Commercial retinol also seems to be beneficial when compared with placebo. A small study in adults over 40 years old with photodamaged skin shows that applying stabilized retinol 0.1% to the face daily for one year improves wrinkles and mottled pigmentation in over 50% of the participants when compared with a placebo treatment (104463).

Atopic disease. Supplementation with oral vitamin A does not seem to reduce the risk of atopy. Details: Clinical research in infants born in Guinea-Bissau shows that a single dose of vitamin A does not reduce the incidence of atopy when compared with placebo (90779,90780). Furthermore, giving a single dose of vitamin A to some infants, such as low birth weight infants and infants given Bacille Calmette-Guerin (BCG) vaccination, was associated with increased atopy and wheeze (90779).
Fetal and premature infant mortality. Giving oral vitamin A to malnourished adults during pregnancy and postpartum does not seem to reduce fetal, early infant, or first year mortality. Giving oral or intramuscular vitamin A to the infant also does not seem to reduce mortality in most patients. Details: Most meta-analyses of clinical research in malnourished patients suggest that vitamin A supplementation during pregnancy or postpartum does not reduce fetal, early infant, or first year mortality (6152,34601,34602,34627,82479,82566,82567,90774,90776,90782,90784,95057,109750,109753). Also, giving vitamin A supplements or intramuscular vitamin A to low birth weight infants does not appear to reduce mortality in these patients (82195,82431,82498,90778,90781,95053,107296,107297). Furthermore, vitamin A supplementation in term infants from low or middle income countries also does not appear to reduce the risk of mortality at 6 or 12 months of age when compared with placebo (95054,103674). Some evidence from a meta-analysis of clinical research shows that vitamin A supplementation may reduce the risk of mortality at 6 months in Asian infants, although it appears to increase the risk of mortality at 6 months in studies conducted in Africa. It also appears to increase the risk of mortality in female term infants by 12 months (95054).
Intestinal parasite infection. Oral high-dose vitamin A does not seem to prevent reinfection with intestinal parasites. Details: Clinical research in children living in Malaysia that were given albendazole 400 mg daily for 3-4 days for parasitic worms, shows that adding a single dose of vitamin A 200,000 IU does not help to prevent reinfection when compared with placebo (90772).
Melanoma. Oral vitamin A in patients with resected melanoma does not seem to improve survival and disease recurrence. Details: A clinical study in patients with completely resected melanoma shows that taking vitamin A 100,000 IU daily for 18 months does not increase disease-free survival when compared with no supplementation (82670).
Miscarriage. Oral vitamin A given to the mother does not prevent miscarriage or stillbirth. Details: A meta-analysis of clinical research shows that maternal supplementation with oral vitamin A, either alone or in combination with other vitamins, prior to or during early pregnancy does not reduce the risk of miscarriage or stillbirth when compared with control (104462).
Sepsis. Most research shows that oral vitamin A does not reduce the risk of sepsis in premature infants. Details: A meta-analysis of three clinical trials in premature infants shows that providing supplemental enteral vitamin A 1500-5000 IU daily, starting within four days of birth, does not reduce the incidence of sepsis when compared with placebo (109753).
Tuberculosis. Oral vitamin A does not seem to improve tuberculosis disease duration or mortality. Details: Low levels of vitamin A are common in patients with tuberculosis. However, taking vitamin A 2000 IU to 200,000 IU by mouth for 2-24 months does not improve symptoms, decrease disease duration, or reduce mortality when compared with placebo in these patients (82570,103668,109754). This may be due to the fact that vitamin A levels may normalize following the initiation of tuberculosis treatment, even without additional vitamin A supplementation.

Head and neck cancer. Oral vitamin A taken for 2 years does not seem to improve survival or prevent head and neck cancer recurrence. Details: A large clinical study n patients with a history of head and neck cancer shows that taking vitamin A as retinyl palmitate 300,000 IU daily for 1 year, and followed by 150,000 IU daily for another year, does not reduce the risk of second primary tumors or tumor recurrence when compared with placebo. Also, vitamin A does not seem to improve survival or event-free survival (1710).
HIV transmission. Oral vitamin A does not reduce vertical HIV transmission risk. There is some concern that vitamin A might increase HIV transmission through breast milk. Details: Observational and intervention research shows that taking vitamin A orally does not decrease the risk of HIV transmission to the fetus during pregnancy, to newborns during delivery, or to infants during early breast-feeding (6376,82470,95059). Preliminary clinical research also shows that vitamin A supplementation of pregnant adults with HIV infection might increase the risk of HIV transmission to their babies through breast milk (9801).
Lower respiratory tract infections. Oral vitamin A does not reduce the risk for lower respiratory tract infections in children. It is unclear if supplementation of oral vitamin A while breast-feeding reduces the risk of lower respiratory tract infections in nursing infants. Details: Taking vitamin A by mouth does not prevent or reduce symptoms of lower respiratory tract infections, such as cough and fever, in children (82288,82443). Furthermore, some research shows that vitamin A is associated with a slight increase in the risk of respiratory tract infections when administered to children with adequate nutritional status (82288). Additionally, one small clinical trial in breast-feeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of febrile illness or respiratory tract infections in the nursing infants when compared with placebo (107293).

Acne. Although prescription vitamin A analogs are approved to treat acne, it is unclear if non-prescription topical vitamin A products help with acne symptoms. Details: The high-dose vitamin A analogs adapalene (Differin) and tazarotene (Tazorac) are prescription drugs approved by the US Food and Drug Administration for the treatment of acne (103712,103713). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol, which have not been extensively evaluated in clinical research. A small preliminary clinical trial in adolescents and young adults with mild to moderate acne shows that applying topical benzoyl peroxide 2.5% each morning and a topical retinol plus salicylic acid product each evening for 12 weeks modestly improves acne severity and other measures of complexion when compared with baseline. All patients also used the same cleanser twice daily (109748). The validity of this finding is limited by the lack of a comparator group.
Alcohol-related liver disease. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with acute alcoholic hepatitis shows that taking vitamin A in combination with coenzyme Q10 and other vitamins and minerals daily for 6 months does not improve survival when compared with placebo (61392).
Asthma. It is unclear if oral vitamin A is beneficial for preventing asthma in children. Details: An observational study in children has found that higher dietary intake of vitamin A is associated with a lower risk of asthma. Children in the highest quartile of vitamin A intake (median of 2267 IU daily) at 7 years of age had improved lung function and 32% lower odds of asthma at 11-14 years of age when compared with children in the lowest quartile of vitamin A intake (median of 870 IU daily) (107291).
Atopic dermatitis (eczema). It is unclear if supplementation of oral vitamin A while breast-feeding is beneficial for preventing eczema in nursing infants. Details: One small clinical trial in breast-feeding parents shows that supplementation of vitamin A 1800 IU and ergocalciferol (vitamin D2) 600 IU daily for 2 months does not reduce the risk of eczema in the nursing infants when compared with placebo (107293).
Autism spectrum disorder. It is unclear if oral vitamin A is beneficial for improving symptoms of autism. Details: Children with autism spectrum disorder are at increased risk for vitamin A deficiency, and vitamin A levels have been inversely associated with autism symptoms. Preliminary clinical research shows that taking a single dose of vitamin A 200,000 IU slightly improves emotional response, communication, and other symptoms when compared to baseline (97168). The lack of a control group limits the validity of these findings. Another preliminary clinical study in children with autism and vitamin A deficiency shows that taking vitamin A 50,000 IU weekly for 6 months, but not as a single dose of 200,000 IU, seems to improve social impairment scores when compared with control. Controls were children with autism without vitamin A deficiency that did not take a supplement (104459).
Breast cancer. Although vitamin A intake has been associated with a reduced risk for breast cancer, it is unclear if vitamin A supplements are beneficial. Details: Epidemiological evidence has found an association between high intake of vitamin A and a reduced risk of breast cancer. A meta-analysis of epidemiological research has found that the adults with the highest intake of vitamin A, either from diet alone or also from supplements, reduces the odds of developing breast cancer by 16% when compared with the lowest intake (1444,34610,109752). However, the effects of supplemental vitamin A, specifically, are unclear.
Cataracts. It is unclear if oral vitamin A is beneficial for cataract prevention. Details: A large-scale population-based study has found that high dietary intake of vitamin A is associated with a reduced risk of nuclear cataracts (6378). Also, other population research has found that the highest dietary intake of vitamin A is associated with a 17% lower risk of cataracts when compared with the lowest intakes (90786). However, there is conflicting evidence regarding the association between blood levels of vitamin A and the risk of cataracts (90786,90944). It is not known if supplemental vitamin A is beneficial.
Cervical cancer. It is unclear if oral vitamin A is beneficial for cervical cancer prevention. Details: A meta-analysis of clinical research shows that increased vitamin A levels in the blood or higher vitamin A intakes are associated with a reduced risk of cervical cancer. However, this effect is observed when both forms of vitamin A, either retinol or carotenoids, are considered. When only the retinol form is considered, vitamin A supplementation does not seem to reduce the risk of cervical cancer (34613,109752). Also, a meta-analysis of epidemiological research has found that vitamin A intake, either from diet alone or supplements, does not affect the risk of cervical cancer (109752).
Chemotherapy-induced diarrhea. It is unclear if oral vitamin A helps to prevent diarrhea caused by chemotherapy. Details: A very small clinical study in children receiving chemotherapy shows that taking vitamin A orally does not seem to prevent GI adverse effects, including diarrhea and mouth pain, when compared with control (9802).
Child development. Oral vitamin A might improve growth and development in children with vitamin A deficiency, but not in those with good nutritional status. Details: Supplementing with vitamin A 60 mg for up to 9 years does not promote or improve child growth in children with appropriate nutritional status (20132). However, in children with vitamin A deficiency, supplementation with vitamin A may improve growth (82246).
Chronic obstructive pulmonary disease (COPD). There is limited evidence on the oral use of vitamin A in patients with emphysema. Details: Observational research has found that consuming recommended amounts of vitamin A in the diet is associated with 33% lower odds of developing emphysema (103678).
Colorectal adenoma. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination supplement containing selenium, zinc, vitamin A, vitamin C, and vitamin E orally daily for 5 years or until the recurrence of an adenoma reduces the risk of recurrent large-bowel adenomas by about 40% when compared with placebo in patients with large-bowel adenomas (92903). It is not clear if this benefit is due to vitamin A or other constituents.
Colorectal cancer. It is unclear if oral vitamin A is beneficial for colorectal cancer prevention. Details: Taking vitamin A alone or in combination with beta-carotene does not seem to reduce the risk of colorectal cancer (12185).
Coronary artery bypass graft (CABG) surgery. It is unclear if oral vitamin A improves recovery after CABG surgery. Details: Preliminary clinical research shows that taking vitamin A 5000 IU daily (as retinol palmitate) for 21 days starting on the day of CABG surgery reduces time in intensive care after surgery by 46% to 69% compared to a control group not given vitamin A (90783). Supplementation with vitamin A also improves total hospitalization time for those patients with adequate zinc status (90783).
Coronavirus disease 2019 (COVID-19). It is unclear if oral vitamin A is beneficial for the treatment of mild to moderate COVID-19. Details: Clinical research in COVID-19 outpatients treated with hydroxychloroquine shows that taking vitamin A 25,000 IU daily for 10 days modestly reduces the number of patients with symptoms of fever, body ache, and fatigue when compared with placebo. However, there was no effect on the number of patients with cough, shortness of breath, lack of appetite, chest pain, diarrhea, loss of smell, or headache (109745).
Depression. It is unclear if oral vitamin A is beneficial for depression. Details: A meta-analysis of observational research has found that dietary intake of vitamin A is inversely associated with depression. The highest intake of vitamin A was associated with a 17% reduced risk of depression when compared with the lowest intake. Also, vitamin A intake was lower in individuals with depression (109743). The effect of vitamin A supplementation is unclear.
Esophageal cancer. It is unclear if oral vitamin A is beneficial for esophageal cancer prevention. Details: Observational research has found that higher beta-carotene and vitamin A intake is associated with a reduced risk of esophageal cancer (34551,103675). However, evidence from higher-quality clinical research shows that taking vitamin A in combination with beta-carotene does not reduce the risk of esophageal cancer (12185).
Gastric cancer. It is unclear if oral vitamin A is beneficial for gastric cancer prevention. Details: Taking vitamin A alone and in combination with beta-carotene does not seem to reduce the risk of gastric cancer (12185).
Glaucoma. It is unclear if oral vitamin A is beneficial for glaucoma prevention. Details: A meta-analysis of observational research has found that a high dietary intake of vitamin A is associated with a 37% reduced risk of glaucoma when compared with a low intake (109742).
HIV/AIDS. It is unclear if oral vitamin A is beneficial for improving HIV/AIDs outcomes. Details: A meta-analysis of clinical trials and population research shows that maternal vitamin A supplementation of mothers with poor vitamin A status at baseline does not influence child or maternal mortality, hospitalization rate, or HIV/AIDS progression. However, pediatric vitamin A supplementation seems to decrease mortality rates in children with HIV/AIDS when compared with placebo (34529,95059).
HIV/AIDS-related diarrhea. It is unclear if oral vitamin A is beneficial for preventing diarrhea associated with HIV. Details: A large clinical trial shows that taking vitamin A can decrease the rate of diarrhea-specific mortality by up to 92% in vitamin A-deficient children with or without HIV/AIDS (1465). However, a meta-analysis of clinical research shows that taking vitamin A does not significantly reduce diarrhea-specific mortality when only children with HIV/AIDS are considered (82511). But vitamin A does appear to reduce overall mortality in these children by 50% to 63% (1465,82511).
Human papillomavirus (HPV). It is unclear if topical or oral vitamin A is beneficial for the resolution of genital warts caused by HPV. Details: A meta-analysis of small clinical trials in patients with genital warts suggests that the oral prescription drugs isotretinoin and etretinate might promote resolution of warts when compared with baseline. However, the topical prescription drug tretinoin 0.05% cream does not seem to help (104460). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol.
Infant development. It is unclear if intramuscular vitamin A improves the development of low birth weight infants. Details: A meta-analysis of clinical research shows that giving intramuscular vitamin A to very low birth weight infants reduces the risk of chronic lung disease at 36 weeks postmenstrual age by about 13% compared to control (95053). Preliminary clinical research also shows that giving intramuscular vitamin A along with inhaled nitric oxide gas for 3 weeks to low birth weight infants on mechanical ventilation might improve mental development at one year in some of these patients when compared with inhaled nitric oxide gas alone (90778). However, a meta-analysis of clinical research shows that intramuscular vitamin A does not improve neurodevelopment in very low birth weight infants (95053).
Iron deficiency anemia. It is unclear if oral vitamin A is beneficial for the prevention or treatment of anemia due to iron deficiency. Details: Some research in children and pregnant adults without anemia shows that taking vitamin A increases plasma levels of hemoglobin and ferritin, and may reduce the risk of developing anemia (9518,34627). However, another study in pregnant patients, half of whom had anemia at baseline and half of whom did not have anemia, shows that taking 3000 mcg retinol orally in combination with iron and folate does not improve hemoglobin or erythropoietin concentrations when compared with taking iron and folate (9188). In preterm infants with existing anemia, taking vitamin A 5000 IU and vitamin B complex 40 mg daily improves serum ferritin, hemoglobin, and reticulocyte levels and reduces the need for blood transfusions when compared with taking either vitamin alone. Taking vitamin A alone, however, does not improve these outcomes (100330).
Leukemia. It is unclear if oral vitamin A is beneficial for leukemia prevention. Details: Preliminary clinical research in adults with chronic myelogenous leukemia shows that taking a specific vitamin A product (Aquasol, Armour Pharmaceuticals) 50,000 IU orally daily in combination with busulfan therapy does not significantly increase progression-free survival or overall survival when compared with busulfan alone. Furthermore, supplementation with vitamin A plus busulfan seems to increase the percentage of patients who experience grade 2 toxicity by about 5-fold when compared with busulfan alone (82652).
Liver cancer. It is unclear if oral vitamin A is beneficial for liver cancer prevention. Details: Population research has found that vitamin A supplementation or serum levels of vitamin A are not associated with the risk of liver cancer (97169).
Lung cancer. It is unclear if oral vitamin A is beneficial for lung cancer treatment or prevention. Details: Population research has found that increased dietary intake of vitamin A is not associated with a reduced risk of lung cancer (35628). Furthermore, supplementation with vitamin A and beta-carotene seems to increase the risk of lung cancer in smokers or those exposed to asbestos (2642,34675). A large clinical trial in patients with existing lung cancer shows that vitamin A 300,000 IU daily for one year followed by 150,000 IU daily for a second year does not increase survival (1710). However, some clinical research shows that high-dose vitamin A 300,000 IU daily following curative lung cancer resection reduces the risk of new primary tumors in patients heavily exposed to tobacco (7875).
Malaria. It is unclear if oral vitamin A is beneficial for reducing symptoms of malaria in young children. Details: Taking vitamin A orally seems to help decrease symptoms of malaria in children less than 3 years of age living in endemic areas (1464). However, other clinical research shows that single doses of vitamin A 100,000 to 200,000 IU do not improve coma resolution, convulsions, fever, parasite clearance, or mortality in infants and children less than 5 years of age with cerebral malaria (90785).
Multiple sclerosis-related fatigue. It is unclear if oral vitamin A is beneficial for reducing fatigue in patients with multiple sclerosis. Details: Preliminary clinical research in patients with relapsing-remitting multiple sclerosis receiving interferon beta-1a shows that taking vitamin A 25,000 IU (as retinyl palmitate) (Zahravi Pharmaceutical) daily for 6 months followed by 10,000 IU daily for 6 months, improves physical, cognitive, and psychosocial fatigue when compared with placebo (95052).
Necrotizing enterocolitis (NEC). A meta-analysis of several small clinical trials suggests that intramuscular vitamin A does not seem to prevent NEC. Details: A meta-analysis of 3 small clinical studies in very low birth weight infants shows that intramuscular administration of vitamin A 1500-5000 IU every other day or three times weekly for 28 days does not reduce the risk of NEC when compared with a control (107297).
Non-Hodgkin lymphoma. It is unclear if oral vitamin A is beneficial for non-Hodgkin lymphoma prevention. Details: Population research has found that intake of vitamin A at levels above 2330 mcg daily is associated with a 17% lower risk of non-Hodgkin lymphoma when compared with those whose daily intake of vitamin A is less than 642 mcg per day (90945).
Nonmelanoma skin cancer. It is unclear if oral vitamin A is beneficial for nonmelanoma skin cancer prevention. Details: Observational research over 26 years found that higher dietary vitamin A intake is associated with a 12% reduced risk for cutaneous squamous cell carcinoma in healthy patients when compared with lower vitamin A intake (101673).
Oral clefts. It is unclear if oral vitamin A is beneficial for oral cleft prevention. Details: A meta-analysis of observational research has found that periconceptional use of vitamin A, from diet and/or supplements, is associated with a 13% reduced incidence of cleft lip alone or with a cleft palate, but is not associated with the risk of cleft palate alone, in the child (109751).
Osteoarthritis. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with osteoarthritis shows that taking a specific product containing vitamin A in combination with selenium, vitamin C, and vitamin E (Selenium ACE, Carls-Berghs Farmaceutiska AB) does not appear to alleviate symptoms when compared with placebo (74449).
Ovarian cancer. It is unclear if oral vitamin A is beneficial for ovarian cancer prevention. Details: Most observational research has found that increased dietary intake of vitamin A is associated with a reduced risk of developing ovarian cancer (9193,103679,109752). The most recent meta-analysis of epidemiological research has found that adults with the highest intake of vitamin A, either from diet alone or supplements, reduces the odds of developing ovarian cancer by 19% when compared with the lowest intake (109752).
Pancreatic cancer. It is unclear if oral vitamin A is beneficial for pancreatic cancer prevention. Details: A meta-analysis of observational research has found that higher intake of vitamin A is associated with a reduced risk of pancreatic cancer; however, this benefit appears to be limited to only hospital-based cases and studies conducted in Europe (95060). In contrast, a meta-analysis of clinical research shows that taking vitamin A in combination with beta-carotene does not reduce the risk of pancreatic cancer (12185).
Parkinson disease. It is unclear if oral vitamin A prevents Parkinson disease development. Details: Population research has found that blood levels or dietary intake of vitamin A are not associated with the risk of Parkinson disease (91164).
Photoreactive keratectomy. Oral vitamin A has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking a specific product (Evitex capsules, Alcon) containing vitamin A along with vitamin E seems to improve healing after photoreactive keratectomy. High dose (50,000 to 75,000 IU) vitamin A in the form of retinol palmitate taken daily with vitamin E (alpha-tocopheryl nicotinate) 460-590 mg daily seems to accelerate re-epithelialization, reduce haze formation, and improve visual acuity in patients undergoing laser surgery for myopia (348).
Pneumonia. Oral vitamin A does not seem to prevent mortality related to pneumonia in children. However, it is unclear if vitamin A reduces symptom severity and hospitalization in children. Details: Clinical research in children living in developing countries shows that taking vitamin A orally does not prevent mortality related to pneumonia (1466,82362,82504,82717,109749). However, the evidence related to symptom duration and severity is mixed. A large study and early meta-analyses show that vitamin A does not prevent pneumonia or decrease the severity or length of hospitalization in children with pneumonia (1466,82362,82504,82717). A more recent meta-analysis also shows that giving vitamin A to children at or below 5 years of age does not affect the duration of hospitalization (109755). The best evidence to date comes from a recent meta-analysis of randomized clinical trials. This meta-analysis shows that, when given in combination with conventional therapy to children up to 10 years of age, vitamin A reduces the duration of symptoms including fever, cough, lung rale, and shortness of breath, as well as the duration of hospitalization and time to a negative X-ray, when compared with conventional therapy alone (109749). However, the number of trials evaluating each endpoint is small and more research is needed to confirm these findings.
Prematurity. It is unclear if vitamin A reduces the duration of hospitalization for premature infants. Details: A meta-analysis of four randomized controlled trials in preterm infants shows that providing supplemental enteral vitamin A 1500-5000 IU daily, starting within four days of birth, does not reduce the duration of hospitalization when compared with placebo (109750).
Prostate cancer. It is unclear if oral vitamin A is beneficial for prostate cancer prevention. Details: Observational studies suggest that dietary intake of vitamin A is not associated with a reduced risk of prostate cancer (14134).
Psoriasis. It is unclear if topical vitamin A is beneficial for psoriasis symptoms. Details: The vitamin A analog tazarotene (Tazorac) is a prescription drug that is approved by the U.S. Food and Drug Administration to treat stable plaque psoriasis covering up to 20% body surface area (103713). This drug is not interchangeable with non-prescription, commercially available vitamin A products, such as retinol.
Radiation proctopathy. It is unclear if oral vitamin A is beneficial for reducing chronic radiation proctopathy symptoms. Details: A small clinical study in patients experiencing chronic radiation proctopathy caused by pelvic radiotherapy shows that taking retinol palmitate 10,000 IU daily for 90 days might reduce rectal symptoms when compared with placebo (82350).
Retinopathy of prematurity. Most small studies show that oral or intramuscular vitamin A does not reduce the risk of retinopathy of prematurity (ROP). Details: A meta-analysis of 4 small clinical studies in very low birth weight infants shows that intramuscular administration of vitamin A 2000-10,000 IU every other day or three times weekly, or oral vitamin A 2000 IU daily, for 28 days does not reduce the risk of ROP when compared with a control (107297). Another meta-analysis of clinical research shows that providing supplemental enteral vitamin A 1500 IU or an average of 5000 IU daily, starting within four days of birth, does not reduce the incidence of severe ROP (109750,109753). However, a very small clinical study in preterm infants, which was not included in the meta-analysis, shows that receiving retinol palmitate drops 3000 IU/kg daily for 28 days reduces the risk of ROP by 88% when compared with no treatment (103672).
Urinary tract infections (UTIs). It is unclear if adding oral vitamin A to antibiotic therapy is beneficial for symptoms of acute pyelonephritis in young females. Details: A small clinical study in females 2-12 years of age with a first occurrence of acute pyelonephritis shows that taking vitamin A 1500 units/kg daily for 10 days in conjunction with antibiotics decreases the duration of fever by about 1.3 days and reduces urinary frequency by about 1.5 episodes per day when compared to taking placebo with antibiotics. Taking vitamin A might also reduce the occurrence of moderate or severe renal scarring after 6 months when compared with placebo (100327). The validity of these findings is limited by small study size and a high dropout rate.
Warts. It is unclear if topical or oral vitamin A improves the resolution of viral warts. Details: A meta-analysis of observational and clinical research in patients with viral warts suggests that receiving prescription oral retinoids (isotretinoin, acitretin, etretinate) seems to produce a 61% rate of wart resolution. Prescription topical retinoids seems to produce a 64% rate of wart resolution (104461). These drugs are not interchangeable with non-prescription, commercially available vitamin A products, such as retinol. More evidence is needed to rate vitamin A for these uses.

VITAMIN B12

Imerslund-Grasbeck disease. Intramuscular vitamin B12 is effective for patients with this condition. Details: Administering intramuscular vitamin B12 (hydroxocobalamin) 1 mg daily for 10 days, followed by monthly injections for the remainder of a patient's life, is effective for treating familial selective vitamin B12 malabsorption (Imerslund-Grasbeck disease) (15,82862).
Vitamin B12 deficiency. Administering vitamin B12 orally, intramuscularly, or intranasally is effective for preventing and treating vitamin B12 deficiency. Details: Vitamin B12 deficiency has varying definitions but is often defined as vitamin B12 (cobalamin) levels less than 180-200 pmol/L (or 240 pg/mL). Some believe that only intramuscular vitamin B12 is effective for treating vitamin B12 deficiency. However, clinical research shows that oral therapy increases cobalamin levels similarly to intramuscular administration, even in patients with pernicious anemia or malabsorption, if a high enough dose is given (2909,2911,2915,9335,82832) (82836,82949,82860,103976,103972,107141,107144). Some evidence suggests that the most effective oral dose is between 647-1032 mcg daily (13106). However, in certain situations, intramuscular treatment might be more appropriate. Guidelines by the British Committee for Standards in Hematology recommend only intramuscular vitamin B12 for initial treatment of severe vitamin B12 deficiency in patients with pernicious anemia, malabsorption disorders, or neurological involvement (94722). Intramuscular vitamin B12 is also appropriate in patients with diarrhea or vomiting and those likely to be nonadherent (103972). Vitamin B12 deficiency is especially common in older adults, primarily due to lack of intrinsic factor and malabsorption (2915,2919,9335). Daily supplementation with vitamin B12 50-100 mcg might be needed to correct deficiency (10126), while daily doses of 25-37.5 mcg help to maintain normal levels over time (9335). In addition to supplements, foods such as milk and bread fortified with vitamin B12 can be used and are approximately 55% to 60% absorbed by people over 60 years of age (10124). Vitamin B12 deficiency is also common in patients that have had gastric surgery, including gastrectomy and bariatric surgery (107144,107145). Taking vitamin B12 in the doses found in multivitamins or generic vitamin B supplements does not seem to prevent vitamin B12 deficiency following bariatric surgery (107145). However, taking methylcobalamin 500 mcg daily is beneficial for treating vitamin B12 deficiency associated with a total gastrectomy and taking cyanocobalamin 5000 mcg daily is beneficial for preventing vitamin B12 deficiency following gastric bypass (107144). Other people at risk for vitamin B12 deficiency include strict vegetarians who eat no animal products (vegans) and people with increased vitamin B12 requirements associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, and hepatic and kidney disease. Moderate consumption of animal products may not be sufficient to restore and maintain vitamin B12 levels, especially in adolescents who had consumed macrobiotic (vegan type) diets for the first 6 years of life. High dietary intake of vitamin B12 or supplements is usually needed in order to restore and maintain optimal vitamin B12 levels in these adolescents (10125).

Cyanide poisoning. Intravenous hydroxocobalamin (Cyanokit) is likely effective as an antidote for patients with suspected or known cyanide toxicity due to inhalation, ingestion, or skin exposure. Details: Treatment of cyanide poisoning with hydroxocobalamin (Cyanokit) up to 10 grams has been approved by the US Food and Drug Administration (FDA) and recommended by the Australian Resuscitation Council (82870,82905,82906). Hydroxocobalamin is also FDA-approved for treating cyanide toxicity during pregnancy (82904).

Canker sores. Sublingual or topical vitamin B12 seems to reduce canker sore symptoms. Details: Clinical research in patients with canker sores shows that applying a topical ointment containing vitamin B12 500 mcg in four divided doses daily for 2 days reduces pain levels by 80% when compared with a control ointment not containing vitamin B12 (96176). Other preliminary clinical research shows that taking vitamin B12 1000 mcg sublingually daily for 6 months reduces the duration of canker sore outbreaks, the number of ulcers, and level of pain when compared with placebo in patients with normal vitamin B12 levels (17242).
Hyperhomocysteinemia. Oral vitamin B12 in combination with folic acid, and sometimes with vitamin B6, reduces homocysteine levels. Details: While folic acid 0.5-5 mg daily lowers fasting homocysteine levels by an average of 25%, adding vitamin B12 0.5 mg daily produces an additional decrease of about 7% on average (6883,9400,9401,9405,9409,50145,107136). Vitamin B12 in combination with folic acid and other vitamins also reduces homocysteine levels in patients with kidney failure, sickle cell disease, and those receiving nitrous oxide general anesthesia (1489,6883,6884,7289,7881,9324,9414,9415,9416,9481,82941). Some researchers recommend routine use of vitamin B12 with homocysteine-lowering regimens to avoid the risk of neuropathy in people with undetected vitamin B12 deficiency (9405). Using vitamin B12 alone has a limited effect on homocysteine levels, and probably only in those people with vitamin B12 deficiency (2147,9410,9512). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,2147,3323,9402,9405,9408,9409). Clinical research suggests that supplementation with folic acid, pyridoxine, and vitamin B12 decreases homocysteine levels and reduces the atherosclerosis progression in patients at risk for atherosclerosis when compared with placebo (50133,50056,82806). However, other research suggests that elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50%, and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9400,9405,9409,96417). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem improve endothelial function or help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50373,50314,97619). There is also some debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials including over 44,000 patients shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo in patients at risk or with a history of CVD (97619). Also, a meta-analysis in adults with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and vascular death by 11% when compared with placebo (107136).
Postherpetic neuralgia. Subcutaneous injections of vitamin B12 seem to reduce postherpetic neuralgia symptoms. Details: Clinical research in patients with subacute herpetic neuralgia shows that subcutaneous injection of vitamin B12 (methylcobalamin) 1000 mcg six times weekly for 4 weeks reduces pain when compared with oral vitamin B12 or subcutaneous lidocaine (90394). Another clinical study shows that administering local subcutaneous injections of methylcobalamin 1000 mcg plus lidocaine up to 20 mg daily for 12 injections over 14 days, starting within 7 days of the onset of subacute ophthalmic herpetic neuralgia, decreases the mean pain score by 63% to 79% when compared with intravenous lidocaine and intramuscular methylcobalamin. Less than 2 patients need to be treated to achieve a pain reduction to ≤3 out of 10. Healing of rash, itching, numbness, and tingling were also improved (96175). Additional clinical research in patients with postherpetic pain and itching shows that this same dosing regimen of subcutaneous vitamin B12 reduces pain and analgesic requirements when compared to baseline (90396).

Age-related cognitive decline. Oral vitamin B12 does not seem to improve cognitive function in older adults when used alone or in combination with other B vitamins. Details: Taking vitamin B12 100-1000 mcg plus folic acid 400-2000 mcg, with or without vitamin B6 3-50 mg, daily for up to about 2 years does not seem to improve tests of cognitive function in adults aged 65 or older, most of whom do not report cognitive impairment at baseline (14392,50225,50510,90392,107140). Also, supplementation with vitamin B12 does not seem to improve cognitive function in elderly individuals with low vitamin B12 levels (12305).
Alzheimer disease. Oral vitamin B12, when used in combination with other B vitamins, does not seem to improve cognitive function in patients with Alzheimer disease. Details: Clinical research in patients with probable Alzheimer disease using routine medication shows that taking vitamin B12 1 mg, folic acid 5 mg, and vitamin B6 25 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, a meta-analysis of clinical research in elderly adults with mild cognitive impairment or dementia shows that taking vitamin B12, usually with other B vitamins, does not improve cognitive function (50510). Observational research has also found that higher vitamin B12 intake over 3 years in a population consuming a folate-fortified diet is not associated with a decreased risk of developing Alzheimer disease (15270). In contrast, preliminary clinical research in patients with probable Alzheimer disease who are not consuming a folate-fortified diet shows that taking vitamin B12 50 mcg daily plus folic acid 1.2 mg daily for 6 months modestly improves some measures of cognitive performance and decreases levels of homocysteine when compared with placebo (107150). More research is needed to determine if any changes in this latter study are clinically relevant.
Cataracts. Oral vitamin B12 does not seem to reduce cataract development. Details: Clinical research in women with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg daily, vitamin B6 50 mg daily, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts and seems to increase the risk of cataract extraction by 28% when compared with placebo (96149).
Circadian rhythm sleep disorders. Oral vitamin B12 does not seem to improve sleep disorders. Details: Oral vitamin B12 (methylcobalamin) does not seem to be effective for treating delayed sleep phase syndrome. Methylcobalamin 0.5-1 mg three times daily, with or without bright light therapy, also does not seem to help people with primary circadian rhythm sleep disorders (1344,1345,1346,1347,1348).
Cognitive impairment. Oral vitamin B12 does not seem to be beneficial for older adults with cognitive impairment. Details: A meta-analysis of clinical research in elderly adults with mild cognitive impairment or dementia shows that taking vitamin B12, usually with other B vitamins, does not improve cognitive function (50510). One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374).
Fall prevention. Oral vitamin B12 does not seem to reduce the risk of falls. Details: Clinical research shows that taking B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg, daily for 2 years does not prevent falls when compared with placebo in elderly individuals also taking vitamin D (96148).
Osteoporosis. Oral vitamin B12 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in elderly patients or patients with a history of cerebrovascular disease shows that taking vitamin B12 500 mcg and folic acid 0.4-2 mg, with or without vitamin B6 25 mg, daily for 2-3 years does not seem to reduce the risk for osteoporotic fractures when compared with placebo (90377,90393). A 5-7 year follow-up of this research has also found no benefit (103981).
Physical performance. Oral vitamin B12 does not seem to improve physical performance in older adults. Details: Clinical research shows that taking B vitamins, including folic acid 400 mcg and vitamin B12 500 mcg, daily for 2 years does not increase hand strength or improve performance such as walking when compared with placebo in elderly individuals also taking vitamin D (96148).

Age-related macular degeneration (AMD). Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B12 1000 mcg, folic acid 2.5 mg, and vitamin B6 50 mg daily, reduces the risk of developing AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or at least three risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B12, other ingredients, or the combination.
Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if high-dose intramuscular vitamin B12 improves the prognosis of ALS. Details: A clinical study in patients with ALS symptoms for 3 years or less shows that intramuscular vitamin B12 (methylcobalamin) 25-50 mg twice weekly for 3.5 years does not slow functional decline or increase the time until ventilation or death when compared with placebo. However, other clinical research in patients with early-stage ALS shows that intramuscular methylcobalamin 50 mg twice weekly for 16 weeks is associated with slower functional decline and a longer period of time until death or full ventilation when compared with placebo (104947,111556). These effects seem to be particularly notable in fine and gross motor skills, but not bulbar or respiratory functions. Furthermore, vitamin B12 and riluzole slowed clinical progression of ALS more than riluzole alone (111556).
Angioplasty. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B12 400 mcg, folic acid 1 mg, and vitamin B6 10 mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412,34540). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, pyridoxine, and vitamin B12 followed by oral administration of folic acid 1.2 mg, pyridoxine 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151,34540). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B12, other ingredients, or the combination.
Anxiety. Although there is interest in using oral vitamin B12 for anxiety and panic attacks, there is insufficient reliable information about the clinical effects of vitamin B12 for these uses.
Asthma. Although there is interest in using oral vitamin B12 for asthma, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
Atherosclerosis. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with intermediate risk for coronary heart disease shows that taking vitamin B12 100 mcg, aged garlic extract 250 mg, folic acid 300 mcg, vitamin B6 12.5 mg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B12, other ingredients, or the combination.
Atopic dermatitis (eczema). It is unclear if topical vitamin B12 reduces the severity of eczema. Details: Preliminary clinical research shows that applying a specific topical vitamin B12 0.07% cream (Regividerm) twice daily reduces the extent and severity of atopic dermatitis when compared with placebo (15765).
Attention. Although there is interest in using oral vitamin B12 for improving attention and focus, there is insufficient reliable information about the clinical effects of vitamin B12 for this use.
Cancer. It is unclear if oral vitamin B12 reduces overall cancer risk when used in combination with other B vitamins. Details: An ancillary clinical study in middle-aged and elderly adults with cardiovascular disease shows that taking a combination of vitamin B12 (cyanocobalamin) 0.02 mg, folic acid 0.56 mg, and vitamin B6 3 mg, with or without eicosapentaenoic acid (EPA) 400 mg plus docosahexaenoic acid (DHA) 200 mg, for a median of 4.7 years does not reduce the risk of cancer when compared with placebo (90666). An additional secondary analysis of clinical research in patients recovering from stroke or transient ischemic attack shows that taking vitamin B12 500 mcg, folic acid 2 mg, and vitamin B6 25 mg daily for around 3.4 years does not reduce the risk of cancer when compared with placebo (90378). The validity of these findings is limited because the studies were not designed nor adequately powered to test for cancer risk.
Cardiovascular disease (CVD). Oral vitamin B12, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly reduce the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B12 in combination with folic acid and/or vitamin B6 does not seem to reduce the risk for secondary death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, other research shows that taking vitamin B12 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). It is unclear which specific combination of B vitamins, if any, might be optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
Cervical cancer. It is unclear if oral vitamin B12 reduces cervical cancer risk. Details: Some epidemiological evidence has found that increasing vitamin B12 intake from dietary and supplement sources, along with folic acid, thiamine, and riboflavin, might decrease the risk of precancerous cervical lesions (11074). Also, an analysis of two case control studies has found that increased intake of vitamin B12 is associated with a 75% reduced odds of cervical cancer (34609).
Chemotherapy-induced peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients receiving chemotherapy shows that a combination of B vitamins that includes vitamin B12 (cyanocobalamin) 1000 mcg, taken daily starting one week prior to treatment and finishing 12 weeks after treatment is completed, does not prevent peripheral neuropathy when compared with placebo (96173).
Child development. It is unclear if oral vitamin B12 is beneficial for child development. Details: Population research has found that daily dietary intake of less than 2.26 mcg vitamin B12 in the third trimester of pregnancy is associated with an increased risk of poorer outcomes in the offspring for some measures of speech and mathematics ability, including vocabulary at 24 months, combining words at 38 months, speech intelligibility at 6 years, and math comprehension between ages 8-11 years, when compared with dietary intakes of at least 2.26 mcg daily. There was no association between prenatal vitamin B12 intake and reading or spelling abilities, vocabulary at other ages, or full-scale Intelligence Quotient (IQ) at ages 8 or 15 (107143).
Chronic obstructive pulmonary disease (COPD). It is unclear if oral vitamin B12 reduces the risk of COPD. Details: Clinical research in patients with COPD shows that taking vitamin B12 500 mg daily for 8 weeks modestly improves endurance on the cycle ergometer, but does not improve oxygen consumption, when compared with placebo (96172).
Cognitive function. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy, middle-aged adults shows that taking a combination product containing vitamin B12, other B vitamins, bacopa, and gingko biloba twice daily for 12 weeks does not improve measures of memory, attention, cognition, mood, or stress reactivity when compared with placebo (111554).
Colorectal cancer. It is unclear if oral vitamin B12 reduces colorectal cancer risk. Details: Some epidemiological evidence has found that increased dietary intake of vitamin B12 is associated with a reduced risk of developing colorectal cancer (90383). However, preliminary clinical research shows that taking vitamin B12 1 mg, folic acid 2.5 mg, and vitamin B6 50 mg daily for up to 7.3 years does not reduce the risk of colorectal adenoma in females at high risk for cardiovascular disease (90389). Furthermore, a secondary analysis of clinical research in elderly patients suggests that taking vitamin B12 500 mcg and folic acid 400 mcg daily for 2 years might increase the risk of colorectal cancer when compared with placebo (90393).
Coronavirus disease 2019 (COVID-19). It is unclear if oral vitamin B12 is beneficial for patients with COVID-19. Details: A small observational study in hospitalized patients with COVID-19 pneumonia has found that higher plasma vitamin B12 levels may be associated with an increased risk of transfer to intensive care or death than lower plasma levels. However, when multivariate regression was conducted, only patient age was associated with worsened outcomes. Additionally, the total study population was small, with only nine of 49 patients experiencing the worsened outcomes (107138).
Dementia. It is unclear if oral vitamin B12 reduces the risk of developing dementia. Details: A large cohort of Danish adults has found that vitamin B12 levels or intake does not seem to impact the risk of developing Alzheimer disease or other dementias (104922). However, vitamin B12 might be beneficial in specific patient populations. A small observational study in patients with Parkinson disease has found that higher vitamin B12 levels (648.5 ng/L) are associated with a lower risk of developing dementia when compared with lower vitamin B12 levels (452 ng/L) (103975). It is not yet known if supplementation with vitamin B12 reduces the risk for dementia in these patients.
Depression. It is unclear if oral vitamin B12 is beneficial for reducing depression risk. Details: A meta-analysis of epidemiological research has found that the highest dietary intake of vitamin B12 is associated with a 14% reduced risk of depression. However, in a sub-analysis, this association was not significant in males (107133). In contrast, one epidemiological study in older males included in the analysis has found that daily dietary intake of at least 4.79 mcg vitamin B12 is linked with a 58% lower risk of depression when compared with daily intake of less than 3.16 mcg. In this study, this inverse association was not observed in females (96168). Other observational research has found that low-normal serum vitamin B12 levels are associated with a 3.8 times increased risk for depression during pregnancy when compared with normal vitamin B12 levels (102384). It is unclear if increased intake of vitamin B12 through the diet or supplements reduces the risk for depression or is beneficial for treating symptoms of depression in any population. However, a meta-analysis of clinical research in elderly populations shows that supplementation with vitamin B12 100-1000 mcg daily, usually in combination with folic acid 400-2000 mcg daily, does not reduce symptoms of depression. Most individuals in these studies were not specifically diagnosed with depression (107140).
Diabetes. It is unclear if oral vitamin B12 improves glycemic indices or prevents loss of skeletal muscle in patients with diabetes. Details: A small clinical study in patients with diabetes in India who are stabilized on metformin and/or a sulfonylurea shows that taking vitamin B12 (methylcobalamin) 500 mcg with or without folic acid 5 mg daily for 8 weeks seems to reduce glycated hemoglobin (HbA1C) by 1.3% to 1.5%, compared with a 0.3% increase with placebo (104917). This study is limited due its small sample size and lack of blinding. In elderly adults with type 2 diabetes, population research has found a lower dietary intake of vitamin B12 (average of 11.2 mcg daily) in individuals with a loss of skeletal muscle mass of at least 1.2%, compared with an average intake of 13.4 mcg daily in those with a skeletal muscle mass loss of less than 1.2%. However, further analysis determined that any relationship between vitamin B12 intake and loss of skeletal muscle mass was only significant in individuals with insufficient energy intake overall (107151).
Diabetic neuropathy. Small clinical studies suggest that oral vitamin B12 may modestly improve pain in patients with diabetic neuropathy. Details: Two small clinical studies in patients with diabetic peripheral neuropathy show that taking vitamin B12 (methylcobalamin) 1-1.5 mg for 4-12 months modestly improves pain when compared with baseline or placebo (82841,104923). Some research also shows that vitamin B12 may be beneficial in combination with other ingredients. Studies have evaluated products containing vitamin B12 (methylcobalamin or cyanocobalamin), benfotiamine, and vitamin B6 daily for 9-12 weeks (82931,82939); and vitamin B12 (methylcobalamin) 2 mg, folic acid (L-methylfolate) 3 mg, and vitamin B6 (pyridoxal-5'-phosphate) 35 mg (Metanx; Pamlab) daily for 24 weeks (90375).
Diarrhea. It is unclear if oral vitamin B12 is beneficial for reducing diarrhea in children. Details: Preliminary clinical research in children aged 6-30 months from low- and middle-income countries shows that taking vitamin B12 at twice the recommended dietary allowance, with or without folic acid, does not reduce the risk for diarrhea when compared with placebo (90391).
Fatigue. It is unclear if intramuscular vitamin B12 is beneficial for improving well-being in those with fatigue or tiredness. Details: A small crossover trial in patients complaining of tiredness or fatigue shows that receiving intramuscular injections of vitamin B12 (hydroxocobalamin) 5 mg twice weekly for 2 weeks seems to improve general well-being and happiness, and has a trend toward improving fatigue, when compared with placebo (10127). The validity of this study is limited by a large drop-out rate and unstandardized outcome measures.
Hearing loss. Oral vitamin B12 has only been evaluated in combination with adenosine triphosphate; its effect when used alone is unclear. Details: A small observational study in adults with idiopathic sudden sensorineural hearing loss has found that taking vitamin B12 1.5 mg with adenosine triphosphate 300 mg daily for 8-16 weeks is associated with modestly reduced hearing loss at 4-6 months after starting treatment when compared with taking the combination for less than 8 weeks (104924). This finding is limited due to its observational nature and lack of a control group.
Hepatitis C. It is unclear if intramuscular vitamin B12 is beneficial for sustaining viral response in patients with chronic hepatitis C infection. Details: A small clinical study in patients with chronic hepatitis C infection shows that intramuscular vitamin B12 (cyanocobalamin) 5000 mcg every 4 weeks along with standard care improves sustained viral response when compared with standard of care alone (90386).
Hypertriglyceridemia. It is unclear if oral vitamin B12 is beneficial for reducing triglyceride levels. Details: Some evidence shows that taking vitamin B12 7.5 mcg with fish oil 5 grams might be superior to fish oil alone when used daily to reduce total serum cholesterol and triglycerides. This suggests vitamin B12 might have an independent effect in lowering serum cholesterol and triglycerides, but further investigation is needed to confirm this effect (8694).
Infant development. It is unclear if taking oral vitamin B12 during pregnancy is beneficial for improving infant development. Giving oral vitamin B12 to infants does not seem to be beneficial. Details: Clinical research shows that supplementation with vitamin B12 50 mcg daily from less than 14 weeks gestation until 6 weeks postpartum does not improve cognitive development in infants by 9 months of age when compared with placebo (96174). When these children were evaluated at 30 months of age, a very small benefit of vitamin B12 on expressive language was identified; however, there was no effect on cognition, receptive language, fine motor skills, or gross motor skills (100169). It is unknown whether a longer duration of postpartum supplementation or supplementation in specific populations might be beneficial. Vitamin B12 supplementation in infants has also been evaluated. A large clinical trial in marginally stunted Nepalese infants aged 6-11 months shows that giving vitamin B12 (cyanocobalamin) 2 mcg daily for 12 months reduces homocysteine levels, but does not improve motor or cognitive development, when compared with placebo (104926).
Inflammatory bowel disease (IBD). Although there is interest in using oral vitamin B12 for IBD, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
Lung cancer. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: The association between vitamin B12 and lung cancer is unclear. Some population research found no relationship between blood levels of vitamin B12 and lung cancer (9454). However, other observational research involving over 5,000 case-control pairs found that higher vitamin B12 levels are linked with an increased risk for lung cancer (102383). It is unclear if increased intake of vitamin B12, either through the diet or supplementation, directly affects the risk of lung cancer.
Male infertility. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A retrospective study in adult males with idiopathic and varicocele-related infertility suggests that taking a combination product containing vitamin B12 1.5 mcg, L-carnitine, acetyl L-carnitine, citric acid, selenium, coenzyme Q10, vitamin C, zinc, and folic acid (Proxeed Plus) twice daily for 6 months is associated with improvements in ejaculate volume, sperm count, sperm concentration, total motility, and progressive motility in patients with idiopathic infertility when compared to baseline. However, improvement in sperm morphology was lacking. Furthermore, patients with more severe varicocele seem to benefit most, especially with regard to progressive motility (111296). The validity of these findings is limited by a lack of comparator group. Further, it is unclear if these effects are due to vitamin B12, other ingredients, or the combination.
Multiple sclerosis (MS). Although there is interest in using oral vitamin B12 for MS, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B12 is beneficial for NAFLD. Details: A small clinical study in adults with NAFLD shows that taking vitamin B12 1000 mcg daily for 12 weeks reduces serum levels of homocysteine but has no effect on serum aminotransferases, measures of steatosis, fibrosis scores, fasting blood glucose, serum insulin, measures of insulin resistance, triglycerides, low-density lipoprotein (LDL) cholesterol, or high-density lipoprotein (HDL) cholesterol when compared with placebo (111555).
Pancreatic cancer. It is unclear if oral vitamin B12 is beneficial for reducing the risk of pancreatic cancer. Details: Most population research has found that increased intake of vitamin B12, as a supplement or in the diet, is not associated with a reduced risk of pancreatic cancer (9327,104927). However, a small, retrospective population study in which smoking and non-smoking adults recalled past eating habits found that increased dietary intake of vitamin B12 is associated with a 33% reduction in pancreatic cancer risk (97976). These conflicting findings may be related to study methodology, as well as the age, gender, or smoking status of the included patients.
Periodontitis. Although there is interest in using oral vitamin B12 for periodontitis, there is insufficient reliable information about the clinical effects of vitamin B12 for this condition.
Peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a specific product containing vitamin B12 3 mcg, folic acid 400 mcg, and uridine monophosphate 50 mg (Keltican) daily for 60 days reduces pain by 44% and decreases analgesic use by over 75% when compared to baseline in patients with peripheral neuropathy, including those with lumbar/lumbosacral radiculopathy, sciatic pain, and cervical radiculopathy (90384). The validity of this finding is limited by the lack of a control group. Furthermore, it is unclear if the benefits are due to vitamin B12, other ingredients, or the combination.
Psoriasis. Topical vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that a specific cream containing vitamin B12 and avocado oil (Regividerm, Regeneratio Pharma AG) reduces symptoms of psoriasis as effectively as calcipotriol ointment (Psorcutan) after 12 weeks of therapy. The vitamin B12 combination cream also causes less irritation than calcipotriol (14909). It is unclear if the benefits are due to vitamin B12, other ingredients, or the combination.
Respiratory tract infections. A small study suggests that oral vitamin B12 does not reduce the rate of respiratory tract infections in children. Details: Preliminary clinical research in children aged 6-30 months from low-and middle-income countries suggests that taking vitamin B12 at twice the recommended dietary allowance with or without folic acid does not reduce the risk for lower respiratory tract infections when compared with placebo (90391).
Schizophrenia. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking a combination of vitamin B12 400 mcg and folic acid 2 mg daily for 16 weeks improves negative symptoms when compared with placebo in patients with schizophrenia who have persistent symptoms and a specific genetic variant of the folate transporter gene FOLHI. This variant normally results in reduced folate absorption. However, in patients without this genetic variant, folate is not beneficial with respect to negative symptom improvement (90387).
Sickle cell disease. Oral vitamin B12 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B12 4.2-6 mcg, folic acid 700 mcg, and vitamin B6 4.2-6 mg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
Stroke. It is unclear if oral vitamin B12, either alone or with other B vitamins, is beneficial for stroke prevention. Details: Epidemiological research has found that people with a higher intake of vitamin B12 from dietary sources do not have a reduced risk of ischemic or hemorrhagic stroke (14316). A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50420,50423,83050,90379,90380,96150). However, a more recent meta-analysis of 10 clinical trials including over 44,000 patients shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk or with a history of CVD (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, a meta-analysis in adults with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and vascular death by 11% when compared with placebo (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis suggests that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Another meta-analysis suggests that exposure to low, but not high, amounts of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
Tinnitus. It is unclear if intramuscular vitamin B12 is beneficial in patients with tinnitus. Details: A small clinical study shows that intramuscular vitamin B12 2500 mcg weekly for 6 weeks reduces tinnitus severity by 22% when compared to baseline in patients with chronic tinnitus and vitamin B12 deficiency, but not in patients with normal levels of vitamin B12. Vitamin B12 does not improve pitch or volume in either group of patients (96170). The validity of this finding is limited by the lack of a control group.
Venous thromboembolism (VTE). It is unclear if oral vitamin B12 is beneficial for preventing VTE. Details: Epidemiological research has found that low levels of vitamin B12 are associated with an increased risk for VTE. However, clinical trials evaluating the use of B vitamins for prevention of VTE have shown conflicting results (90398). More evidence is needed to rate vitamin B12 for these uses.

VITAMIN B6

Pyridoxine-dependent epilepsy. Intravenous vitamin B6 is effective for controlling pyridoxine-dependent seizures. Details: Pyridoxine-dependent seizures are a rare type of refractory seizures in neonates that do not respond to anticonvulsant drugs. These seizures are typically controlled within minutes of intravenous administration of pyridoxine, a form of vitamin B6. Pyridoxine-dependent seizures can be due to genetic (autosomal recessive) pyridoxine dependency, or more commonly, a result of the use of high-dose pyridoxine during pregnancy (8197,8198).
Sideroblastic anemia. Oral vitamin B6 is effective for treating hereditary sideroblastic anemia. Details: Taking vitamin B6 (pyridoxine) orally is effective for treating hereditary sideroblastic anemia (15,9518). Taking the active form of vitamin B6 (pyridoxal-5'-phosphate) also seems to be effective in cases in which the patient does not respond to pyridoxine (93049).
Vitamin B6 deficiency. Oral vitamin B6 is effective for preventing and treating vitamin B6 deficiency. Details: Taking oral vitamin B6 can prevent and treat vitamin B6 deficiency (15).

Hyperhomocysteinemia. Taking vitamin B6 orally, alone or in combination with folic acid, is effective for reducing hyperhomocysteinemia. Details: Vitamin B6 (pyridoxine) seems to lower homocysteine concentrations when folic acid and vitamin B12 are at physiologic levels or when given with folic acid and vitamin B12 supplements (9451,83042,107136). A combination of vitamin B6 100 mg and folic acid 0.5 mg daily seems to lower homocysteine levels by about 35% and is recommended for people with postprandial hyperhomocysteinemia (1489,9406). Other research shows that taking pyridoxine 50-200 mg daily reduces postprandial homocysteine levels by 32% to 35% (9406,10350). Pyridoxine also seems to reduce homocysteine levels in patients with kidney failure, kidney transplant patients (1489,6884,9414,9415), or patients who receive general anesthesia with nitrous oxide (9481). However, some research in healthy adults suggests that adding pyridoxine to folic acid might not provide any additional benefit over folic acid alone (9400,9405,9409,50145). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,3323,9402,9405,9408,9409). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50% and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9308,9400,9405,9409). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem to help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50423,83050,97619). There is also debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired renal function (11387,13482,50423,83050,96150). However, a more recent meta-analysis shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk for or with a history of CVD (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136).

Antipsychotic-induced hyperprolactinemia. It is unclear if oral vitamin B6 is beneficial for patients with antipsychotic-induced hyperprolactinemia. Details: Clinical research in male patients with hyperprolactinemia who are on a consistent antipsychotic dose shows that taking vitamin B6 300 mg twice daily for 16 weeks reduces serum prolactin levels by 68%, compared with 37% in patients taking aripiprazole 5 mg twice daily. Also, 67% of patients taking vitamin B6 had prolactin levels less than 40 mcg/mL versus 2% of those taking aripiprazole (107128).
Kidney stones (nephrolithiasis). Oral vitamin B6 seems to decrease urinary oxalate levels and decrease the risk of kidney stone formation in some patients. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally, alone or in combination with magnesium, can decrease urinary oxalate levels in people with type I primary hyperoxaluria, a hereditary disorder (1201,6437,6438,6439,6440,8548,8549,8550). Additionally, a small clinical study in this population suggests that intravenous pyridoxine hydrochloride can reduce urinary oxalate by 25.5% when compared to baseline (90796). In patients with idiopathic hyperoxaluria, taking a combination of pyridoxine 25mg and magnesium oxide 400 mg for 3 months decreases urinary oxalate by approximately 16%, with 68% of patients experiencing a reduction. However, supplementation is less effective than following a low-oxalate diet, which reduces urinary oxalate in 91% of patients by an average of 31% (107127). There is also preliminary evidence that higher pyridoxine intake in females with no history of kidney stones is associated with decreased risk of kidney stone formation (6441), but this association has not been found in males (6442).
Pregnancy-induced nausea and vomiting. Oral vitamin B6 may reduce nausea and vomiting in some pregnant patients and is sometimes used in combination with doxylamine. Details: While some conflicting evidence exists, most small clinical studies suggest that oral vitamin B6 is effective for improving nausea and vomiting associated with pregnancy when compared with baseline or placebo. However, vitamin B6 may not be as effective as ginger (110459). Two small clinical studies show that taking vitamin B6 (pyridoxine) 25 mg every 8 hours for 3-4 days decreases pregnancy-induced nausea severity and vomiting incidence when compared with placebo (6168,16306). A larger clinical trial shows that taking lower doses of vitamin B6, 10 mg every 8 hours over 5 days, improves pregnancy-induced nausea, but not vomiting, when compared with placebo (6167). A small clinical study in patients with mild to moderate nausea and vomiting shows that taking a higher dose of 40 mg twice daily for 4 days is more effective than placebo, but no better than ginger 500 mg twice daily (99404). The American College of Obstetrics and Gynecology (ACOG) considers vitamin B6 at a dose of 10-25 mg 3 to 4 times daily a first-line treatment for pregnancy-induced nausea and vomiting due to its benign safety profile (111601). However, it is not effective for all patients, such as those with hyperemesis gravidarum, a severe form of pregnancy-induced nausea and vomiting. Adding vitamin B6 20 mg three times daily for 2 weeks to intravenous rehydration, metoclopramide, and thiamine seems to be no more effective than placebo for reducing vomiting in hyperemesis gravidarum (99405). Vitamin B6 is also sometimes used in combination with doxylamine. In fact, a combination of vitamin B6 plus doxylamine (Diclegis or Bonjesta, Duchesnay Inc., and various generics) has been approved by the US Food and Drug Administration (FDA) as a prescription product111601). ACOG recommends vitamin B6 in combination with doxylamine as another first-line treatment option (111601). However, the clinical trial used to obtain FDA approval has some methodological problems, and the significance of the results has been questioned. The improvement in symptom scores seen with Diclegis was less than one point on a 13-point scale, which is unlikely to be clinically significant (97998). Also, some clinical research shows that taking pyridoxine 25 mg and doxylamine 12.5 mg is less effective than ondansetron 4 mg when taken every 8 hours for 5 days. Only 41% of the patients using pyridoxine and doxylamine had a clinically significant reduction in nausea, compared to 92% of patients using ondansetron (90797). The combination of vitamin B6 and doxylamine is also studied with acupuncture. A large clinical study in patients with moderate to severe pregnancy-induced nausea and vomiting conducted in China shows that taking vitamin B6-doxylamine (Diclegis, Duchesnay, Inc) 20 to 40 mg each at bedtime for 14 days in combination with daily acupuncture modestly improves patient-reported nausea and vomiting scores when compared with either intervention alone (111820). However, it is unclear whether this improvement is clinically significant.
Premenstrual syndrome (PMS). Oral vitamin B6 seems to reduce PMS symptoms. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally can improve symptoms of PMS such as breast pain or tenderness (mastalgia) and depression in some patients. Pyridoxine in doses of at least 50 mg daily, plus magnesium oxide 200 mg daily, seems to relieve PMS-related anxiety and other symptoms (8555,39007,82962). Although some clinicians advocate doses of pyridoxine 200-500 mg daily for PMS, doses of 50-100 mg daily seem to work just as well. There is no apparent dose-response curve for PMS, so the lowest effective dose should be used. Higher doses might increase the risk of side effects (3093).

Age-related cognitive decline. Oral vitamin B6 does not seem to slow age-related cognitive decline. Details: One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374). Furthermore, other clinical research shows that taking vitamin B6 (pyridoxine) 3-75 mg daily in combination with folic acid and vitamin B12 does not improve cognitive function in elderly adults (14392,50225,50510).
Alzheimer disease. Oral vitamin B6 does not seem to improve cognitive function in patients with Alzheimer disease when used in combination with other B vitamins. Also, oral vitamin B6 does not seem to reduce the risk of developing this condition. Details: Clinical research in patients with probable Alzheimer disease taking routine medications shows that taking vitamin B6 25 mg with folic acid 5 mg and vitamin B12 1 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, population research in elderly adults has found that a high intake of vitamin B6 from dietary or supplemental sources is not associated with a decreased risk of Alzheimer disease when compared to lower vitamin B6 intake (13165,15270).
Carpal tunnel syndrome. Oral vitamin B6 does not seem to reduce symptoms of carpal tunnel syndrome. Details: Most research shows that people with carpal tunnel syndrome are not generally deficient in vitamin B6 and do not benefit from taking vitamin B6 supplements (8203,8937,9448,9450,9478,9482). Although early studies by a single group of researchers, as well as anecdotal reports, suggest that taking vitamin B6 may relieve carpal tunnel symptoms, more reliable research has not supported these findings (8202,9445,9447,9449,9483,15955,83086).
Cataracts. Oral vitamin B6 does not seem to slow cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg, vitamin B6 (form not specified) 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts when compared with placebo. Furthermore, the risk of cataract extraction was increased by 28% (96149).
Chemotherapy-induced acral erythema. While some conflicting evidence exists, most research suggests that oral or topical vitamin B6 does not seem to prevent or reduce the severity of acral erythema induced by chemotherapy. Details: A meta-analysis of 10 clinical trials and 4 observational studies shows that taking vitamin B6 60-500 mg daily for up to 8 chemotherapy cycles does not prevent chemotherapy-induced acral erythema or reduce the incidence of severe cases when compared with control. Most studies used capecitabine chemotherapy alone or in combination, and one study used pegylated liposomal doxorubicin; however, no subgroup analysis was conducted to differentiate chemotherapy regimens. Results did not seem to vary based on study location, study design, or vitamin B6 dose (104930). However, a more recent preliminary clinical study in patients receiving doxorubicin for multiple myeloma shows that taking vitamin B6 100 mg on the first day of chemotherapy then twice daily for 7 days with each cycle reduces the risk of developing acral erythema by 72%, but does not improve the severity of acral erythema, when compared with no vitamin B6 supplementation (110458). Also, one small, low-quality clinical study suggests that taking vitamin B6 400 mg daily reduces the risk of moderate or severe chemotherapy-induced acral erythema when compared with vitamin B6 200 mg daily; however, the higher dose also seems to be associated with worsened tumor response and increased treatment failure (97620). Topical vitamin B6 has also failed to show benefit. A small clinical study in patients with acral erythema from capecitabine or pegylated liposomal doxorubicin shows that applying vitamin B6 1% cream to affected areas three times daily for 6 weeks does not improve symptoms when compared with placebo (104929).
Colorectal adenoma. Oral vitamin B6 does not seem to reduce the risk of developing colorectal adenomas. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 (pyridoxine) 50 mg, and vitamin B12 1 mg, daily for up to 9.2 years does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389).
Eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of eclampsia when compared with control (83046,96166).
Osteoporosis. Oral vitamin B6 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in patients with cerebrovascular disease shows that taking a combination of B vitamins, including folic acid 2 mg, vitamin B6 (form not specified) 25 mg, and vitamin B12 500 mcg daily for up to 10.5 years does not prevent osteoporotic fractures when compared with placebo (90377). Furthermore, a secondary analysis of two large studies in patients with cardiovascular disease has found that taking vitamin B6 (pyridoxine) 40 mg daily in addition to folic acid and vitamin B12 for 1-3 years is associated with a 42% increased risk of hip fracture over an 11-year period when compared with only folic acid and vitamin B12 (96163). This finding is limited because these studies were not designed to assess the effects of vitamin B6 on fracture risk and the analyses were not adjusted for baseline bone health or fall risk.
Pre-eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of pre-eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of pre-eclampsia when compared with placebo (83046,96166).
Preterm labor. Oral or intramuscular vitamin B6 does not seem to reduce the risk of preterm labor. Details: Meta-analyses of limited clinical research in pregnant patients shows that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of preterm labor when compared with placebo (83046,96166).

Acne. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing vitamin B6 (pyridoxine), nicotinamide, azelaic acid, zinc, copper, and folic acid for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared to baseline (90800). The validity of these findings is limited by the lack of a comparator group.
Age-related macular degeneration (AMD). Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B6 (pyridoxine) 50 mg, vitamin B12 1000 mcg, and folic acid 2.5 mg daily reduces the risk for AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
Angioplasty. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B6 (pyridoxine) 10 mg, folic acid 1 mg, and vitamin B12 400 mcg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6 (pyridoxine), and vitamin B12 followed by oral administration of folic acid 1.2 mcg, vitamin B6 (pyridoxine) 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B6, other ingredients, or the combination.
Antipsychotic-induced metabolic side effects. It is unclear if oral vitamin B6, as an adjunct to progesterone, is beneficial in patients with antipsychotic-induced amenorrhea. Details: A small clinical study in females with antipsychotic-induced amenorrhea shows that taking vitamin B6 80 mg three times daily for 1 month plus intramuscular progesterone daily for 5 days increases levels of estradiol and follicle stimulating hormone, reduces prolactin levels, and increases the rate of clinical efficacy, defined as the normalization of menstruation and improvement in endocrine indicators, by 14% when compared with progesterone alone (110457).
Anxiety. It is unclear if oral vitamin B6 is beneficial in patients with anxiety. Details: Clinical research in college students shows that taking vitamin B6 100 mg daily for one month does not reduce anxiety scores when compared with placebo (110453). However, because a diagnosis of anxiety was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with anxiety.
Asthma. It is unclear if oral vitamin B6 is beneficial in patients with asthma. Details: Preliminary clinical studies show that taking vitamin B6 (pyridoxine) 200-300 mg daily may improve symptoms of asthma in some patients, but not others, when compared with placebo (7064,7065). Studies have yielded conflicting results, with some research suggesting that it may only be beneficial in children with severe asthma (7065). Additionally, some research suggests that theophylline may lower vitamin B6 levels, although it is unclear if vitamin B6 supplementation is beneficial (4522,7066,9503).
Atherosclerosis. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with intermediate risk for coronary heart disease shows that taking a specific supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing vitamin B6 12.5 mg, aged garlic extract 250 mg, vitamin B12 100 mcg, folic acid 300 mcg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
Atopic dermatitis (eczema). It is unclear if oral vitamin B6 is beneficial in patients with eczema. Details: A small clinical study in children with eczema shows that taking vitamin B6 (pyridoxine hydrochloride) 50 mg daily for 4 weeks does not reduce symptoms such as redness and itchiness when compared with placebo (83090).
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral vitamin B6 is beneficial for ADHD. Details: A small crossover study in children with ADHD shows that taking vitamin B6 600 mg, niacinamide and ascorbic acid 3 grams, and calcium pantothenate 1.2 grams daily for 6 weeks does not improve behavior scores when compared with placebo (9957).
Autism spectrum disorder. Although there is interest in using oral vitamin B6 for autism, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Bipolar disorder. It is unclear if oral vitamin B6 is beneficial in patients with bipolar disorder. Details: A small clinical trial in patients with type 1 bipolar disorder who are taking lithium and experiencing an acute episode of mania shows that taking vitamin B6 80 mg daily for 8 weeks does not improve cognitive function or the severity of mania when compared with placebo. Cognitive function was reduced in patients taking vitamin B6; any effect on sleep was unclear (107132).
Cancer. It is unclear if oral vitamin B6 reduces overall cancer risk. Details: Population research has found that higher dietary intake of vitamin B6 is associated with a 22% reduced risk of cancer, including esophageal, pancreatic, gastric, colorectal, and breast cancer. However, when dietary and supplemental vitamin B6 intake is considered, the inverse association between vitamin B6 and cancer risk is weaker and limited to fewer tumor sites. Furthermore, a meta-analysis of 9 clinical studies shows that taking vitamin B6 3-100 mg orally daily for 2-7.3 years, in combination with vitamin B12 and folate, does not reduce the risk of cancer in patients with cardiovascular disease or kidney failure (96164).
Cardiovascular disease (CVD). Oral vitamin B6, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly lower the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B6 in combination with folic acid and/or vitamin B12 does not seem to help with secondary prevention of death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, some research shows that taking vitamin B6 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). Additionally, it is unclear which specific combination of B vitamins is optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
Cognitive function. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy adults aged 40-65 years shows that taking a supplement containing vitamin B6, ginkgo leaf, bacopa, and other B vitamins twice daily for 12 weeks does not improve memory or attention when compared with placebo (111334).
Colorectal cancer. It is unclear if oral vitamin B6 reduces the risk of colorectal cancer. Details: A meta-analysis of observational studies suggests that the highest dietary intake of vitamin B6 is associated with a 20% reduced risk of colorectal cancer when compared with the lowest dietary intake. However, this association was not shown in subgroup analyses of studies conducted in Australia, Europe, or North America (111600). The validity of this analysis is limited by the heterogeneity of the included studies.
Dental caries. There is limited evidence on the oral use of vitamin B6 for dental decay during pregnancy. Details: Meta-analyses of limited clinical research show that taking vitamin B6 (pyridoxine), 25 mg daily or a single dose of 100 mg orally or intramuscularly, may reduce the risk of dental decay during pregnancy when compared with placebo (83046,96166).
Depression. It is unclear if oral vitamin B6 reduces the risk of developing depression or improves symptoms of depression. Details: Clinical research in healthy college students shows that taking vitamin B6 100 mg daily for one month does not reduce depression scores when compared with placebo (1104453). However, because a diagnosis of depression was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with depression. Whether vitamin B6 reduces the risk of developing depression is also unclear. A meta-analysis of population research has found that the highest dietary intake of vitamin B6 is associated with a 19% lower risk of depression when compared with the lowest intake. However, sub-analyses suggest that this association is only relevant in females and not males (107133). In one individual population study in community dwelling older adults included in the analysis, the consumption of at least 1.71 mg of vitamin B6 daily from food was associated with a 43% reduction in the likelihood of becoming depressed when compared with the consumption of 1.33 mg or less daily in females. However, there was no association between vitamin B6 levels and risk of depression in males, and the finding in females was no longer significant when adjusted for total energy intake, since foods rich in vitamin B6 are energy-dense (96168). Another observational longitudinal study in healthy adults starting oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 40% lower risk of depression when compared with no supplementation (90789). Most available studies are cross-sectional in nature, making any conclusions related to causation difficult.
Diabetes. It is unclear if oral vitamin B6 is beneficial in patients with type 2 diabetes or gestational diabetes. Details: Observational research in Chinese adults with type 2 diabetes has found that dietary intake of vitamin B6 in the highest quartile is associated with 53% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with vitamin B6 intake in the lowest quartile (110452). Small clinical studies in patients with gestational diabetes and vitamin B6 deficiency shows that taking vitamin B6 (pyridoxine) 100 mg daily for 2 weeks improves glucose tolerance and blood glucose levels when compared with baseline (82967,83088). However, there is concern that these findings were confounded by dietary alterations. This benefit was not observed in a subsequent small case series in patients with gestational diabetes (22380).
Diabetic neuropathy. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research suggests that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate) for 24 weeks does not improve neural dysfunction based on vibration perception when compared with placebo in patients with diabetic neuropathy. However, taking this combination appears to modestly improve neuropathy symptoms and quality of life related to mental functioning when compared with placebo (90375).
Dysmenorrhea. It is unclear if oral vitamin B6 is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research shows that taking vitamin B6 (form not specified) 200 mg daily reduces pain associated with dysmenorrhea when compared with placebo. However, taking vitamin B6 in combination with magnesium does not reduce pain when compared with placebo (77388).
Fibromyalgia. It is unclear if oral vitamin B6 is beneficial in patients with fibromyalgia. Details: A small clinical study in patients with fibromyalgia shows that taking vitamin B6 80 mg daily for 8 weeks does not improve pain, disease severity, anxiety, depression, or quality of life when compared with placebo (110454).
Gastroenteritis-associated nausea and vomiting. It is unclear if oral vitamin B6 is beneficial in children with gastroenteritis. Details: A small clinical study in children aged 6 months to 12 years with acute viral gastroenteritis shows that taking vitamin B6 (form not specified) does not improve symptoms of dehydration or the frequency of vomiting when compared with placebo (90793).
Hypertension. It is unclear if oral vitamin B6 reduces blood pressure. Details: One small clinical study in patients with essential hypertension shows that taking vitamin B6 (pyridoxine hydrochloride) 5 mg/kg daily for 4 weeks can reduce systolic and diastolic blood pressure when compared with baseline (83091). The validity of this finding is limited by the lack of a control group.
Hypertriglyceridemia. It is unclear if oral vitamin B6 reduces triglyceride levels. Details: Preliminary clinical research shows that vitamin B6 (form not specified) 50 mg daily for 12 weeks does not reduce triglyceride levels in people with hypertriglyceridemia when compared with placebo. However, vitamin B6 appears to decrease total cholesterol and high-density lipoprotein (HDL) cholesterol by approximately 9% in these patients (59028).
Infertility. Although there is interest in using oral vitamin B6 for infertility, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Insomnia. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in healthy adults with self-reported sleep difficulty shows that taking a specific product (LZ Complex3, Sanofi Consumer Healthcare Pty Ltd.) containing vitamin B6, zizyphus extract, hops extract, hydrolyzed milk protein (Lactium), and magnesium oxide nightly, 30 minutes before bed, for 2 weeks does not improve sleep quality, daytime functioning, or physical fatigue when compared with placebo. However, due to the large improvement seen in both the treatment and placebo groups, the effectiveness of this product is unclear (95971).
Isoniazid-induced neuropathy. It is unclear if oral vitamin B6 prevents the development of neuropathy in patients taking isoniazid. Details: Preliminary clinical research in patients taking isoniazid for tuberculosis shows that taking vitamin B6 (pyridoxine) 6 mg daily reduces the development of neuropathy when compared with control (83068).
Lactation. It is unclear if oral vitamin B6 helps to suppress postpartum lactation. Details: A meta-analysis of two small clinical trials shows that taking vitamin B6 (pyridoxine) 400-600 mg daily for 6-7 days postpartum does not suppress lactation when compared with no treatment (83047).
Levetiracetam-induced side effects. While some conflicting evidence exists, several small, low-quality studies suggest that oral vitamin B6 (pyridoxine) may reduce some neuropsychiatric adverse effects related to the use of levetiracetam. Details: In an analysis of case reports, retrospective studies, and a single low-quality prospective study, improvement in levetiracetam-associated neuropsychiatric symptoms occurred in approximately 73% of patients taking pyridoxine (107137). A more recent preliminary clinical trial in children ages 1-17 years shows that taking pyridoxine 10 or 15 mg/kg daily as needed based on symptoms improves behavioral side effects associated with levetiracetam by a small amount when compared with low-dose pyridoxine 0.5 mg/kg daily used as placebo (107124). Also, observational research in children ages 9 months to 14 years has found that taking vitamin B6 is associated with improved behavior and a 44% lower risk of levetiracetam discontinuation when compared with no vitamin B6 supplementation (110455). Some observational research in adults with levetiracetam-associated irritability has found that taking vitamin B6 is associated with an improvement in irritability in 45% of patients when compared to baseline (107129). However, a small clinical trial in adults with epilepsy shows that taking pyridoxine 40 mg daily for 3 weeks does not improve levetiracetam-related psychiatric adverse effects when compared with placebo (110456). This study may have been underpowered to detect differences between groups. Pyridoxine doses used in the studies above have ranged from 50-400 mg daily in children and 40-600 mg daily in adults (107124,107129,107137,110456).
Lung cancer. It is unclear if dietary or oral vitamin B6 reduces lung cancer risk. Details: Epidemiological research has found that higher serum levels of vitamin B6 in male smokers is associated with a lower risk of lung cancer (9454). Also, people with blood levels of vitamin B6 in the top quartile have a modestly lower risk of lung cancer when compared with those whose levels are in the lowest quartile. The association is stronger for males and for people who have smoked (97999). However, other epidemiological research found that increased dietary intake of vitamin B6 is not associated with a reduced risk of lung cancer (96164).
Menopausal symptoms. Although there is interest in using oral vitamin B6 for menopausal symptoms, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Motion sickness. Although there is interest in using oral vitamin B6 for motion sickness, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Nausea and vomiting. It is unclear if oral vitamin B6 is beneficial for nausea and vomiting in patients using oral contraceptives. Details: An observational longitudinal study in healthy females taking oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 43% reduced risk of nausea when compared with no supplementation (90789).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B6 for patients with NAFLD. Details: A small clinical trial in patients with NAFLD shows that taking vitamin B6 (pyridoxine) 30 mg three times daily for 12 weeks does not reduce levels of liver transaminases or plasma lipids when compared with baseline. However, hepatic fat accumulation was modestly reduced (107130). The validity of this study is limited by the lack of a comparator group.
Obesity. It is unclear if oral vitamin B6 in beneficial in overweight or obese individuals. Details: A small clinical trial in females with a body mass index (BMI) of at least 25 kg/m² shows that taking vitamin B6 as pyridoxine 80 mg daily for 8 weeks reduces fat mass and improves insulin resistance and triglyceride levels by a small amount when compared with placebo. Although some other anthropometric and metabolic indices were improved when compared with baseline, there was no effect of pyridoxine on body weight, visceral adiposity, or other endpoints when compared with placebo (107131).
Overall mortality. It is unclear if oral vitamin B6 reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of vitamin B6 in the highest quintile is associated with a 12% to 21% lower risk of all-cause mortality and a 31% to 44% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary vitamin B6 intake (110451).
Pancreatic cancer. It is unclear if oral vitamin B6 reduces the risk of pancreatic cancer. Details: Observational research has found that higher dietary intake of vitamin B6 is associated with a 37% lower risk of developing pancreatic cancer when compared with lower intake (104927).
Postpartum depression. It is unclear if oral vitamin B6 is beneficial in patients with postpartum depression. Details: Preliminary clinical research in individuals considered at increased risk for postpartum depression, but without clinical depression, shows that taking vitamin B6 80 mg daily from the 28th week of pregnancy until birth, and then 40 mg daily for one month, reduces symptoms of depression 1.5 months after birth when compared with baseline (measured during the third trimester) and when compared with placebo. However, it is unclear if any of the patients included in the study developed postpartum depression, as there were no changes in overall symptoms in patients taking placebo (107126).
Restless legs syndrome (RLS). It is unclear if oral vitamin B6 is beneficial in patients with RLS. Details: A small clinical study in adults with RLS who are beginning treatment with pramipexole shows that also taking vitamin B6 40 mg daily for 2 months moderately improves RLS scores and sleep quality scores when compared with pramipexole and placebo (110052).
Schizophrenia. It is unclear if oral vitamin B6 is beneficial for patients with treatment-resistant schizophrenia. Details: Clinical research in male patients with treatment-resistant schizophrenia who are on a consistent antipsychotic dose shows that adding vitamin B6 300 mg twice daily for 16 weeks modestly improves psychotic symptoms and some measures of cognitive performance when compared with adding aripiprazole 5 mg twice daily (107128). More research is needed to determine if these benefits are clinically relevant.
Seizures. It is unclear if oral vitamin B6 is beneficial for preventing seizures in patients with glycosylphosphatidylinositol (GPI) deficiency. Details: Observational case series in a small number of children and young adults with GPI deficiency has found that taking vitamin B6 20-30 mg/kg daily for 3-12 months is associated with some reduction in seizure frequency in 9 of 13 patients. However, no patient reached seizure freedom (107125,107135). In one case series, treatment for 12 months was associated with modest developmental improvements in almost all patients (107135). The study patient populations were slightly different in terms of age and underlying genetic causes for GPI deficiency.
Sickle cell disease. Oral vitamin B6 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B6 4.2-6 mg, vitamin B12 4.2-6 mcg, and folic acid 700 mcg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
Stroke. It is unclear if oral vitamin B6, either alone or with other B vitamins, is beneficial for stroke prevention. Details: There is some debate about whether supplementation with homocysteine-lowering B vitamins, including vitamin B6, can reduce the risk of stroke. A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, another meta-analysis of three clinical trials including 9900 patients with a history of stroke shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% when compared with placebo, although this finding was determined to have a low level of certainty. Based on two clinical trials, there was also a 17% reduced risk of vascular death and an 11% reduction in the combined risk of stroke, myocardial infarction, and vascular death (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis shows that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Exposure to low, but not high amounts, of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
Tardive dyskinesia. It is unclear if oral vitamin B6 prevents tardive dyskinesia in patients taking neuroleptic drugs. Details: A small clinical study in patients taking neuroleptic drugs for schizophrenia shows that taking vitamin B6 (form not specified) 400 mg daily seems to improve Parkinsonian, dystonic, and dyskinetic symptoms when compared with placebo (8558).
Tourette syndrome. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, nonblinded clinical study in children aged 4-17 years with untreated Tourette syndrome or with chronic tic disorder and associated symptoms of anxiety shows that taking a liquid nutritional supplement providing vitamin B6 2.8 mg and L-theanine 200 mg daily for 2 months improves scores on the Yale Global Tic Severity Scale, but does not reduce anxiety, when compared with patients receiving psychoeducation (108555). This study may have been inadequately powered to detect a difference between groups.
Vincristine-induced neuropathy. Oral vitamin B6 has only been evaluated in combination with pyridostigmine; its effect when used alone is unclear. Details: A small clinical study in children ages 11 months to 13 years with neuropathy due to vincristine treatment for acute lymphoblastic leukemia, shows that taking vitamin B6 150 mg/m2 and pyridostigmine 3 mg/kg twice daily for 3 months is associated with reduced severity of sensory and motor neuropathy when compared with baseline (104928). The validity of this finding is limited by the lack of a control group. More evidence is needed to rate vitamin B6 for these uses.

VITAMIN C

Vitamin C deficiency. Oral or intramuscular vitamin C is effective for preventing or treating vitamin C deficiency. Details: Administering vitamin C orally or intramuscularly prevents and treats vitamin C deficiency, including scurvy. Vitamin C administration can reverse complications of scurvy within 2 days to 3 weeks (4844). In newborns with transient tyrosinemia due to vitamin C deficiency, oral or intramuscular vitamin C can correct this condition (15).

Anemia of chronic disease. Oral vitamin C seems to improve markers of anemia in patients on hemodialysis. Details: Meta-analyses of clinical research in hemodialysis patients with anemia shows that treatment with vitamin C 200-300 mg three times weekly for 3-6 months increases hemoglobin levels by approximately 0.9 grams/dL, increases transferrin saturation by about 8%, and decreases the required recombinant human erythropoietin dose by 17 U/kg weekly when compared with standard care (83447,83475).
Atrial fibrillation. Oral and intravenous vitamin C seems to help prevent atrial fibrillation after cardiac surgeries. Details: Meta-analyses of clinical research show that taking vitamin C prior to and after cardiac surgery reduces the risk of postoperative atrial fibrillation by 27% to 53%. Most studies administered vitamin C at doses of 1-2 grams orally daily for 1-3 days prior to cardiac surgery, followed by 1-2 grams in two divided doses daily for 4-5 days after cardiac surgery. Some studies provided vitamin C intravenously at similar doses, but oral vitamin C seems to be more effective (91233,96703,96705). Despite these findings, a meta-analysis of clinical research conducted only in the U.S. does not support the benefit of vitamin C for reducing postoperative atrial fibrillation (96703). These differences may be related to lifestyle factors such as nutrition, as well as differences in hospital treatments. Vitamin C has also been studied in combination with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with evidence of benefit (90701).
Bowel preparation. Powdered vitamin C is approved for use as part of a polyethylene glycol-based bowel preparation for colonoscopy. Details: Clinical research shows that treatment with 2 liters of oral solution containing polyethylene glycol (PEG) plus vitamin C achieves a similar quality of bowel cleansing as treatment with 4 liters of PEG when administered on the evening prior to colonoscopy or when administered in a split-dose regimen. Patients given 2 liters of PEG plus vitamin C solution also have better adherence and experience fewer adverse events, such as nausea, vomiting, or abdominal bloating, compared to patients treated with 4 liters of PEG solution without vitamin C (90413,90415,90420,90424,90428). This treatment also appears to be effective and tolerable in elderly patients aged 60-79 years, including those with poor bowel habits and a high number of comorbidities (108085). Other clinical research in older adults undergoing bowel preparation for colonoscopy also shows that taking 1 liter of PEG plus vitamin C (CleanViewAL, Taejoon Pharm) results in similar quality of bowel cleansing overall and per segment with similar tolerability and adverse effects as sodium picosulfate 170 mL plus magnesium citrate or oral sulfate solution alone (111297,112476). The most common PEG plus vitamin C preparation used in clinical research is MoviPrep (Norgine BV), which contains macrogol 3350 100 grams, sodium sulfate 7.5 grams, sodium chloride 2.7 grams, potassium chloride 1 gram, vitamin C 4.7 grams, and sodium ascorbate 5.9 grams per liter of solution (90413,90415,90424). In the U.S., MoviPrep is approved by the Food and Drug Administration (FDA) for bowel preparation prior to a colonoscopy.
Common cold. Oral high-dose vitamin C might modestly reduce cold symptoms; however, taking vitamin C prophylactically does not seem to prevent the development of a cold. Details: There is substantial controversy about the effectiveness of vitamin C for treating the common cold (1969,1989,7100,9835,9836). The majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patients (1966,1967,1968,1987,6458,7102,9832,83487). However, other studies have found no effect with doses up to 3 grams daily (9833). A meta-analysis of clinical research suggests that vitamin C supplementation decreases the incidence of cold in individuals exposed to physical stress, but not in the general population (83487). Other research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. Also, there may be a dose-dependent response; doses of at least 2 grams daily seem to work better than 1 gram doses (9834). Taking vitamin C supplements prophylactically does not decrease the risk of catching a cold (1966,1967,1968,1987,3042,6458,7101,9832). Dietary intake of vitamin C also does not seem to affect the risk of getting a cold (10780).
Complex regional pain syndrome. Most research shows that taking oral vitamin C after a wrist or distal radius fracture or after orthopedic surgery seems to reduce the risk of developing complex regional pain. Details: Although some research has found no benefit in patients with distal radius (i.e. wrist) fractures (90411,96702), most clinical research shows that taking vitamin C 500 mg daily, and possibly doses of up to 1500 mg daily, for 45-50 days beginning immediately after fracture can reduce the risk of developing complex regional pain syndrome (2045,16302,96700,96706). Reasons for discrepancies are unclear but might relate to differences in diagnostic criteria for complex regional pain syndrome (96702). Research in patients undergoing orthopedic surgery has also shown benefit with the use of vitamin C for the prevention of complex regional pain syndrome (90422,108076,108087). One meta-analysis of clinical research in patients undergoing wrist, foot, or ankle surgery shows that taking vitamin C 500-1000 mg for 42-50 days following surgery reduces the rate of complex regional pain syndrome, and may improve pain following ankle or foot surgery, when compared with placebo (108076). The validity of these findings is limited by the high heterogeneity of included trials. Another meta-analysis of clinical research in patients undergoing orthopedic surgery (i.e. wrist, knee, ankle, foot, lumbar, rotator cuff) suggests that oral and intravenous vitamin C may have similar effectiveness; however, this evidence is low quality (108087).
Exercise-induced respiratory infections. High-dose oral vitamin C seems to reduce the risk of respiratory infections associated with strenuous exercise. Details: Some preliminary clinical research suggests that prophylactic use of vitamin C in doses of 600 mg to 1 gram daily for 3-8 weeks before heavy physical exercise, such as a marathon, might prevent upper respiratory infections that sometimes follow heavy exercise (9831,83370). More recently, high doses of vitamin C have been studied. A large clinical study in army recruits undergoing basic military training shows that taking vitamin C 6 grams daily for one month reduces the odds of getting a cold by 20% when compared with placebo (102975).
Hypercholesterolemia. Oral vitamin C seems to reduce lipid levels in patients with hypercholesterolemia. Details: A meta-analysis of clinical research in patients with hypercholesterolemia shows that taking vitamin C 500 mg daily for at least 4 weeks reduces low-density lipoprotein (LDL) cholesterol by about 8 mg/dL and reduces triglycerides by about 20 mg/dL when compared with control (83445).
Hypertension. Oral vitamin C seems to modestly reduce blood pressure in patients with hypertension. Details: Vitamin C seems to modestly reduce systolic blood pressure, without meaningful effects on diastolic blood pressure (2044,9822,13162,83483,102974). A meta-analysis of 13 clinical trials in patients with hypertension, with or without other comorbidities, shows that taking a median dose of vitamin C 500 mg daily for 8 weeks reduces systolic, but not diastolic, blood pressure by about 5 mmHg. Some of the studies used vitamin C in combination with other supplements, such as vitamin E and magnesium. When studies assessing vitamin C alone were analyzed, the magnitude of reduction in systolic blood pressure decreased (83483). A newer meta-analysis of small clinical studies in patients with essential hypertension shows that taking vitamin C 200 mg or more daily reduces systolic blood pressure by about 4 mmHg and diastolic blood pressure by about 2 mmHg (102974). However, this newer analysis omitted numerous relevant studies and included studies with normotensive patients and those without an adequate control, limiting the validity of its findings.
Laser skin resurfacing. Topical vitamin C seems to reduce erythema occurring after cosmetic laser skin resurfacing procedures intended to reduce scars and wrinkles. Details: There is some evidence that an aqueous formulation of topical vitamin C can decrease the degree and duration of erythema following cutaneous carbon dioxide laser resurfacing for scar and wrinkle removal (1959).
Lead toxicity. Dietary vitamin C seems to lower concentrations of lead in the blood. Details: Observational research has found that consuming more vitamin C from dietary sources is associated with lower blood concentrations of lead. People who consumed at least 340 mg of vitamin C daily as part of the diet had lower blood lead levels than those who consumed less than 100 mg vitamin C daily (3097,3098,3099).
Nitrate tolerance. Oral vitamin C might prevent nitrate tolerance in some patients. Details: Small clinical studies show that taking vitamin C orally seems to prevent the development of nitrate tolerance in patients taking sublingual nitroglycerin. There is some evidence that short-term vitamin C supplementation can prevent tolerance to the vasodilatory effects of nitrates (1441,1961).
Postoperative pain. Oral or intravenous vitamin C might prevent acute postoperative pain following certain surgeries. It is unclear if vitamin C reduces chronic postoperative pain. Details: A meta-analysis of 7 small clinical studies in adults undergoing elective surgery shows that receiving perioperative vitamin C, either as 1 gram orally, 2-3 grams intravenously, or 50 mg/kg intravenously, modestly reduces acute pain and opioid requirements for up to 24 hours when compared with control (105457). Most surgeries were laparoscopic and included cholecystectomy, colectomy, hysterectomy; two non-laparoscopic surgeries included uvulopalatopharyngoplasty with tonsillectomy and major abdominal surgery (90418,99840,105457). A meta-analysis of clinical trials in adults undergoing noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, kidney transplantation) shows that administering perioperative vitamin C, either orally or intravenously, reduces postoperative intravenous morphine requirements at 2, 24, and 48 hours after surgery and improves pain scores at 2, 6, and 24 hours after surgery when compared with placebo. The dose of vitamin C did not appear to impact outcomes. However, when only laparoscopic surgeries are included, perioperative vitamin C does not improve pain or morphine use when compared with placebo (108087). A moderate-sized clinical study in adults undergoing transurethral resection of a bladder tumor under general anesthesia shows that administering intravenous vitamin C 1 gram after induction of anesthesia reduces the incidence and severity of catheter-related bladder discomfort immediately after surgery and at 1 and 2 hours postoperatively, but not 6 hours, when compared with placebo. However, vitamin C does not reduce postoperative pain scores or analgesic requirements when compared with placebo (111645). Further research is needed to determine the effects of vitamin C for acute postoperative pain. Vitamin C has also been evaluated for reducing chronic pain after surgery. Clinical research in patients undergoing surgery for foot or ankle trauma shows that taking vitamin C 500 mg orally twice daily postoperatively for 6 weeks reduces pain scores when compared with placebo at 2 weeks and 6 weeks. The mean total amount of diclofenac used for pain relief over the 6-week period is also reduced, from 5.7 grams with placebo to 3.4 grams with vitamin C (102131).
Wrinkled skin. Topical vitamin C might reduce the appearance of existing wrinkles. Details: Topical preparations containing vitamin C seem to improve the appearance of wrinkled skin. Some evidence shows that vitamin C 3% applied for 12 weeks might reduce facial wrinkles (14008). A small clinical study shows that applying a dissolving microneedle patch containing vitamin C 5.6% every 4 days for 12 weeks to crow's feet on one side of the face reduces wrinkles when compared to control treatment applied on the other side of the face (98780). Other clinical research in females aged 30-60 years shows that applying an oil-soluble cream containing the vitamin C derivative tetra-isopalmitoyl ascorbic acid 1%, 2%, or 3% to the periorbital area twice daily for 8 weeks reduces visual wrinkle grading when compared with placebo. A dose analysis shows greater improvements in wrinkle parameters, average wrinkle depth, and mean depth with the lower concentration, while greater improvements in maximum roughness and maximum depth are observed with the higher concentration (108072). This study only included individuals defined as having Fitzpatrick skin type III or IV; it effects on other skin types is unclear. Preparations containing vitamin C in combination with other ingredients have also been investigated. A small low-quality trial in females with moderately photodamaged and hyperpigmented facial skin shows that applying a moisturizer with vitamin C 30%, vitamin E, and coenzyme Q10 once daily in the morning, along with applying retinol 0.5% once daily or once every other day for 12 weeks, seems to improve skin tone, photodamage, and wrinkles when compared to baseline (99085). In another small trial, a topical preparation containing vitamin C 10% as L-ascorbic acid along with acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months improves fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the beneficial effects of these products are due to vitamin C, other ingredients, or the combination.

Acute bronchitis. Oral vitamin C doesn't seem to improve symptoms of acute bronchitis. Details: A clinical study in adults with acute bronchitis shows that taking vitamin C orally 500 mg on day 1, then 250 mg on days 2 through 5 (similar to an azithromycin regimen) doesn't seem to have any effect on quality of life or bronchitis duration when compared with azithromycin (9827).
Asthma. Oral vitamin C doesn't seem to prevent asthma or improve lung function. Details: Although some observational research has found that some patients with asthma might have lower serum vitamin C levels (5873), other observational research found that increased dietary vitamin C intake is not associated with a reduced risk of asthma or improved lung function (15006,34567). In addition, clinical research shows that supplemental intake of vitamin C does not reduce asthma symptoms, improve lung function, or reduce the use of inhaled steroids in asthma patients (90409).
Atherosclerosis. Oral vitamin C does not seem to reduce the progression of atherosclerosis. Details: A clinical study shows that taking a specific combination product containing slow-release vitamin C 250 mg and vitamin E 136 IU (CellaVie, Ferrosan A/S) twice daily modestly slows the 3-year progression of atherosclerosis of the carotid artery in males, but not females. This result persisted at a 6-year follow-up of this study (1918,10473). However, when this form of vitamin C is used alone, it does not slow the 3-year progression of atherosclerosis of the carotid artery (1918).
Bladder cancer. Oral vitamin C does not reduce the risk of bladder cancer or mortality from bladder cancer. Details: Epidemiological research has found that supplemental vitamin C intake is not associated with mortality rate in patients with bladder cancer (9839). A secondary analysis of a large clinical trial, the Physicians' Health Study II, in healthy men aged at least 50 years also shows that taking vitamin C 500 mg daily alone or with vitamin E 400 IU daily for up to 10 years does not reduce the risk of developing bladder cancer or bladder cancer-related deaths when compared with placebo (90097).
Cardiovascular disease (CVD). Oral vitamin C does not seem to be beneficial for either primary or secondary CVD prevention. Details: Vitamin C does not seem to be beneficial for primary prevention of CVD. Some population research has found that higher supplemental vitamin C or dietary vitamin C has been associated with a reduced risk of developing CVD (10358,14108,109779), while other observational research has found no benefit (34566,10358,14108). However, meta-analyses of clinical research in healthy patients show that vitamin C supplementation does not prevent CVD or coronary heart disease when compared with control (97308,104025). In 2004, the American Heart Association stated that current evidence does not justify use of antioxidants such as vitamin C for reducing the risk of CVD (12142). Evidence is also negative for secondary prevention in people with coronary heart disease. Population studies have found that higher serum vitamin C was associated with no effect or decreased CVD mortality from CVD (3910,5878). A meta-analysis of two large clinical trials shows that vitamin C supplementation does not reduce CVD events or CVD mortality when compared with control (97308).
Colorectal cancer. Oral vitamin C does not seem to prevent colorectal cancer. Details: Population research has found that dietary vitamin C intake is not associated with a reduced risk of developing colon cancer. When total vitamin C intake from food and supplements is considered, there is a modest association (34600). However, most clinical trials show that supplemental vitamin C, alone or along with other antioxidants, does not reduce the risk of colorectal cancer development, colorectal cancer or adenoma recurrence, or colorectal cancer-related mortality (34580,34581,34594,90097,90089,92903).
Coronavirus disease 2019 (COVID-19). Oral vitamin C, even at high doses, does not seem to speed recovery from COVID-19 in non-hospitalized patients. An analysis of clinical research suggests that oral or intravenous vitamin C might reduce mortality in patients hospitalized with COVID-19; however, given that nearly all individual studies are small and do not show benefit, larger and higher-quality studies are needed to confirm these findings. Details: A clinical study in adult outpatients with confirmed COVID-19 shows that taking oral vitamin C (ascorbic acid) 8000 mg in 2-3 divided doses daily, alone or with zinc gluconate 50 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). The study was terminated prior to complete enrollment due to futility and apparent lack of effect from vitamin C and/or zinc supplementation. Limitations of this study include a lack of placebo control and blinding. Additionally, this study has been criticized for methodologic concerns (106624). Another small clinical trial in adult outpatients with confirmed COVID-19 shows that taking vitamin C 1000 mg daily for 14 days does not improve symptoms or quality of life when compared with placebo (109462). Vitamin C has also been evaluated in patients hospitalized with COVID-19. Individual prospective and retrospective studies in critically ill patients hospitalized with COVID-19 in various countries have found that administering vitamin C, either enterally as 500-1000 mg daily or intravenously as 8-24 grams daily or 50 mg/kg daily, does not significantly reduce in-hospital or short-term mortality, hospital length of stay, or end-organ failure when compared with control groups receiving standard care alone. Additionally, all but one study found no change in the need for mechanical ventilation (105458,105465,106937,106938,108075,108079,108081). One small study found a small improvement in survival rate when compared with standard care; however, the overall survival rate in this study was low (108075). Additionally, one clinical study in patients hospitalized in Turkey with COVID-19 shows that adding high-dose intravenous sodium ascorbate 50 mg/kg to a treatment regimen of hydroxychloroquine, azithromycin, and zinc may improve recovery time, with 57% and 39% of patients achieving total recovery at day 15 in the vitamin C and control groups, respectively (108071). However, the validity of this trial is limited due to unclear reporting. Additionally, these small studies were likely underpowered to detect differences between the vitamin C and control groups. A meta-analysis of 10 clinical trials and 9 observational studies in patients hospitalized with COVID-19 shows that receiving oral or intravenous vitamin C daily reduces the odds of in-hospital mortality by 41% when compared with control. When only clinical trials were considered, the odds of in-hospital mortality were decreased by 56%; however, this reduction was only identified in studies using vitamin C 10 grams daily or less. Conversely, supplementation with vitamin C increased the length of intensive care unit (ICU) stay by nearly 2 days and did not impact length of hospital stay or reduce the need for mechanical ventilation, liver injury, or cardiac injury (109955). Given that most individual studies in this analysis did not show improvements in mortality with vitamin C, larger and higher-quality prospective studies are needed to determine the role of vitamin C in hospitalized patients with COVID-19. Vitamin C has also been evaluated in patients with long COVID. Preliminary clinical research in adults with long COVID and persistent fatigue shows that taking a specific combination product containing vitamin C 500 mg and L-arginine 1.66 grams (Bioarginina C, Farmacetici Damor) for 28 days increases 6-minute walk test distance by 10% and reduces self-reported fatigue when compared with placebo (110390).
Fetal and premature infant mortality. Oral vitamin C does not seem to prevent neonatal death. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of neonatal death (83472,96707).
Fractures. Oral vitamin C does not seem to improve fracture healing. Details: Clinical research shows that taking vitamin C 500 mg daily for 50 days following an acute distal radial fracture does not improve physical function, symptoms, or healing rates when compared with placebo (90411).
Helicobacter pylori. Oral vitamin C does not seem to improve eradication of H. pylori. Details: Most clinical research shows that treatment with vitamin C, alone or in combination with vitamin E, does not improve the eradication rate of H. pylori when taken with a standard eradication regimen when compared with the eradication regimen alone (83476,90094).
Hereditary motor and sensory neuropathy. Oral vitamin C does not seem to improve neuropathy in these patients. Details: In a meta-analysis of five studies in patients with Charcot-Marie-Tooth disease type 1A, taking vitamin C 1-4 grams orally daily for 1 year did not improve neuropathy when compared with placebo (99084). Continuing vitamin C 4 grams daily for 2 years also does not improve neuropathy in these patients (90419).
Interferon-related retinopathy. Oral vitamin C does not seem to improve retinopathy associated with interferon therapy. Details: A small clinical study in patients with chronic hepatitis C receiving interferon therapy shows that taking vitamin C 600 daily orally does not seem to reduce the risk of retinopathy from interferon therapy when compared with control (10355).
Leukemia. Oral vitamin C does not seem to reduce the risk of leukemia or mortality from leukemia. Details: A large clinical trial in men aged at least 50 years shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing leukemia or leukemia-related deaths when compared with placebo (90097).
Low birth weight. Oral vitamin C does not seem to reduce the risk of infants being born with a low birth weight. Details: Meta-analyses of clinical research show that maternal use of oral vitamin C alone or with other supplements does not reduce the risk of giving birth to infants with low birth weight when compared with control (83450,83472).
Lung cancer. Oral vitamin C does not seem to reduce the risk of lung cancer. Details: Two meta-analyses of clinical research suggest that taking vitamin C, alone or in combination with vitamin E, does not reduce the incidence of lung cancer or lung cancer-related mortality (34528,34632). Also, a clinical study in females shows that taking supplemental vitamin C 500 mg daily, with or without vitamin E and beta carotene, is associated with an INCREASED risk of lung cancer when compared with placebo (34580).
Melanoma. Oral vitamin C does not seem to reduce the risk of melanoma. Details: Clinical research shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing melanoma or melanoma-related deaths when compared with placebo in men aged at least 50 years (90097).
Miscarriage. Oral vitamin C does not seem to reduce the risk of miscarriage. Details: A meta-analysis of clinical research shows that taking vitamin C alone or with other supplements does not reduce the risk of miscarriage when compared with control (94820).
Overall mortality. Oral vitamin C does not reduce overall mortality. Details: Although population research suggests that higher dietary intake and higher plasma vitamin C levels are associated with a reduced risk of mortality from all causes (3910,109779), vitamin C supplementation does not seem to affect overall mortality. Meta-analyses of clinical research show that taking vitamin C supplements does not reduce overall mortality when compared with control (34622,111641). Clinical studies of vitamin C used in combination with vitamin E, beta carotene, and/or selenium and zinc, also show no benefit for overall mortality (9817,14109).
Pancreatic cancer. Oral vitamin C does not seem to prevent pancreatic cancer. Details: Observational research has found that increased dietary vitamin C intake is associated with up to a 30% reduced risk of pancreatic cancer (99083,99086). However, clinical research shows that supplemental vitamin C 500 mg daily does not reduce the risk of pancreatic cancer in females (34580). Also, taking vitamin C in combination with beta-carotene plus vitamin E does not reduce the risk of pancreatic cancer (12185,34581).
Pre-eclampsia. Oral vitamin C does not seem to prevent pre-eclampsia. Details: Despite some early positive research in high-risk pregnancies, the majority of meta-analyses and clinical studies show that taking vitamin C alone or with vitamin E or other supplements does not reduce the risk of pre-eclampsia when compared with control. There is even some concern that vitamin C supplementation may increase the risk of gestational hypertension (3236,83450,83472,83474,96707).
Preterm labor. Oral vitamin C does not seem to prevent preterm labor. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of preterm labor when compared with control (83450,83472,96707).
Prostate cancer. Oral vitamin C does not seem to prevent prostate cancer. Details: A large-scale clinical study (The SU.VI.MAX study) shows that a combination of vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, selenium 100 mcg, and zinc 20 mg, taken daily for an average of 8 years, does not reduce the risk of prostate cancer overall. However, it might reduce the risk of prostate cancer in those who have normal PSA levels. It does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). Another large scale study (Physician's Health Study II) shows that taking vitamin C 500 mg daily for an average of 8 years does not significantly reduce the risk of prostate cancer when compared with placebo (16708). Similarly, results from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial seem to show that supplemental or dietary intake of vitamin C does not reduce the risk of prostate cancer when compared to individuals not taking vitamin C (14124).
Radiation dermatitis. Topical vitamin C does not seem to prevent radiation dermatitis in cancer patients. Details: A small clinical study shows that applying a 10% vitamin C solution does not appear to protect from radiation dermatitis when applied to the scalps of patients treated with radiation for intracranial tumors (789).
Small for gestational age (SGA). Oral vitamin C does not seem to reduce SGA. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of small for gestational age birth when compared with control (83450,83472).
Stillbirth. Oral vitamin C does not seem to prevent stillbirth. Details: Meta-analyses of clinical research show that maternal use of vitamin C alone or with other supplements does not reduce the risk of stillbirth when compared with control (83472,96707).

Sepsis. Intravenous vitamin C, alone or in combination with thiamine and/or hydrocortisone, does not prevent organ failure, reduce intensive care or hospital length of stay, or reduce mortality in sepsis or septic shock. Details: Observational research suggests that patients with septic shock are more likely to have low plasma levels of vitamin C (100317). However, two randomized clinical trials in patients with sepsis show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027). A clinical study in patients with septic shock shows that administering an intravenous bolus of vitamin C 1000 mg followed by a continuous infusion of 250 mg/hour for 96 hours, starting within 24 hours of vasopressor initiation, does not improve 28-day or intensive care unit (ICU) mortality when compared with placebo. A subgroup analysis shows that the addition of corticosteroids does not affect outcomes in either group (108078). This study may have been inadequately powered to detect a difference between groups. Also, a larger clinical trial in adults with sepsis receiving vasopressor therapy in the ICU shows that intravenous administration of vitamin C 50 mg/kg every 6 hours for up to 4 days increases the risk of death or persistent organ dysfunction at day 28 by 14% to 21% when compared with placebo. There were no differences in mortality at 6 months (109459,111643). Vitamin C has also been frequently studied in patients with sepsis and septic shock in a specific combination regimen (HAT therapy) which includes intravenous vitamin C 1.5-2 grams with hydrocortisone 50 mg every 6 hours and thiamine 200 mg every 12 hours. While some retrospective research has found HAT therapy to be beneficial in sepsis (100315,102980), high quality, prospective clinical research has not confirmed these findings (105447,106620,109956). Several meta-analyses of randomized controlled trials and small clinical studies in patients with sepsis or septic shock show that intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, does not reduce short- or long-term mortality, ICU or hospital length of stay, kidney injury, or duration of mechanical ventilation, but modestly improves duration of vasopressor use and procalcitonin clearance, when compared with placebo or standard care. These analyses also show mixed results with respect to improvement in sequential organ failure assessment (SOFA) scores within 72 hours (105447,106620,106935,108073,109460,111298,111300,111301,111642,112479). Most studies included in the analyses administered HAT therapy for 2-10 days and compared it with normal saline control or with hydrocortisone alone (102129,102998,104027,104028,104032,105446). Although some subgroup analyses suggests that intravenous vitamin C alone in patients with sepsis may improve short-term mortality (106620,111298), other meta-analyses have not shown this benefit in subgroup analyses (111300). In addition, meta-analyses have identified significant publication bias (111298,111300). Long-term follow up from a study in patients with sepsis-induced respiratory and/or cardiovascular dysfunction shows that receiving HAT therapy does not improve cognitive, psychological, or functional status after 6 months and, for some domains, HAT therapy was worse when compared with placebo (111299). Studies evaluating intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, in mixed critically ill populations have also shown mixed findings. One such large meta-analysis of 27 randomized controlled trials and 21 observational studies shows that intravenous vitamin C reduces in-hospital mortality by 19% and ICU stay by about 1 day, but does not have a significant effect on hospital stay, mortality at 1 month, ICU mortality, or kidney injury, when compared with placebo or standard care. Also, effects on in-hospital mortality were no longer significant when data from randomized controlled trials were considered alone (106933). Other meta-analyses including 15-16 randomized controlled trials show that intravenous vitamin C, alone or as a component of HAT therapy, does not reduce overall, ICU, or in-hospital mortality when compared with control (106934,109957). A subgroup analysis in one of these analyses suggests that intravenous vitamin C as monotherapy, or in doses of at least 10 grams daily, may improve overall mortality (106934). Vitamin C also does not appear to benefit complications from sepsis, such as vasoplegic shock. A small clinical study in adults in the ICU with vasoplegic shock mostly secondary to sepsis and requiring moderate vasopressor support shows that administering intravenous vitamin C as sodium ascorbate 1.5 grams every 6 hours for 5 days or until cessation of vasoactive therapy does not reduce the duration of vasopressors, vasopressor dose, hospital or ICU length of stay, or mortality outcomes when compared with placebo (112475).

Atrophic acne scars. It is unclear if applying topical vitamin C after microblading improves atrophic acne scars. Details: A clinical study in adults with mild to severe atrophic acne scarring shows that applying a serum containing vitamin C 17% to the face after a once-monthly home microblade treatment for 4 months improves the appearance of acne scars at month 5 when compared with baseline (108086). Although this study enrolled a control group that used topical insulin in place of vitamin C, no between-group statistical comparisons were conducted, limiting the validity of this study.
Age-related macular degeneration (AMD). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Most clinical research shows that taking the antioxidants vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily, with or without elemental zinc 80 mg, reduces the risk of visual acuity loss by 23% to 27% and reduces the risk of progression to advanced AMD at 5 years by 25% to 32% in patients at high risk for developing advanced AMD (7303,7304,11326,90069). The antioxidant plus zinc combination seems to reduce the risk of progression to advanced AMD in these patients more than taking the antioxidants without zinc (7303,90069). There is not enough evidence to know if taking the antioxidants or antioxidants plus zinc prevents progression to advanced AMD in patients with early stage AMD (7303,7304). The effect of vitamin C intake on developing AMD is unclear. Some population studies have found no association between dietary or supplemental vitamin C intake on risk of developing AMD (14007,14257). In one population study, vitamin C intake was associated with increased odds of developing age-related maculopathy (9823); however, in another population study, intake of vitamin C along with other antioxidants and zinc was associated with a reduced risk of AMD (14257). More evidence is needed to determine what role, if any, vitamin C intake has on the risk of developing AMD.
Aging skin. Topical vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females aged 30-65 years shows that applying a specific liquid (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% to the face nightly for 8 weeks, in addition to regular facial skin products, improves skin color, elasticity, radiance, smoothness, and appearance of wrinkles when compared with regular facial skin products alone (102355).
Albuminuria. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking vitamin C 1250 mg plus vitamin E 680 IU daily for 4 weeks can reduce the excretion of albumin by about 19% when compared with placebo in patients with type 2 diabetes (10434).
Allergic rhinitis (hay fever). It is unclear if oral vitamin C is beneficial in patients with hay fever. Details: Epidemiological research has found that higher vitamin C plasma levels are not associated with a decreased risk of allergic rhinitis (15200). However, clinical research shows that some forms of vitamin C might help. In one small clinical study, intranasal vitamin C administered three times daily for 2 weeks reduces nasal secretions, nasal blockage, and edema in up to 74% of patients with perennial allergic rhinitis (15201). Another small clinical study in patients with seasonal allergic rhinitis shows that taking a single oral dose of vitamin C 2 grams reduces bronchial responsiveness to histamine at one hour after ingestion (15202). However, in another small study in patients with seasonal allergic rhinitis taking vitamin C orally in doses up to 4 grams daily for 3 days does not appear to suppress cutaneous or nasal response to histamine when compared to placebo (15203).
Alzheimer disease. It is unclear if dietary vitamin C helps to prevent this condition. Details: Most epidemiological research has found that dietary intake of vitamin C is associated with a 17% reduced risk of developing Alzheimer disease (4636,9824,10131,13165,90082).
Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral vitamin C helps to prevent ALS. Details: Observational research has found that increased dietary or supplemental intake of vitamin C is not associated with risk of developing ALS (90412).
Anthracycline cardiotoxicity. Although there is interest in using oral vitamin C for anthracycline-induced cardiac toxicity, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
Aspirin-associated gastric damage. It is unclear if oral vitamin C helps to prevent gastric damage caused by aspirin. Details: Some clinical research shows that vitamin C 480 mg might prevent gastric damage associated with taking aspirin 400 mg by decreasing blood loss and preventing decreased gastric blood flow (10357). However, a small clinical study in healthy patients shows that taking vitamin C 500 mg as ascorbic acid with aspirin 600 mg actually increases gastrointestinal permeability to a greater extent than either ingredient taken alone (98781).
Athletic performance. It is unclear if oral vitamin C improves athletic performance. Details: Although some small preliminary clinical studies suggest that vitamin C might improve certain biomarkers during exercise (82922), a meta-analysis of small clinical trials in older and younger adults shows that taking vitamin C 500-1000 mg daily, with or without vitamin E, does not improve endurance, lean mass, or muscle strength when compared with placebo (102973). A more recent, small clinical study in recreationally trained males shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg daily for 10 weeks while participating in a resistance training program does not improve measures of muscle strength when compared with placebo (109959).
Atopic disease. It is unclear if dietary vitamin C helps to prevent atopic disease. Details: Population research has found that higher intake of vitamin C is not associated with a reduced risk of eczema, wheeze, IgE-mediated food allergy, or allergic sensitization (90098).
Attention deficit-hyperactivity disorder (ADHD). Small clinical studies suggest that high-dose oral vitamin C may not improve symptoms in patients with ADHD. Details: Some research suggests that taking megadose vitamins, including vitamin C, does not improve ADHD symptoms (9957,9958,9959). However, other preliminary clinical research shows that taking 25 mg of vitamin C in combination with flaxseed oil providing alpha-linolenic acid 200 mg twice daily might improve measures of attention, impulsivity, restlessness, and self-control in children with ADHD when compared with baseline (14443). It is not clear if these effects are due to vitamin C, flaxseed oil, or the combination.
Autism spectrum disorder. It is unclear if oral vitamin C is beneficial in patients with autism spectrum disorder. Details: One small clinical study shows that taking vitamin C 8 grams per 70 kg daily for 10 weeks modestly reduces autism symptom severity in school children when compared with placebo (83604).
Bleeding. It is unclear if intravenous vitamin C can reduce bleeding after total abdominal hysterectomy. Details: A small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery reduces postoperative hemorrhage volume by around 40 mL when compared with placebo (109465).
Brain tumor. It is unclear if oral vitamin C helps to prevent brain tumors. Details: Population research has found that vitamin C intake is associated with a 14% reduced risk of glioma. This risk reduction was more prevalent in America compared to other geographic locations (98782).
Breast cancer. It is unclear if oral vitamin C helps to prevent breast cancer, its recurrence, or breast cancer-related mortality. Details: Some epidemiological research has found that dietary vitamin C is associated with a reduced risk of breast cancer (1444,10823,10824). However, other epidemiological research has found no association with dietary or supplemental vitamin C (10825,10826,108080). One cohort study found no association between breast cancer risk and total, dietary, or supplemental vitamin C, regardless of dose, treatment duration, or formulation (single ingredient or combination product). Additionally, hormone and menopausal status did not appear to impact risk. Vitamin C intake might be associated with a reduced risk in individuals with a family history of breast cancer in first-degree relatives (108080). In patients with breast cancer, supplemental or dietary intake of vitamin C might be associated with a reduced risk of mortality. A meta-analysis of results from population research shows that vitamin C supplementation following breast cancer diagnosis is associated with a 15% lower risk of breast cancer-related mortality when compared with no supplementation (90416). A large, observational study in patients with breast cancer undergoing radiation therapy has found that vitamin C supplementation does not reduce the risk of breast cancer recurrence over a period of 5 years when compared with no supplementation. Although the vitamin C group had notably less aggressive tumor types, recurrence-free survival was similar in both vitamin C and control groups (108082). The validity of these findings is limited due to unknown doses of vitamin C and the inclusion of various breast cancer subtypes.
Burns. Small studies suggest that intravenous vitamin C may modestly improve symptoms in patients with severe burns. Details: A small clinical study in patients with severe burns shows that administering vitamin C intravenously (IV) 66 mg/kg hourly over 24 hours, as part of fluid resuscitation using lactated ringer solution, reduces wound edema and the volume of fluid needed when compared with fluid resuscitation alone (83145). A retrospective review of adults hospitalized with severe burns has found that those who receive a continuous IV infusion of at least 10 grams of vitamin C within 2 days of admission have an in-hospital mortality rate of 46%, compared with 58% for those who do not receive vitamin C (102128).
Cancer. It is unclear if oral or intravenous vitamin C helps to prevent cancer or cancer-related mortality. Details: Some population research has found that DIETARY intake of vitamin C is linked with a lower risk of cancer and cancer-related mortality (3910,5878,10819,109779). However, clinical research shows that taking vitamin C SUPPLEMENTS does not reduce the risk for cancer (10819,14109,34580,90097). In people with cancer, although some clinical research has shown that taking high-dose vitamin C supplements can improve survival rates (9809,96704), other clinical research has not shown this benefit (4842,4843). In 2003, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that some scientific evidence suggests that antioxidant vitamins, such as vitamin C, may reduce the risk of certain forms of cancer. However, the FDA has determined that there is little scientific evidence supporting this claim (102334). Preliminary clinical research has also evaluated vitamin C supplements in patients with cancer. High-dose oral vitamin C, 10 grams daily, in patients with advanced cancer does not seem to improve survival or decrease disease progression (4842,4843,106617). However, preliminary clinical research suggests high doses of vitamin C, given intravenously, might have a beneficial effect on some outcomes, including survival rate in some patients with cancer (9809,96704,106617). However, there is no benefit to other patients studied in the case reports and this has not been tested in well-designed clinical trials (9809,96704).
Carpal tunnel syndrome. Vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamins C, E, B1, B2, B6, and B12, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, and turmeric twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with control (111702). The validity of these effects is limited by a lack of blinding. The study may also be inadequately powered to detect a difference between groups. Additionally, it is unclear if the effects are due to vitamin C, other ingredients, or the combination.
Cataracts. It is unclear if oral vitamin C helps to prevent cataracts. Details: Population research has found that people with the highest total intake of vitamin C have about a 19% reduced risk of developing cataracts when compared with those with the lowest total intake. The greatest benefit is observed for nuclear cataracts (96711). A separate study found that higher supplemental intake of vitamin C for 10 years is associated with a 60% reduction in the incidence of nuclear and cortical cataracts (4208). Other population research has found that the highest blood levels of vitamin C are associated with a 33% reduced odds of developing age-related cataract, but any benefit seems to be limited to Asian populations (90944). One prospective clinical study shows that taking vitamin C plus vitamin E and beta-carotene does not prevent the development or progression of age-related loss of vision due to cataracts in well-nourished people taking the supplement for an average of 6.3 years (7304).
Cervical cancer. It is unclear if oral vitamin C helps to prevent cervical cancer. Details: Observational research has found that higher vitamin C intake is associated with a 33% to 42% reduced odds of cervical neoplasm. Increasing vitamin C intake by 50 mg daily is associated with an 8% reduced odds of cervical neoplasm (34609,98771).
Chronic fatigue syndrome (CFS). Although there is interest in using oral vitamin C for CFS, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
Colistin-induced nephrotoxicity. It is unclear if intravenous vitamin C helps to prevent nephrotoxicity from colistin. Details: A small clinical study shows that intravenous administration of vitamin C 2 grams every 12 hours along with colistin for around 9-10 days does not prevent nephrotoxicity when compared with colistin therapy alone (99839). However, this study was limited by a lack of statistical power to detect differences between the study groups.
Contrast induced nephropathy. It is unclear if oral vitamin C helps to prevent contrast-induced nephropathy (CIN). Details: Some clinical research shows that taking vitamin C before and after coronary angiography reduces the risk of developing CIN by 33% to 55% when compared with placebo in patients with renal dysfunction (12234,90421). However, other clinical evidence published since 2012 suggests that vitamin C given orally and/or intravenously before and after angiography does not reduce the risk of CIN compared with control in high-risk patients with chronic renal insufficiency or diabetes (91232,91236,90410,90425). Reasons for the discrepancies are not entirely clear. However, it is possible that the lack of significant benefit from vitamin C in the latter studies results from the fact that incidences of CIN have become less common than in the past due to avoidance of dehydration, use of smaller catheters, and use of contrast agents with reduced nephrotoxicity (90429).
Coronary artery bypass graft (CABG) surgery. It is unclear if intravenous vitamin C helps to improve patient outcomes after CABG surgery. Details: A small clinical study shows that giving vitamin C 5 grams intravenously (IV) before anesthesia induction and 5 grams in the cardioplegia solution used during surgery shortens the length of stay in the intensive care unit (ICU) by about 8 hours (102127). However, some limited research suggests that IV vitamin C does not resolve cardiac surgery complications. A small clinical study in patients with vasoplegia after receiving CABG and other cardiac surgeries shows that receiving IV vitamin C 1.5 grams every 6 hours after being admitted to the ICU does not improve vasoplegia when compared with control (102981).
Delirium. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research in adults with septic shock has found that receiving intravenous thiamine 400 mg daily with vitamin C 6 grams daily, both in divided doses, is not associated with reduced delirium when compared with control (103001).
Dental plaque. It is unclear if vitamin C in a chewing gum helps to reduce dental plaque formation. Details: A small clinical study in patients with calculus shows that chewing 10 pieces of gum, each containing 60 mg of vitamin C, daily for 3 months reduces the formation of dental calculus, visible plaque, and the number of bleeding sites when compared not chewing gum (83303). The validity of this finding is limited by a lack of placebo group.
Depression. It is unclear if oral vitamin C is beneficial for the treatment or prevention of depression. Details: A small clinical study in children and adolescents shows that taking vitamin C 500 mg orally twice daily in combination with fluoxetine 10-20 mg daily for 6 months reduces most symptoms of major depressive disorder when compared with taking fluoxetine alone (90404). However, a small clinical study in adults shows that taking vitamin C up to 1000 mg daily for 2 months does not improve the response rate or decrease symptoms of depression in adults also taking citalopram when compared with citalopram alone (96708). Reasons for these conflicting results may relate to the age of the patients, study duration, or differences in antidepressant medication being taken. One clinical guideline also provisionally recommends against the use of oral vitamin C to treat patients with depression based on low-quality evidence (110318). Some research has also evaluated vitamin C intake for the prevention of depression. A secondary analysis of pre- and peri-menopausal adults enrolled in the Study of Women's Health Across the Nation (SWAN) program suggests that vitamin C intake is inversely associated with depressive symptoms. This association persisted regardless of age, race, physical activity, body mass index, antidepressant use or menopausal status (108083). The validity of these findings is limited due to the secondary nature of this study; additionally, follow-up time is unclear.
Diabetes. It is unclear if oral vitamin C prevents diabetes. Some low-quality research suggests that vitamin C might improve glycemic control in patients with diabetes. Details: Population research has not found a link between dietary vitamin C and the risk of developing type 2 diabetes (14004). However, low certainty clinical research has found some benefit of taking vitamin C supplements for glycemic control. Two meta-analyses of several small, heterogeneous clinical studies in patients with type 2 diabetes show that taking vitamin C 200-3000 mg daily for 2-48 weeks reduces fasting blood glucose by approximately 11 mg/dL (112478) and glycated hemoglobin (HbA1c) by an average of 0.5% when compared with placebo, standard treatment, or no treatment (105461,112478). Subgroup analyses suggest that durations of supplementation longer than 12 weeks show greater glycemic benefit, and although one meta-analysis suggests there is no dose-response relationship (105461), another meta-analysis suggests that doses of vitamin C 1000 mg and higher are most beneficial for improving glycemic indices (112478). Some research has evaluated the effects of vitamin C supplementation on the lipid profile in patients with diabetes, with mixed findings. One meta-analysis of 17 small clinical studies shows that taking vitamin C 200-3000 mg daily for 2 to 48 weeks improves levels of triglycerides and total cholesterol, but not low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. Subgroup analysis suggests that study durations of at least 12 weeks show greater benefit (106621). However, two other meta-analyses in patients with diabetes, one of 16 small heterogenous clinical studies and one of 11 small clinical studies, show no clinically important improvement in lipid levels after vitamin C supplementation (105461,105464).
Dry mouth. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical trial in patients receiving radiotherapy for head and neck cancer shows that taking vitamin E 100 IU and vitamin C 500 mg twice daily for an average of 3 months improves dry mouth when compared to baseline (99080). The validity of these results is limited by the lack of comparison with a control group.
Endometrial cancer. Increased dietary vitamin C has been linked to reduced risk of endometrial cancer. Details: Population research has found that intake of vitamin C from dietary sources is associated with a slightly decreased risk of endometrial cancer when compared with control. However, this benefit is not observed when results from a prospective cohort study are assessed (34578).
Endometriosis. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with endometriosis and pelvic pain shows that taking vitamin C 1000 mg and vitamin E 800 IU daily for 8 weeks improves dysmenorrhea, dyspareunia, and chronic pelvic pain scores when compared with placebo. Vitamin C and vitamin E supplementation also reduces some biochemical markers of oxidative stress when compared with placebo (106622).
Endoscopy-associated adverse effects. It is unclear if a topical vitamin C spray reduces mucosal irritation in patients undergoing Lugol chromoendoscopy. Details: A small clinical trial in patients receiving a Lugol chromoendoscopy shows that spraying a vitamin C 2% solution after the application of the Lugol iodine 2% solution reduces the severity of mucosal irritation, heartburn, and pain when compared with using a normal saline spray after the Lugol iodine 2% solution (104030).
Esophageal cancer. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Population research has found that higher dietary intake of vitamin C is associated with reduced odds of esophageal adenocarcinoma. A 50 gram increase in dietary vitamin C intake is associated with a 13% reduced odds of esophageal cancer (34551,98770). However, a meta-analysis of clinical research shows that taking a vitamin C supplement in combination with beta-carotene and vitamin E does not reduce the risk of esophageal cancer (34581).
Exercise-induced asthma. Small clinical studies suggest that oral vitamin C may modestly improve symptoms in patients with exercise-induced asthma. Details: A meta-analysis of the available clinical research shows that vitamin C supplementation might reduce exercise-induced breathlessness when compared with placebo or control. However, the available research is of poor quality, and no clear conclusions can be drawn regarding its benefits for exercise-induced asthma (90409).
Exercise-induced muscle damage. It is unclear if oral vitamin C is beneficial in exercise-induced muscle damage. Details: A small clinical study in healthy females shows that taking vitamin C 1000 mg before moderate intensity cycling does not prevent muscle damage when compared with placebo (99837). Another small clinical study in endurance-trained runners shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg 2 hours prior to an exercise protocol does not reduce delayed onset muscle soreness or improve other markers of exercise-induced muscle damage when compared with placebo (109961).
Gallbladder disease. It is unclear if oral vitamin C reduces the risk of gallbladder disease. Details: Cross-sectional epidemiological evidence has found that vitamin C supplementation and increased vitamin C serum levels are associated with a decreased risk of developing gallbladder disease in females, but not males (5877).
Gastric cancer. It is unclear if dietary or supplemental vitamin C reduces the risk of gastric cancer. Details: Most population research has not found an association between DIETARY intake of vitamin C and gastric cancer risk (9194,10822,10819,90083). Also, clinical research shows that taking vitamin C supplements in combination with other antioxidants does not reduce the risk of gastric cancer or precancerous gastric lesions (14447,34581,90085). However, some research suggests that it might be associated with a reduced risk for specific forms of gastric cancer (9838,90083). One clinical study shows that taking vitamin C orally 500 mg daily for 6 months after eradication of Helicobacter pylori infection decreases the incidence of precancerous changes in stomach tissue when compared with no treatment (10359). Also, other clinical research shows that taking vitamin C orally 1 gram daily helps promote the regression of precancerous gastric lesions in people at high risk for gastric cancer (2579). In 2009, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that vitamin C supplements may reduce the risk of gastric cancer. However, the FDA has concluded that it is highly uncertain that vitamin C supplements actually reduce the risk of gastric cancer (102332).
Gastritis. There is limited evidence on the oral use of vitamin C in omeprazole-induced corpus gastritis. Details: A small clinical study shows that taking vitamin C orally 1200 mg daily along with omeprazole decreases corpus gastritis associated with omeprazole therapy in patients with H. pylori infection (10360).
Gout. It is unclear if oral vitamin C helps to prevent or manage gout. Details: Population research in men has found that taking vitamin C 500-1500 mg daily from the diet and/or supplements is associated with up to a 34% reduced risk of gout when compared with less than 250 mg daily (16755). Also, men who ingest over 500 mg of vitamin C daily from the diet and supplements have serum uric acid levels that are slightly lower than men who consume less than 90 mg daily (16820). However, taking supplemental vitamin C 500 mg daily for 8 weeks does not seem to lower serum uric acid levels in patients who already have gout (90423).
Hearing loss. There is limited evidence on the intravenous use of vitamin C in idiopathic sudden sensorineural hearing loss. It is unclear if dietary vitamin C intake can affect the risk of hearing loss. Details: A small clinical study in patients with idiopathic sudden sensorineural hearing loss shows that receiving intravenous high-dose vitamin C 200 mg/kg daily in combination with steroid therapy for 10 days, followed by oral vitamin C 2000 mg daily for 30 days, increases recovery rate two-fold and modestly improves hearing threshold levels when compared with receiving steroid therapy only (90417). In addition, population research in females has found that high dietary intake of vitamin C is associated with a 22% increased risk of developing self-reported hearing loss over a 22-year period when compared with low intake (109807).
Heart transplant complications. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial shows that a combination of vitamin C 500 mg and vitamin E 400 IU, taken twice daily for 1 year starting within the first 2 years after cardiac transplant, reduced the progression of vasculopathy as measured by intravascular ultrasonography (IVUS) when compared with placebo. This suggests that the combination may help slow the progression of CAV (82826).
Hepatitis C. It is unclear if oral vitamin C is beneficial in patients with hepatitis C. Details: A small clinical study in patients with confirmed hepatitis C shows that taking vitamin C 1000 mg daily with conventional therapy (sofosbuvir plus daclatasvir) for 4 weeks improves serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, and albumin when compared with conventional therapy alone (109463).
HIV/AIDS. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, low-quality study in men with HIV shows that taking vitamin C 250 mg daily in combination with vitamin A, beta-carotene, vitamin E, selenium, and coenzyme Q10 does not improve viral load, although it seems to improve markers of oxidative stress when compared to baseline. However, a 1000 mg dose of vitamin C, as well as higher doses of the other antioxidants, do not seem to provide any additional effect (9830).
HIV transmission. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in HIV-positive mothers shows that taking vitamin B, vitamin C, and vitamin E daily during pregnancy and while breast-feeding for 20 weeks seems to reduce child mortality and HIV transmission through breast milk when compared with taking vitamin A (9801).
Hyperphosphatemia. Intravenous vitamin C might be beneficial for reducing phosphate levels in patients with end-stage renal disease. Details: A small clinical study in hemodialysis patients with elevated phosphorus levels suggests that administering vitamin C 500 mg intravenously three times weekly for 8 weeks reduces phosphorus levels about seven-fold when compared with placebo (90414).
Idiopathic interstitial pneumonia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with idiopathic pulmonary fibrosis, a form of idiopathic interstitial pneumonia, shows that taking a combination of vitamin C 250 mg every other day, vitamin D 50,000 IU daily, and vitamin E 200 IU daily for 12 weeks improves some, but not all, measures of lung function and reduces markers of inflammation and oxidative stress when compared to baseline (109464). The validity of these findings is limited by a lack of placebo control group.
Infertility. It is unclear if oral vitamin C is beneficial in anovulatory females. Details: A very small clinical study suggests that taking vitamin C 400-1000 mg daily might improve fertility, resulting in ovulation and pregnancy in some anovulatory females, when compared with baseline (14018). The validity of these findings is limited by the small study size and lack of a comparator group.
Male infertility. It is unclear if oral or intravenous vitamin C is beneficial in males with infertility. Details: A meta-analysis of three small, low-quality clinical trials in males with infertility shows that taking vitamin C up to 1000 mg daily for up to 12 weeks can improve sperm count, motility, and vitality, but does not seem to increase semen volume or sperm concentration, when compared with control (109461). It is unclear if vitamin C can increase pregnancy rates, as these studies did not assess this outcome. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing vitamin C 90 mg, zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, coenzyme Q10 20 mg, folic acid 0.2 mg, selenium 0.05 mg, and vitamin B12 0.015 mg (Proxeed Plus, Sigma-Tau) orally twice daily for 6 months improves sperm count, sperm concentration, and sperm motility when compared with baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles. The validity of this study is limited by the lack of a comparator group (111296).
Mastalgia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with mastalgia shows that taking a combination of vitamin C 100 mg, vitamin B12, and gamma-linolenic acid daily for 12 weeks does not improve the proportion of patients with minimal or no pain when compared with placebo (111059).
Melasma. It is unclear if topical vitamin C is beneficial in patients with melasma. Details: A small clinical study in patients with bilateral symmetrically distributed facial melasma shows that topical application of 0.5 mL of vitamin C (Cosmotech, Alpha Medical Cosmotech) following dermapen microneedling every 2 weeks for 6 weeks is similarly effective to tranexamic acid for improving melasma severity and pigmented, but not vascular, findings on dermoscopic examination (106939).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin C is beneficial in patients with NAFLD. Details: A clinical study in patients with NAFLD shows that taking vitamin C 250 mg, 1000 mg, or 2000 mg daily for 12 weeks improves some biochemical markers of liver health and glucose metabolism when compared with baseline. However, the improvement from baseline was similar between groups (106942).
Nonalcoholic steatohepatitis (NASH). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research suggests vitamin C in combination with vitamin E might improve hepatic fibrosis in patients with NASH. However, it does not seem to decrease liver inflammation (14005).
Non-Hodgkin lymphoma. It is unclear if oral vitamin C reduces the risk of developing diffuse large B-cell lymphoma. Details: In one population study, higher dietary or supplemental intake of vitamin C was associated with a reduced risk of diffuse large B-cell lymphoma, a type of non-Hodgkin lymphoma, when compared with lower intake in postmenopausal adults (90945).
Oral cancer. It is unclear if oral vitamin C reduces the risk of developing oral cancer. Details: Population research has found that higher dietary intake of vitamin C is associated with a reduced risk of oral cancer (10821). However, clinical research has not shown benefit with oral vitamin C supplements. A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
Oral leukoplakia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not improve leukoplakia symptoms or reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
Osteoarthritis. It is unclear if dietary vitamin C reduces the risk of developing osteoarthritis. Details: Observational research has found that increased vitamin C from dietary sources is associated with a reduced risk of cartilage loss and disease progression in people with osteoarthritis (5881).
Osteoporosis. It is unclear if dietary vitamin C improves bone density or reduces fracture risk in patients at risk for osteoporosis. Details: Some cross-sectional observational research in postmenopausal patients without a history of smoking or estrogen use has found that higher serum vitamin C levels are associated with lower bone mineral density (9828). However, other observational research in a larger population of adults at risk for osteoporosis has found that higher dietary vitamin C intake is not associated with fracture risk (104415).
Ovarian cancer. Dietary vitamin C might not affect the risk of ovarian cancer. Details: Epidemiological research has found that dietary vitamin C intake is not linked with ovarian cancer risk (9193,102977).
Pancreatitis. It is unclear if intravenous vitamin C is beneficial in patients with acute pancreatitis. Details: A small meta-analysis of clinical studies in patients with acute pancreatitis shows that intravenous vitamin C does not improve the odds of developing organ failure when compared with placebo or no intervention. Intravenous vitamin C seems to reduce hospital stay, but not in-hospital mortality (106941).
Parkinson disease. Dietary vitamin C might not affect the risk of developing this condition. Details: Observational research has found that moderate or high dietary intake of vitamin C is not associated with a reduced risk of Parkinson disease (83316).
Periodontitis. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is also unclear if dietary vitamin C reduces the risk of periodontitis. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a supplement containing vitamin C 100 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin E, and zinc twice daily for 8 weeks in addition to standard nonsurgical therapy does not improve periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation, among others, when compared with placebo (111708). It is unclear if these effects are due to vitamin C, other ingredients, or the combination. There is also interest in whether dietary vitamin C intake impacts the risk of periodontitis. Observational research in US adults has found that individuals with dietary intake of vitamin C in the third quartile, but not the second or fourth quartiles, have lower odds of periodontitis when compared with vitamin C intake in the lowest quartile. Furthermore, the investigators identified a non-linear relationship between vitamin C intake and periodontitis risk, suggesting that individuals with intakes either much lower or much higher than 158 mg daily are at increased risk of developing periodontitis (109958).
Peripheral arterial disease (PAD). It is unclear if dietary vitamin C helps to reduce the risk of developing PAD. Details: In females, epidemiological evidence has found that dietary intake of vitamin C of 142 mg daily or greater is associated with a 36% reduced risk of PAD when compared with lower intake levels of less than 80 mg daily (10130).
Physical performance. It is unclear if oral vitamin C helps to improve physical performance and muscle strength in older people. Details: Population research has found that higher intake of dietary vitamin C is associated with improved physical performance and muscle strength in elderly people (14006). In contrast, a small clinical study in elderly men undergoing strength training shows that taking vitamin C 1000 mg and vitamin E 258IU daily for 12 weeks does not increase strength, and might even attenuate increases in muscle mass, when compared with strength training alone (96701).
Pneumonia. It is unclear if oral vitamin C helps to prevent pneumonia. Details: A meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the occurrence of pneumonia when compared to control (104033).
Postoperative recovery. It is unclear if oral or intravenous vitamin C improves postoperative recovery. Details: Meta-analyses of clinical research show that oral or intravenous vitamin C can shorten the duration of hospitalization after cardiac surgery when compared with control (91233,96703). However, other research shows no decrease in intensive care or hospital stay with vitamin C supplementation (96705). A meta-analysis of 37 clinical trials in adults undergoing low- to high-risk noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, or kidney transplantation), shows that receiving perioperative vitamin C, either orally or intravenously, does not improve duration of hospitalization or overall mortality when compared with control (108087). There's also some limited evidence that vitamin C might reduce postoperative pulmonary complications such as lung infection, pleural effusion, and pneumothorax. A small clinical trial in low-risk cardiac surgery patients shows that receiving intravenous vitamin C 1 gram 10 minutes after anesthesia might slightly reduce the rate of postoperative pulmonary complications when compared with receiving a saline injection (104034).
Premature rupture of membranes (PROM). Oral vitamin C seems to reduce the risk of PROM in some patients; however, the addition of oral vitamin E seems to negate any benefit. Details: A meta-analysis of clinical research shows that taking vitamin C alone decreases the risk of both term and preterm PROM by 45% and 34%, respectively, when compared with placebo or control (96707). Also, a more recent clinical study in patients with a history of PROM shows that taking vitamin C 100 mg daily, starting at 14 weeks' gestation, increases the gestational age at recurrent PROM by around 1 week and increases the gestational age at birth by around 1.3 weeks when compared with placebo (109960). Taking vitamin C in combination with vitamin E, however, does not seem to reduce the risk of term or preterm PROM; some research suggests that it might even increase the risk of non-preterm PROM (83472,96707). However, other research shows that taking vitamin C 1000 mg plus vitamin E 400 IU daily, beginning at 24 to 34 weeks gestation and continuing until delivery, may help increase the latency period until delivery by 5 days and increase gestational age at delivery by almost 1 week when compared with placebo in patients with preterm PROM (90078).
Pressure ulcers. It is unclear if oral vitamin C, when used alone or in combination with other ingredients, can improve the healing of pressure ulcers. Details: A small clinical study in institutionalized patients with pressure ulcers shows that taking vitamin C 500 mg twice daily for 12 weeks does not improve wound closure or increase healing rates when compared with vitamin C 10 mg twice daily (83617). Oral vitamin C has also been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients with pressure ulcers shows that administering an oral nutritional supplement enriched with vitamin C, L-arginine, and zinc improves ulcer healing when compared with a standard diet (31953,87173). Also, clinical research in patients living in long-term care facilities shows that taking an oral nutritional supplement enriched in protein, vitamin C, L-arginine, and zinc daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
Radiation proctopathy. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with chronic radiation proctitis shows that vitamin C 500 mg plus vitamin E 400 IU three times daily might improve symptoms when compared with baseline (9825). The validity of these findings is limited by the lack of a comparator group.
Renal cell carcinoma. It is unclear if increased dietary intake of vitamin C helps to reduce the risk of renal cell carcinoma. Details: Population research has found that increased dietary intake of vitamin C is associated with a 12% reduced risk of renal cell carcinoma (98779).
Respiratory tract infections. It is unclear if oral vitamin C is beneficial for preventing respiratory tract infections or reducing the duration of these infections. Details: A meta-analysis of clinical research in children and adults shows that, when compared with placebo, oral vitamin C supplementation reduces the average number of symptomatic days per individual, but does not reduce the average symptom days per respiratory episode. Also, vitamin C intake does not reduce the incidence or severity of respiratory disease or improve recovery in hospitalized patients with respiratory tract infections (108077). The validity of this trial is limited by the high heterogeneity of included studies, which evaluated various vitamin C regimens, ranging from 100 mg to 8 grams daily, as preventive therapy or as an adjuvant to active treatment. A clinical study in children aged 3-10 years shows that taking vitamin C 50 mg in combination with a specific product (Lab4) containing Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium animalis subsp. lactis daily for 6 months reduces the incidence of cough and sore throat by 16% and 20%, respectively, when compared with placebo. However, it did not improve total symptoms, nasal congestion, nasal discharge, or sneezing. Also, aside from a 33% reduction in the average number of days with a sore throat, daily supplementation does not reduce the duration of individual symptoms or total symptoms (106943). It is unclear if these effects are due to vitamin C, the probiotics, or the combination.
Restless legs syndrome (RLS). It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in hemodialysis patients with RLS shows that taking vitamin C 200 mg daily, alone or in combination with vitamin E 400 mg, for 8 weeks reduces the severity of RLS when compared with placebo (90093). More research is needed to determine if vitamin C is beneficial in treating RLS that is not associated with hemodialysis.
Sunburn. Topical and oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking vitamin C orally in combination with vitamin E seems to prevent ultraviolet (UV) radiation-induced erythema (sunburn) (4715,4716). Vitamin C in combination with high dose oral RRR-alpha-tocopherol (natural vitamin E) seems to protect against skin inflammation after exposure to UV radiation (4715). Also, applying topical vitamin C in combination with topical vitamin E and melatonin seems to provide modest photoprotective effects when used prior to UV exposure. However, it has no effect when used during or after UV exposure (4713,4714).
Stress. It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in healthy adults shows that taking vitamin C 3000 mg daily for 14 days modestly reduces blood pressure and subjective stress response to psychological stress when compared with placebo (10353).
Stroke. Observational research has found that although taking vitamin C supplements does not seem to be beneficial, eating more vitamin C-rich food is linked with reduced risk of stroke. Details: Lower plasma levels of vitamin C have been associated with increased stroke risk (90408). Additionally, population research has found that higher dietary intake of vitamin C is associated with a 8% to 19% reduction in stroke risk when compared to lower intake (90408,109779). This reduction appears to be dose-dependent, with each 100 mg/day increase in dietary vitamin C intake associated with about a 17% reduction (90408). However, taking vitamin C supplements has not been found to be associated with reduced stroke risk (1449,90408).
Tetanus. It is unclear if intravenous vitamin C helps to reduce symptoms of tetanus. Details: A low quality clinical trial in children and young adults with tetanus shows that intravenous vitamin C 1 gram daily along with conventional treatment reduces fatality when compared to control (21539).
Tooth extraction. It is unclear if oral vitamin C is beneficial for reducing pain or improving healing after tooth extraction. Details: A small clinical study in healthy patients aged 14-41 years who are undergoing bilateral premolar extraction shows that taking vitamin C 200 mg three times daily, beginning immediately after extraction and continued for 10 days, improves pain on days 1-3, and may reduce mesio-distal wound size between days 1 and 7, when compared with placebo, but not when compared with vitamin C 500 mg three times daily. A dose of 500 mg three times daily did not improve pain scores or extraction wound healing when compared with placebo (108084). The validity of this trial is limited by the short duration of treatment; additionally, this study did not report baseline vitamin C levels.
Urinary tract infections (UTIs). Although there is interest in using oral vitamin C for UTIs, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
Vascular dementia. It is unclear if oral vitamin C reduces the risk of vascular dementia. Details: Population research has found that supplemental intake of vitamin C and vitamin E is associated with a reduced risk of vascular dementia in Japanese-American men (4636). However, when cases in which dementia was diagnosed prior to the study are excluded from data analysis, intake of vitamin C and vitamin E is not associated with a reduced risk of vascular dementia in these patients (9824).
Wound healing. It is unclear if oral vitamin C improves the healing of chronic foot ulcers. It is also unclear if intravenous vitamin C improves healing of surgical wounds after total abdominal hysterectomy. Details: A very small clinical study in adults with chronic foot ulcers shows that taking slow-release vitamin C 500 mg daily for 8 weeks seems to result in a median of 100% ulcer healing, compared with a median of 14% ulcer healing in patients taking glucosamine 1000 mg daily (105456). This finding is limited due to the small and heterogeneous patient population, which included patients with diabetes, vascular disease, and/or vitamin C deficiency. Another small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery does not reduce the rate of surgical site infection or wound dehiscence when compared with placebo (109465). However, this study may not have been adequately powered to detect differences between groups. More evidence is needed to rate vitamin C for these uses.

VITAMIN D

Familial hypophosphatemia. Oral vitamin D in combination with phosphate is effective for bone disorders in patients with familial hypophosphatemia. Details: Taking calcitriol or dihydrotachysterol orally in combination with phosphate supplements is effective for treating bone disorders in people with familial hypophosphatemia (11818).
Hypoparathyroidism. Oral vitamin D increases serum calcium concentrations in people with hypoparathyroidism or pseudohypoparathyroidism. Details: Vitamin D2 (ergocalciferol) is effective in high doses for increasing serum calcium concentrations in people with hypoparathyroidism or pseudohypoparathyroidism (11820). Also, taking vitamin D (form unspecified) or calcitriol postoperatively is effective for preventing hypocalcemia in people with hypoparathyroidism due to thyroidectomy (39045).
Osteomalacia. Oral vitamin D is effective for osteomalacia. Details: Oral calcifediol is effective for treating osteomalacia secondary to liver disease (hepatic osteodystrophy) and anticonvulsant-induced osteomalacia. Vitamin D2 (ergocalciferol) is effective for osteomalacia due to malabsorption syndromes, Fanconi syndrome, and corticosteroid-induced osteomalacia (11819,11821).
Renal osteodystrophy. Oral calcitriol prevents renal osteodystrophy in patients with chronic renal failure. Details: Taking calcitriol orally manages hypocalcemia and prevents renal osteodystrophy in patients with chronic renal failure undergoing dialysis (11823).
Rickets. Oral vitamin D prevents and treats rickets. Details: Vitamin D is effective for preventing and treating rickets, a consequence of vitamin D deficiency. Calcitriol should be used in patients with renal failure (11824).
Vitamin D deficiency. Oral vitamin D prevents and treats vitamin D deficiency. Details: Vitamin D is effective for preventing and treating vitamin D deficiency using a wide range of doses (7555,16888,16891,17476). Optimal blood levels of 25-hydroxyvitamin D for maintaining bone density is controversial; however, it is typically estimated that blood levels of 20-100 ng/mL are needed. Toxicity usually does not occur until levels exceed 150 ng/mL (17476,93945). Vitamin D also alleviates symptoms and syndromes associated with vitamin D deficiency. Administering vitamin D2 (ergocalciferol) intramuscularly or orally seems to help treat severe proximal myopathy associated with severe vitamin D deficiency. Several case reports suggest vitamin D therapy can provide prompt relief of muscle weakness and restore mobility (11923,84348,84687).

Corticosteroid-induced osteoporosis. Oral vitamin D prevents corticosteroid-induced osteopenia and osteoporosis. Details: Taking calcifediol, cholecalciferol, calcitriol, or alfacalcidol orally prevents corticosteroid-induced osteopenia and osteoporosis (7555,83933). Vitamin D3 metabolites, including calcitriol and alfacalcidol, seem to be more effective at preventing bone loss compared to cholecalciferol in these patients, although the vitamin D3 metabolites seem to be inferior to bisphosphonates (83955). Furthermore, taking activated vitamin D or other forms of vitamin D alone or along with calcium improves bone mineral density in people with corticosteroid-induced osteoporosis (38493,38581).
Osteoporosis. Adequate intake of vitamin D in conjunction with adequate calcium intake helps to prevent the progression of osteoporosis. It might also reduce the risk of a first fracture in some patients. However, its place in the prevention of secondary facture is unclear. Details: The Bone Health and Osteoporosis Foundation (BHOF) recommends ensuring adequate vitamin D intake of 800-1000 IU daily along with adequate calcium intake for the prevention and treatment of osteoporosis in adults over 50 years of age. Supplementation can be used to augment dietary intake, with a target serum vitamin D level of 30 ng/mL (109425). In the US, foods that contain at least 120 IU vitamin D can be labelled with a health claim regarding the relationship between adequate vitamin D intake and a reduced risk for osteoporosis (97001). However, vitamin D supplementation is not recommended specifically for the primary prevention of osteoporosis. The US Preventive Task Force (USPSTF) states that the current evidence is insufficient to assess the balance of benefits and harms of vitamin D and calcium supplementation, alone or in combination, for the primary prevention of fractures in community dwelling adults without osteoporosis (95695). Clinical research shows that vitamin D3 (cholecalciferol) and calcium can decrease postmenopausal bone loss, help prevent osteoporosis, and decrease the risk of fractures (10932,12926,12930,12934,12952) (38973,39015,39026,84003). According to one analysis, taking oral vitamin D3 700-800 IU daily with or without calcium reduces fracture risk in ambulatory and institutionalized elderly people (12933). Other analyses suggest that taking vitamin D as cholecalciferol, ergocalciferol, calcifediol, calcitriol, or alfacalcidol with or without calcium can reduce the risk of all fractures by up to 17%, nonvertebral fractures by up to 49%, and hip fractures by up to 30% in older adults. However, the incidence of vertebral fractures does not appear to be reduced with vitamin D supplementation (38942,38970,38973,39015,39026,84660,109053). Despite the majority of research showing benefit, some studies have not found a positive effect of vitamin D on fracture risk. Some analyses of clinical evidence, including patients with and without osteoporosis, show that taking vitamin D3 or vitamin D2 (ergocalciferol) alone does not reduce fracture risk, suggesting that adequate calcium intake is needed for any benefit to be realized (39015,84471). Also, some evidence suggests that vitamin D3 400 IU daily is not effective for the prevention of osteoporotic fractures in elderly nursing home residents (109053). Another clinical trial found that taking vitamin D3 800 IU daily with calcium 1200-1500 mg daily for 2 years does not increase bone mineral density (BMD) in Black postmenopausal adults. This may be due to the fact that Black females have a lower rate of bone remodeling, an increased calcium absorption efficiency, and reduced calcium excretion when compared with other ethnic groups; therefore, supplementation with vitamin D3 and calcium might not be as beneficial in these patients (16878). There is concern that vitamin D might not be effective for secondary prevention of fractures in elderly patients. A meta-analysis of clinical studies, including many studies cited above, and a large clinical study in elderly adults with a previous osteoporotic fracture show that taking vitamin D3 400-4000 IU daily or as a single dose up to 500,000 IU orally or injected annually with or without calcium 480-1200 mg daily for up to 5 years does not reduce the risk of hip, vertebral, or other fractures when compared with placebo or no treatment (13073,112486). Another study also shows that taking vitamin D3 800 IU and calcium 1000 mg daily does not prevent a second fracture in elderly patients, or prevent a first fracture in elderly patients with other risk factors such as low body weight (under 58 kg, 127.6 pounds), smoking, family history of hip fracture, or fair or poor self-reported health (12929). However, these studies have been criticized for failing to measure vitamin D levels and low adherence to study protocol (12931). Also, one of these studies did not use a placebo control (12929). Taking alfacalcidol orally seems to maintain BMD in prostatic carcinoma patients at risk for osteoporosis when treated with luteinizing hormone-releasing hormone analogue (LHRH-a). Alfacalcidol maintains, but does not increase, BMD in these patients (6360).
Psoriasis. Topical vitamin D or vitamin D analogues improve symptoms of psoriasis. This benefit is not seen with oral vitamin D. Details: Topical application of vitamin D in the form of calcitriol or other vitamin D analogues, such as calcipotriene, maxacalcitol, and paricalcitol, effectively treats plaque psoriasis in some patients, including those with chronic plaque psoriasis (11822,84325). Applying topical vitamin D or its analogues in combination with topical corticosteroids such as betamethasone seems to be more effective for treating plaque psoriasis than either agent used alone (22283,82572,84325,84536,84647). Despite evidence that patients with psoriasis have low baseline serum levels of vitamin D, taking oral vitamin D does not seem to prevent psoriasis, improve symptoms, or reduce the severity of psoriasis in general (11822,22283,82572,84325,84536,84647,98193,108426,112481,112482). An analysis of a large clinical study in older adults with mild psoriasis shows that taking a vitamin D3 (cholecalciferol) loading dose of 200,000 IU followed by vitamin D3 100,000 IU monthly for 1 year does not affect the severity or spread of psoriasis when compared with placebo (98193).

Allergic rhinitis (hay fever). Some research suggests that oral vitamin D reduces symptoms of allergic rhinitis in children and adults. It is unclear if oral vitamin D during pregnancy is beneficial for the prevention of allergic rhinitis in the child. Details: Preliminary clinical research in adults with allergic rhinitis and vitamin D deficiency shows that taking vitamin D 50,000 IU weekly for 8 weeks along with cetirizine improves overall symptom severity when compared with placebo and cetirizine. This improvement was not significant at 4 weeks, suggesting that symptom improvement might not occur until vitamin D has been adequately replenished (102120). Another moderate-sized clinical study conducted in China in adults with moderate to severe allergic rhinitis and vitamin D levels at the low end of the normal range shows that taking vitamin D 800 IU daily for 4 weeks along with mometasone nasal spray improves runny nose, itchy nose, and nasal congestion but does not reduce sneezing when compared with placebo and mometasone (112483). In children aged 5-15 years, 4 small- or moderate-sized clinical trials show that taking vitamin D 800 IU or 1000 IU daily for 1-6 months modestly reduces symptoms such as nasal congestion and rhinorrhea when compared with placebo or no supplementation (109728). It is unclear whether these children had vitamin D deficiency at baseline. Vitamin D supplementation during pregnancy has also been evaluated. A meta-analysis of three large clinical studies shows that prenatal vitamin D supplementation does not reduce the risk of the child developing allergic rhinitis when compared with low-dose vitamin D, placebo, or no intervention (108438).
Dental caries. Some research suggests that oral vitamin D reduces the risk of dental caries in children. Details: A meta-analysis of clinical research suggests that vitamin D3 (cholecalciferol) reduces the risk of cavities by 49%, and vitamin D2 (ergocalciferol) reduces the risk by 36% when compared with placebo in infants, children, and adolescents (84690). The validity of this finding is limited by the heterogeneity of the included trials. Also, clinical research shows an inverse correlation between cord blood vitamin D status and the number of decayed primary teeth in the infant at 12 months of age (104620). However, this same research shows that taking two oral prenatal doses of vitamin D2 50,000 IU during pregnancy does not prevent dental caries in the infant at 12 months of age or increase vitamin D levels in the cord blood (104620).
Heart failure. Limited research suggests that oral vitamin D reduces the risk of developing heart failure in some patients. However, vitamin D does not seem to improve outcomes in patients that have already developed heart failure. Details: Population research has found that vitamin D levels below 15 ng/mL are associated with increased risk of developing heart failure (16615). A meta-analysis of 17 trials, including the landmark Randomized Evaluation of Calcium Or vitamin D (RECORD) trial, shows that vitamin D reduces the risk of heart failure by 21% compared to not taking vitamin D in patients 60 years or older (91343). This finding is limited because none of the included trials were designed to determine effects on cardiovascular outcomes. In contrast, a secondary analysis of data from the Women's Health Initiative trial shows that taking vitamin D 400 IU with calcium 1000 mg daily is not associated with a reduced risk of heart failure in postmenopausal adults. However, a subgroup analysis of that trial shows that taking vitamin D plus calcium is associated with a 37% lower risk of developing heart failure in postmenopausal adults classified as low-risk for heart failure at baseline. It is speculated that high-risk patients might not benefit from vitamin D plus calcium due to negative interactions with medications used to manage cardiovascular risk factors in this group (97307). While vitamin D might be associated with a reduced risk of developing heart failure, most evidence suggests that vitamin D is not beneficial in patients already diagnosed with heart failure. In one small clinical trial, taking vitamin D3 50,000 IU weekly along with calcium citrate 800 mg daily for 6 months was not associated with an improvement in 6-minute walk test, timed get up and go test (TGUG), electrocardiographic variables, or health status when compared with placebo in adults with heart failure; mortality was not evaluated (97299,97300). In another clinical trial, taking vitamin D3 2000 IU daily did not decrease the risk of mortality when compared with placebo in New York Heart Association (NYHA) class 2 heart failure patients (16620).
Hyperparathyroidism-related bone loss. Limited evidence suggests that oral vitamin D is beneficial in patients with this condition. Details: Taking vitamin D3 (cholecalciferol) orally seems to help decrease secondary hyperparathyroidism and bone turnover in females. In one study, supplementation with vitamin D3 increased serum levels of 25-hydroxyvitamin D, reduced levels of parathyroid hormone, and decreased production of markers of bone turnover (3463).
Respiratory tract infections. Oral vitamin D supplementation reduces the risk for respiratory tract infections in children. However, this benefit is not seen with the use of prenatal vitamin D supplements, or in adults taking vitamin D. It is unclear if oral vitamin D is beneficial for the treatment of respiratory tract infections. Details: Prenatally, increased levels of vitamin D during pregnancy have been associated with a lower incidence of childhood respiratory tract infections (98197). However, two meta-analyses of small clinical studies and one meta-analysis of large clinical studies show no effect of prenatal vitamin D supplementation on the incidence of infant or childhood respiratory tract infections, including lower respiratory tract infections, when compared with control. Results related to risk of wheeze are conflicting (95910,95912,108438). In children, most research shows that vitamin D supplementation reduces the risk of respiratory infections. A meta-analysis of clinical trials in children aged 1-16 years shows that taking vitamin D decreases the odds of having a respiratory tract infection by about 29% when compared with control, although this study also identified a high likelihood of publication bias (105721). Daily or weekly vitamin D doses seem to be more beneficial than single bolus doses, although the largest meta-analysis failed to confirm this result (84689,93766,105721). One clinical study in preterm Black infants shows that taking vitamin D3 (cholecalciferol) 200 IU daily and then 400 IU daily until 6 months of age does not affect the rate of respiratory tract infections, but does reduce wheeze by 11%, when compared with a normal diet without vitamin D supplementation (98191). This study may not have been powered to detect a difference in respiratory tract infection between groups. In adults, vitamin D supplementation does not seem to reduce the risk of respiratory infections. Observational research in adults has found that low levels of vitamin D are associated with worsened respiratory tract infection complications, and even increased mortality from respiratory tract infections in older adults ages 50-75 years (103659). However, meta-analyses of prospective clinical trials in adults show that taking vitamin D supplements 300-4000 IU daily for 7 weeks to 5 years does not reduce the odds of developing a respiratory infection or severe respiratory complications, such as emergency department utilization, hospitalization, and death, when compared with placebo. These results were similar in subgroup analyses evaluating overall vitamin D dose and baseline vitamin D status (84689,105721). The largest single clinical trial, conducted in adults at least 60 years of age, shows that taking vitamin D3 (cholecalciferol) 60,000 IU once monthly for up to 5 years reduces the duration of total and severe respiratory symptoms by approximately 0.5 days, but does not reduce the incidence of respiratory illness or hospitalization, when compared with placebo (105726,110825). A large meta-analysis of clinical studies in both children and adults shows that taking vitamin D does not reduce the risk of acute respiratory infections. While subgroup analyses revealed a reduced risk of acute respiratory infection in studies not exceeding 11 weeks' duration and with daily supplementation, these beneficial effects only persisted in studies considered to be of low quality (108435). Baseline vitamin D status was not assessed and the validity of these findings is limited by publication bias. Vitamin D has also been evaluated for the treatment of acute respiratory infections. A large meta-analysis of clinical studies in both children and adults shows that taking vitamin D improves outcomes (e.g., sputum conversion, survival rate, therapeutic success, need for intensive care admission) by a small, but not clinically relevant, amount. In subgroup analyses, these beneficial effects only persisted in studies considered to be of low quality (108436). The validity of these findings is limited by publication bias.
Tooth retention. Oral vitamin D with calcium seems to help with tooth retention in the elderly population. Details: A clinical trial in the elderly population shows that taking vitamin D3 (cholecalciferol) 700 IU daily along with calcium citrate malate 500 mg daily orally for 3 years reduces the risk of tooth loss by about 52% when compared with placebo (8816).

Cardiovascular disease (CVD). Most research shows that taking vitamin D with or without calcium does not reduce the risk of CVD or CVD complications. There is some speculation that there might be modest benefit in the elderly, but more research is needed to confirm. Details: Population research has found that low vitamin D levels, especially those below 15 ng/mL, are associated with an increased risk of developing CVD (15630,16618,93944). However, taking vitamin D supplements does not seem to prevent CVD. The majority of evidence from clinical research, population research, and meta-analyses shows that vitamin D supplementation, with or without calcium, does not reduce the risk of mortality, myocardial infarction, cardiac-related hospitalizations, or stroke when compared with placebo in patients with or without CVD risk factors (91343,97296,97305,97308,98902,98916,99762,109729,110811,110827)(112021,112022). The most reliable evidence comes from two recent meta-analyses of mainly high-quality clinical research investigating the effect of supplementation with vitamin D alone or with calcium for at least 1 year. These analyses show that vitamin D does not reduce major adverse cardiovascular events, stroke, CVD mortality, or all-cause mortality, regardless of baseline vitamin D level, vitamin D dosage, sex, formulation, or concomitant calcium supplementation (99762,109729). One large clinical trial in individuals at increased CVD risk shows that taking vitamin D as cholecalciferol 60,000 IU monthly modestly INCREASES the risk of CVD- and presumed CVD-related mortality (110827). However, in some research, taking vitamin D 700-1000 IU daily shows a trend towards lower CVD events and reduced risk of major adverse cardiovascular events in elderly patients (11931,98916,99762). Larger, high-quality trials with prespecified primary outcomes are needed to determine whether or not vitamin D supplementation reduces CVD risk in elderly populations.
Critical illness (trauma). Taking vitamin D 540,000 IU as a single oral dose does not reduce death or hospital stay in critically ill patients. However, limited research suggests that taking a smaller dose of vitamin D long-term might have a modest benefit. Details: The most robust evidence to date shows that correcting vitamin D levels in critically ill patients with vitamin D deficiency does not reduce mortality rate or duration of hospital stay. A large, multicenter clinical study in critically ill patients with vitamin D deficiency shows that administering a single, enteral dose of vitamin D 540,000 IU does not reduce 90-day all-cause mortality, duration of hospital stay, ventilator-free days, or other clinical outcomes when compared with placebo (103656). A previous meta-analysis of clinical research showed that vitamin D supplementation administered for a duration of 7 days or up to 6 months reduces the risk of death by 30% in critically ill hospitalized patients (95913). However, included studies were of low methodological quality, had high heterogeneity, assessed patients with and without vitamin D deficiency, and used variable vitamin D dose regimens and administrations methods (95913,95914).
Fractures. Most evidence shows that oral vitamin D alone does NOT prevent factures in people who do not have osteoporosis. Some research shows that taking vitamin D with calcium prevents fractures; however, more research is needed to determine who is most likely to benefit. Details: Clinical research shows that taking vitamin D alone does not seem to prevent fractures in older adults. Most adults in these studies did not have osteoporosis, although osteoporosis status was unclear in some research (10140,12933,14282,38970,39015,84660,95822,97296,102145,104619)(109059,110827). However, several meta-analyses suggest that taking higher doses of vitamin D (about 800 IU daily) in combination with calcium might reduce overall fracture risk in older patients (38942,38970,39015,84660,102145,110809). One meta-analysis of clinical research in community- or long-term care-living males and females at least 65 years of age shows that taking vitamin D 800 IU daily in combination with calcium reduces the risk of hip and non-vertebral fractures by 25% and 20%, respectively, compared with placebo (110809). However, discrepancies exist which are possibly related to the dose and form of calcium used in combination with vitamin D and/or the patient population. Some research shows that taking vitamin D 800 IU daily in combination with calcium 1200 mg daily as tricalcium phosphate reduces fracture risk by up to 31% while taking vitamin D with calcium carbonate does not reduce fracture risk (12929,14282,16878,110809). Some individual clinical studies in postmenopausal females aged 50-79 years show that taking vitamin D plus calcium daily for 2-7 years does not prevent fractures when compared with placebo (14282,16878). Other confounding variables include the possible additional effects of hormonal therapy when given with calcium to postmenopausal adults and/or the inclusion of institutionalized patients with unclear osteoporotic status (95822,97296). Most research shows that taking vitamin D in combination with omega-3 fatty acids does not prevent fractures. A large clinical study shows that taking vitamin D 2000 IU daily alone or with omega-3 fatty acids 1 gram daily and/or strength training three times weekly does not prevent fractures in adults over 70 years of age when compared with placebo (104619). Another large clinical trial shows that taking vitamin D 2000 IU daily, alone or with omega-3 fatty acids 1 gram daily, over approximately 5 years does not prevent overall fractures, nonvertebral fractures, or hip fractures in adults over 50 (males) or 55 (females) years old when compared with placebo. Although the osteoporosis status of the population was unclear, findings were consistent in adults at high fracture risk based on use of osteoporosis medications and/or a history of fragility fractures (109059). As of April 2018, the US Preventative Services Task Force (USPSTF) recommends against supplementing with vitamin D 400 IU daily or less along with calcium 1000 mg daily or less for preventing primary fractures in community-dwelling postmenopausal adults. The USPSTF also concludes that there is insufficient evidence to determine whether supplementing with doses of vitamin D greater than 400 IU daily along with calcium doses greater than 1000 mg daily is safe or effective for preventing fractures in community dwelling adults without vitamin D deficiency, osteoporosis, or a history of fracture (95695). For information on patients WITH osteoporosis, refer to the Osteoporosis discussion. There is limited research available regarding the effects of vitamin D supplementation for fracture prevention in children. Preliminary research in children aged 2 to 17 years with vitamin D insufficiency and one or more previous fractures shows that taking vitamin D 2000 IU daily with calcium 600 mg daily for 6 months modestly reduces the risk of forearm fractures over 12 months compared with children not given vitamin D or calcium (110820).
Hypertension. Overall, vitamin D does not seem to prevent or lower high blood pressure in most patients; however, it may lower blood pressure in hypertensive patients with vitamin D deficiency. Details: Although population research has found that lower vitamin D levels are associated with a higher risk of developing hypertension, clinical research shows vitamin D supplementation does not prevent hypertension (15630) A large clinical trial in postmenopausal adults shows that taking vitamin D3 400 IU with calcium 1000 mg daily does not reduce the risk of developing hypertension (16714). Most meta-analyses and clinical trials in patients with existing hypertension show that vitamin D supplementation does not lower blood pressure when compared with placebo, regardless of vitamin D formulation, dose, or duration of supplementation (16714,91340,96405,103657,104619). However, a meta-analysis of five clinical studies in patients with hypertension and vitamin D deficiency shows that supplementation with vitamin D reduces systolic and diastolic blood pressure by about 7 mmHg and 3 mmHg, respectively, when compared with placebo (100895). Similarly, an individual clinical study in patients with hypertension and vitamin D deficiency or insufficiency shows that taking vitamin D 50,000 IU weekly or 1000 IU daily reduces systolic blood pressure by about 6 mmHg and mean arterial pressure by about 4 mmHg, but does not affect diastolic blood pressure, when compared with baseline (108440). The validity of these findings is limited by the lack of a comparator group.
Prostate cancer. Oral vitamin D does not appear to affect prostate cancer progression or cancer-related mortality. Details: A meta-analysis of three clinical trials shows that vitamin D supplementation does not affect prostate cancer progression as measured by prostate-specific antigen (PSA), or mortality in patients with prostate cancer (99770).
Psychosis. Oral vitamin D does not seem to improve symptoms in patients with a functional psychotic disorder. Details: A clinical study in adults with a functional psychotic disorder shows that taking oral vitamin D3 (cholecalciferol) 20,000 IU monthly for 6 months has no effect on total positive and negative syndrome scale score (PANSS) when compared with placebo. The majority of patients included in this study were deficient in vitamin D at baseline (107226).
Tuberculosis. Oral vitamin D seems to be ineffective for reducing the severity of tuberculosis or mortality from tuberculosis. Limited research suggests that vitamin D may have small benefits in newly diagnosed patients receiving tuberculosis treatment for the first time. Details: Although population research has found that tuberculosis is associated with vitamin D deficiency, most clinical research shows that taking vitamin D does not improve clinical outcomes in people with tuberculosis infection. Meta-analyses and individual clinical studies show that taking vitamin D as a single 100,000 IU dose, or as 400 IU daily for 2 months, along with standard care does not improve tuberculosis severity or reduce the risk of mortality in children or adults with tuberculosis, regardless of their baseline vitamin D levels (82570,82475,98913,103655,103668,104022). However, some research has identified modest benefits in newly diagnosed patients receiving anti-tuberculosis treatment for the first time. A meta-analysis of clinical research in this population shows that taking vitamin D at a dose of 1000 IU daily or 600,000 IU monthly modestly increases the odds of sputum smear conversions by 1.2-fold, but does not improve the time to sputum smear conversions, when compared with placebo (98235). A small clinical study in treatment-naïve adults with low levels of serum vitamin D shows that taking calcitriol 0.25 mcg twice daily for up to 6 months, starting with anti-tuberculosis treatment initiation, decreases the time to sputum smear conversion and 50% lesion absorption by about 3 days when compared with not taking vitamin D (109045). Additionally, a small clinical study in children aged 6-18 years with vitamin D insufficiency receiving standard treatment for newly diagnosed pulmonary tuberculosis shows that taking vitamin D 1000 IU daily reduces the duration of fever and cough by 1 and 2 weeks, respectively, when compared with placebo (108437).

Acne. It is unclear if oral vitamin D is beneficial for acne. Details: A small clinical trial in patients with acne and vitamin D deficiency shows that taking cholecalciferol 1,000 IU daily for 2 months reduces the number of inflammatory lesions by about 35%, compared with 6% in those taking placebo. There was no effect on the total or non-inflammatory lesion count (106127). Other preliminary clinical research shows that taking alfacalcidol (One Alpha, LEO Company, Denmark) 0.25 mcg daily for 3 months modestly improves acne severity when compared with taking placebo (106128). In addition, population research has found that individuals with acne have modestly lower vitamin D levels than healthy controls. The odds of vitamin D deficiency were approximately three times higher in patients with acne when compared with healthy controls (106105).
Age-related cognitive decline. It is unclear if oral cholecalciferol is beneficial for preventing age-related cognitive decline. Details: Pooled results of two large clinical sub-studies in community-dwelling adults aged 60 years or older show that taking cholecalciferol 2000 IU daily for 2-3 years has no effect on cognitive decline when compared with placebo. A subgroup analysis in Black patients suggests a modest effect of vitamin D when compared with placebo (108428).
Alzheimer disease. It is unclear if oral vitamin D is beneficial for this condition. Details: Some population research has found that lower serum concentrations of vitamin D are associated with higher risk of Alzheimer disease, and also with decreased cognition. People with Alzheimer disease seem to have serum concentrations of vitamin D that are about 2.5 ng/mL lower than patients without Alzheimer disease (84672,103666). However, other population research has found that vitamin D deficiency (<25 nmol/L) or insufficiency (25-50 nmol/L) is not associated with increased risk of Alzheimer disease (100899).
Asthma. Oral vitamin D might reduce asthma exacerbations in adults and children with mild, but not severe or persistent, asthma. Vitamin D supplementation during pregnancy or the first 6 months of an infant's life does not seem to prevent the development of asthma later in infancy or childhood. Details: Population research in patients with asthma suggests that low vitamin D levels are associated with an increased risk of exacerbations and increased need for medication therapy (94693). However, findings from clinical research are mixed. Some meta-analyses of clinical trials in adults and children with asthma show that taking vitamin D for 3 months to 1 year reduces the rate of asthma exacerbations by 31% to 36% when compared with control (92690,94686). However, findings from more recent meta-analyses show that vitamin D supplementation does not reduce the risk of asthma exacerbations when compared with placebo (109728,109732,110833). The reasons for this discrepancy are not clear. However, some clinical research suggests that vitamin D supplements might only prevent asthma in people with non-persistent asthma (92690,94685,94686,94688,104020). Also, many studies are small and do not represent patients with severe asthma exacerbations (92690,94687). Baseline levels of vitamin D may play a role. A clinical study in children aged 6-16 years with persistent asthma and low vitamin D levels shows that taking vitamin D 4000 IU daily for 48 weeks does not reduce severe asthma exacerbations when compared with placebo (104020). However, a meta-analysis including this study shows that taking vitamin D does reduce risk of asthma exacerbations in children with low baseline vitamin D levels (109728). One meta-analysis shows that taking vitamin D seems to modestly improve pulmonary function when compared with placebo (109732). Vitamin D doses have varied, with oral doses of 500-4000 IU daily, 1000 IU once weekly, 60,000 IU once monthly, 120,000 IU every 2 months, 100,000 IU 14 days apart, or 100,000 to 600,000 IU as a bolus dose followed by 400-4000 IU daily (92690,94686,104020,109728,110833). Vitamin D supplementation for the prevention of asthma in infants has also been evaluated. A meta-analysis of 4 large clinical studies shows that taking vitamin D 400-1200 IU daily for the first 6 months of life does not reduce the risk of asthma or wheezing at 6-30 months of age when compared with control (112031). Vitamin D supplementation during pregnancy has also been evaluated (97306,99763,102146,112031). A meta-analysis of 3 large clinical studies shows that taking vitamin D 2800-4400 IU daily during the 2^nd and 3^rd trimesters of pregnancy reduces the risk of recurrent wheezing by 23% but does not reduce the risk of asthma diagnosis within the first 3-6 years of life when compared with vitamin D 400 IU daily (112031). Some research suggests that the dose of vitamin D plays a role. A meta-analysis shows that prenatal vitamin D 800 IU daily reduces the odds of wheeze or asthma by 32%, while lower or higher vitamin D doses were not beneficial (103661).
Athletic performance. It is unclear if oral vitamin D is beneficial for athletic performance. Details: One small clinical trial in athletes shows that taking vitamin D 20,000 or 40,000 IU once weekly for 2 doses does not affect performance on vertical jumps, sprints, or leg and bench presses when compared with placebo (98188). Another small clinical trial in professional rugby players shows that taking vitamin D3 (cholecalciferol) 50,000 IU once every two weeks over 12 weeks does not improve sprinting speed or the ability to perform bench presses, bench pulls, and chin-ups when compared with placebo (98189). Also, most research shows that taking vitamin D does not improve measures of cardiorespiratory fitness. One small study in young males undergoing resistance training shows that taking vitamin D 8000 IU daily for 12 weeks does not improve cardiorespiratory fitness compared with taking placebo (110812).
Atopic dermatitis (eczema). Most research shows that oral vitamin D reduces eczema severity in children. However, most research shows that oral vitamin D, taken during pregnancy or infancy, does not prevent eczema in the child. Details: A meta-analysis of eight moderate-quality clinical trials in children shows that taking vitamin D, most commonly 1000-2000 IU daily for 4-12 weeks, modestly reduces severity of eczema when compared with placebo (109728). Most of the children in these studies were also given conventional medications. Oral vitamin D has also been evaluated for eczema prevention. A meta-analysis of two clinical studies shows that consuming vitamin D 2800-4400 IU daily during the 2^nd and 3^rd trimesters of pregnancy is not associated with a reduced risk for eczema in children during the first 3 years of life when compared with vitamin D 400 IU daily (97306). Another meta-analysis of five large clinical studies shows that prenatal or infant vitamin D supplementation does not reduce the risk of developing eczema when compared with low-dose vitamin D, placebo, or no intervention (108438).
Atrial fibrillation. It is unclear if oral vitamin D is beneficial for preventing atrial fibrillation. Details: A large clinical trial in adults without cardiovascular disease shows that taking vitamin D 2000 IU daily for an average of 5 years does not reduce the incidence of atrial fibrillation when compared with placebo or fish oil 840 mg daily (105209). However, observational research in postmenopausal adults with osteoporosis found that vitamin D supplementation is associated with a lower occurrence of atrial fibrillation when compared with not taking vitamin D (98922). Also, one large observational study in vitamin D-deficient patients with no history of atrial fibrillation has found that vitamin D supplementation for at least 6 months is associated with up to a 16% decreased risk of atrial fibrillation when compared with not taking vitamin D. There were also modest improvements in atrial fibrillation-free survival. In males 65 years and older with hypertension or diabetes at baseline, blood levels of at least 30 ng/mL following vitamin D supplementation were associated with decreased risk of atrial fibrillation; a post-supplementation blood level of 21-29 ng/mL was not associated with decreased risk (109043).
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral vitamin D is beneficial for ADHD. Details: A small clinical trial in children 5-12 years of age with ADHD and vitamin D insufficiency shows that taking vitamin D 2000 IU daily along with methylphenidate for 8 weeks seems to improve parental ratings of evening, but not morning or overall, symptoms of inattentiveness and impulsivity when compared with methylphenidate alone. Vitamin D insufficiency was defined as levels less than 30 ng/mL (98196). Based on these and other preliminary findings, Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that vitamin D in doses of 1500 to 4000 IU daily is weakly recommended for adjunctive use in children with ADHD, especially those with insufficient intake or skin exposure to sunlight (110318).
Autism spectrum disorder. It is unclear if oral vitamin D is beneficial for autism spectrum disorder. Details: A small clinical study in children aged 2.5-8 years with autism spectrum disorder shows that taking vitamin D 2000 IU daily for 12 months modestly reduces irritability and hyperactivity when compared with placebo (99767).
Bacterial vaginosis. It is unclear if oral vitamin D is beneficial for bacterial vaginosis. Details: Preliminary clinical research in females at high risk for sexually transmitted disease shows that taking vitamin D along with standard therapy for bacterial vaginosis does not reduce the prevalence of bacterial vaginosis when compared with placebo. Patients in this study had been treated with metronidazole 500 mg orally twice daily for 7 days along with vitamin D3 (cholecalciferol) 50,000 IU each week for 4 weeks and then every 4 weeks for the remaining 20 weeks (91348).
Breast cancer. It is unclear if oral vitamin D is beneficial for the prevention of breast cancer. Details: Some population research evaluating intake of calcium plus vitamin D suggests that higher vitamin D intake is not associated with a reduced risk of breast cancer in premenopausal or postmenopausal adults (15631). Similarly, a large observational study in females with a biological sibling with breast cancer has found that taking vitamin D recently or prior to enrollment is not associated with a reduced risk of breast cancer when compared with nonrecent vitamin D use or never taking vitamin D, respectively (107215). However, other research found that higher vitamin D intake is associated with a 17% reduced risk of breast cancer in premenopausal and perimenopausal, but not postmenopausal, adults (39001). Observational research has also examined the association between blood levels of vitamin D and risk of developing breast cancer. A meta-analysis found that those with serum levels of about 52 ng/mL had a 50% lower risk of developing breast cancer when compared with those with serum levels of less than 13 ng/mL. This high serum level of vitamin D corresponds to a high dose of about 4000 IU daily (16049). Other observational research has found that baseline vitamin D levels of more than 20 ng/mL are associated with a 48% reduced risk of developing breast cancer over approximately 9 years in Latina females in the US when compared with levels below 20 ng/mL; however, this association was not present in Black females (109058). Despite the contradictory findings from observational research, results from clinical research are generally negative. Evidence from one large-scale clinical trial (Women's Health Initiative) shows that postmenopausal adults who take vitamin D3 (cholecalciferol) 400 IU daily plus calcium 1000 mg daily for 7 years do not have a significantly reduced risk of developing breast cancer (16715,98895). Also, a meta-analysis of two large-scale clinical trials, which did not include the Women's Health Initiative trial, shows that taking vitamin D 800-1000 IU daily, alone or with calcium, for 3-4 years does not reduce the incidence of breast cancer in postmenopausal adults, although there was a trend towards reduced risk with higher doses of vitamin D supplementation (97301). While vitamin D and calcium supplementation during the intervention period of the Women's Health Initiative trial was not associated with a reduced risk of developing breast cancer or ductal carcinoma in situ (DCIS), a precursor to breast cancer, a secondary post-hoc analysis of the data shows that supplementation reduces the risk of developing DCIS by 18% over a median follow-up of 19 years (107216). Additional research is needed regarding an optimal dose of vitamin D, timing of initiation, and whether any benefit is affected by menopausal status.
Bronchopulmonary dysplasia. Limited research suggests that vitamin D deficiency is linked with bronchopulmonary dysplasia in the infant. Details: Observational research has found that vitamin D deficiency at birth is associated with about a 2-fold increased odds of developing bronchopulmonary dysplasia (104021). However, it is unclear if vitamin D supplementation is beneficial.
Cancer. Vitamin D does not seem to reduce overall cancer risk. However, some research shows that vitamin D might slightly reduce the risk of metastatic cancer and cancer-related mortality. Details: There is interest in vitamin D for cancer PREVENTION, as observational research suggests that higher vitamin D intake and higher 25-hydroxyvitamin D levels are associated with a lower risk of cancer (111150). While individual clinical trials evaluating vitamin D for cancer have produced inconsistent findings, most meta-analyses and clinical trials show that taking vitamin D3 (cholecalciferol) or vitamin D2 (ergocalciferol) alone or with calcium does not significantly reduce the risk of developing cancer (15629,91344,93943,97296,98916,104024,104618,110811). However, vitamin D supplementation might reduce the risk of metastatic cancer and cancer-related mortality. A large clinical trial shows that taking vitamin D3 2000 IU daily for a median of 5.3 years slightly reduces the risk of advanced metastatic or fatal cancers when compared with placebo (104618). Additionally, meta-analyses of several large clinical trials show that taking vitamin D 400-4000 IU daily, with or without calcium, for 1-7 years reduces the risk of cancer-related mortality by 12-13% when compared with control, while intermittent bolus dosing of vitamin D at high doses for 1-5 years does not appear to reduce the risk of cancer-related mortality (104024,111149). The role of vitamin D in cancer TREATMENT is unclear. A meta-analysis of clinical and observational research suggests that supplementation of vitamin D after a cancer diagnosis is associated with a modest improvement in overall survival, but not progression-free or cancer-specific survival (109726). Doses used in clinical research ranged between 1200 IU and 8000 IU daily or 100,000 IU every 50 days, after surgery and/or during treatment (99195,99196,109726). Other clinical research in patients with luminal gastrointestinal cancers shows that taking vitamin D 2000 IU daily does not reduce the risk of relapse when compared with placebo (99195). It is unclear which, if any, types or stages of cancer respond best to vitamin D, and what dose of vitamin D is optimal.
Child growth. It is unclear if oral vitamin D is beneficial for improving infant growth or bone structure. Details: Meta-analyses and individual clinical trials show that vitamin D supplementation during pregnancy modestly increases length at birth and bone mineral density at up to 6 years of age when compared with control, usually placebo or vitamin D 400 IU daily. However, there was no effect on length in the infant up to one year of age, weight at birth or up to one year of age, head circumference at birth or up to 6 years of age, bone mineral content at up to 6 years of age, or neonatal bone mineral density, bone mineral content, bone area, or femur or humoral length (98198,109737,112028). In the available research, vitamin D was taken in doses of 200 IU to 4400 IU daily, 4200 IU to 50,000 IU weekly, 50,000 IU every 2 weeks, or 60,000 IU every 4-8 weeks, starting from the early to late stages of pregnancy and usually continued until birth (98198,109737).
Chronic kidney disease (CKD). It is unclear if oral vitamin D is beneficial in patients with CKD. Most research suggests that it does not reduce the risk for adverse cardiovascular events. Details: Population research in patients on dialysis has found that vitamin D levels less than 17.8 ng/mL are associated with a higher risk of all-cause mortality compared with higher levels (16619). A meta-analysis and individual clinical studies show that vitamin D and vitamin D analogues decrease parathyroid hormone (PTH) levels and urine protein levels in people with CKD (84376,84377,84628,98233,98236). However, taking vitamin D does not appear to decrease the risk of death or parathyroidectomy in CKD patients (84376,84377). Also, taking vitamin D increases the risk for hypercalcemia and hyperphosphatemia in this patient population (84376,84377,98236). Vitamin D has also been evaluated for the prevention of cardiovascular events in adults with CKD. Observational research has found that vitamin D deficiency in patients with CKD is associated with adverse cardiovascular events. However, vitamin D supplementation does not seem to be beneficial. One clinical study shows that taking paricalcitol, an active form of vitamin D, titrated to maintain adequate serum calcium levels, for 48 weeks does not affect the size of the left ventricle or heart function when compared with placebo (98233). Other clinical research in Japanese patients on hemodialysis for CKD shows that adding alfacalcidol, another active form of vitamin D, 0.5 mcg daily to standard treatment for 4 years does not affect mortality or cardiovascular events such as myocardial infarctions, stroke, aortic dissection, and others compared to standard treatment only (98920). Also, a large clinical trial in patients with CKD shows that taking vitamin D as cholecalciferol 2000 IU daily, alone or with omega-3 fatty acids 1 gram daily, does not affect major cardiovascular events or invasive cancer when compared with placebo (110811). Vitamin D has also been evaluated for musculoskeletal health in adults with CKD. A small clinical study shows that taking cholecalciferol 4000 IU daily, with or without physical activity, for 3 months improves bicep strength, but not back flexibility or aerobic fitness capacity, when compared with baseline. In patients taking cholecalciferol in combination with physical activity, musculoskeletal health was similar when compared with cholecalciferol alone (108431). However, this study was inadequately powered to detect a difference between groups, and it is unclear if the improvement from baseline differed between groups. Vitamin D has also been evaluated for the improvement of iron status in adults with CKD and secondary hyperparathyroidism. Clinical research shows that taking Vitamin D as cholecalciferol (Vitamin D3 Forte Renapharma) 8000 IU daily for 12 weeks does not improve iron status compared with taking placebo. However, a sub-analysis shows that hemoglobin levels are modestly improved in patients with a low Vitamin D status at baseline suggesting that Vitamin D might improve iron availability in these patients (110819).
Chronic obstructive pulmonary disease (COPD). It is unclear if oral vitamin D is beneficial for COPD; benefits may be limited to patients with vitamin D deficiency. Details: Population research has found an association between low vitamin D levels and reduced lung function, increased risk of developing COPD, and worsening COPD severity (17685,96401). In contrast, 2 meta-analyses of clinical research in adults with COPD and with or without vitamin D deficiency show that oral vitamin D does not have beneficial effects on mortality, rate of COPD exacerbations, pulmonary function, or most measures of symptom severity when compared with placebo (109732,112485). However, other research suggests that vitamin D may be beneficial in patients with vitamin D deficiency. Some clinical research in patients with moderate to severe COPD and severe vitamin D deficiency shows that taking a specific vitamin D supplement (D-Cure, Laboratoires SMB) 100,000 IU once every 4 weeks for 1 year seems to reduce the rate of exacerbations by 43% when compared with placebo (98194).
Cognitive function. It is unclear if oral vitamin D is beneficial for cognitive function. Details: Population research has found that low vitamin D levels are associated with worse cognitive performance and cognitive decline when compared to high vitamin D levels in healthy adults (84672,95916). However, the effect of vitamin D supplementation on cognitive function is unclear. One small meta-analysis of clinical research shows that vitamin D supplementation does not improve cognitive function (95916). However, the included trials evaluated a widely heterogeneous study population and utilized variable measures of cognitive function.
Cognitive impairment. It is unclear if oral vitamin D is beneficial for older adults with mild cognitive impairment. Details: A small clinical study in older adults with mild cognitive impairment shows that taking vitamin D3 10,000 IU three times weekly for 20 weeks in addition to exercise and cognitive training does not improve cognitive function when compared with placebo and exercise with or without cognitive training. However, most participants had sufficient serum vitamin D levels at baseline (112489).
Colorectal cancer. It is unclear if oral vitamin D is beneficial for the treatment or prevention of colorectal cancer. Details: Epidemiological research has found that a higher serum vitamin D level is associated with decreased risk of mortality and increased survival in patients with colorectal cancer (16101,99196). However, it is unclear whether vitamin D supplementation improves survival in patients with colorectal cancer, as research has generally involved small populations and results are somewhat conflicting. A subgroup analysis of one clinical study shows that taking vitamin D 2000 IU daily does not reduce the risk of relapse or death, death due to any cause, or relapse over 5 years when compared with placebo in patients with colorectal cancer (99195). However, this subgroup may have been underpowered to detect between-group differences. Another small clinical trial in patients with advanced or metastatic colorectal cancer shows that taking high-dose vitamin D 8000 IU daily during the first cycle of chemotherapy, and then 4000 IU daily for subsequent cycles, does not increase median progression-free survival when compared with taking vitamin D 400 IU daily. However, patients taking high-dose vitamin D were 36% less likely to experience disease progression or death during follow-up when compared with patients taking the lower dose of vitamin D (99196). This latter result suggests that high-dose vitamin D supplementation might be beneficial for patients with advanced or metastatic colorectal cancer, but larger, multicenter studies are needed to confirm. The role of vitamin D in colorectal cancer prevention has also been investigated. A meta-analysis of epidemiological research has found that a higher serum vitamin D level is associated with a decreased colorectal cancer risk; however, sub-analyses suggest that this association only occurs in females, not males (109740). Most studies have evaluated vitamin D supplements in combination with calcium; the effects of vitamin D supplementation alone are unclear. One meta-analysis of clinical research suggests that taking vitamin D plus calcium is not associated with a decreased incidence of colorectal cancer in people with a low baseline risk of colorectal cancer (39042). Another meta-analysis of clinical research shows that vitamin D supplementation, with or without calcium, does not reduce the incidence of colorectal cancer or colorectal adenomas (109730). Additionally, a large clinical trial suggests that postmenopausal adults who take calcium 1000 mg daily plus vitamin D 400 IU daily do not have a reduced risk of developing colorectal cancer (14290,98895). One clinical study shows that taking calcium supplements reduces the risk of colorectal adenomas, but not in people with lower than average vitamin D levels (12118).
Coronavirus disease 2019 (COVID-19). The evidence is mixed with respect to oral vitamin D supplementation for the prevention and treatment of COVID-19. Also, although some observational research has suggested a correlation between vitamin D status and risk for COVID-19, not all studies agree, and this association may be due to other confounders such as age and comorbidities. Details: Clinical and observational research has evaluated vitamin D supplementation for COVID-19 prevention. A preliminary clinical trial shows that oral vitamin D 800 IU or 3200 IU daily for 6 months in individuals with lower serum levels of vitamin D does not reduce the risk of COVID-19 or any respiratory tract infection when compared with no vitamin D supplementation (109721). However, groups were not matched for baseline vitamin D status and many individuals in the untreated group took their own vitamin D supplements. Two meta-analyses of clinical and observational studies show no relationship between vitamin D supplementation and the primary prevention of COVID-19 infection, although baseline vitamin D status is unclear (109040,112488). Also, a quasi-experimental cohort study in Italian adults who had supplemented with vitamin D in the 3 months prior to COVID-19 diagnosis found no reduction in risk for hospitalization, as well as a trend towards increased risk for in-hospital mortality, when compared with those who had not received vitamin D supplementation (104625). However, some research disagrees. Clinical research in highly exposed healthcare workers shows that taking vitamin D as cholecalciferol 4000 IU daily for 30 days reduces the risk of COVID-19 infection by 77% when compared with placebo (109052). Also, in the UK population, observational research has found that habitual use of vitamin D supplements between 2006 and 2010 is associated with a 34% lower risk of COVID-19 infection. This finding remained positive after adjusting for baseline health status and use of other micronutrients (104717). Further research is needed to determine whether vitamin D supplementation prevents COVID-19 infection. Vitamin D supplementation as treatment in outpatients with COVID-19 has also been evaluated. Preliminary clinical research discussed in a systematic review suggests that supplementation might be associated with less severe symptoms; however, there is inadequate information to determine if supplementation in patients with mild symptoms is associated with reduced hospital admission (109040). Conversely, a large cross-sectional study found an association between pre-hospital supplementation and increased risk for COVID-19, as well as increased rates of death and/or invasive mechanical ventilation. However, this association was no longer significant after adjusting for sex, age, and comorbidities (107205). Most research on vitamin D supplementation has been conducted in children and adults hospitalized with COVID-19. However, meta-analyses of clinical and observational research in these patients provides conflicting results on whether vitamin D supplementation as single dose or multiple doses is associated with a reduced risk of mortality, length of hospitalization, admission to the intensive care unit (ICU), or need for ventilation when compared with placebo or standard care alone (109040,109733,112488,112490). The quality of evidence of most individual clinical trials is low to moderate due to a lack of placebo and blinding in many of the studies. Most individual studies evaluating single doses of vitamin D, administered either after diagnosis or after hospital admission, have not identified benefit for major outcomes, such as hospital length of stay, in-hospital mortality, or ICU admission. Many of these studies were small, low quality, and conducted in heterogenous populations, with doses ranging from 80,000 IU to 500,000 IU (104624,104626,107208,108434,109051,112490). One small, unblinded study in at-risk older adults admitted to the hospital or living in a long-term care facility shows that taking a single dose of 400,000 IU within 72 hours of diagnosis modestly improves survival at 14 days, but not 28 days, when compared with 50,000 IU (109039). The evidence related to multi-dose regimens in hospitalized patients is mixed. A cohort study shows that giving calcifediol 0.532 mg at hospital admission, followed by calcifediol 0.266 mg on days 3 and 7 and then weekly until discharge or ICU admission, reduces odds of in-hospital death within 30 days by 78% when compared with those not given vitamin D (106099). A small clinical trial in patients with vitamin D deficiency shows that taking vitamin D 25,000 IU daily for 4 days and then weekly for up to 6 weeks reduces length of hospital stay and duration of supplemental oxygen by 4 days and 3 days, respectively, and also reduces disease severity and ICU admission after 7 days (109050). A small, unblinded study in patients with suboptimal vitamin D status and mild to moderate COVID-19 shows that taking vitamin D3 5,000 IU daily for 2 weeks reduces the time to recovery from cough and loss of taste by 2.9 and 5.5 days, respectively, when compared with vitamin D3 1,000 IU daily. However, there was no difference in time to recovery from fever, dyspnea, body aches, or other symptoms (106117). However, some research disagrees. A small unblinded study has found that although vitamin D status at 9 days is negatively associated with the number of bed days, vitamin D 50,000 IU on days 1 and 8 does not affect the number of bed days, time to discharge, or ICU admission when compared with no supplementation (109047). An additional preliminary study in patients with severe COVID-19 and low blood levels of vitamin D shows that taking vitamin D (Plivit D3, Pliva) 10,000 IU daily while in the ICU or for at least 14 days does not reduce the number of days on respiratory support, or in the ICU or hospital, or improve survival rates when compared with no supplementation (110813). The relationship between vitamin D levels and COVID-19 has also been evaluated in pregnant patients. A meta-analysis of observational research suggests that, while lower vitamin D levels are not associated with an increased risk of COVID-19, the presence of severe COVID-19 symptoms in pregnant patients may be linked to lower vitamin D levels when compared with non-severe COVID-19 symptoms (112025). Limited research has investigated the effect of vitamin D in combination with other ingredients. Preliminary clinical research in patients with mild to moderate COVID-19 shows that taking vitamin D3 (Davalindi, Medical Union Pharma, Cairo, Egypt) 2000 IU daily in combination with black seed (Baraka, Pharco Pharmaceuticals, Cairo, Egypt) 900 mg twice daily for 14 days modestly reduced the severity of some symptoms, including cough, diarrhea, fatigue, and pharyngitis, as well as the percent patients with viral positivity at day 7, but not headache, rhinorrhea, anosmia, or shortness of breath, or vomiting, when compared to standard care alone. However, taking vitamin D alone did not provide significant benefit (110265). The validity of individual studies is limited by generally poor designs. More research is needed to evaluate varying vitamin D dosing levels and schedules, as well as evaluated outcomes, and whether patients with vitamin D insufficiency are more likely to benefit from vitamin D supplementation. The relationship between vitamin D status and risk of COVID-19 infection or severe disease is unclear. Despite some observational research suggesting that low vitamin D levels are associated with an increased risk for COVID-19 mortality, development of severe disease, such as pulmonary involvement, and extended hospitalization or admission to intensive care (107206,107207,108434), several meta-analyses of observational research as well as individual observational studies have found that vitamin D deficiency in adults is not associated with a higher risk for COVID-19 infection or with disease severity or mortality (104627,107208,107209). Additional observational research has found no association between vitamin D status and hospital length of stay, need for mechanical ventilation, mortality, or experiencing persistent feelings of fatigue or reduced exercise tolerance, otherwise known as "long-COVID" (106102,106116,106120,107206). However, one meta-analysis has found that when compared with mild disease, 65% more individuals with severe disease had vitamin D deficiency. Also, vitamin D insufficiency, defined as blood levels less than 30 ng/mL, is associated with a more than 80% increased chance of hospitalization or mortality due to COVID-19. Notably, many of these studies did not control for patient age or other comorbidities (104627). A more recent observational study has found that vitamin D status in patients with severe COVID-19 symptoms is inversely correlated with both ICU admission and death, with a 1% reduction in risk of ICU admission and 4% reduction in risk of death for every 1 ng/mL increase in 25-hydroxyvitamin D (106112). In one individual observational study, the association between vitamin D status and COVID-19 infection is no longer significant after adjusting for socioeconomic status, age, health status, body mass index, ethnicity, and other covariates (104628). In contrast, a small observational study of adults admitted to the hospital with COVID-19 has found that low vitamin D levels are associated with an increased risk of mechanical ventilation and in-hospital mortality, even after adjustment for ethnicity and pre-existing conditions, such as cardiovascular disease, respiratory disease, and diabetes. However, this study is small and does not adjust for socioeconomic factors (105720). Also, another individual observational study has found that the likelihood of testing positive for COVID-19 is increased in Black, but not White, adults who had a vitamin D level of 30-40 ng/mL at some point in the past year when compared with a level of at least 40 ng/mL, with risk decreasing as levels increased from 30 ng/mL to 40 ng/mL (104716). Patients should be encouraged to maintain adequate vitamin D levels. A joint task force has recommended 400-1000 IU (10-25 mcg) daily for those who are unable to spend 15-30 minutes in the sun each day (103659,104629).
Crohn disease. Limited evidence suggests that vitamin D reduces relapses in patients with Crohn disease. Details: A meta-analysis of small, low-quality clinical studies in patients with IBD, including Crohn disease and ulcerative colitis, shows that taking high- or low-dose vitamin D for up to 1 year reduces the rate of relapse when compared with control (98915). The validity of these findings is limited by the heterogeneity of the included studies.
Dementia. It is unclear if oral vitamin D is beneficial for dementia. Details: Population research has found that patients with any type of dementia have serum concentrations of vitamin D that are about 2.5 ng/mL lower than patients without dementia (84672). However, it is unclear if vitamin D supplementation is beneficial.
Depression. It is unclear if oral vitamin D is beneficial for treating depression. Vitamin D does not seem to prevent the development of depression. Details: The role of vitamin D in the treatment of depression is unclear. Earlier meta-analyses of clinical research show that vitamin D supplementation does not improve overall symptoms of depression. However, some subgroup analyses suggest that vitamin D may be beneficial for improving the symptoms of depression in people with clinically significant symptoms, as well as those with baseline vitamin D deficiency (97295,97298). More recent meta-analyses of several clinical trials, that include some of the same studies, show that vitamin D modestly improves symptoms of depression in adults; however, subgroup analysis suggests that vitamin D does not improve depressive symptoms in older adults (110832,112786). These analyses are mixed over whether baseline vitamin D status affects results (110832,112786) and one of these analyses shows no evidence that the type of depression affects findings (110832). Another meta-analysis of generally small clinical trials in patients with type 2 diabetes and depression shows that taking vitamin D modestly improves depressive symptoms when compared with placebo or no intervention (110814). Although, results of an individual clinical trial in patients with type 2 diabetes are in contrast (108423). The evaluated research implemented one-time doses of 150,000-500,000 IU, as well as daily and weekly doses ranging between 400-5000 IU daily or 5000-100,000 IU weekly for 6 weeks to 2 years, with the most evidence of benefit related to one-time high doses. Cholecalciferol was the most common form of vitamin D used (97295,97298,108423,110814,110832,112786). Significant heterogeneity between studies and the wide variability in dosing strategies limit the validity of these findings, as well as identification of an effective dose or target population. Vitamin D has also been evaluated for the prevention of depression. One large clinical study (VITAL-DEP) in healthy patients 50 years and older shows that taking vitamin D 2000 IU daily for about 5.3 years does not prevent depression or depressive symptoms, or improve mood, when compared with placebo (103670). An analysis of a cohort of patients from the VITAL-DEP trial also shows that taking vitamin D 2000 IU daily for 2 years does not reduce the risk of major depressive disorder or improve mood scores in patients with subthreshold depression or risk factors for late-life depression when compared with placebo (112032). In addition, a meta-analysis of several clinical studies suggests that vitamin D supplementation does not prevent depression based on subgroup analysis of patients without depression at baseline (112786). Based on these and other preliminary findings, Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that vitamin D in doses of 1500 to 4000 IU daily is weakly recommended for adjunctive or monotherapy use in patients with depression, especially those with insufficient intake or skin exposure to sunlight (110318).
Diabetes. Oral vitamin D might improve glycemic indices in some patients with type 2 diabetes and gestational diabetes. It is unclear if oral vitamin D is beneficial for the prevention of type 1 or gestational diabetes. It is also unclear if intramuscular vitamin D is beneficial for the treatment of gestational diabetes. Details: Most meta-analyses of mainly small clinical trials show that vitamin D supplementation is beneficial for measures of glycemic control in patients with diabetes. However, the best evidence of benefit is in patients with baseline vitamin D deficiency. Three meta-analyses of small trials in patients with type 2 diabetes show that vitamin D supplementation reduces glycated hemoglobin (HbA1c) by 0.20% to 0.25%, and improves serum insulin, fasting blood glucose, and measures of insulin resistance when compared with control (96403,110822,112487). Supplemental vitamin D seems to be most beneficial in patients with baseline vitamin D deficiency (96403,110822,112487). Furthermore, correlation analysis suggests an inverse relationship between serum vitamin D levels and serum insulin, fasting blood glucose, and measures of insulin resistance (112487). However, another meta-analysis of small trials in patients with vitamin D insufficiency or deficiency and type 2 diabetes shows that oral vitamin D modestly improves fasting blood glucose and postprandial blood glucose, but not HbA1c, when compared with control (107210). Most of the evaluated research implemented daily or weekly doses of vitamin D for 4-48 weeks (96403,107210,110822). However, one meta-analysis of clinical research in patients with diabetes shows that vitamin D improves HbA1c, insulin resistance, and insulin measures in studies lasting less than 6 months, but not in studies lasting longer than 6 months (99764). An additional meta-analysis suggests that most evidence of benefit is associated with doses of more than 2000 IU daily for 4-12 weeks (110822). One small, long-term clinical study in middle-aged and elderly patients with type 2 diabetes shows that taking vitamin D 800 IU daily for 30 months reduces insulin levels and insulin resistance when compared with no supplementation. However, there was no effect on HbA1c or fasting blood glucose levels (109734). Thus, conflicting results may be related to the dose and duration of vitamin D supplementation, as well as patient characteristics at time of study entry, such as vitamin D status, baseline HbA1c levels, obesity, and medication regimen (97304,99764,109734,110822). Vitamin D has been evaluated for the prevention of type 1 diabetes. There is preliminary evidence that daily vitamin D supplementation (form not specified) in infants during the first year of life is associated with a reduced incidence of type 1 diabetes development later in life (10139). Also, a meta-analysis of population studies has found that vitamin D supplementation in early childhood is associated with a 29% reduced risk of developing type 1 diabetes later in life (84225). Vitamin D has been evaluated in patients with gestational diabetes. Some research has evaluated the effects of oral or intramuscular vitamin D on glycemic indices. The evidence from clinical research comparing vitamin D with placebo is mixed. Most studies show modest evidence of benefit for some markers of glycemic control. One clinical trial shows that vitamin D modestly reduces levels of insulin, as well as measures of insulin resistance, with no effect on fasting blood glucose (106125). However, other clinical research shows that taking vitamin D modestly reduces levels of fasting blood glucose and HbA1c, with no effect on insulin measures (106126). Two other trials show that taking vitamin D modestly improves all measures of glycemic indices (101775,106122). Additionally, a large clinical trial shows that taking vitamin D 1600 IU daily modestly reduces fasting blood glucose when compared with vitamin D 400 IU daily (112020). Some clinical research has also evaluated the effects of oral vitamin D on lipid indices in patients with gestational diabetes. Although some individual clinical research disagrees (106126), most research shows that taking vitamin D modestly improves levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides when compared with control (106125,110823). Also, a meta-analysis of clinical research in patients with gestational diabetes shows that taking vitamin D reduces the risk of premature birth and neonatal hospitalization by approximately 63% and 62%, respectively (110823). Oral vitamin D 50,000 IU (eg. D-Vitin50000; Zahravi Pharm Co.) once or twice monthly, starting at week 24 of gestation and continuing for 6 weeks, 8 weeks, or until delivery, has been used in most of these studies (106122,106125,106126). One study provided oral vitamin D 500 IU twice daily in yogurt from the beginning of the second trimester for 16 weeks (101775). However, other preliminary clinical research shows that giving vitamin D 300,000 IU as a single intramuscular injection at 24-28 weeks' gestation does not affect HbA1c (106124). Some research has examined the effect of vitamin D supplementation on insulin resistance during pregnancy in the absence of gestational diabetes. A meta-analysis of clinical research shows that taking vitamin D for 6 to 26 weeks modestly decreases measures of insulin resistance when compared with placebo. However, there was no evidence to suggest that higher doses were more beneficial than lower doses. Although this population did not have gestational diabetes, these results suggest that adequate vitamin D might be beneficial for its prevention (110821). Vitamin D has also been evaluated in combination with omega-3 fatty acids in adults with gestational diabetes. One study evaluated vitamin D in combination with eicosapentaenoic acid (EPA) 360 mg plus docosahexaenoic acid (DHA) 240 mg twice daily. There is some evidence that this combination offers benefit over vitamin D alone and plasma triglyceride levels were also improved (106122). Other clinical research in patients with gestational diabetes shows that taking vitamin D with omega-3 fatty acids 8,000 mg twice daily for 6 weeks modestly improves glycemic indices and most lipid markers when compared with placebo (106114). Vitamin D has also been evaluated for the prevention of gestational diabetes. A meta-analysis of four clinical trials shows that vitamin D supplementation reduces the risk of gestational diabetes by 49% when compared with placebo (100897). In addition, a meta-analysis of population studies has found that there is a U-shaped association between serum vitamin D concentrations and the risk of developing gestational diabetes, with serum concentrations between 40 and 90 nmol/L associated with the lowest risk (106109).
Diabetic foot ulcers. It is unclear if oral vitamin D is beneficial for diabetic foot ulcers. Details: A meta-analysis of clinical research in patients with diabetic foot ulcers shows that taking vitamin D modestly reduces ulcer size and improves glycemic and lipid indices when compared with placebo (110835). This meta-analysis is limited by the availability of three small clinical trials, as well as the heterogeneous doses of vitamin D in the included studies.
Diabetic nephropathy. Limited evidence suggests that vitamin D improves some markers of kidney function in patients with diabetic nephropathy. Details: A meta-analysis of small clinical studies in patients with diabetic nephropathy shows that taking vitamin D or its analogs reduces inflammatory markers and protein in the urine, but does not affect measures of kidney function such as serum creatinine or glomerular filtration rate, when compared to control (99771).
Dysmenorrhea. Limited evidence suggests that oral vitamin D reduces pain in patients with dysmenorrhea. Details: A meta-analysis of 9 small clinical studies in patients with dysmenorrhea shows that taking vitamin D in doses ranging from 5000 IU daily to 300,000 IU monthly modestly reduces pain when compared with control (112029). However, the validity of these findings is limited by a high degree of heterogeneity across the studies, including differences in blinding and control interventions, vitamin D doses and frequency of supplementation, and baseline vitamin D levels. Another small clinical study in adolescent patients with dysmenorrhea shows that taking vitamin D3 50,000 IU weekly for 9 weeks modestly reduces pain when compared to baseline (98912). The validity of this finding is limited by the lack of a control group.
Exercise-induced muscle damage. Small studies suggest that vitamin D does not improve exercise-induced muscle damage. Details: A meta-analysis of 6 small studies shows that taking vitamin D before and/or during exercise does not improve circulating levels of creatine kinase, lactate dehydrogenase, or myoglobin when compared with placebo (107218).
Fall prevention. The role of vitamin D in fall prevention is confusing and controversial. Oral vitamin D should be considered for those with vitamin D deficiency. Details: Higher serum levels of vitamin D have been associated with improved lower-extremity function in elderly adults (15636). Clinical research shows that taking vitamin D or vitamin D analogues, with or without calcium, reduces the number of people who have a fall by up to 19% (39038,84215,84374,84539,94130,104023). Other research shows that vitamin D, with or without calcium, reduces number of falls by 19% to 50% (11939,16275,84404,93941,109053). In these studies that show beneficial effects, the form of vitamin D (ergocalciferol, cholecalciferol) does not appear to influence results (39038,84374). Some clinical research shows a decreased rate of falls in patients with low baseline levels of vitamin D, but not in those with adequate vitamin D levels (84670,84684,109053). One meta-analysis also suggests that taking vitamin D as cholecalciferol up to 1000 IU daily reduces fall risk by up to 19%, whereas studies using higher doses did not reduce the risk of falling (109053). Also, daily dosing, but not intermittent dosing, seems to be associated with a reduced risk of falling (109053). Despite a substantial amount of positive research, more recent clinical studies show that vitamin D does not reduce the risk of falling (84404,84670), the rate of falls overall (84670,93942), or the rate of injurious falls (93942) in elderly patients (93942). One study in adults over 70 years of age with a history of falling actually found that taking high-dose vitamin D, either as 60,000 IU monthly or 24,000 IU plus calcifediol 300 mcg monthly, increased both the risk of falling and the mean number of falls compared to a lower dose of 24,000 IU monthly (93940). One meta-analysis of 20 trials including nearly 30,000 patients shows that taking vitamin D, with or without calcium, does not reduce the risk of falling in elderly patients, regardless of baseline 25-hydroxyvitamin D levels, level of 25-hydroxyvitamin D achieved with treatment, duration of treatment, or residential status of the patients (91342). While a meta-analysis of 10 trials in nearly 6,000 patients shows that taking vitamin D 700-1000 IU daily with calcium 1000-2000 mg daily reduces the risk of falling in the elderly by 12% when compared with placebo or no treatment, a meta-analysis of 21 trials in nearly 52,000 patients shows that vitamin D alone is only associated with a reduced risk of falls in patients with baseline vitamin D levels of less than 50 nmol/L when compared with placebo or no treatment (107224). The 2018 US Preventative Services Task Force (USPSTF) guidelines for fall prevention acknowledges this research by recommending AGAINST vitamin D supplementation for fall prevention in community dwelling adults 65 years of age and older who do not have osteoporosis or vitamin D deficiency (95703). The reasons for the disparate study results may have to do with the way in which clinical trials have reported outcomes. Clinical trials assessing the effect of vitamin D on fall risk may report results as the number of patients who experience one or more falls, the total number of falls, or the rate of falls per individual. This can affect ultimate conclusions and, in some cases, can be misleading. For example, when studies report on only the total number of falls, it is unclear if vitamin D reduces the rate of falls across the study population, or if it only reduces falls in a small subset of patients. Also, analyses of research suggest that the size of the clinical study appears to affect the trial results. Most trials showing significant reductions in fall risk have been small and of short duration (91342,94132); whereas larger and longer-term studies tend to show no benefit (13073,84399).
Fetal and premature infant mortality. Taking vitamin D during pregnancy might reduce the risk of fetal or early infant death. Details: A meta-analysis of clinical research shows that vitamin D supplementation during pregnancy reduces the risk of intrauterine or neonatal death by 31% when compared with not supplementing with vitamin D. A sub-analysis shows that this benefit was limited to doses of up to 4000 IU daily (109055).
Fibromyalgia. A small clinical study suggests that vitamin D might improve pain in patients with fibromyalgia. Details: A small clinical study in fibromyalgia patients with low vitamin D levels shows that taking vitamin D3 (cholecalciferol) 1200-2400 IU daily seems to reduce pain, but not mood or quality of life, when compared with placebo (91349).
Food allergies. It is unclear if prenatal or infant oral vitamin D supplementation reduces the risk of developing food allergies. Details: A meta-analysis of two large clinical studies shows that prenatal or infant vitamin D supplementation does not reduce the risk of developing food allergies when compared with low-dose vitamin D or no intervention (108438).
Frailty. It is unclear if oral vitamin D is beneficial for the prevention or treatment of frailty in older adults. Details: Frailty involves a combination of muscle loss and weakness, with exhaustion and reduced ability for physical activity. Some observational research has found that low vitamin D status is associated with frailty occurrence. However, clinical research in community dwelling older adults shows that taking vitamin D as 1000 IU, 2000 IU, or 4000 IU daily for 24 months does not prevent frailty or attenuate the worsening of frailty when compared with low-dose vitamin D 200 IU daily. Baseline vitamin D status did not affect these findings. Also, a sub-analysis suggests that vitamin D 2000 IU might increase frailty; however, only a small number of participants were randomized to this dose (109046). Other clinical research in community dwelling adults at least 70 years of age shows that taking cholecalciferol 2000 IU daily for 3 years does not reduce the odds of becoming pre-frail or frail over 36 months when compared with placebo. However, when taken in combination with omega-3 fatty acids 1 gram daily and a home exercise program, the odds of becoming pre-frail is reduced by 39% (110829).
Generalized anxiety disorder (GAD). A small clinical study suggests that vitamin D may modestly improve anxiety in patients with GAD. Details: A small clinical study in patients with GAD shows that taking vitamin D 50,000 IU once weekly for 3 months, in addition to taking an antidepressant and an anxiolytic, moderately reduces anxiety scores when compared with taking these medications alone (103654).
Hematopoietic stem cell transplant (HSCT). It is unclear if oral vitamin D is beneficial for improving outcomes in patients receiving HSCT. Details: A small clinical study in patients who have undergone an autologous HSCT shows that taking calcitriol 0.25 mcg three times daily for 30 days can reduce the time to absolute lymphocyte count recovery, but does not affect time to recovery of absolute neutrophil and platelet counts, when compared with placebo (103665).
Hepatitis C. Low levels of vitamin D have been associated with an inadequate response to hepatitis C therapy. Adding vitamin D to standard therapy for hepatitis C may improve viral response, especially in specific genotypes. Details: A small clinical trial in patients with hepatitis C genotypes 2-3 receiving standard therapy with PEG-interferon and ribavirin shows that adding vitamin D 2000 IU daily for 24 weeks results in 95% of patients achieving undetectable levels of hepatitis C RNA, compared to only 77% of patients treated with standard therapy alone (98917). Another small clinical study in patients with hepatitis C genotype 1b receiving the same standard therapy shows that adding vitamin D 1000 IU daily for 16 weeks results in about 79% of patients achieving undetectable levels of hepatitis C RNA, compared to about 55% of patients treated with standard therapy alone. The TT genotype seems to be especially susceptible to vitamin D supplementation, while TG/GG genotype does not seem to be susceptible (98923).
HIV/AIDS. It is unclear if oral vitamin D is beneficial for improving bone mineral density (BMD) in children and young adults with HIV. Details: Vitamin D deficiency and hyperparathyroidism are common in children and young adults with HIV. A meta-analysis of two clinical trials in this population shows that taking cholecalciferol for 12 months does not improve spine BMD when compared with placebo. Also, an analysis of two clinical trials shows that taking doses of 1600 IU to 4000 IU daily does not improve spine BMD when compared with taking doses of 400-800 IU daily. However, taking higher dose vitamin D has a small beneficial effect on total BMD when compared with taking lower doses. There was no improvement on parathyroid hormone levels (110824). This meta-analysis is limited by the availability of small clinical trials, as well as the heterogeneous doses of vitamin D used in the included studies.
Hyperlipidemia. Although population research has found that higher vitamin D levels are associated with improved lipid levels, it is unclear if vitamin D supplementation is beneficial. Details: Population research has found that higher vitamin D levels are associated with lower low-density lipoprotein (LDL) cholesterol and triglyceride levels and higher high-density lipoprotein (HDL) cholesterol levels when compared with lower vitamin D levels (15630,98919). However, supplementation might not be beneficial. A meta-analysis of small clinical studies suggests that taking vitamin D as cholecalciferol, ergocalciferol, alfacalcidol, or calcitriol slightly increases LDL cholesterol, but does not affect total cholesterol, triglycerides, or HDL cholesterol, when compared with placebo (84642). The validity of these findings is limited by the variability in patient populations, vitamin D dose and formulation, and study duration. Also, none of the included studies were prospectively designed to test the effect of vitamin D on lipid levels. Another meta-analysis of clinical studies in a mixed population of healthy patients and patients with metabolic disease shows that taking vitamin D 1400-50,000 IU weekly with calcium 500-2000 mg daily results in very modest improvements in total cholesterol, triglyceride, and HDL cholesterol levels, but not LDL or very low-density lipoprotein (VLDL) cholesterol levels, when compared with placebo. Subgroup analyses suggest that effects are more pronounced in patients with metabolic disease (107227). The validity of these findings is limited by the heterogeneity of the included studies, which persisted throughout subgroup analyses.
Hyperthyroidism. Oral vitamin D has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research suggests that serum vitamin D levels are decreased in patients with newly diagnosed Graves' disease. A small preliminary clinical trial in patients with newly diagnosed Graves' disease taking methimazole and low levels of selenium and vitamin D shows that taking vitamin D as cholecalciferol for 270 days, in combination with selenium for the first 180 days, modestly reduces levels of serum free thyroxine and improves quality of life when compared with no vitamin D or selenium. However, taking vitamin D and selenium did not affect levels of free triiodothyronine or positive thyroid stimulating hormone (TSH) receptor antibody (109049).
Hypothyroidism. It is unclear if vitamin D is beneficial in the treatment of subclinical hypothyroidism. Details: A preliminary clinical study in patients with vitamin D deficiency and subclinical hypothyroidism shows that taking vitamin D 50,000 IU weekly for 2 weeks improves mean thyroid stimulating hormone levels by 3.55 mIU/L from baseline. The validity of this finding is limited by the lack of a comparator group (107213).
Ichthyosis. It is unclear if oral vitamin D is beneficial in patients with inherited ichthyosis. Details: A small clinical study in patients with congenital non-syndromic ichthyosis shows that taking vitamin D 2000 IU daily for 24 weeks reduces the clinical severity of disease at 12 weeks, but not 24 weeks, when compared with baseline. When compared with patients taking acitretin 0.5 mg/kg daily, results were similar at both 12 and 24 weeks, but it is unclear if the improvement from baseline differed between groups (108441).
IgA vasculitis. It is unclear if oral alfacalcidol is beneficial in children with IgA vasculitis. Details: A clinical study in children with IgA vasculitis shows that taking alfacalcidol 0.25 mcg daily along with vitamin C, rutin, dipyridamole, cimetidine, calcium, and glucocorticoids for 4 weeks improves rates of recurrence and incidence of kidney damage when compared with those receiving the same regimen without alfacalcidol. Alfacalcidol also improves cellular immune function and reduces levels of inflammatory biomarkers (107212).
Irritable bowel syndrome (IBS). It is unclear if oral vitamin D is beneficial for IBS; the available research is conflicting. Details: Although some meta-analyses show that taking vitamin D is moderately more effective than placebo for improving IBS symptom severity and quality of life, other analyses disagree. Doses of vitamin D have included 50,000 IU weekly or every 2 weeks or 2000-4000 IU daily for up to 6 months (109041,109054,109057). The reasons for these discrepancies might be attributed to the inclusion criteria related to the individual trials, the small sample sizes, and varied dosing strategies used in the available research.
Kidney transplant. It is unclear if oral cholecalciferol is beneficial for improving allograft function or preventing non-skeletal complications in kidney transplant recipients. Details: Following a kidney transplant, patients are at increased risk of vitamin D insufficiency and related outcomes. A large clinical trial shows that taking a high dose of cholecalciferol for 2 years does not reduce the composite risk of developing type 2 diabetes, major cardiovascular events, or cancer, or death when compared to taking a lower dose. The high and low doses of vitamin D were 100,000 IU or 12,000 IU, respectively, every 2 weeks for 2 months, followed by monthly doses for the next 22 months (110830). The effect of a high dose of vitamin D on these outcomes individually is not clear. However, taking vitamin D does not seem to improve allograft function. A clinical study in kidney transplant recipients shows that taking cholecalciferol 4000 IU daily, beginning 1-month posttransplant and continuing for 11 months, has no effect on allograft function when compared with placebo (108425).
Kidney transplant-related bone loss. Oral vitamin D might be beneficial for preventing bone loss associated with kidney transplantation. Details: A large clinical trial shows that taking a high dose of cholecalciferol for 2 years modestly reduces the odds of a fracture by 76% when compared to taking a lower dose. The high and low doses of vitamin D were 100,000 IU or 12,000 IU, respectively, every 2 weeks for 2 months, followed by monthly doses for the next 22 months (110830). A prespecified secondary analysis of a clinical study in patients at 1-month post-kidney transplant from a living donor in Japan shows that taking vitamin D (cholecalciferol) 4000 IU daily for months 1-12 posttransplant reduces whole blood parathyroid hormone levels by 15%, but does not alter levels of tartrate-resistant acid phosphatase 5-b or bone-specific alkaline phosphatase, when compared with placebo. The greatest effects on parathyroid hormone levels are observed in those with more severe vitamin D deficiency, hypocalcemia, and more preserved kidney function. Vitamin D supplementation also attenuates changes in bone mineral density (BMD) at the lumbar spine, but not the distal radius, from prior to transplant. Patients taking vitamin D had a loss of only 0.2%, compared with a loss of 2% in those receiving placebo. The greatest effects are observed in those with osteoporosis or osteopenia (107220). Conversely, a small clinical trial shows that taking calcitriol (1,25-dihydroxyvitamin D3) 0.25 mcg daily in combination with calcium carbonate 500 mg daily does not decrease bone loss associated with kidney transplantation. However, calcitriol might reduce osteoclast suppression, help maintain trabecular bone volume and wall thickness, and improve axial BMD (4823).
Impaired glucose tolerance (prediabetes). Taking vitamin D might slow prediabetes progression to diabetes in people with low baseline levels of vitamin D or in people achieving high levels of vitamin D following supplementation. It is unclear if vitamin D supplementation is beneficial in people with prediabetes and sufficient vitamin D levels. Details: Observational research has found that low vitamin D levels are linked with a higher risk of prediabetes and higher dietary vitamin D is linked with a lower chance of developing diabetes (84594,103669). Meta-analyses and individual clinical studies in patients with prediabetes and unclear or sufficient vitamin D levels show that vitamin D supplementation might improve some glycemic indices, but does not seem to prevent progression of prediabetes to diabetes (84594,91347,99769,108421). However, a more recent meta-analysis of three clinical studies that were designed to evaluate the preventative effects of oral vitamin D in patients with type 2 diabetes shows that taking vitamin D reduces the risk of developing diabetes with an absolute risk reduction of 3.3% over 3 years compared with taking placebo. However, the actual risk reduction was highly dependent on the intra-trial vitamin D status. Patients achieving the highest serum vitamin D levels had absolute 3-year risk reductions of 11.4% to 18.1%. Doses of vitamin D used in this research include cholecalciferol 4000 IU daily or 20,000 IU weekly or eldecalcitol 0.75 mcg daily (110810). In patients with vitamin D deficiency and prediabetes, vitamin D might improve beta-cell function, suggesting reduced disease progression (99768,107210). One clinical study in adults with vitamin D deficiency shows that taking vitamin D 50,000 IU weekly for 3 months, and then monthly for 3 months, modestly improves insulin resistance and beta-cell function as measured by the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), but does not affect fasting or postprandial glucose levels when compared with placebo (99768). Further, a meta-analysis of randomized controlled trials in patients with vitamin D deficiency and prediabetes shows that oral vitamin D at a median dose of 50,000 IU weekly for 26 weeks modestly improves fasting blood glucose and some markers of islet function, but not postprandial blood glucose or glycated hemoglobin (HbA1c) levels, when compared with control. Additionally, a significantly greater proportion of patients receiving vitamin D supplementation regressed from prediabetes to normal glucose status (107210). Conversely, a study in females with vitamin D deficiency and prediabetes shows that taking vitamin D 60,000 IU weekly for 8 weeks, followed by a maintenance dose of 200 IU daily after repletion, has no effect on the incidence of type 2 diabetes at 2 years (107211).
Infant development. It is unclear if giving oral vitamin D in doses above the recommended dietary allowance during infancy is beneficial for improving neurodevelopment. It is also unclear if oral vitamin D during pregnancy is beneficial for improving cognitive development in the offspring. Details: Clinical research shows that giving vitamin D 1200 IU daily to healthy term infants of Northern European ethnicity starting at 2 weeks of age does not improve measures of neurodevelopment at 2 years of age when compared with giving the standard dose of vitamin D 400 IU (106121). Overall, the evidence from population research is mixed as to whether vitamin D status during gestation is associated with infant developmental outcomes. However, some population research has found that increased vitamin D status during pregnancy is associated with improved anthropomorphic and neurodevelopmental outcomes (104621,105724). Two meta-analyses of observational research show that low vitamin D status during pregnancy is associated with reduced head circumference and cognitive development scores, and higher odds of the offspring developing autism and attention deficit hyperactivity disorder (105724,105725). However, one meta-analysis suggests these risks may be limited to those with very low vitamin D status (serum level < 12 ng/mL) (105724). Multiple meta-analyses show that vitamin D status during pregnancy does not appear to affect motor development (105724,105725). In one observational study, plasma vitamin D concentrations in the second trimester of pregnancy was associated with increased IQ scores in the offspring at age 4-6 years. Each 10 ng/mL increase in vitamin D levels was associated with a 1.17-point increase in IQ (104621). In contrast, clinical research shows that taking vitamin D3 2800 IU daily during the third trimester does not improve neurodevelopmental outcomes in the first 6 years of life when compared to taking lower doses of 400 IU daily (104623).
Infertility. It is unclear if oral or intramuscular vitamin D is beneficial in females with infertility. Details: A meta-analysis of clinical research in infertile females shows that although there was no effect of taking vitamin D on implantation rate or miscarriage, taking vitamin D increases the odds of clinical pregnancy by 49% compared with taking placebo. However, sub-analyses of clinical and observational research found that benefits on clinical pregnancy rates were limited to populations with vitamin D insufficiency, but not vitamin D deficiency, and for doses between 1000 to 10,000 IU daily for 30-90 days (110818). Most studies included in the analysis used oral vitamin D; however, intramuscular vitamin D was used in one cohort study. A smaller meta-analysis of clinical studies in females with infertility and vitamin D insufficiency undergoing IVF shows that taking vitamin D increases the rate of chemical pregnancy by 50%, but has no effect on the clinical pregnancy rate (108432).
Lung cancer. It is unclear if oral vitamin D prevents lung cancer or improves lung cancer prognosis. Details: A small meta-analysis of randomized controlled trials and observational research has found that high intake of vitamin D is associated with a 10% reduction in the risk of developing lung cancer when compared with low vitamin D intake. In terms of prognosis, high vitamin D intake is associated with improvements in both overall survival and relapse-free survival (107217).
Low birth weight. It is unclear if oral vitamin D can reduce the risk for low birth weight; the available evidence is conflicting. Details: A meta-analysis of observational research has found that a very low vitamin D status (serum level <12 ng/mL) during pregnancy is associated with lower birth weight and increased odds of SGA births. However, these risks have not been demonstrated in those with less severe vitamin D deficiency (serum level <20 ng/mL) (105724). Most research also shows that vitamin D supplementation during pregnancy reduces the risk of low birth weight. A meta-analysis of three clinical trials shows that supplementation with vitamin D 800-1000 IU daily starting between 27 and 32 weeks' gestation, or 200,000 IU administered as a single dose or in two divided doses during the seventh and eighth month of pregnancy, reduces the risk of delivering a low birth weight infant by 60% (84659). Other meta-analyses of clinical research confirm that supplementation with vitamin D during pregnancy results in a 45% to 60% reduced risk of low birth weight and a 103 gram greater average birth weight (99766,100897). However, some meta-analyses show that vitamin D supplementation during pregnancy does not reduce the risk of low birth weight when compared with no supplementation (95910,109055). One meta-analysis that included studies that did not directly measure birth weight shows no effect of vitamin D supplementation during pregnancy on the rate of low birth weight, despite showing an increase in overall birth weight of about 58 grams (95910).
Male infertility. It is unclear if oral cholecalciferol is beneficial in males with infertility. Details: A small clinical study in males with infertility shows that taking cholecalciferol 2500 IU daily for 6 months modestly improves progressive sperm motility, sperm concentration, and sperm morphology when compared with baseline (108427). The validity of these findings is limited by the lack of a comparator group.
Melanoma. It is unclear if oral vitamin D is beneficial in patients with melanoma. Details: A meta-analysis of 14 observational studies suggests that vitamin D deficiency is associated with a 45% greater risk of melanoma when compared with normal vitamin D levels (112027). However, a small clinical study in patients with newly resected stage II melanoma shows that taking vitamin D3 100,000 IU every 50 days for 3 years does not improve disease-free survival when compared with placebo. Most patients in this study had vitamin D deficiency or insufficiency at baseline (106113).
Metabolic syndrome. It is unclear if oral vitamin D is beneficial for preventing or treating metabolic syndrome. Details: In patients with metabolic syndrome, clinical research shows that taking vitamin D 50,000 IU weekly for 16 weeks does not affect most metabolic or anthropometric factors when compared with placebo, although there was a modest decrease in triglyceride levels (106123). However, almost all of the individuals in this study were vitamin D deficient or insufficient, and many remained in that category even after supplementation. It is unclear if vitamin D supplementation is beneficial in vitamin D sufficient patients with metabolic syndrome. There is conflicting evidence about the association between vitamin D and metabolic syndrome (14265,16713,98234). Some population research has found that higher vitamin D levels are associated with a lower risk of metabolic syndrome, while other research found no association (14265,16713). Furthermore, a small clinical trial in patients with metabolic syndrome shows that taking vitamin D 20,000 IU or 40,000 IU weekly for 8 weeks does not affect metabolic risk factors when compared with placebo (98234).
Migraine headache. It is unclear if oral vitamin D reduces the frequency of migraine. Details: A meta-analysis of three small high-quality clinical studies in patients with migraine shows that taking vitamin D 2000 or 4000 IU daily for 12-24 weeks or 500,000 IU weekly for 2 months reduces the frequency of migraines by 2-3 attacks monthly when compared with usual care or placebo (108439).
Multiple sclerosis (MS). Although vitamin D supplementation has been linked with a lower risk of developing MS, taking oral vitamin D supplements does not seem to reduce MS relapses. Details: Population research suggests that long-term supplementation with vitamin D 400 IU is associated with a 40% lower risk of MS in females. The effect seems to be dose-dependent. Consumption of at least 400 IU daily, mainly in the form of a multivitamin supplement, appears to have the greatest protective effect (11356). Additional population research in over 7 million people suggests that higher levels of calcifediol are associated with a lower risk of developing MS. In White adults, for every 20 ng/mL increase in vitamin D levels, there appears to be a 41% decrease in MS risk. However, this was not found in Black and Hispanic adults (15159). Vitamin D supplementation has also been examined in patients with MS. Population research suggests that taking vitamin D supplements and the maintenance of optimal blood levels of vitamin D are associated with a reduction in the development of new areas of demyelination detected by magnetic resonance imaging (MRI) over 24 months. However, there were no correlations between taking vitamin D or vitamin D blood levels and clinical outcomes (110816). Also, vitamin D supplementation does not seem to impact MS relapses or most symptoms in patients with MS. Meta-analyses of preliminary clinical research show that vitamin D supplementation does not affect the rate of MS relapses, overall symptoms, or the number of MS nerve lesions detected by MRI, regardless whether the vitamin D was low-dose or high-dose (98192,98914,106119). However, one meta-analysis of 6 small clinical studies shows that taking vitamin D for 8-96 weeks slightly improves fatigue scores when compared with placebo (112024). These analyses are limited by the small size and heterogeneity of most of the included studies and variability in dosing and duration of vitamin D regimens.
Muscle strength. It is unclear if oral vitamin D improves muscle strength in middle aged or older adults with low or sufficient levels of vitamin D. The available research is conflicting. Details: Clinical research in healthy older adults who are not deficient in vitamin D shows that oral vitamin D3 (cholecalciferol) supplementation, with 800 IU, 1000 IU, or 2000 IU daily or 50,000 IU monthly, alone or in combination with a resistance training program, does not increase muscle strength when compared with placebo (11814,104619,108429). In patients 40-80 years of age with low vitamin D levels, taking vitamin D3 100,000 IU (2500 mcg) once, followed by 20,000 IU (500 mcg) weekly for 4 months, does not improve muscle strength when compared with placebo (103658). Similarly, one meta-analysis of clinical research shows that vitamin D does not increase grip strength, muscle mass, or muscle power when compared with control (91341). However, some research has found some benefit with the use of vitamin D supplements. One meta-analysis shows that taking vitamin D increases grip strength after menopause when compared with placebo or low-dose vitamin D, although a sub-analysis shows that beneficial effects are limited to individuals aged 60-69 years, when vitamin D is taken without calcium, when baseline vitamin D levels are at least 30 ng/mL, or when the treatment consists of the vitamin D analog alfacalcidol. This suggests heterogeneity between studies (109048). Another meta-analysis in elderly adults shows that taking vitamin D as calcifediol 10-30 mcg daily for a median of 24 weeks modestly improves hand grip strength and leg extension, but not leg flexion, when compared with baseline (109042). Also, some individual clinical research in older adults with low levels of vitamin D at baseline shows that taking vitamin D3 800 IU daily or vitamin D2 (ergocalciferol) 1000 IU daily for 12 months in combination with calcium 1000 mg daily modestly improves lower extremity or hip strength by 8% to 23% when compared with calcium alone (38915,84530).
Myalgia. It is unclear if oral vitamin D is beneficial for reducing myalgia associated with obesity. Details: Preliminary clinical research in obese individuals with vitamin D deficiency who are on a low-calorie diet shows that taking vitamin D 50,000 IU weekly, alone or in combination with an aerobic exercise program three times weekly for 12 weeks, modestly reduces muscle pain when compared with only aerobic exercise three times weekly (106118).
Myelodysplastic syndromes. It is unclear if oral vitamin D is beneficial for patients with myelodysplastic syndromes. Details: A small observational study in patients with myelodysplastic syndromes has found that taking calcitriol or calcifediol orally is associated with slowed disease progression (11825).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral or intramuscular vitamin D is beneficial in children or adults with NAFLD. Details: Although findings from individual research are mixed, one meta-analysis of mainly small clinical trials in patients with NAFLD shows that vitamin D modestly improves insulin resistance and serum alanine aminotransferase (ALT) levels, with no effect on serum aspartate aminotransferase (AST) levels. Most studies included in the analysis used oral vitamin D 1000 IU daily or 50,000 IU weekly or biweekly for 3-6 months and compared with placebo; however, one study used a single intramuscular injection of vitamin D 600,000 IU compared with lifestyle modifications (109056). Vitamin D has also been evaluated in combination with fish oil. A clinical study in adults with NAFLD shows that taking oral vitamin D3 1680 IU daily in combination with fish oil or fish oil alone for 3 months improves serum ALT levels similarly to a control group (107186). Vitamin D has also been evaluated for use in children with NAFLD. One clinical study in children with obesity and biopsy-proven NAFLD shows that taking oral vitamin D3 2000 IU daily for 6 months with a hypocaloric diet improves liver histopathology in terms of steatosis, lobular inflammation, and NAFLD activity score at 6 months, but not hepatocyte ballooning or fibrosis, when compared with baseline. These improvements were not seen in the group receiving placebo with a hypocaloric diet, but it is unclear if the improvement from baseline differed between groups (107222).
Nonmelanoma skin cancer. It is unclear if oral vitamin D is beneficial for preventing keratinocyte carcinomas. Details: In middle aged and older adults recently diagnosed with a colorectal adenoma, clinical research shows that taking vitamin D3 1000 IU daily for 3-5 years does not reduce the incidence of keratinocyte cancer when compared with placebo over a median of 8 years. A sub-group analysis shows that taking vitamin D3 with calcium 1200 mg daily as calcium carbonate reduces the risk of invasive cutaneous squamous cell carcinoma by a moderate amount, but has no effect on the risk of basal cell carcinoma. Vitamin D taken alone has no effect on the risk for either type of cancer (104622).
Obesity. The evidence for the use of oral vitamin D in obesity is conflicting and unclear. Details: Population research has found that people with lower vitamin D levels are significantly more likely to be obese when compared to people with higher vitamin D levels (15630). Also, a large-scale, high-quality clinical trial in postmenopausal adults taking calcium 1000 mg plus vitamin D3 (cholecalciferol) 400 IU daily for 3 years shows that these patients are more likely to lose weight and maintain their weight when compared with those taking placebo. This beneficial effect is mainly seen in females who have inadequate intake of calcium, less than 1200 mg/day, before starting a calcium supplement (15604). However, other evidence suggests that vitamin D alone does not improve weight loss. One clinical trial shows that taking vitamin D3 2000 IU/day without calcium for 12 months does not increase weight loss when compared with placebo in overweight and obese postmenopausal adults who are deficient in vitamin D at baseline (91345).
Orthostatic hypotension. It is unclear if oral vitamin D is beneficial for prevention of orthostatic hypotension. Details: A secondary analysis of a clinical study in older patients with vitamin D insufficiency who are at an increased risk for falls shows that taking vitamin D 1000-4000 IU daily for up to 2 years has no effect on the risk of orthostatic hypotension or orthostatic symptoms when compared with those receiving vitamin D 200 IU daily (107223).
Osteoarthritis. It is unclear if oral vitamin D is beneficial for osteoarthritis. Details: The evidence for the use of vitamin D in osteoarthritis is conflicting. Some clinical research shows that taking vitamin D3 (cholecalciferol) 2000 IU daily, or at a higher dose to reach serum vitamin D levels over 36 ng/mL, for 2 years does not reduce knee pain or loss of cartilage when compared with placebo in patients with symptomatic osteoarthritis (84688). However, another clinical study shows that taking vitamin D3 daily for 10 days and then vitamin D3 60,000 IU monthly for 12 months modestly reduces pain and improves function when compared with placebo in patients with osteoarthritis and vitamin D insufficiency (98199). It is possible that higher doses of vitamin D have an effect on osteoarthritis, while lower doses do not. Due to this conflicting and low-quality evidence, the American College of Rheumatology (ACR) recommends against the use of vitamin D for any form of osteoarthritis (102114).
Otitis media. It is unclear if oral vitamin D is beneficial in patients with otitis media. Details: The relationship between vitamin D status and otitis media is unclear. Population research has found that having otitis media is associated with lower blood levels of vitamin D; however, lower vitamin D levels were not associated with greater risk of otitis media (98194).
Overactive bladder. It is unclear if oral vitamin D is beneficial for overactive bladder. Details: A large clinical trial in older males shows that taking vitamin D3 (cholecalciferol) 2000 IU daily for 5 years does not reduce the odds of weekly overactive bladder when compared with placebo. In males with low serum vitamin D, taking vitamin D reduces the odds of overactive bladder at 5 years by 49%, including 34% reduced odds of overactive bladder with urinary incontinence and 81% reduced odds of overactive bladder without incontinence. However, urinary incontinence while sleeping or napping was increased (109738).
Overall mortality. Taking oral vitamin D alone does not seem to reduce mortality; however, there is some evidence that taking certain forms of vitamin D with calcium might have a modest benefit. Details: While higher vitamin D levels have been associated with a small reduction in mortality when compared with lower vitamin D levels (98187), clinical research shows that taking vitamin D does not reduce the risk of mortality. The most comprehensive meta-analysis to date shows that vitamin D supplementation alone does not reduce all-cause mortality when compared to control (100900). However, giving vitamin D with calcium may modestly reduce the risk of mortality. Meta-analyses show a 4% to 9% reduced risk of mortality when trials of vitamin D alone and vitamin D with calcium are pooled together (16102,97296,98186,112022). Finally, some research suggests that the type of vitamin D supplementation might influence the results. A meta-analysis of clinical research found that vitamin D3 (cholecalciferol) with or without calcium reduces mortality risk by 6%, while alfacalcidol, calcitriol, and vitamin D2 (ergocalciferol) do not have benefit (84595,98186).
Pain (chronic). It is unclear if oral vitamin D is beneficial for chronic pain. Details: A meta-analysis of clinical research in patients with chronic pain shows that taking vitamin D for 1-24 months produces a 43% greater decrease in pain score when compared with placebo. However, the final follow-up pain score is similar for both groups (96402). The effect of vitamin D on pain based on pain-related diagnosis, vitamin D status, or dose is unknown.
Parkinson disease. It is unclear if oral vitamin D is beneficial for this condition. Details: Population research found that higher levels of vitamin D are associated with milder Parkinson disease symptoms, while deficiency is associated with increased risk of Parkinson disease (97000,99772). One small study shows that taking vitamin D3 (cholecalciferol) 1200 IU daily for one year might modestly slow the progression of Parkinson disease based on the Hoehn and Yars staging criteria. However, there was no improvement in disease severity according to the more widely used Unified Parkinson Disease Rating Stage (UPDRS). The UPDRS includes measures of activities of daily living and non-motor symptoms. Vitamin D had no effect on most quality of life measures (95915).
Periodontitis. It is unclear if oral vitamin D is beneficial for periodontal disease. Details: A meta-analysis of mostly observational research suggests that vitamin D levels are not associated with an increased or decreased risk of periodontitis (112026). Other population research suggests that higher blood levels of vitamin D may be associated with a reduced risk of periodontal disease in adults 50 years of age or older. However, this association was not found for adults younger than 50 years (15634).
Physical performance. It is unclear if oral vitamin D improves muscle strength in elderly adults. Details: Some clinical research in healthy older adults who are not deficient in vitamin D shows that oral vitamin D3 (cholecalciferol) supplementation, with 800 IU, 1000 IU, or 2000 IU daily or 50,000 IU monthly, alone or in combination with a resistance training program, does not improve physical performance when compared with placebo (11814,104619,108429). Also, results from one meta-analysis of clinical research in postmenopausal females with low levels of vitamin D shows that taking vitamin D does not improve the timed up and go test when compared with placebo or low-dose vitamin D (109048). One meta-analysis that included studies specifically evaluating the use of calcifediol in older adults shows a large benefit on gait speed; however, only one study included in the analysis used this endpoint and other measures of physical performance were not affected (109042).
Pneumonia. High-dose oral vitamin D does not reduce pneumonia severity in children. Details: Although vitamin D supplementation might prevent respiratory tract infections in children, it might not prevent recurrent pneumonia. A small clinical study in children under 5 years of age with recurrent pneumonia and variable vitamin D blood levels shows that taking vitamin D 300,000 IU quarterly for 1 year does not reduce respiratory infections, severity of pneumonia, hospital admissions, or disease complications when compared with placebo (103667). However, it's unknown if vitamin D supplementation using lower and more frequent doses, or supplementation in patients with vitamin D deficiency, might be beneficial. Some observational research has found that having vitamin D deficiency is linked to a higher risk for developing community-acquired pneumonia (CAP) (102118). For information on other respiratory infections, refer to the Respiratory Tract Infection discussion.
Polycystic ovary syndrome (PCOS). It is unclear if vitamin D improves pregnancy outcomes and symptoms in patients with PCOS. Details: A meta-analysis of several mostly low quality clinical studies in patients with PCOS and vitamin D deficiency at baseline shows that intramuscular or oral vitamin D 200-10,000 IU daily for up to 24 weeks in addition to fertility treatment improves certain pregnancy outcomes including the rate of pregnancy, premature miscarriage, and premature delivery but does not impact the incidence of pregnancy complications including gestational hypertension or gestational diabetes mellitus when compared with control. This analysis also suggests vitamin D supplementation improves certain IVF-related outcomes including ovulation rate, fertilization rate, and number of mature oocytes (112787). Observational research in infertile adults with PCOS and insulin resistance suggests that normal vitamin D levels are associated with better embryo quality and increased pregnancy rate when compared with vitamin D deficiency or insufficiency (100834). It is unclear if supplementation with vitamin D improves pregnancy rates in patients with PCOS. Some research has evaluated the effects of vitamin D supplementation on menstruation and follicular development in these patients. A meta-analysis of clinical research shows that taking vitamin D 400-12,000 IU daily for 2-6 months improves follicular development when compared with placebo. Taking vitamin D in combination with metformin 1500 mg daily also appears to increase the number of regular menstrual cycles by 85% when compared with metformin alone. However, no effect on follicular development was seen with the combination. Vitamin D alone does not appear to improve menstrual cycle regularity. Most studies included calcium supplementation as well; therefore, the benefits of vitamin D alone in patients with PCOS are unclear (96404).
Post-stroke fatigue. It is unclear if oral vitamin D is beneficial for post-stroke fatigue. Details: A retrospective study in patients with post-stroke fatigue and vitamin D deficiency suggests that vitamin D (cholecalciferol) 600 IU daily is associated with improvements in fatigue severity at months 1 and 3 when compared with control. Neurologic disability also showed improvement at 3 months, but not at 1 month, when compared with control. It is unclear if improvements from baseline differed between groups (107225).
Pre-eclampsia. It is unclear if oral vitamin D during pregnancy is beneficial for pre-eclampsia prevention. Details: A meta-analysis of four small clinical trials shows that supplementation with vitamin D alone or with calcium during pregnancy reduces the risk of pre-eclampsia in pregnant adults by about 50% when compared with placebo (100897).
Precocious puberty. It is unclear if oral vitamin D is beneficial for the prevention or treatment of precocious puberty. Details: A meta-analysis of 43 studies, most of which are observational and involve young female subjects in China, suggests that vitamin D deficiency or insufficiency is associated with 2.25-fold greater odds of precocious puberty when compared with normal vitamin D levels. Further, this analysis suggests that taking vitamin D 200-1000 IU daily for 3-12 months along with a gonadotropic-releasing hormone analog (GnRHa) is associated with lower luteinizing hormone, follicle-stimulating hormone, and estradiol levels and reduced bone age when compared with GnRHa therapy alone (112019).
Pregnancy-induced hypertension. It is unclear if oral vitamin D is beneficial for patients with gestational hypertension. Details: A subgroup meta-analysis of two low-quality clinical trials shows that vitamin D supplementation during pregnancy does not reduce the risk for gestational hypertension when compared with control (95910).
Premenstrual syndrome (PMS). It is unclear if oral vitamin D is beneficial in patients with PMS. Details: Observational research has found that increasing dietary intake of vitamin D above 706 IU daily is linked to a reduced risk of developing PMS when compared with consuming 112 IU daily (13094). Furthermore, a clinical study shows that taking vitamin D 400 IU daily in combination with calcium 1000 mg daily can decrease the severity of PMS symptoms (16869). But it's unclear if the effects are due to vitamin D, calcium, or the combination. Another clinical study in adolescent females with PMS shows that taking vitamin D3 50,000 IU weekly for 9 weeks modestly reduces PMS symptoms when compared to baseline (98912). The validity of this finding is limited by the lack of a control group.
Preterm labor. It is unclear if oral vitamin D is beneficial for preterm labor. Details: Vitamin D deficiency, defined as serum levels less than 20 ng/mL, during pregnancy has been associated with a 25% increased risk of preterm birth (95911). The risk seems to be especially prominent in those with darker colored skin (103662). However, meta-analyses of clinical research show that vitamin D supplementation during pregnancy does not reduce the risk of a preterm birth when compared with no supplementation with vitamin D (84659,95910,100897,109055). The effect vitamin D specifically in vitamin D-deficient patients is still unclear. Some small, heterogeneous, and low-quality studies show that vitamin D supplementation might reduce the rate of preterm birth in vitamin D-deficient patients (84659,95910,100897). Additional studies are needed to determine the effect of vitamin D supplementation on the risk of preterm birth.
Rheumatoid arthritis (RA). Small clinical studies suggest that oral vitamin D may not improve symptoms in patients with RA. Details: Population research has found that higher intake of vitamin D from foods or supplements is associated with a lower risk of developing RA (12206,98200). However, a meta-analysis of two small clinical trials shows that vitamin D supplementation does not reduce pain or recurrence of RA when compared with placebo (98190).
Rhinosinusitis. Oral vitamin D has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients over 12 years of age with chronic sinusitis shows that taking 1 or 2 sachets of a specific combination product (Flogostop Forte, Humana Italia) containing vitamin D 600 IU, black currant, Boswellia serrata, and bromelain along with a nasal corticosteroid daily for 15-30 days reduces symptoms of nasal hyperemia and rhinorrhea when compared with corticosteroid nasal spray alone (111501). It is unclear if these findings are due to vitamin D, other ingredients, or the combination.
Sarcopenia. It is unclear if oral vitamin D is beneficial in older adults with sarcopenia. Details: A meta-analysis of randomized trials in older adults with sarcopenia shows that taking vitamin D3 (cholecalciferol) 100-800 IU daily, with protein 10-44 grams daily or amino acids 2.5-6 grams daily, for 2-6 months moderately improves muscle strength, but not muscle mass or walking speed, when compared with placebo (105727). The validity of this study is limited by high heterogeneity and an unreported baseline vitamin D status. Similarly, a small network meta-analysis of randomized trials shows that taking vitamin D 500-1600 IU daily or 2500-5000 IU weekly with protein 20-80 grams daily or amino acids 3-32 grams daily with and without exercise for 3-18 months increases hand grip strength and shortens time to chair-stand, respectively, but not gait speed or lower-limb mass when compared with usual care (107221). It is unclear if these effects are due to vitamin D, protein/amino acid supplementation, exercise, or the combinations.
Schizophrenia. It is unclear if oral vitamin D is beneficial for schizophrenia. Details: Based on preliminary clinical evidence, Guidelines from The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that vitamin D in doses of 1500 to 4000 IU daily is not recommended for adjunctive use in patients with schizophrenia (110318).
Seasonal affective disorder (SAD). One small study suggests that a large dose of oral vitamin D can improve symptoms of SAD. Details: A small clinical study in patients with SAD suggests that a single dose of vitamin D2 (ergocalciferol) 100,000 IU improves symptoms after one month when compared to baseline (83791). The validity of this finding is limited by the lack of a control group.
Seborrheic keratosis. It is unclear if topical vitamin D analogues improve symptoms of seborrheic keratosis. Details: Preliminary clinical research suggests that topical ointments containing activated vitamin D in the form of tacalcitol, calcipotriol or maxacalcitol, applied for 3-12 months, can reduce tumor volume by at least 40% in 75% of patients with seborrheic keratosis. Additionally, over 30% of patients seem to experience complete tumor resolution or a reduction in tumor volume of at least 80% (84033). The validity of this finding is limited by the lack of a control group.
Sexual dysfunction. One small study suggests that injecting a large dose of vitamin D might improve sexual function. Details: A small clinical study in females with vitamin D deficiency and sexual dysfunction shows that receiving an intramuscular injection of vitamin D as cholecalciferol 300,000 IU once at baseline and a second time 4 weeks later improves sexual function at 4 and 8 weeks when compared with placebo (100896).
Sickle cell disease. One small study suggests that oral vitamin D reduces pain and improves quality of life in children with sickle cell disease with vitamin D insufficiency or deficiency. Details: A small clinical study in children with sickle cell disease shows that taking vitamin D3 (cholecalciferol) 40,000-100,000 IU weekly for 6 weeks reduces days with pain and improves physical activity and quality of life for up to 6 months when compared with placebo. Of the children included in the study, 82.5% had vitamin D insufficiency, while 52.5% were deficient in vitamin D (98918). It is unclear if vitamin D is effective for patients with sickle cell disease who have adequate levels of vitamin D.
Small for gestational age (SGA). It is unclear if oral vitamin D can reduce the risk for SGA births; the available evidence is conflicting. Details: Two meta-analyses of clinical research show no effect of vitamin D on the risk of SGA birth (84659,109055). However, one meta-analysis shows a 40% reduction in the risk of SGA births with vitamin D supplementation (95910). Also, one meta-analysis shows that when vitamin D supplementation is initiated before the 20^th week of gestation, the risk of SGA is reduced by 54% (109055). Most individual clinical trials are small and heterogeneous. Also, the formulation of vitamin D and/or vitamin D status at baseline may explain part of the discrepant findings. For example, a meta-analysis of observational research has found that a very low vitamin D status (serum level <12 ng/mL) during pregnancy is associated with increased odds of SGA births. This association does not seem to be present with less severe vitamin D deficiency (serum level <20 ng/mL) (105724).
Statin-induced myalgia. It is unclear if oral vitamin D is beneficial for patients with statin-induced myalgia. Details: Observational research has found that taking oral vitamin D supplements is associated with decreased symptoms of myalgia in patients taking statin drugs. In a small case series, patients who discontinued statins due to myalgia were able to resume statin therapy after starting vitamin D supplements. The majority of patients with myalgia were found to be vitamin D deficient, with vitamin D levels less than 12 ng/mL at baseline (16829). An observational study has also found that administering 50,000 units of vitamin D2 (ergocalciferol) once a week for 12 weeks reversed symptoms of myalgia in 92% of statin treated patients with low serum vitamin D levels of less than 32 ng/mL (16831).
Stroke. Although low vitamin D levels are associated with higher risk of stroke, taking vitamin D supplements does not seem to reduce stroke risk. Details: Population research has found that low vitamin D levels are associated with an increased risk of stroke. Furthermore, increased dietary intake of vitamin D is associated with a reduced risk of stroke (15630,16618,93944,97303,106106). However, clinical research shows that vitamin D supplementation does not reduce stroke risk. Several meta-analyses and randomized controlled trials show that taking vitamin D alone or with calcium does not reduce the risk of stroke in patients with or without cardiovascular disease risk factors (16616,91343,97296,97308,106106,112022). It is difficult to draw firm conclusions from these studies, as they did not assess whether patients had adequate vitamin D levels at baseline. It is unclear if vitamin D supplementation might prevent strokes in patients with vitamin D deficiency.
Sunburn. Although there is interest in using oral vitamin D for the treatment of sunburns, there is insufficient reliable information about the clinical effects of vitamin D for this purpose.
Systemic lupus erythematosus (SLE). It is unclear if oral vitamin D is beneficial in patients with SLE. Details: While some observational research has found that adults with SLE are more likely to have vitamin D deficiency than healthy controls (102119), a small cross-sectional study in females has found no association between serum levels of 25-hydroxyvitamin D, SLE disease activity, and the presence or absence of lupus nephritis (107214). A meta-analysis of three small clinical studies shows that taking vitamin D3 (cholecalciferol) 2000 IU daily or 50,000 IU weekly seems to reduce anti-dsDNA positive, a marker of disease activity, when compared with placebo in patients with SLE (98190). However, the clinical significance of this finding is unclear. A small clinical trial in females with SLE shows that taking vitamin D3 5000 IU daily for 12 weeks modestly improves overall disease activity, but not quality of life, when compared with placebo (109735).
Thyroid cancer. It is unclear if oral vitamin D is beneficial in patients with thyroid cancer. Details: Observational research in patients undergoing thyroidectomy for differentiated thyroid cancer suggests that taking vitamin D daily for at least 6 months after surgery is associated with a 38% lower risk of all-cause mortality and a 33% lower risk of total cancer-related mortality when compared with no vitamin D supplementation at around 10 years' follow-up. However, vitamin D does not appear to be linked to a lower risk of thyroid cancer-related mortality in these patients (112018).
Ulcerative colitis. Limited evidence suggests that vitamin D may be beneficial in patients with ulcerative colitis. Details: A meta-analysis of mainly small clinical trials in patients treated with mesalazine shows that taking vitamin D for up to 24 weeks modestly increases clinical efficacy and reduces disease score when compared with mesalazine alone (109044). Also, a meta-analysis of small, low-quality clinical studies in patients with IBD, including Crohn disease and ulcerative colitis, shows that taking high- or low-dose vitamin D for up to 1 year reduces the rate of relapse when compared with control (98915). These findings are limited because of the heterogeneity of the included studies.
Upper respiratory tract infection (URTI). It is unclear if oral vitamin D is beneficial for dementia. Details: A large clinical trial shows that taking vitamin D 2800 IU daily, starting at gestational week 24 and continuing until one week after birth, reduces the risk of the child developing croup by 3 years of age by 40% when compared with olive oil as placebo. This risk reduction did not change after adjusting for the use of omega-3 fatty acids 2.4 grams daily, as well as for concomitant persistent wheeze and/or lower respiratory tract infections (109304).
Urinary incontinence. Limited evidence suggests that vitamin D may be beneficial in middle-aged, but not older, adults with urinary incontinence. Details: Clinical research in middle-aged premenopausal females with stress urinary incontinence and low vitamin D status shows that taking vitamin D 5000 IU once weekly for 12 weeks has a moderate to large beneficial effect on the severity of incontinence and quality of life when compared with placebo. Kegel exercises were performed by all participants (109736). However, vitamin D supplementation does not seem to be beneficial for reducing urinary incontinence in older adults. In older females and males, a large clinical trial shows that vitamin D3 (cholecalciferol) 2000 IU daily for 5 years does not reduce the incidence or progression of urinary incontinence when compared with placebo (109738,109741). In older males with low vitamin D status, vitamin D supplementation may actually increase some types of incontinence (109738).
Urinary tract infections (UTIs). It is unclear if oral vitamin D is beneficial for the prevention of UTIs in children. Details: A meta-analysis of 13 small observational studies in children suggests that lower levels of vitamin D are associated with 2.8-fold greater odds of UTI when compared with higher vitamin D levels. Further, this analysis shows that vitamin D deficiency in children is linked to 5.5-fold greater odds of UTI when compared with normal vitamin D levels (112030).
Urticaria. It is unclear if oral vitamin D is beneficial for the prevention or treatment of urticaria. Details: A meta-analysis of population research has found that having urticaria is associated with a slightly lower vitamin D blood level and a greater likelihood of vitamin D deficiency when compared with individuals without urticaria. In addition, a meta-analysis of 6 clinical trials shows that taking high-dose vitamin D at an average daily dose of at least 4100 IU has a modest effect on the severity of urticaria symptoms (106115).
Uterine fibroids. It is unclear if oral vitamin D is beneficial for preventing the recurrence of uterine fibroids. Details: A clinical study in patients with low vitamin D levels undergoing hysteroscopic myomectomy for uterine fibroids shows that taking vitamin D 1000 IU daily for 12 months has no effect on the rate of uterine fibroid recurrence when compared with placebo (108422).
Vaginal atrophy. It is unclear if oral vitamin D is beneficial for vaginal atrophy. There is limited evidence on the topical use of vitamin D in vaginal atrophy in postmenopausal adults or patients taking tamoxifen. Details: A small cross-sectional study in postmenopausal adults has found that taking a vitamin D supplement for at least one year improves the maturation index of superficial vaginal wall cells when compared with those who do not take vitamin D. However, symptoms of vaginal atrophy were not different between groups (16879). Vitamin D has also been evaluated for vaginal atrophy due to tamoxifen. A small clinical trial in females with breast cancer using tamoxifen shows that receiving vitamin D 1000 IU vaginal suppositories daily for 8 weeks improves maturation index of vaginal walls and self-reported symptoms when compared with placebo (99773).
Vertigo. Vitamin D with calcium might reduce positional vertigo. It is unclear if the benefit is from vitamin D, calcium, or the combination. Details: A large clinical study in adults with recurrent benign paroxysmal positional vertigo shows that taking vitamin D 400 IU and calcium 500 mg twice daily for one year reduces annual recurrence of vertigo by 27% when compared with no treatment. The number needed to treat to prevent vertigo was 3.7 (103681). It is unclear if this benefit is due to vitamin D, calcium, or the combination.
Vitiligo. Although there is interest in using oral vitamin D for vitiligo, there is insufficient reliable information about the clinical effects of vitamin D for this condition.
Warts. Although there is interest in using topical vitamin D derivatives for warts, there is insufficient reliable information about the clinical effects of vitamin D for this condition. More evidence is needed to rate vitamin D for these uses.

VITAMIN E

Ataxia with vitamin E deficiency (AVED). Oral vitamin E is effective for treating vitamin E deficiency due to the genetic disorder AVED. Details: This genetic disorder occurs when the gene that produces alpha-tocopherol transfer protein (alpha-TTP) is defective. This causes severe vitamin E deficiency. Symptoms such as cerebellar ataxia, dysarthria, absence of deep tendon reflexes, and sensory loss usually appear between 4 and 18 years of age. Vitamin E supplements are used in the treatment of AVED (13498,101437,101438).
Vitamin E deficiency. Oral vitamin E is effective for preventing or treating vitamin E deficiency and associated conditions. Details: Taking vitamin E orally is effective for preventing and treating vitamin E deficiency (4844). However, vitamin E deficiency is rare in humans. It most commonly occurs in people with malabsorption disorders such as abetalipoproteinemia; cystic fibrosis; gastrectomy; hepatic-biliary tract disease including chronic cholestasis, hepatic cirrhosis, biliary atresia, and obstructive jaundice; in infants receiving formula with insufficient vitamin E; intestinal diseases including celiac and tropical sprue; and regional enteritis (4844,104411).

Alzheimer disease. Oral vitamin E might slow functional decline in some patients with this condition. However, it does not seem to prevent Alzheimer disease onset. Details: A clinical study in patients with moderate Alzheimer disease shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) 2000 IU daily for 2 years might be similar to selegiline (Eldepryl), and superior to placebo, for slowing cognitive decline. Benefit was only apparent when outcomes were adjusted for baseline Mini-Mental State Examination (MMSE) scores. This study is limited by attrition bias, or incomplete outcome reporting (4635,97070). Another clinical study in patients with mild-to-moderate Alzheimer disease shows that taking all-rac-alpha-tocopherol 2000 IU daily reduces the annual rate of decline in activities of daily living by 19% when compared with placebo. This translates to a delay in disease progression of 6.2 months. This is comparable to the effect of acetylcholinesterase inhibitors (e.g., rivastigmine) in this population. Despite these positive findings, the World Health Organization (WHO) recommends against the use of vitamin E for the management of dementia due to the increased risk for adverse effects with the extended use of high-dose vitamin E (104823). Interestingly, the combination of vitamin E and memantine (Namenda) 20 mg per day is not superior to placebo in this population. Researchers speculate that this lack of effectiveness may be due to an interaction between vitamin E and memantine, but this proposed interaction has not been validated in research (19060,97070). Vitamin E supplementation doesn't seem to prevent Alzheimer disease or slow progression of mild cognitive impairment. Patients with mild cognitive impairment who take vitamin E 2000 IU daily for 3 years progress to Alzheimer disease at the same rate as those who take placebo (13060,97070). Furthermore, although population research has found that greater intake of foods high in vitamin E is associated with a lower risk of developing Alzheimer disease (34597,90082), taking vitamin E supplements does not seem to help. Evidence from a large clinical study that was later converted into an observational study shows that taking vitamin E 400 IU orally daily does not prevent Alzheimer disease when compared with placebo in cognitively intact men (93570). However, this study is limited by the fact that the participants were well-educated and were assessed for dementia in their 60s; the prevalence of dementia is typically low in this age group (93571).
Beta-thalassemia. Oral vitamin E seems to be beneficial for children with this condition. Details: A small clinical study in children with beta-thalassemia and low vitamin E plasma concentrations shows that taking vitamin E orally seems to correct erythrocyte membrane abnormalities when compared with control (4642). Another small clinical trial in children 5-18 years of age with beta-thalassemia shows that taking an age-based dose of vitamin E (alpha-tocopherol) 200-600 mg daily for 4 weeks seems to increase haptoglobin levels, suggesting reduced hemolysis, when compared with placebo (104412).
Dysmenorrhea. Oral vitamin E seems to reduce pain in adults with dysmenorrhea. Details: Small clinical studies in younger adults with primary dysmenorrhea show that taking vitamin E 200-500 IU daily, starting 2 days before menstruation and continuing through the first 3 days of bleeding for 2-4 cycles, decreases the severity and duration of pain and reduces blood loss when compared with placebo (10361,14432,99367). One study also shows that taking vitamin E 200 IU with fish oil provides better pain relief when compared with taking either vitamin E or omega-3 fatty acids alone (99367). A meta-analysis of 8 small clinical studies, including those described above, in individuals with dysmenorrhea shows that taking vitamin E reduces the severity of pain when compared with placebo (112170).
Exercise-induced muscle damage. Oral vitamin E seems to modestly reduce exercise-induced muscle damage. Details: A meta-analysis of 17 very small clinical studies in trained and untrained adults shows that taking vitamin E 300-1200 IU daily for up to 12 weeks reduces markers of exercise-induced muscle damage, including creatine kinase and lactate dehydrogenase, when compared with placebo. Vitamin E appears to be most beneficial in athletes and at doses under 500 IU daily (112160). However, a small clinical study in endurance-trained runners, not included in the analysis above, shows that taking vitamin E (as alpha-tocopherol) 235 mg and vitamin C 1000 mg 2 hours prior to an exercise protocol does not reduce delayed onset muscle soreness or improve markers of exercise-induced muscle damage when compared with placebo (109961).
Glucose-6-phosphate dehydrogenase (G6PD) deficiency. Oral vitamin E seems to be beneficial in patients with G6PD deficiency. Details: Individual clinical studies evaluating the use of vitamin E in patients with G6PD deficiency show mixed results (4682,4683,4684). However, a meta-analysis of 6 small clinical studies in patients with G6PD deficiency shows that taking vitamin E improves hemoglobin levels and reduces reticulocyte levels when compared with placebo in the setting of both acute and chronic hemolysis (112164).
Intracranial hemorrhage. Oral vitamin E might reduce the risk of intracranial hemorrhage in premature infants. Details: Clinical research shows that giving premature neonates vitamin E orally might reduce the risk of intracranial hemorrhage when compared with control (4655,85074).
Intraventricular hemorrhage. Oral vitamin E might reduce the risk of intraventricular hemorrhage in premature infants. Intravenous vitamin E does not provide this benefit. Details: A meta-analysis of the available clinical research shows that oral, but not intravenous, administration of vitamin E can reduce the risk for intraventricular hemorrhage in premature neonates when compared with control. However, it might not reduce the risk for severe (grade III-IV) intraventricular hemorrhage. Additionally, high serum levels of vitamin E have been associated with an increased risk for sepsis in premature infants (85062).
Nitrate tolerance. Oral vitamin E might reduce tolerance to nitrates. Details: Nitrate tolerance might involve increased vascular superoxide anion production, and antioxidants may help prevent this (4705). Clinical research in patients with ischemic heart disease shows that taking vitamin E 447-894 IU daily can help prevent nitrate tolerance when compared with placebo (4705,11543).
Nonalcoholic steatohepatitis (NASH). Oral vitamin E seems to improve outcomes in patients with NASH. Details: Clinical studies and meta-analyses in adults with NASH shows that taking vitamin E 800 IU daily for up to 24 months improves liver enzymes, hepatic fibrosis, steatosis, and lobular inflammation (14005,17517,97077,104413). Taking vitamin E 400-1200 IU in children with NASH also seems to improve liver enzyme levels after 4-10 months of treatment (89). Furthermore, a small study in patients with NASH shows that taking vitamin E 800 IU daily for 1 year seems to improve liver histology to a similar degree as taking telmisartan 40 mg daily (104405). In fact, practice guidelines by the American Association for the Study of Liver Diseases (AASLD) recommend taking vitamin E 800 IU daily as a first-line therapy in non-diabetic adults with biopsy-proven NASH. However, vitamin E isn't recommended in NASH patients with diabetes, cirrhosis, or cryptogenic cirrhosis (98130).
Premenstrual syndrome (PMS). Oral vitamin E seems to improve PMS symptoms. Details: Clinical research in adults with PMS shows that taking vitamin E 400-600 IU daily for 3 cycles reduce subjective reports of symptoms, including anxiety, craving, and depression, when compared with placebo (4719,4720). Another small clinical study in Japanese patients with PMS shows that taking vitamin E, as gamma-tocopherol 180 mg, twice daily for 7 days during the luteal phase of 2 consecutive cycles reduces fatigue, irritability, and leg swelling when compared with placebo (112337).
Tardive dyskinesia. Oral vitamin E might attenuate worsening of tardive dyskinesia in patients taking antipsychotic medications. Details: Small clinical studies suggest that taking vitamin E orally improves Abnormal Involuntary Movement Scale (AIMS) scores in patients with tardive dyskinesia. It seems to be more effective in higher doses and in people who have had tardive dyskinesia for less than 5 years (3942,3943,3944,3945,3946,3948,85323). Both RRR-alpha-tocopherol (natural vitamin E) and unspecified forms were used in clinical trials. However, some conflicting findings have been reported. A meta-analysis suggests that vitamin E does not improve symptoms of tardive dyskinesia when compared with placebo; however, taking vitamin E seems to prevent the deterioration of symptoms when compared with placebo (97079).

Age-related macular degeneration (AMD). Oral vitamin E does not seem to slow AMD progression. Details: Results from clinical trials and meta-analyses of clinical trials show that vitamin E when taken alone or in combination with other antioxidants does not prevent the development (4667,7303,7304,34625) or progression of AMD (34633). In contrast, taking vitamin E 400 IU orally with elemental zinc 80 mg, vitamin C 500 mg, and beta-carotene 15 mg daily does seem to be beneficial. When taken for 5 years, this combination reduces visual acuity loss and reduces the risk of progression of AMD by 25% in patients with advanced AMD (7303,11326). A 10-year follow-up on this study confirmed these findings (90069). It is not known if this combination is beneficial for people with less advanced macular disease or for preventing AMD. Additionally, it is not clear if this benefit is due to vitamin E, the other ingredients, or the combination.
Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). Oral vitamin E does not seem to slow ALS progression. Details: Clinical research in patients with ALS shows that taking alpha-tocopherol 1490 IU daily for up to 12 months in addition to riluzole does not influence survival or motor function when compared with riluzole alone. However, these patients seem to be less likely to progress to a more severe disease state from a milder disease state (83180). Additionally, a large population study has found that dietary intake of vitamin E is not associated with risk of developing ALS (90087).
Angina. Oral vitamin E does not seem to reduce angina symptoms. Details: Clinical research shows that taking vitamin E orally may have some effect on endothelial dysfunction, but does not improve angina in nonsmokers or smokers, when compared with placebo (3896,4634,4649,4650,4651,4652).
Atherosclerosis. Oral vitamin E does not seem to reduce atherosclerosis progression. Details: Taking RRR-alpha-tocopherol (natural vitamin E) orally does not appear to have any effect on atherosclerosis progression or mortality in patients with atherosclerosis when compared with placebo (3899,3936). However, there is preliminary evidence that a combination of vitamin E and vitamin C might help prevent the progression of atherosclerosis in men, particularly smokers and cardiac transplant patients (1918).
Atopic dermatitis (eczema). Oral vitamin E does not seem to reduce eczema symptoms. Details: Clinical research shows that taking vitamin E 600 IU in combination with selenium daily for 12 weeks does not improve symptoms of atopic eczema when compared with placebo or selenium alone (74456). Also, while some clinical research shows that taking 600 IU of all-rac-alpha-tocopherol (synthetic vitamin E) daily for 60 days with vitamin D 1600 IU improves overall atopic dermatitis symptoms, pruritus, and erythema when compared with placebo, taking vitamin E alone does not seem to have this effect. However, vitamin E alone does improve hard, leathery skin symptoms and dryness when compared with placebo (84491).
Breast cancer-related hot flashes. Oral vitamin E does not seem to reduce hot flashes related to breast cancer. Details: Clinical research shows that taking vitamin E 800 IU daily for 4 weeks does not reduce hot flashes in females who have had breast cancer when compared with placebo (454).
Bronchopulmonary dysplasia. Oral vitamin E does not seem to reduce the risk for bronchopulmonary dysplasia in premature infants. Details: Clinical research in premature infants weighing less than 1500 grams at birth shows that taking vitamin E orally does not prevent bronchopulmonary dysplasia when compared with placebo (4657,85062).
Cataracts. Oral vitamin E does not seem to reduce cataract risk. Details: Some population research has found that dietary and supplemental vitamin E intake is associated with a reduced risk of developing age-related cataracts (4208,4663,4665,4759). However, other population research has not found this association (2395,4664,92902). Additionally, higher quality evidence from clinical trials and a meta-analysis consistently shows that vitamin E, taken alone or with other vitamins, does not prevent the progression of age-related cataracts or decrease vision loss when compared with control (4666,7304,34626).
Chemotherapy-induced peripheral neuropathy. Oral vitamin E does not seem to reduce peripheral neuropathy due to chemotherapy. Details: Although some small, low-quality clinical studies and a meta-analysis of these studies suggest that vitamin E 600 mg daily for 3 months might be beneficial for preventing chemotherapy-induced peripheral neuropathy induced by cisplatin, carboplatin, or oxaliplatin when compared with placebo (10366,85117,90072), these studies have found no effect with lower doses of vitamin E or in those receiving paclitaxel chemotherapy (107862). In addition to the low methodological quality of the studies, the validity of these finding is limited by high heterogeneity, as the studies included patients with several different cancer types. Also, a large, high-quality clinical study shows that taking vitamin E 400 mg daily is not beneficial for preventing peripheral neuropathy induced by taxanes or platinum analogues when compared with placebo (101457). The American Society of Clinical Oncology does not recommend the use of vitamin E for the prevention or management of chemotherapy-induced peripheral neuropathy (101434).
Colorectal cancer. Oral vitamin E does not seem to reduce colorectal cancer risk. Details: Some population research has found that intake of vitamin E and multivitamins is associated with a reduced risk of colorectal cancer (1047). Some preliminary clinical research also shows that taking vitamin E orally in combination with other vitamins might have a protective effect in patients with a history of colorectal adenomas (3954,3956,92903). However, higher quality evidence from larger clinical trials and meta-analyses of clinical research consistently show that taking vitamin E supplements alone, or in combination with other vitamins, does not prevent colorectal cancer incidence or recurrence when compared with control (3953,3955,3957,12185,13036,13131,34594,90361). Despite this conflicting research, the US Food and Drug Administration (FDA) approved a qualified health claim in 2009 regarding vitamin E and colorectal cancer risk. However, the FDA has determined that it is highly unlikely that vitamin E supplements reduce the risk of colorectal cancer (102332).
Congestive heart failure (CHF). Oral vitamin E does not seem to reduce CHF symptoms or prevent CHF development. Details: Clinical research in adults with New York Heart Association (NYHA) functional class III or IV heart failure shows that taking vitamin E (RRR- α tocopherol) 500 IU orally daily for 12 weeks does not improve prognostic or functional indices of CHF or quality of life measurements when compared with placebo (3906). Additionally, population research shows that taking vitamin E 600 IU every other day does not affect the risk of developing heart failure in healthy females 45 years or older when compared with placebo (90068).
Head and neck cancer. Oral vitamin E does not seem to reduce the risk of head and neck cancer recurrence. In fact, it might increase recurrence risk. Details: A large clinical trial in patients with stage I or II head and neck cancer shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) 400 IU daily, during radiation therapy and for 3 years after the end of radiation therapy, does not reduce the risk of recurrence of the first tumor or development of a second primary tumor when compared with placebo. In fact, there is some concern that patients taking vitamin E seem to have an increased risk of tumor recurrence or a second primary tumor when compared with patients taking placebo (13055). Advise patients with head and neck cancer to avoid taking vitamin E supplements in doses of 400 IU/day or more.
Hypertension. Oral vitamin E does not seem to reduce blood pressure. Details: A clinical study in patients with hypertension who are receiving conventional treatment shows that taking vitamin E 300 mg daily orally for 3-4 years does not lower blood pressure when compared with control (5210).
Intrauterine growth restriction (IUGR). Oral vitamin E during pregnancy does not seem to reduce IUGR risk. Details: A meta-analysis of clinical research shows that taking vitamin E along with other ingredients throughout pregnancy does not reduce the risk for IUGR when compared with placebo (97075).
Liver disease. Oral vitamin E does not seem to reduce liver disease-associated mortality. Details: A meta-analysis of clinical research shows that taking vitamin E does not reduce all-cause-or liver related-mortality or morbidity in patients with liver diseases, including autoimmune liver diseases, viral hepatitis, alcoholic liver disease, or cirrhosis (34608). Additional clinical research in male smokers over 50 years old shows that taking vitamin E 75 IU orally, alone or with beta-carotene 20 mg orally, daily for 5-8 years does not reduce the risk of mortality due to chronic liver disease when compared with placebo (91383).
Oral leukoplakia. Oral vitamin E does not seem to reduce the risk for oral leukoplakia in male smokers. Details: Although there is some conflicting evidence (3951,4708), the largest randomized controlled trial indicates that supplementation with all-rac-alpha-tocopherol (synthetic vitamin E) 55.6 IU daily for 5-7 years has no effect on the incidence of oral lesions in male cigarette smokers when compared with placebo (3951).
Osteoarthritis. Oral vitamin E does not seem to be beneficial for osteoarthritis treatment or prevention. Details: Taking vitamin E 500 IU daily for 6 months does not seem to decrease symptoms of pain or stiffness in patients with osteoarthritis when compared with placebo (5264). Additional clinical research show that taking vitamin E 500 IU daily for up to 2 years does not slow cartilage loss when compared with placebo (13066). Population research has shown that taking vitamin E supplements does not reduce the risk of developing osteoarthritis or slow the progression of existing osteoarthritis (5881).
Pancreatic cancer. Oral vitamin E does not seem to reduce pancreatic cancer risk. Details: Taking vitamin E supplements alone or in combination with other antioxidants such as beta-carotene and vitamin C does not reduce the risk of developing pancreatic cancer (12185,85147). Taking all-rac-alpha-tocopherol (synthetic vitamin E) 55.6 IU daily for 5 to 8 years also does not seem to reduce the incidence of or mortality from carcinoma of the pancreas in male smokers (3961).
Parkinson disease. Oral vitamin E does not seem to reduce Parkinson disease symptoms or progression, although the risk of developing the disease may decrease with increased dietary vitamin E intake. Details: Observational research has found that dietary vitamin E intake might be associated with a decreased occurrence of Parkinson disease (4712). A meta-analysis of 12 studies evaluating the risk of developing Parkinson disease has found that the highest daily intake of vitamin E is associated with a 20% lower risk than those with the lowest intake (107858). However, clinical research in patients with stage I or II Parkinson disease shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) 2000 IU daily for up to 24 months doesn't seem to have any benefit when compared with baseline or control (4709,4710,4711,85318).
Pharyngeal cancer. It is unclear if oral vitamin E reduces the risk of developing cancer of the pharynx. Details: A sub-group analysis of a large-scale clinical trial (The HOPE Trial) in patients with diabetes or cardiovascular disease suggests that taking RRR-alpha-tocopherol (natural vitamin E) 400 IU daily for about 7 years is not linked with a reduced risk of developing oral or pharyngeal cancer when compared with placebo (13036).
Pre-eclampsia. Oral vitamin E does not seem to reduce pre-eclampsia risk. Details: The majority of clinical research shows that taking a combination of vitamins E and C, at the same doses, does not reduce the risk of pre-eclampsia in low-, moderate-, or high-risk patients, when compared with placebo or no treatment. Also, the risk of gestational hypertension might increase in some cases, although results are inconsistent (83312,83356,83383,83472,83474,97075,97059). Other researchers using vitamin E in combination with vitamin C and allopurinol beginning at 24-32 weeks gestation found the combination similar to placebo (4718). However, some clinical research suggests that taking a combination of vitamin E 400 IU and vitamin C 1000 mg daily reduces the risk of proteinuric hypertension in high-risk patients when started in weeks 16-22 of pregnancy (3236).
Preterm labor. Oral vitamin E does not seem to reduce risk for premature labor. Details: A meta-analysis of clinical research shows that taking vitamin E along with other ingredients throughout pregnancy does not reduce the risk for preterm labor when compared with placebo (97075).
Prostate cancer. Oral vitamin E does not seem to reduce the risk of prostate cancer. Details: A meta-analysis of over 30 large clinical trials and observational studies shows that neither dietary nor supplemental vitamin E reduces the risk of prostate cancer when compared with a control (112159). However, individual study results are mixed. Population research on the use of dietary or supplemental vitamin E intake for prostate cancer risk reduction is conflicting (12872,14124,12873,15607). Although one large-scale study in smokers found that taking 55.6 IU daily of all-rac-alpha-tocopherol (synthetic vitamin E) reduced the risk of prostate cancer and mortality (3959,11303), most large-scale randomized, controlled trials show that vitamin E is not beneficial. A sub-group analysis of a large-scale clinical study (The HOPE trial) in patients with diabetes or cardiovascular disease suggests that taking 400 IU of RRR-alpha-tocopherol (natural vitamin E) daily for about 7 years is not linked with a decreased risk of developing prostate cancer when compared with placebo (13036). Another large scale study (Physician's Health Study II) shows that taking vitamin E 400 IU every other day for an average of 8 years does not reduce the risk of prostate cancer when compared with placebo (16708,90097). Similarly, another large clinical study (The SU.VI.MAX study) shows that a combination of vitamin E (alpha-tocopherol) 44.7 IU, vitamin C 120 mg, beta-carotene 6 mg, selenium 100 mcg, and zinc 20 mg daily for an average of 8 years does not reduce the risk of prostate cancer overall when compared with placebo (14135). A fourth large-scale clinical trial (The SELECT trial) in men over the age of 50 years shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) 400 IU daily, alone or in combination with selenium 200 mcg daily, for an average of about 5.5 years does not reduce prostate cancer risk when compared with placebo (16707). Also, an extension of this initial study found that taking vitamin E alone was associated with a 17% increased of developing prostate cancer (17688).
Respiratory tract infections. Oral vitamin E does not seem to reduce respiratory infections in most patients. However, there's some evidence that it might reduce incidence of the common cold in patients living in long-term care facilities. Details: Taking oral vitamin E 298 IU daily, alone or in supplemental multivitamin form, does not appear to decrease the incidence, duration, or severity of upper or lower respiratory infections in elderly persons when compared with placebo (10788,12094). However, some research shows that taking vitamin E reduces the incidence of the common cold in elderly long-term care patients when compared with placebo (12094). More evidence is needed to determine how effective vitamin E might be for reducing the incidence of the common cold.
Retinitis pigmentosa. Oral vitamin E does not seem to reduce retinitis pigmentosa and related visual decline. Details: Taking all-rac-alpha-tocopherol (synthetic vitamin E) orally does not appear to slow visual decline is people with retinitis pigmentosa and has been associated with more rapid loss of visual acuity, although the validity of the study with these findings has been questioned (83,84,85,86,87,88).
Scarring. Topical vitamin E does not seem to improve scar appearance. Details: Some clinical research shows that applying ointment containing vitamin E topically does not reduce surgical wound scarring when compared with a placebo ointment (4721,4722).
Stillbirth. Oral vitamin E does not seem to reduce risk of a stillborn baby. Details: A meta-analysis of clinical research shows that taking vitamin E along with other ingredients during pregnancy does not reduce the risk for stillbirth when compared with placebo (97075).

Breast cancer. Oral vitamin E does not reduce breast cancer risk. Details: Some evidence suggests that higher serum levels of vitamin E might be associated with a reduced risk of breast cancer (10132). However, increasing vitamin E intake from the diet or supplements does not seem to reduce the risk of developing breast cancer (4658,4659,85147,112334). Also, a large-scale randomized trial in patients with diabetes or cardiovascular disease shows that patients who take 400 IU of RRR-alpha-tocopherol (natural vitamin E) daily do not have a reduced risk of developing breast cancer (13036). In other large-scale studies, females who take RRR-alpha-tocopherol (natural vitamin E) 600 IU every other day for up to 10 years also do not have a lower risk of developing breast cancer (13131,34580).
Cancer. Oral vitamin E does not reduce the risk of cancer in most patients. Details: Some research suggests that a combination of vitamin E 44.7 IU daily with vitamin C, beta-carotene, selenium, and zinc does not lower the overall risk of cancer, although it might reduce the risk of cancer when only males are evaluated (14109). However, clinical research from a large scale study (Physician's Health Study II) shows that taking vitamin E 400 IU every other day for an average of 8 years does not reduce the overall risk of cancer in males when compared with placebo (16708,90097). Also, clinical research published in a meta-analysis shows that taking vitamin E does not reduce the overall risk of cancer (85147). In 2003, the US Food and Drug Administration (FDA) approved a qualified health claim regarding antioxidant vitamins, such as vitamin E and overall cancer risk. However, the FDA has determined that the evidence is limited and inconclusive (102334). The US Preventive Services Task Force (USPSTF) states that there is no net benefit to supplementation with vitamin E for the prevention of cancer in general and therefore recommends against its use (108641,112166).
Cardiovascular disease (CVD). Most evidence shows that oral vitamin E does not reduce the risk for CVD events or complications. Details: Most clinical research in various populations shows that taking vitamin E supplements orally is not effective for preventing heart disease or adverse cardiovascular outcomes such as myocardial infarction (MI), stroke, hospitalizations for unstable angina, morbidity, or cardiovascular death (12492,12493,13036,14108,66140,83050,85084,85224). The US Preventive Services Task Force (USPSTF) states that there is no net benefit to supplementation with vitamin E for the prevention of CVD in general and therefore recommends against its use (108641,112166). With few exceptions (3357,3936), large-scale controlled clinical trials show that vitamin E supplements offer no benefit for primary prevention in healthy or high-risk patients (3907,3935,3937,13036,13131), or for secondary prevention of heart disease and cardiovascular events such as MI, stroke, and death (3896,3899,13036). While one analysis of clinical research found that in mostly healthy patients 70 years or younger without CVD, vitamin E supplementation reduces the risk of cardiovascular mortality, the authors performed more than 20 statistical tests and did not adjust for multiple comparisons. Therefore, it possible that the positive effect was due to chance. This analysis was also limited because it excluded adults older than 70 years of age and adults that are more likely to suffer an exacerbation from a chronic condition. Furthermore, the analysis showed that vitamin E supplementation does not reduce the risk of all-cause mortality or the risk of CVD compared with placebo or no intervention (97078). There's additional conflicting evidence. One large-scale trial shows that healthy females who take RRR-alpha-tocopherol (natural vitamin E) 600 IU every other day for up to 10 years also do not have a lower risk of major cardiovascular events but might have a 24% lower risk of cardiovascular death when compared with placebo (13131). This finding is contradictory to previous findings. One notable limitation of this trial is a lack of systematic assessment of the use of statins or other cardiovascular therapies by the participants throughout the 10-year period. Meta-analyses of clinical trials involving patients with type 2 diabetes and the haptoglobin 2-2 genotype show that taking vitamin E, up to 600 IU daily for up to 8 years, reduces the incidence of non-fatal myocardial infarction and death due to CVD (85179,85221). Because these meta-analyses included only specific patients, the generalizability of the results is questionable. There is debate about whether some forms of vitamin E might work differently than others. Some people suggest that RRR-alpha-tocopherol (natural vitamin E) is more effective than all-rac-alpha-tocopherol (synthetic vitamin E). This has not been verified by studies. A meta-analysis of vitamin E studies indicates that there is no significant difference in cardiovascular outcomes based on the form of vitamin E used (13132). The FDA has refused to allow labeling claims for vitamin E supplements for prevention of CVD (3939). A Science Advisory from the American Heart Association also states that the evidence doesn't justify use of antioxidants such as vitamin E for reducing the risk of CVD (12142). Advise patients not to rely on vitamin E supplements for preventing heart disease.
Fetal and premature infant mortality. Oral vitamin E does not seem to reduce death in preterm infants. Details: Meta-analyses of clinical research show that taking vitamin E throughout pregnancy does not affect morbidity or mortality in preterm infants when compared with placebo (85074,97075).
Fibrocystic breast disease. Oral vitamin E does not improve fibrocystic breast disease in most patients. Details: Clinical research shows that taking alpha-tocopherol 150 IU, 300 IU, or 600 IU daily for 2-3 months does not improve subjective or objective measures of fibrocystic breast disease when compared with placebo (4660,4661,4662).
Lung cancer. Oral vitamin E does not seem to reduce lung cancer risk. Details: Taking all-rac-alpha-tocopherol (synthetic vitamin E) 55.6 IU daily for 5-8 years is not associated with a lower risk of developing lung cancer for male smokers (3949). A sub-group analysis of a large scale clinical trial in patients with diabetes or cardiovascular disease who take RRR-alpha-tocopherol (natural vitamin E) 400 IU daily for about 7 years do not have a lower risk of developing lung cancer when compared with placebo (13036). In another large-scale study, females who take RRR-alpha-tocopherol (natural vitamin E) 600 IU every other day for up to 10 years also do not have a lower risk of developing lung cancer (13131). Meta-analyses of clinical research suggest taking vitamin E as alpha-tocopherol for up to approximately 10 years does not prevent lung cancer or reduce the incidence of lung cancer mortality when compared with placebo (34632,85147).
Overall mortality. Oral vitamin E does not seem to reduce the risk of mortality from all causes. Details: Although some population research suggests that increased dietary vitamin E intake is associated with reduced overall mortality (98260), most meta-analyses of clinical research in adults show that taking vitamin E supplements for at least 1 year does not affect all-cause mortality (34622,85164,85200). Furthermore, when only high quality clinical trials were analyzed, mortality was increased by 3% in adults taking vitamin E when compared with control (34622).
Prematurity. Oral vitamin E does not seem to reduce the risk of premature birth and complications. Details: Clinical research shows that vitamin E does not improve blood parameters or prevent the development of anemia in premature infants (4648,10362). One clinical study in premature infants weighing less than 1500 grams at birth shows that giving vitamin E 25 IU daily for six weeks does not improve hemoglobin concentration, reticulocyte counts, or platelet counts when compared with placebo (4648). Another clinical study in premature infants weighing less than 1250 grams at birth shows that giving vitamin E 50 IU daily for eight weeks does not increase the response to erythropoietin and iron when compared with placebo (10362).

Aging skin. Topical vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in Asian females aged 30-65 years shows that applying a specific liquid product, (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) containing vitamin E 1%, vitamin C 20%, and red raspberry leaf cell culture extract 0.0005%, to the face nightly for 8 weeks, in addition to regular facial skin products, improves skin color, elasticity, radiance, smoothness, and appearance of wrinkles when compared with regular facial skin products alone (102355).
Anemia of chronic disease. Small clinical studies suggest that oral vitamin E might improve response to anemia treatment in patients on chronic hemodialysis. Details: Two small studies in adults and children on chronic hemodialysis have shown improved response to erythropoietin with vitamin E supplementation (4640,4647). In one study, children given vitamin E 22.4 IU/kg in combination with erythropoietin had significantly increased hemoglobin and hematocrit levels after 2 weeks of combination treatment, compared with eight and five weeks in patients receiving erythropoietin alone (4640). In a study of adults, concurrent supplementation with vitamin E 745 IU daily allowed dose reductions of erythropoietin from an average of 93 U/kg/week to 74 U/kg/week with the same resultant hemoglobin levels (4647).
Anthracycline cardiotoxicity. Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with breast cancer receiving doxorubicin and cyclophosphamide chemotherapy shows that taking vitamin E 600 mg three times daily and L-carnitine 3000 mg by intravenous infusion on day 1 followed by 300 mg by mouth four times daily thereafter for 3 weeks reduced the risk of cardiovascular events by 63% and improved laboratory markers of cardiotoxicity when compared with chemotherapy alone (112338). It is unclear if these findings are due to vitamin E, L-carnitine, or the combination.
Anxiety. It is unclear if oral vitamin E is beneficial in patients with anxiety. Details: A meta-analysis of 5 mostly small clinical studies in patients without anxiety shows that taking vitamin E 200-400 IU daily for up to 10 weeks does not improve anxiety symptom scores when compared with placebo (112158). It is unclear if these findings can be generalized to patients with anxiety disorders.
Asthma. It is unclear if oral vitamin E is beneficial for asthma treatment or prevention. Details: There is inconsistent evidence about the role of vitamin E in asthma. Some population research has found that increased dietary intake of vitamin E is associated with a lower risk of asthma; however taking vitamin E supplements are not associated with decreased risk (6058,15006). Low vitamin E intake also appears to be associated with an increased risk of asthma (315,401,422). A small clinical study in children with asthma suggests that adding vitamin E 74.5 IU by mouth daily to fluticasone treatment for 8 weeks may decrease cough, wheezing, and dyspnea when compared with baseline (90077). This study was limited because it did not compare the vitamin E intervention to the control group.
Atopic disease. It is unclear if oral vitamin E reduces the risk of atopic disease in infants. Details: Population research has found that increased maternal vitamin E intake isn't associated with decreased odds of developing eczema, food allergy, wheeze, allergic sensitization, or any allergic disease in infants (90098).
Bladder cancer. It is unclear if oral vitamin E reduces bladder cancer risk. Details: A meta-analysis of clinical research shows that the highest intake of vitamin E is associated with a reduced risk for bladder cancer when compared to the lowest intake in patients followed for more than 10 years. This benefit was not seen in those followed for less than 10 years. This effect appears to be dose-dependent, although it is not clear how much vitamin E intake is required to reduce bladder cancer risk. Additionally, it is not clear whether this benefit differs for dietary or supplemental intake of vitamin E (101435). In 2009, the US Food and Drug Administration (FDA) approved a qualified health claim regarding vitamin E and bladder cancer risk. However, the FDA has determined that it is highly unlikely that vitamin E supplements reduce the risk of bladder cancer (102332). Some population research also shows that regular use of vitamin E supplements for more than 10 years is associated with a reduced risk of bladder cancer mortality; however, use for less than 10 years is not associated with reduced mortality (9839).
Burns. It is unclear if topical vitamin E is beneficial for healing of burn wounds. Details: A small clinical study in patients with moderate and deep burn wounds (25% to 67%) shows that applying a specific alpha-tocopherol product (Filme Olio) daily seems to reduce infection and improve healing when compared with usual treatment (104407).
Chemotherapy-related infection. It is unclear if oral vitamin E is beneficial in patients with infection due to chemotherapy. Details: Observational research suggests that greater dietary intake of vitamin E may lower the incidence of infection in children undergoing chemotherapy for lymphoblastic leukemia (11997).
Chronic fatigue syndrome (CFS). Although there is interest in using oral vitamin E for CFS, there is insufficient reliable information about the clinical effects of vitamin E for this condition.
Cisplatin-associated ototoxicity. It is unclear if oral vitamin E is beneficial for preventing ototoxicity due to cisplatin. Details: A small clinical study in patients receiving cisplatin for solid tumors shows that taking a specific vitamin E supplement (Rigentex, Bracco) as alpha-tocopherol 400 IU daily for 3 months attenuates hearing loss when compared with placebo (97082).
Colistin-induced nephrotoxicity. It is unclear if oral vitamin E is beneficial for preventing nephrotoxicity due to colistin. Details: A small clinical study in patients receiving colistin therapy shows that taking vitamin E (alpha-tocopherol) 400 IU orally daily for the duration of colistin therapy does not reduce the incidence or duration of acute kidney injury when compared with colistin alone (107867).
Contrast induced nephropathy. It is unclear if oral or intravenous vitamin E is beneficial in patients with nephropathy due to contrast dye. Details: A small clinical study in patients receiving elective computer-assisted tomography with nonionic radiocontrast agents shows that receiving vitamin E 3218 IU emulsion in 0.45% saline intravenously infused at the rate of 1 mL/kg/hr over 24 hours does not decrease the risk of contrast agent-induced nephropathy when compared with normal saline alone (90081). However, oral vitamin E may modestly reduce the risk of contrast induced nephropathy. A clinical trial shows that taking vitamin E as alpha-tocopherol 522 IU or gamma-tocopherol 447 IU orally daily, starting 5 days prior to the procedure and continuing 2 days post-procedure, results in a 9% to 10% lower incidence of contrast induced acute kidney injury when compared with standard treatment with normal saline (90096). Another clinical study shows that taking a single dose of vitamin E 1490 IU orally before elective coronary angiography reduces the risk of contrast induced kidney injury by 7% when compared with placebo (97074).
Coronary artery bypass graft (CABG) surgery. It is unclear if oral vitamin E is beneficial for recovery after CABG. Details: When taking vitamin E orally with vitamin C and allopurinol two days prior to CABG and one day postoperatively, patients had fewer perioperative infarctions and lower creatine kinase-MB release (4699); however, this benefit was not found when using vitamin E alone or in combination with vitamin C without allopurinol (4697,4698).
Critical illness (trauma). An analysis of several small clinical studies suggests that oral or intravenous vitamin E is not beneficial in patients admitted to the intensive care unit (ICU). Details: A meta-analysis of 5 small clinical studies in patients admitted to the ICU shows that administration of oral or intravenous vitamin E 400-3000 IU daily for up to 4 weeks does not decrease the length of hospital or ICU stay or reduce the risk of mortality when compared with control (112335). The validity of these findings is limited by a high degree of heterogeneity among the studies, which included differences in vitamin E dosing, duration of therapy, and reasons for ICU admission.
Dementia. It is unclear if oral vitamin E is beneficial for dementia prevention; the available research is conflicting. Details: A longitudinal cohort study in Japanese adults aged 40 years or older at baseline who were followed for a median of about 20 years, shows that total daily dietary intake of vitamin E is inversely associated with the risk of developing dementia, with a hazard ratio of about 0.8 for the highest compared with lowest quartiles of intake (107857). In a longitudinal cohort study of males aged 71-93 years, consuming supplemental vitamin E and vitamin C decreased the risk of developing vascular and mixed or other dementias; however, there was no protective effect for Alzheimer dementia (4636). Evidence from clinical research that evolved into an observational study shows that taking vitamin E 400 IU daily does not decrease the incidence of dementia in males 60 years or older (93570). However, the results from this study are limited by selection bias due to the high education levels and relatively young age of the participants, limitations with case ascertainment, and problems with follow-up (93570,93571). Also, these studies did not distinguish between different forms of vitamin E (4636,93570).
Depression. It is unclear if oral vitamin E is beneficial in patients with depression. Details: A meta-analysis of 7 mostly small clinical studies in patients without major depressive disorder shows that taking vitamin E 400-2000 IU daily for up to 6 months modestly improves depression symptom scores when compared with placebo (112158). It is unclear if these findings can be generalized to patients with depression.
Developmental coordination disorder (DCD). Oral vitamin E has only been evaluated in combination with other ingredients for DCD; its effect when used alone is unclear. Details: A small clinical study in children with developmental coordination disorder (DCD), also known as dyspraxia, shows that taking vitamin E orally, in combination with evening primrose oil, thyme oil, and fish oils, for 4 months seems to improve movement when compared with control (5708). The effects of vitamin E alone on DCD are unclear.
Diabetes. It is unclear if oral vitamin E is beneficial for the treatment or prevention of diabetes. Details: Population research has found that higher vitamin E dietary intake is associated with a lower risk of developing type 2 diabetes (14004). However, individual clinical studies in patients with existing diabetes show mixed results (13496,13497,90095,90099,98259). A meta-analysis of 36 small clinical studies in patients with diabetes suggests that vitamin E may slightly improve some measures of glycemic control. In patients with type 2 diabetes, vitamin E seems to reduce glycated hemoglobin (HbA1c) by around 0.2% and improve insulin resistance, but not fasting blood glucose, when compared with placebo. In patients with type 1 diabetes, vitamin E seems to reduce HbA1c by around 0.8%, but does not improve fasting blood glucose, when compared with placebo (112161). The validity of this analysis is limited by a high degree of heterogeneity across the studies, including differences in vitamin E dose, treatment duration, concomitant medications, patient populations, and study designs.
Diabetic foot ulcers. Oral vitamin E has only been evaluated in combination with other ingredients for diabetic foot ulcers; its effect when used alone is unclear. Details: A small clinical study in adults with a grade 3 diabetic foot ulcer shows that taking vitamin E 400 IU and magnesium oxide 250 mg daily for 12 weeks reduces ulcer length, width, and depth when compared with placebo (101436). A small clinical study in adults with non-healing diabetic foot ulcers being treated with a platelet-rich plasma fibrin glue dressing shows that taking vitamin E 200 IU and vitamin C 12.5 mg orally twice daily for 8 weeks increases the rate of ulcer healing when compared with placebo. In those receiving vitamins, 46% of wounds closed completely, compared with 17% of those receiving placebo (107870). It is not clear if the effects seen in these studies are due to vitamin E, the other nutrients, or the combinations.
Diabetic nephropathy. It is unclear if oral vitamin E is beneficial in patients with diabetes and impaired kidney function. Details: A meta-analysis of clinical research in adults with diabetic nephropathy shows that taking vitamin E 600-1200 mg daily, alone or with other antioxidants, modestly reduces urinary albumin excretion when compared with placebo or no treatment, but seems to have no effect on glomerular filtration rate (GFR) (97069). A small clinical study in patients with diabetic nephropathy shows that taking a specific tocotrienol-rich vitamin E supplement (Tocovid SupraBio, Hovid Nutriworld) 200 mg twice daily for 12 weeks seems to modestly reduce serum creatinine, with a corresponding increase in GFR, when compared with placebo. According to a sub-group analysis, these improvements remain statistically significant in patients with low tocopherol levels (less than 42 mcmol/L) at baseline, but not in those with higher levels at baseline (103010). Another small clinical study shows that taking this same supplement regimen for 12 months reduces serum creatinine levels and improves GFR at 8 months, but not 12 months, when compared with placebo. In a subgroup analysis of patients with stage 3 chronic kidney disease, these benefits persisted at 12 months when compared with placebo (107390).
Diabetic neuropathy. It is unclear if oral vitamin E is beneficial for improving diabetic neuropathy symptoms. Details: A small clinical trial in patients with uncontrolled type 2 diabetes and neuropathy shows that taking a specific vitamin E supplement (Evion) 400 IU daily for 12 weeks modestly decreases neuropathic pain scores when compared to baseline (90091). Another very small clinical trial shows that taking vitamin E 1341 IU daily for 6 months improves nerve conduction in diabetic neuropathy when compared with placebo (4724).
Down syndrome. Oral vitamin E does not seem to slow cognitive decline in patients with this condition. Details: A clinical study in patients over 50 years old with Down syndrome shows that taking vitamin E 1000 IU twice daily for 3 years does not slow cognitive decline when compared with placebo (97076).
Endometriosis. Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with endometriosis and pelvic pain shows that taking vitamin E 800 IU and vitamin C 1000 mg daily for 8 weeks improves dysmenorrhea, dyspareunia, and chronic pelvic pain scores when compared with placebo (106622).
Extravasation. Topical vitamin E has only been evaluated in combination with dimethylsulfoxide (DMSO); its effect when used alone is unclear. Details: A very small clinical study in patients receiving chemotherapy shows that applying vitamin E topically, in combination with DMSO, seems to prevent skin ulceration after chemotherapy extravasation (4668).
Gastric cancer. It is unclear if oral vitamin E is beneficial for preventing gastric cancer or reducing associated mortality. Details: Population studies have found that increasing dietary vitamin E intake by 22.4 IU daily is associated with a 21% decreased risk of gastric cancer (3360,90083). However, clinical trials have not found that vitamin E supplements reduce gastric cancer risk (3960,4676,4677,12185). Studies evaluating vitamin E in combination with other supplements have been inconsistent. In one large-scale clinical trial a specific combination of vitamin E 100 IU with selenium 37.5 mcg and vitamin C 250 mg twice daily for about 7 years did not reduce risk of gastric cancer in patients from Shandong Province in China where there is a very high prevalence of gastric cancer (14447,90085). In another large-scale clinical study of 29,584 people in China, the combination of oral vitamin E, beta-carotene, and selenium over 5 years did reduce total mortality, total cancer mortality, and stomach cancer mortality (4679). A meta-analysis of clinical research shows that taking vitamin E plus beta-carotene with or without vitamin C does not reduce gastric cancer incidence (12185).
Glomerulosclerosis. It is unclear if oral vitamin E reduces proteinuria due to glomerulosclerosis in children. Details: A very small clinical study in children with focal segmental glomerulosclerosis who are refractory to standard medical management shows that taking vitamin E 200 IU daily orally might reduce proteinuria when compared with baseline (4675). The validity of this finding is limited by a lack of control group.
Granuloma annulare. Although there is interest in using topical vitamin E for granuloma annulare, there is insufficient reliable information about the clinical effects of vitamin E for this condition.
Helicobacter pylori. Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in patients with Helicobacter pylori dyspepsia without ulcers shows that taking vitamin E 200 IU and vitamin C 500 mg by mouth twice daily for 30 days in addition to standard triple therapy increases eradication rates by 37% when compared with triple therapy alone (90094). It is not clear if this benefit is due to vitamin E, vitamin C, or the combination.
Huntington disease. It is unclear if oral vitamin E improves Huntington disease symptoms. Details: A small clinical study shows that taking RRR-alpha-tocopherol (natural vitamin E) might improve symptoms in patients with early Huntington disease, but this benefit is not seen in patients with more advanced disease when compared with placebo (4686).
IgA nephropathy. It is unclear if oral vitamin E is beneficial for IgA nephropathy in children. Details: A small clinical study in children with IgA nephropathy shows that taking vitamin E (400 IU for those weighing less than 30 kg; 800 IU for those weighing more than 30 kg) improves urinary protein to creatinine ratio, but not glomerular filtration rate, creatinine clearance, or hematuria, when compared with placebo (85063).
Infertility. It is unclear if oral vitamin E improves pregnancy rates in females with infertility of unknown cause. Details: A small clinical study in females experiencing implantation failure shows that taking vitamin E 400 IU daily for 12 weeks improves endometrial thickness when compared with placebo (99852). Vitamin E has also been studied in combination with selenium. In a small clinical study in patients with premature ovarian insufficiency (POI), taking vitamin E 400 IU with selenium 200 mcg orally daily for 90 days increases anti-Mullerian hormone index, antral follicle count, and mean ovarian volume after 12 months of follow-up when compared with placebo (107866). It is unclear if these improvements correlate to higher pregnancy or live birth rates.
Inflammatory bowel disease (IBD). Although there is interest in using oral vitamin E for IBD, there is insufficient reliable information about the clinical effects of vitamin E for this condition.
Insomnia. It is unclear if oral vitamin E is beneficial in patients with insomnia. Details: A moderate-sized clinical study in postmenopausal patients with chronic insomnia shows that taking vitamin E 400 IU daily for 1 month improves sleep quality ratings and reduces the need for sedative medications when compared with placebo (112163).
Intermittent claudication. It is unclear if oral vitamin E improves intermittent claudication symptoms. Details: A large clinical study in male smokers with intermittent claudication shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) 50 mg orally daily for about 3.7 years does not appear to have any effect when used alone or in combination with beta-carotene for treating symptoms or disease progression when compared with placebo (4732). However, according to poor-quality clinical research included in a meta-analysis, taking vitamin E 447-2384 IU daily for up to 18 months appears to reduce symptoms of intermittent claudication (85023).
Lice. Topical synthetic vitamin E might be beneficial for head lice eradication. Details: A small clinical study in children and adults with head lice shows that topical application of a specific tocopheryl acetate 20% spray (LiceKO, Panin SRL) once, and then again 7 days later, is more effective for eliminating lice when compared with permethrin 1% cream rinse (90067).
Male infertility. An analysis of several small, low-quality clinical studies suggests that oral vitamin E might improve pregnancy rates and measures of sperm health in males with infertility. Details: Several small clinical studies in males with infertility show conflicting results (3583,4695,107865). However, a meta-analysis of 7 small, low-quality clinical trials shows that taking vitamin E 300-600 IU for 12-48 weeks increases pregnancy rates by 86% and modestly improves sperm count, concentration, motility, and vitality, but does not seem to increase semen volume, when compared with a control (109461). Vitamin E has also been used in combination with other nutrients with unclear results. Small studies show that taking vitamin E 800 mg daily with vitamin C 1000 mg daily for 8 weeks doesn't seem to improve sperm functionality (4696), while vitamin E 400 IU plus selenium 200 mcg daily for at least 100 days improves sperm functionality, but not fertilization rates, when compared with baseline (3585). In another small clinical study in infertile males undergoing varicocelectomy, taking vitamin E 400 IU, selenium 200 mcg, and folic acid 5 mg daily for 6 months improved sperm count and motility when compared with control (102968). Another small clinical study shows that taking vitamin E 100 mg and coenzyme Q10 10 mg three times daily for 3 months modestly increases levels of testosterone and improves progressive sperm motility and morphology when compared to baseline. However, taking an L-carnitine nutrient complex 15 grams twice daily was more effective for increasing testosterone and improving sperm parameters (109390). However, it is unclear if any of these combination therapies increases live birth rates.
Melanoma. It is unclear if oral vitamin E is beneficial for reducing melanoma risk. Details: A sub-group analysis of a large-scale clinical trial in patients with diabetes or cardiovascular disease suggests that taking RRR-alpha-tocopherol (natural vitamin E) 400 IU daily for about 7 years is not linked with a reduced risk of developing melanoma when compared with placebo (13036).
Menopausal symptoms. It is unclear if oral vitamin E is beneficial for reducing menopausal symptoms such as hot flashes. Details: A small clinical study in postmenopausal patients shows that taking vitamin E 200 IU twice daily for 8 weeks reduces hot flashes, but does not affect other menopausal symptoms or anxiety, when compared with placebo. The improvement in hot flashes was no longer present 4 weeks after the intervention (102969). However, a meta-analysis of 3 small clinical studies in postmenopausal patients, including the study above, shows that taking vitamin E 400 IU daily for 8 weeks does not reduce hot flash frequency when compared with placebo (111460).
Methotrexate toxicity. It is unclear if oral vitamin E reduces the risk of liver toxicity due to methotrexate. Details: An observational study in patients taking methotrexate for rheumatoid arthritis has found that taking vitamin E 400 mg twice daily for 3 months is associated with reductions in serum glutamic pyruvic transaminase (SGPT) and serum glutamic-oxaloacetic transaminase (SGOT) levels when compared with no supplementation. This suggests a reduction in liver injury in the treatment group (104414).
Muscular dystrophy. Small clinical studies suggest that oral vitamin E may not improve muscular dystrophy symptoms or progression. Details: Small clinical studies in patients with myotonic or Duchenne muscular dystrophy show that taking vitamin E along with penicillamine or selenium doesn't appear to slow disease progression or improve symptoms when compared with placebo (4703,4704).
Nocturnal leg cramps. It is unclear if oral vitamin E reduces leg cramps in veterans or in patients on hemodialysis. Details: A small clinical study in adults undergoing hemodialysis shows that taking vitamin E 400 IU at bedtime for 2 months seems to reduce the frequency of nocturnal leg cramps when compared with placebo (4701). However, another small clinical study in male veterans shows that taking vitamin E 800 IU at bedtime for 4 weeks does not reduce cramp frequency or severity or reduce sleep disturbances when compared with placebo (4702).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin E is beneficial in adults or children with NAFLD. Details: One meta-analysis of studies assessing both NAFLD patients and patients in whom NAFLD progressed to nonalcoholic steatohepatitis (NASH) shows that taking vitamin E 100-800 IU daily for 1-24 months improves liver enzyme levels, hepatic steatosis, and lobular inflammation when compared with control. However, taking vitamin E does not appear to improve hepatic fibrosis in these patients (97077). Methodological limitations such as publication bias and unclear calculations limit the reliability of these results. Another meta-analysis of 8 small clinical trials in adults with NAFLD shows that taking vitamin E 400-800 IU daily for up to 24 weeks improves liver enzyme levels when compared with placebo (112336). Vitamin E has also been evaluated in children with NAFLD. A meta-analysis of studies in this population shows that taking vitamin E 15-900 IU daily for up to 24 months reduces total and low-density lipoprotein (LDL) cholesterol levels, but does not affect liver enzyme levels, measures of insulin resistance, body mass index (BMI), ballooning degeneration of the liver, or liver fibrosis when compared with placebo (107861). Until additional data showing its benefit becomes available, practice guidelines by the American Association for the Study of Liver Diseases (AASLD) state that vitamin E is not recommended in patients with NAFLD without liver biopsy (98130).
Obesity. It is unclear if oral vitamin E is beneficial for improving weight loss. Details: A meta-analysis of 24 small clinical studies shows that taking oral vitamin E, 67-900 mg daily does not affect weight, body mass index (BMI), or waist circumference in adults with obesity. In fact, in people with a normal BMI, vitamin E seems to increase body weight (107859).
Oral mucositis. It is unclear if oral or topical vitamin E is beneficial in patients with oral mucositis from chemotherapy or radiotherapy. Details: Vitamin E has been evaluated in both chemotherapy- and radiation-induced mucositis. A small clinical study in children with chemotherapy-induced oral mucositis shows that a specific vitamin E product (Evion Paediatric Drops, Merck Limited) 200 IU applied topically in three divided doses daily for 1 week improves healing, pain, and the ability to eat when compared with placebo (94585). However, another small clinical study in patients receiving radiotherapy for head and neck cancer shows that taking vitamin E 1000 mg once daily with pentoxifylline 400 mg twice daily does not reduce the incidence or severity of oral mucositis and dysphagia when compared with control (102972).
Osteopenia. It is unclear if oral vitamin E helps slow the progression of osteopenia. Details: A small clinical study in postmenopausal adults with osteopenia who are taking calcium and vitamin D supplements shows that taking vitamin E (mixed tocopherols) 400 IU daily for 12 weeks prevents the increase in serum C-terminal telopeptide, a marker of bone resorption, seen with placebo over that same time period (107868).
Osteoporosis. It is unclear if oral vitamin E helps to reduce complications of osteoporosis such as fractures. Details: Observational research has found that vitamin E supplementation is associated with a 22% lower risk of hip fracture and a 14% lower risk of all fractures in elderly females with osteoporosis (90086). Additional observational research has found that higher dietary vitamin E intake is also associated with a 34% reduced risk of fractures in adults at risk for osteoporosis (104415).
Peyronie disease. It is unclear if oral vitamin E reduces Peyronie disease symptoms. Details: A small clinical study in patients with Peyronie disease shows that taking vitamin E 894 IU daily in addition to conservative treatment for 6 months does not improve pain, but may reduce plaque, when compared with using conservative treatment alone. Conservative treatment included verapamil 10 mg biweekly injection and iontophoresis, blueberries 160 mg orally daily, propolis 600 mg orally daily, and topical diclofenac 4% twice daily (90090). It is not clear if this effect is due to vitamin E, the other interventions, or the combination.
Photoreactive keratectomy. Oral vitamin E has only been evaluated for recovery after photoreactive keratectomy in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients undergoing laser surgery for myopia shows that taking vitamin A (retinol palmitate) 50,000-75,000 units with vitamin E (alpha-tocopheryl nicotinate) 343 IU daily seems to accelerate re-epithelialization, reduce haze formation, and improve visual acuity when compared with placebo (348).
Physical performance. It is unclear if oral vitamin E improves physical performance in the elderly. Details: Population research has found that increasing intake of dietary vitamin E is associated with increased physical performance and muscle strength in elderly people (14006).
Polycystic ovary syndrome (PCOS). Analyses of small clinical studies suggest that oral vitamin E may modestly reduce lipid levels in patients with PCOS. It is unclear if vitamin E can improve glycemic control, body weight, hormone levels, or symptoms of PCOS. Details: Meta-analyses of several small clinical studies in patients with PCOS show that taking vitamin E, alone or in combination with coenzyme Q10, fish oil, magnesium, or vitamin D, reduces total cholesterol by 9-18 mg/dL, low-density lipoprotein (LDL) cholesterol by 7-16 mg/dL, and triglycerides by 13-21 mg/dL when compared with placebo. However, vitamin E does not appear to increase high-density lipoprotein (HDL) cholesterol, reduce body weight, or improve hirsutism. The effects of vitamin E on glycemic indices and levels of testosterone, estradiol, and sex hormone binding globulin are unclear; individual meta-analyses show mixed results (112167,112168,112169). The validity of these findings is limited by a high degree of heterogeneity across the included studies, which varied in vitamin E dosing, treatment duration, and concomitant supplements used.
Premature rupture of membranes (PROM). Oral vitamin E does not seem to prevent PROM, although it's unclear if it might prevent premature delivery due to PROM. Details: Vitamin E has been evaluated for the prevention and management of PROM. A meta-analysis of clinical research shows that taking vitamin E with other ingredients throughout pregnancy does not affect the risk of developing PROM when compared with placebo (97075). However, a clinical study in patients with PROM shows that taking vitamin E (RRR-alpha-tocopherol acetate) 400 IU and vitamin C 1000 mg daily, starting within 1 hour of membrane rupture and continuing for an unspecified amount of time, seems to hold back premature delivery by about 5 days when compared with placebo. However, maternal or neonatal outcomes did not seem to be affected (90078). It is not clear if this effect is due to vitamin E, vitamin C, or the combination.
Radiation-induced sialadenitis. It is unclear if oral vitamin E is effective for the prevention or treatment of radiation-induced sialadenitis. Details: A small clinical study in patients undergoing radiation therapy for thyroid cancer shows that taking vitamin E 200 mg daily for 5 weeks, starting 1 week before radiotherapy, improves several measures of parotid and submandibular salivary gland function when compared to baseline, suggesting that vitamin E might prevent radiation-induced sialadenitis and its associated complications (112332). The validity of these findings is limited by a lack of control group.
Radiation dermatitis. It is unclear if topical vitamin E is effective for the prevention or treatment of radiation dermatitis. Details: A small clinical study in patients undergoing radiation therapy for breast cancer shows that applying a cream containing nanoparticles of vitamin E 2%, three times daily and after each radiation session until 2 weeks after radiation therapy is complete, does not reduce the severity of radiation dermatitis or improve quality of life when compared with a placebo cream. However, in patients that did not receive a boosted radiation dose, this vitamin E cream seems to slightly delay the onset of dermatitis when compared with placebo (112333).
Radiation fibrosis. It is unclear if topical vitamin E reduces radiation fibrosis symptoms. Details: Clinical research shows that taking vitamin E 1000 IU orally with pentoxifylline 800 mg daily seems to reverse radiation fibrosis (4672,4673). Regression of radiation fibrosis becomes significant after three months of treatment and continues to improve thereafter. After 12 months of treatment, mean surface area of fibrosis can decrease by 66% (4672). It is unclear if the benefit is due to vitamin E, pentoxifylline, or the combination. One very small study suggests that vitamin E alone does not seem to be effective when compared with placebo (10363).
Renal cell carcinoma. It is unclear if oral vitamin E reduces renal cell carcinoma risk. Details: In 2009, the US Food and Drug Administration (FDA) approved a qualified health claim regarding vitamin E and renal cell carcinoma risk. This qualified health claim was based on one weak and limited study. The FDA has determined that it is highly uncertain that vitamin E supplements reduce the risk of renal cell carcinoma (102332).
Restless legs syndrome (RLS). Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in hemodialysis patients shows that taking vitamin E 596 IU, vitamin C 200 mg, or a combination of both daily for 8 weeks modestly reduces severity of restless legs syndrome when compared with placebo (90093).
Retinopathy of prematurity. It is unclear whether oral or parenteral vitamin E reduces the risk for retinopathy in prematurity (ROP). Details: A clinical study in very low birth weight infants with respiratory distress syndrome suggests that giving vitamin E 12.5 IU twice daily from 72 hours after birth through 28 days of age might reduce the incidence of stage 1 ROP when compared with placebo. However, the difference reached significance in the per-protocol analysis, but not in the intention-to-treat analysis (107864). Also, a meta-analysis that did not include this more recent study shows that administering oral, intravenous, or intramuscular vitamin E daily does not reduce the risk for ROP. Additionally, high levels of vitamin E and large intravenous doses of vitamin E have been associated with an increased risk for sepsis in premature infants (85062).
Rheumatoid arthritis (RA). It is unclear if oral vitamin E is beneficial in patients with RA. Details: A small clinical study in adults with RA shows that taking vitamin E 600 mg twice daily in conjunction with standard therapy for 12 weeks is superior to standard therapy alone for reducing pain, but not inflammation (4723). However, other studies show mixed results. A meta-analysis of 7 small clinical studies in patients with RA shows that taking vitamin E up to 1200 IU daily for up to 12 weeks does not reduce pain, tenderness, swelling, or morning stiffness when compared with control (112330).
Schizophrenia. Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking vitamin E (RRR-alpha-tocopherol) 135.8 IU and a specific ascorbic acid supplement (CellaVie) 250 mg with or without ethyl eicosapentaenoate 500 mg daily for 16 weeks does not improve negative or positive symptoms of schizophrenia when compared with placebo (89234).
Sickle cell disease. Although there is interest in using oral vitamin E for sickle cell disease, there is insufficient reliable information about the clinical effects of vitamin E for this condition.
Stretch marks (striae gravidarum). Topical vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that using a moisturizer containing vitamin E, rosehip oil, hydroxyprolisilane C, and gotu kola triterpenes at least twice daily on affected areas does not decrease incidence of new stretch marks, but does decrease the severity of new stretch marks by about 30%, when compared with control cream in pregnant patients (90076). It is not clear if this effect is due to vitamin E, other ingredients, or the combination.
Stroke. It is unclear if oral vitamin E is beneficial for reducing stroke risk. Details: A trial-sequential meta-analysis of 12 clinical trials with 148,000 patients shows that vitamin E does not seem to reduce the risk of total stroke when compared with placebo. However, in a subgroup analysis, vitamin E was associated with an 8% lower risk of ischemic stroke and a trend to an increased risk of hemorrhagic stroke when compared with placebo. Based on subgroup analyses, there was no difference on risk based on vitamin E dosage, use of synthetic versus natural vitamin E, and whether prevention was primary or secondary (104408). This analysis was limited due to high heterogeneity, small study size, and insufficient power to detect differences between treatments. Older meta-analyses also found mixed results of using vitamin E 74.5-1192 IU daily alone or in combination for up to 10 years. However, there was a similar sub-group analysis finding that vitamin E might reduce the risk of ischemic stroke, but it might also increase the risk of hemorrhagic stroke (14621,85201). Some clinical research shows that taking all-rac-alpha-tocopherol (synthetic vitamin E) might reduce the risk of ischemic stroke in male smokers with hypertension and diabetes (3359).
Sunburn. Topical vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Oral vitamin E alone does not seem to prevent sunburn. Details: Two small, double-blind, placebo-controlled studies suggest that taking high dose oral RRR-alpha-tocopherol (natural vitamin E) up to 2 grams daily in combination with vitamin C 3 grams protects against skin inflammation after exposure to ultraviolet (UV) radiation. However, taking vitamin E alone does not seem to be beneficial when compared with control (4715,4716). This combination was also tried topically. In one study, topically applied vitamin E in combination with topical vitamin C and melatonin provided modest photoprotective effect when used prior to UV exposure, but had no effect when used during or after UV exposure (4713,4714).
Uveitis. Oral vitamin E has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research shows that taking vitamin E 149 IU twice daily with vitamin C 500 mg daily for 8 weeks improves visual acuity in patients with acute anterior uveitis, but does not seem to decrease inflammation measured by laser flare, when compared with placebo (4730). It is not clear if this effect is due to vitamin E, vitamin C, or the combination.
Vaginal atrophy. It is unclear if a vitamin E suppository is beneficial in patients with vaginal atrophy. Details: A small clinical study in females with breast cancer and tamoxifen-induced vaginal atrophy shows that intravaginal administration of a vitamin E 1 mg suppository nightly before bed for 8 weeks improves self-reported symptoms of vaginal atrophy, decreases vaginal pH, and improves vaginal estrogenization, as measured by the Vaginal Maturation Index, when compared with placebo (99773). More evidence is needed to rate vitamin E for these uses.

VITAMIN K

Hemorrhagic disease. Oral or intramuscular vitamin K1 is effective for preventing hemorrhagic disease in newborns. Details: Vitamin K1 (phytonadione) administered orally or intramuscularly can prevent classic hemorrhagic disease of newborns (15,85367,85484). A single intramuscular administration of vitamin K1 1 mg is considered to be the most effective method, while oral administration of three doses of vitamin K1 1-2 mg over 8 weeks is considered to be an acceptable alternative (85506). The effects of vitamin K on late hemorrhagic disease of newborns is less clear (85367,85484). In the Netherlands, an oral dose of 25 mcg daily for 3 months was used until 2011, when it was increased to 150 mcg daily. A reduction of late intracranial vitamin K deficiency bleeding in the general pediatric population, from 1.6 per 100,000 to 1.3 per 100,000, was associated with this dose increase (102351).
Hypoprothrombinemia. Oral or parenteral vitamin K1 is effective for treating and preventing hypoprothrombinemia. Details: Vitamin K1 (phytonadione) 2.5-25 mg, used orally or parenterally, can prevent and treat hypoprothrombinemia caused by vitamin K deficiency or induced by salicylates, sulfonamides, quinine, quinidine, or broad-spectrum antibiotic therapy (15).
Vitamin K-dependent clotting factors deficiency (VKCFD). Oral and intravenous vitamin K1 is the primary treatment for VKCFD. Details: Oral supplementation with vitamin K 10 mg two to three times weekly seems to prevent major hemorrhages and reduce mucocutaneous bleeding in individuals with VKCFD. Also, intravenous vitamin K may improve the prothrombin time-international normalized ratio (PT-INR) values in these patients. While vitamin K supplementation is the primary treatment method for VKCFD, the response to treatment varies significantly (85481).
Warfarin anticoagulation. Oral and intravenous vitamin K1 reverse warfarin-related excessive anticoagulation. Evidence for the use of oral vitamin K1 in patients with an unstable INR is conflicting. Details: Taking vitamin K1 (phytonadione) orally or parenterally, but not subcutaneously, can counteract excessive warfarin anticoagulation and restore therapeutic international normalized ratio (INR) levels. Usually a single dose of 1-5 mg is used (85406,85425,85429). Vitamin K might also be effective for stabilizing warfarin anticoagulation in patients with low intake of vitamin K. Patients with a low dietary vitamin K intake are significantly more likely to have an unstable INR than those who ingest higher amounts of vitamin K (16803). It is thought that vitamin K-depleted patients become more sensitive when vitamin K is ingested, even in small quantities, resulting in erratic or unstable INR (16804). One small clinical study and one small retrospective chart review show that taking oral vitamin K1 (phytonadione) 100-150 mcg daily improves INR stability in patients taking warfarin who previously had an unstable INR (16805,16806). However, a larger clinical study found no significant differences in INR stability in patients taking vitamin K 100 mcg daily when compared with placebo (16807). Also, some research suggests that, although taking vitamin K 1250 mcg daily may reduce INR in patients with excessive warfarin anticoagulation more significantly than placebo, there may not be a significant difference in the risk of bleeding complications (23380). It is important to keep in mind that, if a patient is stabilized on warfarin therapy plus vitamin K supplementation, discontinuing vitamin K can significantly increase the INR within 2-3 weeks after discontinuation (17714). The most recent guidelines by the American College of Chest Physicians do not recommend routine use of vitamin K supplementation for patients on warfarin therapy with unstable INR (94926). However, the previous guidelines recommended vitamin K 100-200 mcg daily for these patients. Therefore, some providers still use vitamin K for this purpose (16808).

Osteoporosis. Oral vitamin K might reduce the risk of fractures and bone loss in patients with osteoporosis. However, it may not be beneficial in patients at risk for developing osteoporosis. Details: Although observational and clinical research on dietary and supplemental vitamin K for osteoporosis has been conflicting (14364,85392,85445,102354), overall, vitamin K supplementation seems to slightly reduce fracture risk (102354). A meta-analysis combining data from 36 heterogeneous studies in osteoporotic or postmenopausal patients shows that taking different regimens of either vitamin K1 or vitamin K2 is associated with a small reduction in clinical fractures (from 3.1% to 2.2%), but not with changes in vertebral fractures or BMD when compared with control (102354). This analysis is limited by the high variability in study designs and a lack of subgroup analyses stratifying different patient populations and forms of vitamin K. An older meta-analysis of 19 clinical studies in osteoporotic or postmenopausal patients shows that taking vitamin K2 (menaquinone) 45 mg, primarily used in the MK-4 form, daily does not reduce the risk of fractures when compared with control, although there was a non-significant trend towards a reduction (91451). A sensitivity analysis that excluded the largest negative study of over 4000 postmenopausal Japanese females with mild osteoporosis (85456), showed that vitamin K2 45 mg daily reduces the risk of fractures by 53% and improves lumbar and vertebral BMD in patients with osteoporosis when compared with control (91451). This effect was not seen in patients without osteoporosis (91451). Vitamin K2 also does not seem to benefit patients with osteopenia. A recent clinical trial in postmenopausal patients with osteopenia shows that taking a larger dose of vitamin K2 (375 mcg, MK-7) with calcium 800 mg and vitamin D 1500 IU daily for 3 years does not seem to affect BMD, bone turnover, or bone microarchitecture when compared with placebo (105035). Vitamin K1 (phytonadione) has also been evaluated, with mixed findings. One clinical study in postmenopausal patients with osteopenia shows that taking vitamin K1 5 mg daily with calcium 1500 and vitamin D 800 IU for up to 4 years reduces clinical fractures, but does not reduce clinical fragility fractures or improve BMD, when compared with placebo and vitamin D with calcium (85453). In healthy, non-osteoporotic patients ages 60-80 years, one clinical study shows that taking vitamin K1 500 mcg daily with calcium 600 mg and vitamin D 400 IU for 3 years does not affect BMD, despite increased plasma vitamin K levels and reduced undercarboxylated osteocalcin concentrations, when compared with taking calcium and vitamin D alone (16404). The same null effect on BMD and a reduced undercarboxylated osteocalcin was shown in a small clinical study in patients with Crohn disease without osteoporosis, taking vitamin K1 1-2 mg in combination with vitamin D3 400 IU and calcium 500 mg daily for 12 months (91454).

Intraventricular hemorrhage. Oral vitamin K does not reduce the risk of periventricular hemorrhage in preterm infants. Details: A meta-analysis of results from clinical research shows that administering vitamin K to pregnant patients at risk for very preterm birth does not reduce the overall risk of periventricular hemorrhage in preterm infants, perinatal mortality, or the associated neurological injury by the age of 7 years when compared to control. A subgroup analysis shows that vitamin K might reduce the risk of severe periventricular hemorrhage by 42% in preterm infants. However, when trials with inadequate blinding were excluded, this result was not statistically significant (85469).

Athletic performance. It is unclear if oral vitamin K2 improves athletic performance. Details: A small clinical study shows that taking vitamin K2 (menaquinone) 320 mcg orally daily for 4 weeks followed by 160 mg daily for 4 weeks, increases maximal cardiac output by 12% when compared with placebo in trained athletes performing standardized cycle ergometer exercise tests (95937).
Beta-thalassemia. Oral vitamin K2 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking the menaquinone-7 (MK-7) form of vitamin K2 50 mcg daily plus vitamin D3 (calcitriol) 5 mcg daily for 12 months modestly improves bone mineral density (BMD) at the lumbar spine when compared to baseline in children with beta-thalassemia aged 3-18 years (91456). It is not clear if this improvement can be attributed to vitamin K, vitamin D3, or the combination.
Breast cancer. It is unclear if dietary intake of vitamin K2 reduces the risk of breast cancer. Details: Population research has found that higher dietary intake of vitamin K2 (menaquinone) or vitamin K1 (phytonadione) is not associated with a reduced risk of premenopausal or postmenopausal breast cancer (85474).
Cancer. It is unclear if dietary intake of vitamin K reduces the risk of cancer or cancer-related mortality. Details: One large population study involving healthy German patients has found that consuming more than 42-46 mcg of vitamin K2 (menaquinone) daily is associated with a 27% reduced risk of cancer mortality, but not cancer incidence, when compared with consuming less than 23-26 mcg daily. Dietary intake of vitamin K1 (phytonadione) was not associated with the risk of cancer or cancer mortality (85474). Another population study involving Mediterranean patients at high risk for cardiovascular disease has found that consuming about 630 mcg of vitamin K1 daily is associated with a 46% lower risk of cancer mortality when compared with consuming about 171 mcg of vitamin K1 daily. However, higher dietary intake of vitamin K2, 87 mcg daily, was not associated with a lower risk of cancer mortality when compared to those with lower dietary intake (79 mcg daily) (91452). Reasons for these discrepancies may relate to the definitions for high and low intake, the use of different databases to calculate vitamin K intake, and the different populations studied.
Cardiovascular disease (CVD). It is unclear if dietary or supplemental vitamin K reduces the risk of CVD events; the available research is conflicting. Details: Most population research, including a meta-analysis of 21 observational cohort studies, has found that dietary intake of vitamin K1 (phytonadione) or vitamin K2 (menaquinone) is not associated with reduced risk for most cardiovascular events, such as CVD mortality, nonfatal MI, or stroke, although there might be a slightly reduced risk for CHD (85414,85482,91452,102353,103922). However, some population studies have found benefit. Observational research in a Danish cohort aged 50-65 years with no history of atherosclerotic cardiovascular disease at baseline shows that those in the highest quintile of dietary vitamin K1 intake have a 21% lower risk of CVD-related hospitalization and complications, such as ischemic heart disease, ischemic stroke, or peripheral artery disease, over 17-22 years when compared with the lowest quintile of intake. This inverse association tapers off at intakes above 100 mcg daily. For vitamin K2 intake, the highest quintile has a 14% lower risk of hospitalization when compared with the lowest quintile, although the association is U-shaped, indicating an increased risk at high doses. The researchers theorize that this may be due to the fact that vitamin K2-rich foods include cheese, eggs, and butter (109910,109920). There is also interest in using vitamin K to slow aortic valve calcification (AVC) and coronary artery calcification (CAC), which are CVD risk factors. In healthy patients ages 60-80 years with pre-existing CAC, taking a multivitamin with vitamin K1 (phytonadione) 500 mcg orally daily for 3 years reduces CAC progression by 6% when compared with the multivitamin alone (85461). However, research in patients with AVC has found no benefit. One small clinical study in patients on hemodialysis shows that taking the menaquinone-7 form of vitamin K2, 200 mcg orally daily for 1 year, does not affect the rate of AVC progression when compared with placebo (102352). Also, clinical research in males with significant AVC shows that taking the menaquinone-7 form of vitamin K2 720 mcg and vitamin D 25 mcg orally daily for 2 years does not reduce the rate of AVC progression or the rate of cardiovascular events, heart valve surgery, or all-cause mortality when compared with placebo (109916).
Cataracts. It is unclear if dietary vitamin K reduces the risk of cataracts in older adults. Details: A secondary analysis of results from clinical research has found that higher dietary vitamin K1 (phytonadione) intake over a mean 5.6 years' follow-up is associated with a lower risk of cataracts and a lower incidence of cataract surgery in older adults at high risk for cardiovascular disease. The hazard ratio for developing cataracts was 0.71 and the hazard ratio for cataract surgery was 0.75 for people in the highest tertile of dietary vitamin K1 intake when compared with the lowest tertile (95936).
Cognitive impairment. It is unclear if dietary vitamin K alters the rate of decline in adults with cognitive impairment. Details: Clinical research in adults aged 55-75 years with overweight or obesity, metabolic syndrome, and cognitive impairment shows that the largest increases in dietary vitamin K intake over a 2-year period are linked to a slower rate of cognitive decline when compared with the lowest increases in intake. This is demonstrated by higher scores on the mini-mental state examination (MMSE) and verbal fluency tests, and a greater number of patients maintaining an MMSE score of at least 24 (109919).
Colorectal cancer. It is unclear if dietary intake of vitamin K2 reduces the risk of colorectal cancer. Details: Population research has found that higher dietary intake of vitamin K2 (menaquinone) or vitamin K1 (phytonadione) is not associated with a reduced risk of colorectal cancer (85474).
Cystic fibrosis. It is unclear if oral vitamin K improves coagulopathy in patients with cystic fibrosis. Details: Suboptimal vitamin K status is common in patients with cystic fibrosis, especially those with pancreatic insufficiency, due to problems with fat digestion (85359,85479). Preliminary clinical research in patients with cystic fibrosis shows that taking vitamin K 1-5 mg orally for one month might decrease osteocalcin levels when compared with baseline, which suggests a lower risk of bone fractures (103920). Also, a small clinical trial in adults and children with cystic fibrosis and pancreatic insufficiency shows that taking a supplement containing fat-soluble vitamins A, D, E, and K for an average of 8.6 months reduces the number of patients with abnormal levels of protein induced by vitamin K absence (PIVKA-II), a defective form of prothrombin (85374).
Depression. It is unclear if dietary intake of vitamin K reduces depression. Details: Population research has found that a dietary intake of vitamin K greater than 232 mcg daily is associated with reduced odds of depressive symptoms when compared with intakes of less than 83 mcg daily in older adults who are not taking vitamin D supplements. For every 100 mcg increase in vitamin K intake per day, the study found an 18% reduction in odds of depressive symptoms. However, there was no association identified in individuals taking vitamin D (100181). The effect of vitamin K for the prevention or treatment of clinical depression has not been investigated.
Diabetes. It is unclear if oral vitamin K1 improves glycemic control in patients with diabetes. Details: A small clinical study in patients with diabetes who are taking oral antidiabetes medications shows that taking vitamin K2 (MK-7) 180 mcg twice daily for 12 weeks seems to reduce glycated hemoglobin by 1.6%, compared with a slight increase in the placebo group (105034). This study is limited due to high dropout rate in the placebo group.
EGFR inhibitor-induced acneiform rash. It is unclear if topical vitamin K is beneficial for the treatment or prevention of acneiform rash caused by EGFR inhibitors. Details: Preliminary clinical research in adults receiving treatment with cetuximab, an EGFR inhibitor, shows that applying vitamin K1 (phytonadione) 0.1% cream (Vigorskin, Merck Serono SpA) twice daily to the face and trunk for 12 weeks may modestly reduce the percentage of patients who develop a moderate to severe acneiform rash (91455). The validity of this finding is limited by the lack of a control group. In patients with an existing rash after receiving the EGFR inhibitors cetuximab and panitumumab, a small clinical study shows that applying vitamin K1 (phytonadione) 1% ointment twice daily for 8 weeks to half of the affected area does not reduce the number of acneiform eruptions when compared with using placebo ointment on the other half of the affected area (103919). Patients in this study were allowed to use concomitant antibiotics and moisturizing agents, which may have confounded the results.
Kidney failure. It is unclear if oral vitamin K2 reduces the incidence or severity of muscle cramps in adults with kidney failure. Details: Preliminary clinical research in patients on maintenance hemodialysis for at least 3 months with treatment-resistant muscle cramps shows that taking the menaquinone form of vitamin K2 360 mcg orally daily for 8 weeks reduces the frequency, severity, and duration of muscle cramps when compared with placebo (109917).
Kidney transplant. It is unclear if vitamin K is beneficial for reducing cardiovascular risk in kidney transplant recipients. Details: Preliminary clinical research in adults with a stable kidney transplant for at least 1 year shows that taking vitamin K (menadiol diphosphate) 5 mg orally three times weekly for 1 year does not reduce aortic stiffness or coronary artery calcification, which are markers of cardiovascular disease, when compared with placebo (109913). The effects of long-term supplementation are unclear.
Liver cancer. Small clinical studies suggests that vitamin K2 reduces mortality and the risk for hepatocellular carcinoma recurrence. Details: Meta-analyses of 9-11 small clinical trials in patients with resectable hepatocellular carcinoma show that adding vitamin K2 45 mg daily for up to 3 years seems to reduce cancer recurrence by 9.5% and reduce the risk of mortality by 7% when compared with control. Meta-analyses of 3-4 small clinical trials in patients with non-resectable carcinoma show that taking vitamin K2 45 mg for up to 2 years seems to reduce cancer recurrence by 3% and reduce mortality by 16% when compared with control (105032). Most of the included studies were conducted in Japan, so it is unclear if these results are generalizable to other geographic locations.
Liver disease. It is unclear if dietary intake of vitamin K reduces the risk of liver disease. Details: A small observational study in patients with chronic liver failure due to cholestatic liver disease has found that receiving intramuscular vitamin K1 10 mg daily for an average of 16 days is associated with a lower risk of death when compared with control (103926).
Lung cancer. It is unclear if dietary intake of vitamin K reduces the risk of lung cancer. Details: Population research has found that consuming greater than 42-46 mcg of vitamin K2 (menaquinone) daily is associated with a 62% lower risk of lung cancer occurrence and a 59% lower risk of lung cancer mortality when compared to those who consume less than 23-26 mcg of vitamin K2 daily. Dietary intake of vitamin K1 (phytonadione) is not associated with a reduced risk of lung cancer or lung cancer mortality (85474).
Multiple sclerosis (MS). It is unclear if topical vitamin K reduces cutaneous adverse effects of MS treatment. Details: In patients with relapsing-remitting MS, burning and pain can accompany subcutaneous interferon treatment. Preliminary clinical research shows that topical application of vitamin K cream (dose not specified) for 8 weeks reduces burning by approximately 8% and pain by 9% when compared with no prophylactic treatment. Redness of the skin is also reduced with vitamin K (91453).
Overall mortality. It is unclear if dietary intake of vitamin K reduces overall mortality. Details: Observational research in healthy older adults has found that serum vitamin K levels 0.5 nmol/L or less, which corresponds to consuming about 50% of the recommended vitamin K adequate intake, is associated with a 19% higher risk of overall mortality when compared with higher serum levels of vitamin K (103922). In a Danish cohort of adults with a median age of 56 years at baseline, the comparative risk for all-cause mortality between the highest and lowest quintiles of K1 intake over a period of 17-23 years was 0.76. The risk for cardiovascular mortality was 0.72, and the risk of cancer-related mortality in smokers or former smokers, specifically, was 0.8. However, the correlation tapered off above a daily intake of 100 mcg (109911).
Pancreatic cancer. It is unclear if dietary intake of vitamin K reduces the risk of pancreatic cancer. Details: Observational research in over 100,000 Americans aged 55-74 years at baseline has found no association between dietary vitamin K2 intake and pancreatic cancer incidence over an average follow-up of 9 years. However, the hazard ratio for development of pancreatic cancer was 0.57 for the highest quintile of dietary vitamin K1 intake when compared with the lowest quintile (109912).
Polycystic ovary syndrome (PCOS). It is unclear if vitamin K improves PCOS symptoms. Details: Small clinical study in patients with PCOS show that taking vitamin K2 (menaquinone-7) 90 mcg daily for 8 weeks does not reduce fasting blood glucose, acne, hirsutism, or weight, although it improves depression and seems to reduce fasting insulin, when compared with placebo (105036,109918).
Prostate cancer. It is unclear if dietary intake of vitamin K reduces the risk of prostate cancer. Details: Population research has found that higher dietary intake of vitamin K2 (menaquinone), but not vitamin K1 (phytonadione), is associated with a reduced risk of prostate cancer, particularly advanced prostate cancer (85443,85474).
Rheumatoid arthritis (RA). It is unclear if oral vitamin K improves RA symptoms. Details: One small clinical study in patients with RA shows that adding the MK-7 form of vitamin K2 (menaquinone) 100 mcg daily to treatment with conventional antirheumatic agents for 3 months improves disease activity and inflammatory markers when compared with antirheumatic agents alone. When compared to the control group, vitamin K2 reduced disease activity scores by 41% (91449). However, another small clinical study in patients with mild to moderate RA shows that taking vitamin K1 (phytonadione) 10 mg daily for 8 weeks with conventional antirheumatic agents does not improve disease activity or inflammatory markers when compared with placebo (100182). These contrasting outcomes may be related to the type of vitamin K used, the duration of treatment, and the severity of the illness.
Rosacea. Although there is interest in using topical vitamin K1 for rosacea, there is insufficient reliable information about the clinical effects of vitamin K for this condition.
Stroke. It is unclear if dietary intake of vitamin K1 reduces the risk of stroke. Details: Population research has found that higher dietary intake of vitamin K1 is not associated with a reduced risk of stroke (85482).
Wound healing. Although there is interest in using topical vitamin K1 for wound healing, there is insufficient reliable information about the clinical effects of vitamin K for this condition. More evidence is needed to rate vitamin K for these uses.

ZINC

Zinc deficiency. Orally or intravenously, zinc is effective for treating and preventing zinc deficiency. Details: Taking zinc orally or intravenously prevents and treats zinc deficiency (2619). However, routine zinc supplementation is not recommended (403). Zinc deficiency requiring supplementation may occur in patients with severe diarrhea, malabsorption syndromes, liver cirrhosis, and alcoholism; after major surgery, renal failure, and dialysis; or during long-term administration of total parenteral nutrition (3900,24321). Zinc supplementation (136 mg of elemental zinc per day) in patients with cirrhosis and zinc deficiency seems to improve liver function and glucose tolerance, possibly by increasing insulin-like growth factor (8624,87520).

Diarrhea. Oral zinc reduces duration and severity of acute diarrhea in malnourished children. Doses of 5-20 mg seem to be effective, while 5-10 mg daily is less likely to cause vomiting. Details: Most research, including meta-analyses and over 30 clinical trials, show that taking zinc orally reduces the duration and severity of acute and persistent diarrhea in malnourished or zinc-deficient children, but not in well-nourished children (87236,96074). Most studies have been conducted in Bangladesh and India, so it is unclear if these findings are generalizable to other geographic locations. The most comprehensive meta-analysis of clinical studies in children older than 6 months shows that zinc supplementation reduces the duration of acute diarrhea by about 11 hours and the duration of persistent diarrhea by about 16 hours when compared with placebo. However, zinc does not seem to reduce the duration of acute diarrhea in children younger than 6 months. Zinc supplementation seems to have the greatest benefit in children with clear malnutrition and diarrhea. In these children, zinc reduces diarrhea duration by about 26 hours and reduces the risk of diarrhea persisting through days 3, 5, and 7 by 18% to 24% when compared with placebo. There was no clear benefit of using zinc in a specific dose or salt form. The most common dose of zinc was 20 mg daily and salt forms included zinc sulfate, gluconate, and acetate (96074). Also, a large clinical trial in children with acute diarrhea shows that taking zinc 5 or 10 mg daily for 14 days is non-inferior to taking 20 mg. Furthermore, zinc 5 or 10 mg results in a respective 29% and 19% lower risk of vomiting within the first 30 minutes when compared with zinc 20 mg (104045). It's unclear whether zinc supplementation reduces mortality in children with diarrhea. A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of mortality from diarrhea by 15% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). However, many studies were conducted in hospitals where rates of mortality are low and were not adequately powered to determine whether zinc has an effect on mortality in children with acute diarrhea (87210,96074,106239).
Wilson disease. Taking zinc orally improves symptoms of this condition. Details: Zinc acetate (Galzin) is an FDA-approved orphan drug for treating this condition. Zinc blocks copper absorption and increases copper elimination in the stool of people with Wilson disease (2692,2693,87327). Small clinical studies suggest that taking zinc after 8 weeks of treatment with tetrathiomolybdate alone can improve Kayser-Fleischer rings, urine copper levels, and neurological symptoms for up to 6 years post-treatment (63588,87491).

Acne. Orally, zinc might help to reduce symptoms of acne. However, it's unclear how oral zinc compares to conventional acne treatments. Topical zinc doesn't seem to be beneficial if used alone. Details: Observational research has found that people with acne seem to have lower zinc levels in the serum and skin (104056). A meta-analysis of small, low quality clinical trials suggests that taking zinc sulfate or zinc gluconate 137-300 mg 2-3 times daily by mouth can modestly improve acne when compared with placebo (104056). However, not all individual trials show benefit (87002,104056). So far, it is not clear how oral zinc compares to other treatments. Trials comparing zinc sulfate with various tetracyclines have yielded conflicting results (6505,6506,86946,106233). One large open-label clinical trial shows that taking zinc sulfate 200 mg twice daily for 12 weeks is at least as effective as lymecycline 300 mg daily for reducing acne severity. Quality of life related to acne was modestly improved in the patients using zinc sulfate (106233). However, in another clinical trial, a 3-month treatment of oral zinc gluconate 30 mg daily reduced the number of acne lesions from baseline, but was not as effective as minocycline (86946). When applied topically, clinical research shows that zinc does not help treat acne when compared with placebo (87297,104056). However, when used in combination with erythromycin, topical zinc seems to result in improvement (819,820,2687,2688).
Acrodermatitis enteropathica. Oral zinc seems to improve symptoms of this rare genetic disorder. Details: Multiple case reports have found that taking oral zinc seems to help improve symptoms of acrodermatitis enteropathica, a rare disorder (821,2689,2690,2691). One case report in a female with necrolytic acral erythema and hepatitis C suggests that adding oral zinc sulfate 225 mg twice daily to interferon alfa-2b for 6 months contributed to resolving all lesions. Necrolytic acral erythema is categorized in the family of necrolytic erythemas that includes acrodermatitis enteropathica (6192).
Age-related macular degeneration (AMD). Oral zinc, especially in combination with antioxidant vitamins, seems to slow the progression of AMD. Details: Clinical research shows that taking elemental zinc 80 mg plus vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily reduces the odds of progression to advanced AMD by 28%. In patients with more severe AMD, this combination reduced the odds of progression to advanced AMD by 34%. This combination also reduced the odds of visual acuity loss by 27% in patients with severe AMD (7303,11326). However, there is contradictory evidence about the effects of zinc plus antioxidants on visual acuity loss or the progression to advanced AMD in low-risk patients with AMD (6583,6584,7303). Some clinical evidence shows that, when taken without antioxidant vitamins, zinc supplementation does not slow the progression of existing AMD (6580,90069). However, a subgroup analysis of results from a large clinical trial that included patients with intermediate or advanced AMD suggests that the effect of zinc on AMD progression might vary depending on a patient's genetic predisposition. Complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) are two genes for which specific variations (i.e., risk alleles) have been associated with an increased risk of AMD. Results from the retrospective subgroup analysis suggest that zinc supplementation may DECREASE the progression of AMD in patients with ARMS2 risk alleles and INCREASE the progression of AMD in patients with CFH risk alleles (90193). However, some experts question the results from this analysis due to the retrospective nature of the study (93045). Another retrospective analysis of similar data found that only zinc plus antioxidants, but not zinc alone, was beneficial for slowing the progression of AMD, regardless of the patient's genotype (93046). Consequently, the American Academy of Ophthalmology does not currently recommend routine genetic screening to determine which patients would benefit from zinc, antioxidants, or the combination. Instead, patients with intermediate or advanced AMD are recommended to take an antioxidant and zinc supplement similar to those used in the Age-Related Eye Disease Study (AREDS) and the Age-Related Eye Disease Study 2 (AREDS2) (93047). Large scale population studies suggest that increasing dietary intake of zinc might reduce the risk of developing AMD (6579,14257).
Child growth. Oral zinc seems to increase growth when taken by children and improve infant growth in the first year of life when taken by pregnant adults. Details: A meta-analysis of 8 clinical studies in healthy children over 2 years old shows that taking supplemental zinc 5-15 mg daily for 6-56 weeks modestly increases height and weight when compared with placebo. This analysis also shows that taking zinc may improve height for age, but not weight for age when compared with placebo (112474). Most of these studies were conducted in developing countries; results may not apply elsewhere. Another clinical study in pregnant adults in Peru shows that taking zinc 15 mg daily in addition to iron and folic acid, starting during the first or second trimester and continuing up to one month after delivery, modestly improves growth measures of infants at one year when compared with taking iron and folic acid alone. Improved growth measures include body weight, calf and chest circumference, and calf muscle area (87130).
Common cold. Oral zinc seems to help treat cold symptoms in adults. However, it is unclear if zinc is beneficial for common cold prevention. Details: Using zinc oral lozenges seems to be beneficial in helping TREAT the common cold in adults. The majority of clinical trials and analyses of clinical research show a significant decrease in the duration of symptoms of the common cold when adults take zinc gluconate or zinc acetate lozenges providing 9-24 mg of elemental zinc per dose. It is recommended that lozenges be taken every 2 hours while awake, starting within 48 hours of symptom onset for a total daily dose of at least 75 mg in order to attain a mean cold duration reduction of 3 days (333,334,335,337,6703,6705,87501,92212,106902). However, not all studies have been positive (333,338,339,6522,6700,87512). The reasons for these different findings are not clear, but might be due to differences in zinc formulations and doses and study methodologies. In some cases, flavoring agents such as citric acid, mannitol, and sorbitol might chelate zinc and decrease zinc ionization. Since ionization is thought to be necessary for zinc activity, a decrease in zinc ionization could decrease effectiveness (300,340,6522). Some of the positive studies have also been criticized for inadequately blinding the unpleasant, distinctive taste of zinc (6522,6706). Allergy and smoking status do not appear to impact the efficacy of zinc acetate lozenges (92212). Overall, zinc products may be beneficial for modestly reducing the duration of symptoms of the common cold in adults, but adverse effects such as bad taste and nausea may limit their usefulness (18216). There is conflicting evidence for the use of oral zinc products to PREVENT colds. Some clinical research suggests that taking zinc prophylactically does not prevent the common cold in adults (10780,10784) or children (341). However, other clinical research suggests that administering zinc gluconate lozenges can reduce the incidence of colds in children and adolescents (10803,86972). In a meta-analysis of 28 randomized controlled trials with a total of 5446 participants, oral zinc prevented 5 viral upper respiratory tract infections per 100 person months of zinc use when compared with placebo, with a number needed to treat (NNT) of 20 (106902). Intranasal zinc is not recommended for the prevention or treatment of the common cold due to the risk for anosmia. See the Adverse Effects section for more information. Some research shows that zinc nasal spray (as a sulfate, gluconate emulsion, or gluconium gel) reduces the severity and duration of cold symptoms; however, other research has found no effect (6471,8628,8629,10247,87035). Zinc nasal spray does not seem to prevent experimentally-induced colds (8628).
Coronavirus disease 2019 (COVID-19). While oral zinc does not seem to speed recovery from COVID-19 in non-hospitalized patients, an analysis of a small number of studies suggests that oral or intravenous zinc might reduce the risk of death in hospitalized patients with COVID-19. Details: A small observational study in patients with COVID-19 has found that lower serum zinc levels are associated with worse clinical outcomes, such as admission to the intensive care unit (ICU) and death, when compared with higher zinc levels (105681). Another small observational study has found that 96% of patients with confirmed COVID-19 were zinc-deficient based on plasma levels of zinc, and that these patients had lower plasma zinc levels than a group of individuals without COVID-19. However, plasma zinc concentrations were only weakly correlated with length of hospital stay and there was no correlation with morbidity or mortality (106236). One clinical study in adult outpatients with COVID-19 shows that taking zinc gluconate 50 mg daily at bedtime, alone or with vitamin C (ascorbic acid) 8000 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). This study was terminated prior to complete enrollment due to a lack of effect with zinc and/or vitamin C supplementation. Limitations of this study include a lack of placebo control and blinding. Zinc supplementation also does not appear to enhance the clinical efficacy of hydroxychloroquine in patients with confirmed COVID-19 infection. Taking zinc sulfate 220 mg twice daily during a 6-day course of hydroxychloroquine does not improve the clinical recovery rate, reduce the mortality rate, or reduce the need for mechanical ventilation when compared with hydroxychloroquine alone (104818). Other research has evaluated zinc in hospitalized patients. Multiple meta-analyses of small and low-quality clinical studies, including randomized controlled trials and retrospective studies, involving hospitalized patients with COVID-19 shows that supplementation with oral or intravenous zinc is associated with a 29% to 43% reduction in the odds of in-hospital mortality when compared with control (109451,110631). However, in one meta-analysis, the odds of 30-day mortality were not different between groups (110631). These meta-analyses did not elevate the most effective form, dose, frequency, or duration of zinc supplementation (109451,110631). Additionally, a retrospective study in adults admitted to the ICU with COVID-19 has found that those who received oral zinc sulfate, 220 mg daily for a median of 11 days, had a lower 30-day mortality rate when compared with those who did not receive zinc. However, there was no difference in hospital length of stay or in-hospital mortality (106903).
Depression. Oral zinc seems to be beneficial when used in combination with antidepressant treatments. Details: Population research has found that higher zinc levels and higher dietary intake of zinc are associated with a 28% lower incidence of depression (90227,97139,104057). Oral zinc seems to be beneficial as an adjunct therapy in depression. A meta-analysis of small, low-quality studies in patients with major depression shows that taking zinc in addition to antidepressant therapy is associated with modestly improved depression symptoms when compared with antidepressant therapy alone (104044). Clinical studies used zinc doses of 7-25 mg daily for up to 12 weeks (86985,90221,104044). One small clinical study also shows that adding zinc to imipramine therapy might improve depression that was previously resistant to antidepressant treatment (87158). One clinical guideline also provisionally recommends use of zinc 25 mg elemental orally daily to treat patients with depression based on low-quality evidence. This guideline recommends use of chelated or picolinate zinc products over other forms of zinc (110318).
Diabetes. Oral zinc might modestly improve glycemic control in some patients. Details: A meta-analysis of 12 clinical studies in patients with diabetes shows that taking zinc supplements reduces fasting blood glucose by up to 20 mg/dL and glycated hemoglobin (HbA1c) by 0.35% when compared with control. However, when only high quality studies were included, the reduction in fasting blood glucose dropped to 12 mg/dL. Zinc seems to only have glycemic benefit in patients living in the Eastern hemisphere, and not the Western hemisphere. Also, glucose reduction seems to be higher with inorganic zinc formulations at doses of at least 30 mg daily taken for at least one month (104080). Zinc has also been evaluated for improving lipid parameters in patients with diabetes. A meta-analysis of nine studies in patients with diabetes shows that taking zinc reduces triglycerides by 17 mg/dL, but does not seem to affect low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol levels, when compared with placebo (104041). The findings from these meta-analyses are limited by the high heterogeneity and small size of the included studies. Zinc has also been studied for gestational diabetes. Some clinical research in patients with gestational diabetes shows that taking zinc gluconate for 6 weeks, starting at 24-28 weeks' gestation, reduces fasting plasma glucose levels by about 10% and improves insulin resistance by 14% when compared to baseline (96072). However, taking zinc gluconate does not reduce the need for caesarean section or insulin therapy, or improve infant outcomes, such as size or health at birth, in these patients (96073).
Diaper rash. Topical and oral zinc seem to reduce the incidence and severity of diaper rash in infants. Details: Clinical research shows that administering oral zinc gluconate 10 mg daily for 4 months can reduce the incidence of diaper rash in infants when compared with placebo (87281). Other clinical research shows that applying 47% zinc oxide paste to affected areas for 5 days can improve the healing of diaper rash. However, the effect of zinc oxide paste is inferior to eosin 2% solution (86918).
Gingivitis. Topical zinc seems to reduce the development of gingivitis. Details: While some clinical research shows that zinc, in combination with triclosan, does not prevent plaque and gingivitis (24093,87020), most clinical research shows that using zinc toothpaste or mouthwash, alone or in combination with triclosan, can prevent plaque accumulation, gingivitis, or the formation of calculus (6523,6524,6525,6526,6527,6528,6529,87418,87507). However, most studies used zinc citrate in combination with triclosan, which is not available in the US (6523). For treating existing plaque, calculus, and gingivitis, some clinical research suggests that using zinc citrate 0.5% toothpaste three times daily for 3 months reduces calculus scores by 14% when compared with placebo (87205). However, other evidence suggests that stannous fluoride 0.454% toothpaste is more effective than zinc citrate 0.75% toothpaste for reducing plaque levels (87136).
Halitosis. Oral zinc seems to reduce halitosis when taken as a gum, mouth rinse, or candy. Details: Clinical research shows that chewing zinc-containing gum reduces volatile sulfur compounds and related odor levels when compared with placebo gum in patients with moderate to severe halitosis (87538). Clinical research also shows that using one of two mouth rinses (Halita, which contains 0.05% chlorhexidine and 0.14% zinc lactate, or Meridol, which contains 0.025% fluoride plus 0.2% zinc lactate) improves breath odor and volatile sulfur compounds by approximately two-fold when compared with mouth rinse containing only 0.05% fluoride or chlorhexidine 0.12% (90206). Additional clinical research shows that sucking a candy containing abrasive substances and zinc gluconate 0.5% or candy containing abrasive substances plus zinc 0.25% and propolis 1% improves breath malodor two- to three-fold when compared with sucking placebo candy (90196).
Herpes labialis (cold sores). Topical zinc seems to reduce the severity and duration of cold sores. Details: Applying zinc topically seems to help treat herpes simplex infection (6538,6539,8623,11051). Zinc sulfate seems to reduce the severity and duration of symptoms in both orolabial and genital herpes (6538,6539). Zinc oxide (0.3%) in combination with glycine cream applied topically every 2 hours to facial and circumoral herpes seems to reduce symptoms such as blistering, soreness, itching, and tingling. It can also reduce the duration of lesions from 6.5 days to 5 days when treatment is begun within 24 hours of onset of symptoms (8623). A specific combination product containing zinc oxide and L-lysine plus 14 other ingredients (Super Lysine Plus +) also seems to help decrease symptoms and duration of herpes lesions when applied topically every 2 hours (11051). However, zinc may not be effective for recurrent herpes simplex infections. In one clinical study, applying zinc sulfate 0.0025% or 0.05% solution to affected areas did not reduce the frequency, severity, or duration of herpes episodes when compared with a placebo solution in patients experiencing more than five episodes per year (87330).
Hypogeusia. Oral zinc might improve taste disturbance and taste acuity in people with hypogeusia of various etiologies. Details: A meta-analysis of low-quality studies in patients with taste disorders that are idiopathic or due to zinc deficiency shows that taking oral zinc modestly improves taste acuity when compared with placebo (104055). Studies tested zinc gluconate, zinc sulfate, zinc acetate, and zinc-carnosine as Polaprezinc (Promac, Zeria Pharmaceutical Co., Ltd.), containing 17-68 mg elemental zinc, daily for up to 12 weeks (104055). Zinc also might improve hypogeusia conditions unrelated to zinc deficiency, such as gustin/carbonic anhydrase VI deficiency, captopril-induced taste disturbances, hypogeusia due to chronic renal failure, and post-traumatic olfactory disorder (6543,6544,104055). It also seems be beneficial in radiation-induced dysgeusia. A meta-analysis of three small clinical trials shows that oral zinc reduces the risk of radiation-induced dysgeusia by 28%, but does not improve taste acuity when compared with placebo (104043). However, patients with hypogeusia from other causes may not benefit. Zinc supplementation does not seem to improve taste perception when compared with placebo in patients with acetazolamide-induced taste dysfunction or chemotherapy-induced taste dysfunction (87388,90214).
Leishmania lesions. Oral zinc and intralesional injections of zinc might improve healing of these lesions. Details: Clinical research shows that taking zinc sulfate 2.5-10 mg/kg orally in three divided doses daily, improves the cure rate of cutaneous leishmania lesions after 45 days when compared with no treatment (86935). Other clinical research shows that intralesional injections of zinc sulfate 2% solution for 6 weeks improves cure rates of cutaneous leishmania lesions when compared with no treatment (6587). However, intralesional injections with zinc sulfate solution does not appear to be more effective than intralesional injections of meglumine antimoniate (Glucantime), hypertonic saline, or sodium stibogluconate (6587,86996,87008).
Leprosy. Oral zinc seems to be beneficial when used in combination with anti-leprosy drugs. Details: Zinc levels appear to be reduced in people with leprosy. Early clinical research suggests that the addition of zinc improves tolerance of the anti-leprosy drug regimen and might allow for lowering or eliminating steroid doses in erythema nodosum leprosum, a severe form of leprosy (6534,6535,6536,6537).
Low birth weight. Oral zinc supplementation seems to improve growth in low birth weight infants. Whether oral zinc can improve other outcomes, including mortality, is unclear. Taking oral zinc during pregnancy does not seem to reduce the risk of having a low birth weight infant. Details: While there is some mixed evidence regarding the effects of zinc supplementation on weight gain and length in infants born with low birth weight (87172,87452,90229), a meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, increases weight by around 380 grams, length by around 3 cm, and head circumference by around 0.6 cm when compared with control (109455). There is also mixed evidence regarding the effect of zinc supplementation on other outcomes in low birth weight infants. A large clinical trial in full-term, underweight infants aged 1-6 months in developing countries shows that adding zinc to nutritional supplementation reduces the risk of mortality by about 68% when compared with nutritional supplementation not containing zinc (8920). A small clinical trial in very low birth weight preterm infants born in an industrialized country shows that adding zinc to multivitamin supplementation appears to reduce the occurrence of necrotizing enterocolitis and mortality. However, adding zinc does not appear to prevent late-onset sepsis, bronchopulmonary dysplasia, or retinopathy of prematurity (90229). A meta-analysis of these trials and two other studies in low birth weight infants shows that supplementation with zinc reduces the risk of all-cause mortality by 52% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). Another small clinical study in low birth weight and preterm infants born in a developing country shows that zinc supplementation seems to improve alertness and attention when compared with placebo (97140). However, a meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, does not improve mental or psychomotor development or reduce the risk of mortality, hospitalization, acute respiratory infection, or sepsis when compared with control (109455). Some of these discrepant findings may be due to differences in patient populations (hospitalized, non-hospitalized), milk sources (breastfed, formula-fed, or both), and duration of follow-up. The effect of zinc intake or supplementation during pregnancy has also been evaluated. Population research has found that low dietary intake of zinc during pregnancy is associated with low birth weight in infants; similarly, zinc supplementation is associated with increased infant weight at birth (87471,105678). However, a meta-analysis and a large clinical study show that zinc supplementation during pregnancy does not reduce the risk of having a low birth weight infant (97142,105679). Reasons for the discrepancies may be due to differing zinc status prior to supplementation. Also, numerous factors contribute to the risk of low birth weight, which may confound research on the use of zinc supplementation alone.
Peptic ulcers. Oral zinc seems to treat and prevent peptic ulcers. Details: Taking zinc orally seems to help treat and prevent peptic ulcers (6588,6589,6591). Some clinical research shows that zinc acexamate improves peptic ulcers when compared with placebo (6589,87285), and seems to be as effective as H2-receptor antagonist drugs (6589,87533). It is not known if other zinc salts are effective.
Pneumonia. Oral zinc might reduce the risk for pneumonia in children, but it doesn't seem to improve symptoms in children that already have pneumonia. Details: A meta-analysis of four clinical studies shows that giving zinc supplements to children, ages 3 months to 5 years living in developing countries, some of whom were undernourished, reduces the risk of pneumonia incidence by 21% when compared with placebo (104047). Another meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of pneumonia mortality by 21% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). The research on TREATING existing pneumonia in children is inconsistent. Most meta-analyses and clinical studies in children ages 2 months to 5 years with severe pneumonia show that taking elemental zinc in addition to antibiotic therapy does not improve symptom resolution or the time to recovery when compared with antibiotic therapy alone. Zinc also does not seem to reduce mortality in these patients (87248,90197,96080,98131,104042). However, two clinical studies in children in the same age group with pneumonia suggest that adding zinc to standard antibiotic therapy improves symptom resolution and decreases hospital stay when compared with placebo (11052,87242). Reasons for these discrepancies are not clear, but may be related to zinc status prior to treatment.
Prematurity. Analyses of clinical studies suggest that oral zinc improves growth in premature infants. Whether zinc improves development or reduces the risk of mortality in these patients is unclear. Details: A meta-analysis of small clinical trials in hospitalized infants born prematurely suggests that receiving enteral zinc supplementation at a dose of up to 10 mg daily reduces mortality and might improve short-term weight gain when compared with placebo (105687). Another meta-analysis of small clinical studies in preterm infants shows that adding zinc to formula or to a multivitamin seems to modestly increase infant weight and height and improve motor development when compared with control (105676). A larger meta-analysis of 14 clinical trials in preterm or low birth weight infants receiving breastmilk shows that zinc supplementation, typically 5-7 mg daily started at birth and continued for up to 12 months with or without other micronutrients, increases weight by around 380 grams, length by around 3 cm, and head circumference by around 0.6 cm when compared with control. However, zinc supplementation did not improve mental or psychomotor development or reduce the risk of mortality, hospitalization, acute respiratory infection, or sepsis when compared with control (109455). These analyses are limited by imprecision as well as a high risk of bias in some of the included studies. Some of the discrepant findings may be due to differences in patient populations (hospitalized, non-hospitalized), milk sources (breastfed, formula-fed, or both), and duration of follow-up.
Pressure ulcers. Topical zinc paste seems to work as a skin barrier and improve pressure ulcer healing. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that applying zinc oxide paste to pressure ulcers daily for 8 weeks reduces necrotic tissue and decreases the surface area of skin pressure ulcers similarly to using a topical streptokinase-streptodornase product (Varidase) (87331). Other small clinical studies show that applying zinc oxide paste to pressure ulcers daily for 8-12 weeks improves healing similarly to a hydrocolloid dressing (Duoderm) (87181) or a specific barrier film product (Cavilon No Sting Barrier Film) (87017). Oral zinc has been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients shows that administering an oral nutritional supplement enriched with zinc, L-arginine, and vitamin C improves ulcer healing when compared with a standard diet (31953,87173). Also, clinical research in patients living in long-term care facilities shows that taking an oral nutritional supplement enriched in protein, zinc, L-arginine, and vitamin C daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
Sickle cell disease. Oral zinc seems to improve symptoms of sickle cell disease in patients with zinc deficiency. Details: Taking zinc orally seems to help reduce symptoms of sickle cell disease in people with zinc deficiency (6594,6595,6596,8626,87343). Taking zinc supplements also seems to decrease the occurrence rate of sickle-cell crises and infections (6594,6596,90228). Additionally, zinc might reduce the number of hospitalizations for sickle cell crises, although the severity of the crises that do develop is not necessarily decreased by taking zinc supplements (6594,6596). In prepubertal children and adolescents with homozygous sickle cell disease, taking zinc seems to improve growth, height, and weight gain (8626,87403).
Warts. Oral and topical zinc seem to improve the cure rate of cutaneous warts. Details: A small clinical study suggests that applying zinc sulfate 10% solution three times daily for 4 weeks improves plane warts, but not common warts, when compared with distilled water (87094). Another small clinical study suggests that applying topical zinc oxide 20% ointment twice daily for up to 3 months seems to have a similar cure rate as ointment containing salicylic acid 15% with lactic acid 15% (87082). Taking zinc orally may also be effective in treating warts (87227). A meta-analysis of low quality clinical studies shows that taking zinc sulfate orally improves the odds of curing cutaneous warts nearly 17-fold when compared with respective controls (87227). Preliminary clinical research in adults treated with cryotherapy for anogenital warts shows that taking zinc gluconate 30 mg orally three times daily for 2 months does not reduce the number of warts when compared with placebo (111445).

Alopecia areata. Oral zinc does not seem to improve symptoms of this condition. Details: Although there is preliminary evidence that suggests zinc in combination with biotin might be helpful for alopecia areata (6932), most studies indicate that zinc is not effective for alopecia areata, alopecia totalis, or alopecia universalis (6931,6932).
Cystic fibrosis. Oral zinc does not improve cystic fibrosis symptoms or progression. Details: Clinical research shows that taking supplements providing 30-90 mg of elemental zinc for 6 weeks to one year does not improve lung function when compared with placebo in children and adolescents with cystic fibrosis (87066,87113,96079). One clinical study also shows that taking elemental zinc for one year does not reduce the number of days requiring oral or intravenous antibiotics for pulmonary infections (96079). However, one study shows that taking zinc can reduce the number of days of oral antibiotic use when compared with placebo (87113).
HIV/AIDS. Oral zinc does not seem to improve outcomes in patients with HIV. Details: Clinical research in adult HIV patients with normal or low zinc levels shows that taking elemental zinc 12-15 mg daily orally for 18 months along with antiretroviral therapy does not improve viral load, CD4/8 counts, or mortality when compared with placebo (87036,87216,105686). In children with HIV-1, clinical research shows that administering zinc sulfate, providing 10 mg elemental zinc, daily for 6 months does not improve mortality, viral load, or CD4 counts when compared with placebo (82377).
HIV/AIDS-related pregnancy complications. Oral zinc does not prevent pregnancy complications related to HIV infection. Details: Adding zinc 25 mg orally during pregnancy does not seem to reduce parent-to-child vertical transmission of HIV, infant mortality, birth weight, or gestational period in HIV-infected females with low zinc levels (11054,87034). Also, one clinical study in HIV-1-infected pregnant patients suggests that supplemental zinc can increase the risk of wasting, as assessed by weight and mid-upper arm circumference, by 170% when compared with placebo (87034).
HIV/AIDS-related wasting. Oral zinc does not seem to improve HIV-related wasting syndrome. Details: A clinical study in patients with HIV-related wasting syndrome shows that taking zinc orally in combination with vitamins and albendazole does not seem to improve diarrhea or mortality when compared with taking albendazole alone (6564).
Infant development. Oral zinc does not seem to improve infant mental and psychomotor development. Details: Clinical research, including a meta-analysis of eight studies, shows that giving zinc to infants or children at high risk for zinc deficiency does not improve mental and psychomotor development when compared with placebo (87013,90209). In another meta-analysis of studies in children whose baseline zinc status was not specified, there was no beneficial effect of zinc supplementation on mental or psychomotor development at 6 or 12 months of age (104817).
Inflammatory bowel disease (IBD). Oral zinc does not improve symptoms of IBD. Details: Some clinical research shows that taking zinc orally does not seem to help treat IBD (6913,6915,6916).
Influenza. Oral zinc does not seem to reduce the risk for influenza. Details: Supplemental zinc seems to improve cell-mediated immune response in elderly people (824), but it does not seem to have a significant effect on antibody response and incidence of influenza infection after the vaccine (6553,6563). Additionally, zinc supplementation in patients on hemodialysis, who have a high risk of zinc deficiency, does not seem to improve response to influenza vaccine (10809). Taking zinc supplements orally is unlikely to improve immune function in people without risk factors for zinc deficiency (10789). However, there is preliminary evidence that suggests zinc along with selenium might reduce the incidence of infections in institutionalized older patients (8921).
Otitis media. Oral zinc does not prevent otitis media in children. Details: A meta-analysis of clinical research shows that taking elemental zinc 3-70 mg daily for up to 24 months does not prevent the occurrence of ear infections in children from low- or middle-income countries (87258).
Pre-eclampsia. Oral zinc taken prenatally does not seem to be beneficial for pre-eclampsia prevention. Details: A meta-analysis and a large clinical study show that zinc supplementation during pregnancy does not reduce the risk of pre-eclampsia when compared with placebo (97142,105679).
Prostate cancer. Oral zinc does not reduce the risk for prostate cancer or prostate cancer-related mortality. Details: Some epidemiological research has found an inverse relationship between dietary zinc intake and prostate cancer (96075). Also some clinical research shows that taking zinc 20 mg in combination with vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, and selenium 100 mcg daily for an average of 8 years might reduce the risk of prostate cancer in men with normal PSA levels; however, it does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). However, some evidence raises concern that zinc might actually INCREASE the risk of prostate cancer. A large-scale population study found that taking more than 100 mg of supplemental zinc daily or taking supplemental zinc for 10 or more years doubles the risk of developing prostate cancer (10306). Another large-scale population study shows that men who take a multivitamin more than seven times per week and who also take a separate zinc supplement have a significantly increased risk of prostate cancer-related mortality (15607). Despite these studies suggesting the potential for adverse effects of zinc, a meta-analysis of mainly population research has found that there is no association between zinc intake and the risk of prostate cancer (96075).
Psoriasis. Oral zinc does not reduce the severity of psoriasis symptoms. Details: Zinc epidermal levels are reportedly lower in people with psoriasis (6509). However, taking zinc orally does not seem to help treat psoriasis (6513,6514,6912,87363). Zinc supplementation has no effect on the psoriasis area and severity index (6513,6514).
Rheumatoid arthritis (RA). Oral zinc does not treat symptoms of RA. Details: Multiple clinical studies in patients with RA show that taking zinc orally does not improve function or symptoms when compared with baseline or control (6517,6518,6519,87406).
Sexual dysfunction. Oral zinc does not improve sexual function in males with chronic kidney disease (CKD). Details: Clinical research shows that zinc supplementation does not improve sexual activity or libido when compared with placebo in males with sexual dysfunction secondary to CKD (6708,6568,87220,87386,87416). In fact, one clinical study shows that taking zinc can decrease the frequency of intercourse by 76% when compared with placebo in patients with CKD-related sexual dysfunction (87220).
Tinnitus. Oral zinc does not improve severity of tinnitus or reduce tinnitus-related disability. Details: A meta-analysis of three small clinical trials in adults with tinnitus shows that taking elemental zinc 50 mg daily for up to 16 weeks does not improve tinnitus severity, or disability from tinnitus when compared with placebo (104051).

Malaria. Oral zinc does not prevent or treat malaria in undernourished children or pregnant adults in developing countries. Details: A meta-analysis of clinical research in children or pregnant adults shows that taking zinc orally, alone or in combination with other supplements, for does not reduce the risk of malaria parasitemia (111444). A large multi-country study in zinc-deficient preschool children with acute malaria shows that taking zinc supplements does not affect fever, parasitemia, or hemoglobin when compared with placebo (10246). An even larger clinical study of over 40,000 children with malaria aged 1-36 months shows that taking zinc 5-10 mg daily orally for approximately 17 months does not reduce mortality when compared with placebo (87078). Zinc supplements also do not appear to protect against infection by Plasmodium falciparum (8638,87235,86937). However, one small study in children with low and high levels of parasitemia shows that taking zinc 10 mg daily for 46 weeks may lower the incidence of fever episodes by 38% and 69%, respectively, when compared with placebo (86937).

Age-related cognitive decline. It is unclear if oral zinc is beneficial in patients with age-related cognitive decline. Details: An epidemiological study based on elderly adults enrolled in the National Health and Nutrition Examination Survey (NHANES) has found that taking zinc may improve cognition in a non-linear manner. Daily doses below 9 mg and 8 mg in males and females, respectively, showed a positive association with cognitive function, but doses above that level showed no association. Additionally, high intake of both zinc and selenium was associated with improved cognition in females, but not in males (108446). Dietary intake was collected from two patient-reported 24-hour recalls and cognition was only measured once, limiting the validity of these findings.
Alcohol-related liver disease. It is unclear if oral zinc is beneficial in patients with alcoholic-related liver cirrhosis. Details: A small clinical study in patients with alcoholic liver cirrhosis shows that taking zinc sulfate 600 mg daily for 6 weeks improves liver function, based on increased alkaline phosphatase activity and reduced serum bilirubin, when compared to baseline (87325).
Anorexia nervosa. Oral zinc seems to improve weight gain in people with anorexia nervosa. Details: Anorexia nervosa might be linked with zinc deficiency. Small clinical trials in adolescents and adults with anorexia nervosa show that oral zinc supplements might help increase weight gain and improve depressive symptoms when compared with placebo (6905,6906).
Arsenic poisoning. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking zinc 4 mg in combination with spirulina extract 500 mg daily for 16 weeks can decrease skin manifestations and reduce arsenic levels in the urine and in hair of patients with chronic arsenic poisoning (18301).
Asthenopia (eye strain). Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults without dry eye disease shows that taking a specific combination product containing zinc 10 mg, L-carnitine 50 mg, elderberry fruit extract 300 mg, currant 100 mg, and Eleutherococcus root 50 mg (Meramirt CM) orally once daily for 1 month improves measures of eye strain and contrast sensitivity when compared to baseline. Improvements in these measures were lacking in the control group (111295). Statistical comparison between the two groups was not reported. It is unclear if these effects are due to zinc, other ingredients, or the combination.
Athletic performance. Although there is interest in using oral zinc for athletic performance, there is insufficient reliable information about the effects of zinc for this purpose.
Atopic dermatitis (eczema). It is unclear if oral zinc is beneficial for alleviating eczema in children. Details: A small clinical study in children with eczema shows that taking zinc sulfate 185.4 mg orally daily for 8 weeks does not appear to improve the surface area affected and degree of erythema, symptom scores of itch and sleep disturbance, or topical steroid use when compared with placebo. Also, plasma zinc levels appear to be normal in children with eczema (6911).
Attention deficit-hyperactivity disorder (ADHD). Oral zinc might improve certain symptoms in children with ADHD. Details: Observational research has found that lower serum zinc levels are both more prevalent in children with ADHD and are linked to worsened response to stimulant therapy (9965,9966,9967). Based on this evidence, there is some interest in using zinc to improve symptoms in children with ADHD. A meta-analysis of six small clinical trials shows that although taking zinc modestly improves overall symptoms of ADHD when compared with placebo, there is no effect on hyperactivity or inattention when these outcomes are examined separately. The sub-analyses conducted for these two separate outcomes included only 3 studies. Most, but not all, of the included studies were conducted in children also receiving methylphenidate treatment (106240). Elemental zinc, usually as sulfate, was typically used in doses of 10-40 mg daily for 6-12 weeks (11350,12060,106240). There is some evidence that zinc could be most helpful in children with a high body mass index (BMI), low zinc levels, and low free fatty acid levels (11350). It is unclear if zinc is beneficial in children who are not already taking stimulant medications. One clinical guideline also provisionally recommends against use of oral zinc to treat patient with ADHD based on low-quality evidence (110318).
Autism spectrum disorder. It is unclear if oral zinc is beneficial in children with autism spectrum disorder. Details: One small clinical study conducted in children with autism spectrum disorder shows that taking zinc 15-30 mg orally, alone or as add-on therapy to amphetamine, does not improve attention deficit hyperactivity disorder (ADHD) symptoms when compared with placebo (98711). However, the optimal mg/kg dose of amphetamine was shown to be 37% lower for those children also taking zinc 15 mg twice daily when compared with those taking placebo (98711).
Behcet disease. It is unclear if oral zinc is beneficial in patients with Behcet disease. Details: A small clinical trial in patients with Behcet disease shows that taking zinc gluconate 30 mg daily for 12 weeks does not improve disease activity scores, quality of life, or measures of inflammation when compared with placebo (109453).
Benign prostatic hyperplasia (BPH). Although there is interest in using oral zinc for BPH, there is insufficient reliable information about the clinical effects of zinc for this condition.
Beta-thalassemia. It is unclear if oral zinc is beneficial in patients with beta-thalassemia major. Details: A small clinical study in children recently diagnosed with beta-thalassemia major shows that initiating zinc sulfate in addition to standard blood transfusions increases linear growth rate when compared with transfusions alone (87329). Another small clinical study in adult and pediatric patients with thalassemia major and low bone mass shows that taking zinc 25 mg daily (as zinc sulfate) for 18 months improves whole-body bone mineral content, as well as hip and spine bone mineral density, by small amounts when compared with placebo (90208).
Brain tumor. It is unclear if dietary zinc is beneficial for reducing the risk for brain cancer. Details: Population research has found that zinc intake is not associated with a reduced risk of developing brain cancer (87098).
Breast cancer. It is unclear if increased dietary zinc intake is beneficial for reducing the risk for breast cancer. Details: Population research has found that neither zinc intake nor blood levels of zinc are associated with a reduced risk of breast cancer (106229).
Bronchiolitis. It is unclear if oral zinc is beneficial for viral bronchiolitis in infants and children. Details: A small clinical study in children 2 years or younger with acute viral bronchiolitis shows that taking elemental zinc 10-20 mg as zinc sulfate for 5 days improves clinical recovery and reduces the duration of hospital stay by almost one day when compared with placebo. After 72 hours, 98% of infants and children taking zinc were considered fully recovered, compared to only 52% of infants taking placebo (96076).
Burning mouth syndrome. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with burning mouth syndrome shows that taking zinc 15 mg and vitamin C 35 mg once daily, along with a vitamin B complex twice daily, for 30 days modestly decreases pain and burning when compared to baseline (105195). The validity of this finding is limited by the lack of a comparator group. Furthermore, it is unclear if the benefit is due to zinc, other vitamins, or the combination.
Burns. Intravenous zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. The effects of oral zinc for burn healing are unclear. Details: Administering zinc intravenously in combination with other minerals seems to improve the outcomes of burn patients. Supplementation with zinc, copper, and selenium appears to improve wound healing, reduce pulmonary infections, and shorten intensive care unit stay in patients with serious burns (6520,87085). The effect of supplementation with zinc alone is unclear.
Canker sores. It is unclear if oral zinc is beneficial in patients with canker sores. Details: Evidence for the use of zinc in canker sores is conflicting. A small clinical crossover study in patients with recurrent canker sores shows that taking zinc sulfate 660 mg daily for 3 months does not improve the size or frequency of canker sore ulcers when compared with control (6592). However, another clinical study in patients with recurrent sores and low or normal zinc levels shows that taking zinc sulfate 220 mg daily for 1 month reduces recurrence of sores when compared with placebo (86964). Reasons for conflicting results are unclear. Zinc might be beneficial when used in a muco-adhesive formulation. A small clinical study in patients with canker sores shows that taking a muco-adhesive zinc sulfate 5 mg tablet three times daily for 7 days reduces pain and speeds up healing when compared with placebo (104048).
Cataracts. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking zinc orally in combination with antioxidant vitamins does not seem to help treat or prevent cataracts. Taking elemental zinc 80 mg plus vitamin C 500 mg, vitamin E 400 IU, and beta-carotene 15 mg daily does not seem to have any effect on the development or progression of age-related lens opacities (cataracts) or the need for cataract surgery in well-nourished people 55-80 years of age. However, it is unknown whether earlier intervention and/or a longer period of treatment with supplements would have any effect on cataracts (7304).
Chemotherapy-induced acral erythema. It is unclear if oral zinc reduces the severity of acral erythema induced in patients treated with the vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs) treatment regorafenib. Details: A small study in patients with metastatic colorectal cancer undergoing treatment with regorafenib shows that taking zinc gluconate 78 mg twice daily reduces the proportion of patients with more severe acral erythema when compared with control. Though there is no association in the zinc treatment group, lower serum zinc levels seem to correlate with more severe acral erythema in the control group, suggesting a possible role of zinc deficiency in the pathogenesis of acral erythema (112472). The validity of this study is limited by the lack of blinding.
Chemotherapy-related fatigue. It is unclear if oral zinc improves symptoms in patients with fatigue due to chemotherapy. Details: A small clinical study in patients undergoing 4 or more cycles of chemotherapy for colorectal cancer shows that taking zinc 70 mg daily for 16 weeks does not improve fatigue or quality of life when compared with placebo (97141).
Chronic fatigue syndrome (CFS). Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females with CFS shows that taking zinc 10 mg as zinc sulfate plus melatonin 1 mg daily for 16 weeks modestly reduces self-reported symptoms of physical fatigue when compared with placebo. However, there was no effect on cognitive or psychological symptoms, sleep, or symptoms of anxiety or depression (106241). This study may not have been adequately powered to detect differences between groups.
Cirrhosis. It is unclear if zinc is beneficial for reducing cirrhosis-related mortality. Details: A meta-analysis of four small clinical trials shows that zinc supplementation does not seem to reduce mortality in patients with cirrhosis when compared with control (104054). This finding is limited due to the heterogeneity and small size of the available studies.
Cognitive function. It is unclear if zinc is beneficial for cognitive function. Details: A very small clinical study in adults with overweight and obesity shows that taking supplemental zinc 30 mg daily for 12 weeks improves some measures of cognitive function and executive processing but does not improve verbal fluency when compared with placebo (112471). Zinc has also been evaluated in combination with other ingredients. A small clinical trial in healthy adults shows that taking a specific product containing a combination of zinc 9 mg, Lactobacillus helveticus, Lactiplantibacillus plantarum, Bifidobacterium longum, and other ingredients (Puraflor, GSK Consumer Healthcare, Milano, Italy) orally daily for 4 weeks does not affect cognitive performance during acute stress when compared with placebo (110923).
Colorectal adenoma. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large clinical study shows that taking a combination supplement containing zinc 30 mg, selenium 200 mcg (as l-selenomethionine), vitamin A 2 mg (as retinol), vitamin C 180 mg, and vitamin E 30 mg (as D-a-tocopherol acetate) by mouth daily for 5 years or until the recurrence of an adenoma reduces the risk of recurrent large-bowel adenomas by approximately 40% when compared with placebo (92903). It is not clear if the benefit is due to zinc, other supplements, or the combination.
Colorectal cancer. It is unclear if oral zinc is beneficial for reducing colorectal cancer risk. Details: Population research has found that increased intake of zinc is associated with a 17% to 20% reduced risk of colorectal cancer (90213,90220).
Congenital heart disease. It is unclear if oral zinc is beneficial for reducing the risk of congenital heart defects. Details: An observational study in pregnant adults has found that consuming the recommended nutritional intake of zinc may be associated with a lower risk of total congenital heart defects in infants, including atrial and ventricular septal defects, when compared with low zinc intake. This association appears to persist despite copper or selenium intake (108445).
Critical illness (trauma). It is unclear if oral zinc is beneficial for critically ill patients. Details: A meta-analysis of two small randomized clinical trials in adults with head trauma shows that supplementing zinc, given as 120 mg elemental zinc orally daily or 12 mg elemental zinc intravenously daily for 15 days to 3 months, regardless of serum zinc levels, does not improve the risk of 30-day mortality when compared with control (111290). However, the study may have been inadequately powered to detect a difference between groups.
Dementia. Although there is interest in using oral zinc for dementia, there is insufficient reliable information about the clinical effects of zinc for this condition.
Diabetic foot ulcers. Although there is interest in using oral zinc for diabetic foot ulcers, there is insufficient reliable information about the clinical effects of zinc for this condition.
Diabetic neuropathy. It is unclear if oral zinc is beneficial in patients with diabetic neuropathy. Details: A small clinical study in patients with poorly-controlled diabetic neuropathy shows that taking zinc sulfate 660 mg daily for 6 weeks improves motor nerve conduction velocity and reduces fasting and postprandial blood sugar when compared to baseline (86933). The validity of this finding is limited by the lack of statistical comparison to the control group.
Down syndrome. It is unclear if oral zinc is beneficial for improving immune function in people with this condition. Details: A very small clinical study in Down syndrome patients with zinc deficiency shows that taking zinc sulfate 1 mg/kg daily for 2 months seems to improve immune function and reduce recurrent infections when compared with baseline (87289). The validity of this finding is limited by the lack of a control group. Another small clinical study in children with Down syndrome shows that zinc 25-50 mg daily for 6 months does not improve immune function when compared with placebo (87278). Reasons for the discrepancies may be related to the dose of zinc or zinc status at baseline.
Dysmenorrhea. It is unclear if oral zinc is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research in females aged 13 to 21 years with primary dysmenorrhea shows that taking zinc sulfate 40 mg orally daily for the first 3 days of menstruation for three cycles reduces mean pain scores by 51% when compared with placebo (111446).
Epilepsy. There is limited evidence on the oral use of zinc in children with intractable seizures. Details: A small clinical study in children with intractable epilepsy shows that taking elemental zinc 1 mg/kg daily as zinc sulfate heptahydrate for 6 months reduces seizures when compared with placebo. About 31% of children taking zinc experienced a 50% decrease in seizure frequency, compared to only 5% of children taking placebo (96078).
Esophageal cancer. It is unclear if oral zinc is beneficial for esophageal cancer prevention. Details: Population research in Chinese and Iranian patients has found that low intake of zinc is associated with an increased risk of esophageal squamous cell cancer (17205,87059). However, other population research in patients from America, Europe, or Asia has found that dietary zinc intake is not associated with esophageal cancer risk (90213).
Fatigue. It is unclear if oral zinc is beneficial for reducing fatigue in older individuals. Details: A clinical study in adults 50 years and older, some with below-normal levels of zinc at baseline, shows that taking zinc 30 mg daily for 70 days improves subjective fatigue when compared with no intervention (105675). The validity of this finding is limited due to a lack of placebo control and potential performance bias. Additionally, it is unclear whether baseline zinc status alters the benefits of zinc supplementation.
Fecal incontinence. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in females with fecal incontinence shows that topically applying an ointment containing zinc sulfate 1% and aluminum sulfate 5% to the anal canal mucosa three times daily for 4 weeks improves symptoms approximately twice as much as a placebo ointment. Quality of life related to the incontinence also improved (90219).
Gastric cancer. It is unclear if dietary zinc is beneficial for gastric cancer prevention. Details: Population research has found that increased dietary zinc intake is not associated with a decreased risk of gastric cancer (90213).
Head and neck cancer. It is unclear if oral zinc improves survival in patients with head and neck cancers. Details: Preliminary clinical research in patients with head and neck cancers shows that zinc supplementation does not improve disease-free or metastasis-free survival rates after 3 years when compared with placebo (87103).
Hepatic encephalopathy. It is unclear if oral zinc is beneficial for reducing the severity of hepatic encephalopathy or preventing recurrence. Details: A meta-analysis of small clinical studies, as well as some individual clinical studies, show that short-term zinc supplementation improves cognitive function and possibly quality of life in patients with hepatic encephalopathy. These findings are based on results from the number connection test and other tests (87377,90202,106227). One study in patients with minimal hepatic encephalopathy used zinc bisglycinate 75 mg three times daily, providing elemental zinc 45 mg daily for 12 weeks (106227). However, other preliminary clinical research shows that short-term zinc supplementation does not improve hepatic encephalopathy severity when compared with placebo when assessed using Conn's index, which includes evaluation of mental state, asterixis (flapping tremor), number connection test, electroencephalogram (EEG) record, and plasma ammonia (87144). Also, a meta-analysis of clinical research shows that zinc sulfate supplementation does not reduce encephalopathy recurrence (90202). Based on these results, zinc supplementation may marginally improve cognitive function in hepatic encephalopathy patients, but it does not appear to improve disease severity or reduce the risk of recurrence.
HIV/AIDS-related diarrhea. It is unclear if oral zinc is beneficial for preventing diarrhea in adult HIV patients. Details: Short-term zinc supplementation does not appear to TREAT diarrhea in adult HIV patients with persistent diarrhea. Clinical research shows that taking zinc 50 mg twice daily for 7 days does not reduce the duration of HIV-related diarrhea when compared with placebo (87055). However, zinc supplementation may help PREVENT HIV-related diarrhea when administered long-term. Clinical research shows that taking elemental zinc 12-15 mg daily for 18 months reduces the rate of diarrhea by about half when compared with placebo in adult HIV patients with zinc deficiency (87216). In HIV-infected children, clinical research shows that taking elemental zinc 10 mg daily for 6 months can reduce the occurrence of diarrhea by 49% when compared with placebo (82377). However, administering zinc in combination with vitamin A until 2 years of age does not reduce the occurrence of diarrhea when compared with vitamin A alone in HIV-infected children (82417).
HIV/AIDS-related opportunistic infections. It is unclear if oral zinc is beneficial in opportunistic infections in patients with HIV/AIDs. Details: A small clinical study in patients with AIDS shows that taking zinc supplements orally in combination with zidovudine (AZT, Retrovir) might reduce opportunistic infections of Pneumocystis carinii and Candida when compared with taking zidovudine without zinc (6566).
Human papillomavirus (HPV). It is unclear if oral zinc is beneficial for preventing relapse in patients with vulvar warts or for treating HPV infections and cervical lesions in patients with abnormal cervical cytology. Details: One small clinical study in patients with vulvar warts shows that taking zinc sulfate 400 mg daily for 8 weeks in addition to topical treatments including podophyllin 20%, imiquimod 5%, or cryotherapy, does not affect the duration of response, but does reduce the relapse rate by approximately 66% after 6 months, when compared with topical treatments alone (90190). Additionally, a small, open-label study in zinc-sufficient females with HPV shows that taking zinc sulfate 220 mg twice daily for 3 months reduces the odds of persistent HPV infection by 87% and improves the resolution of pre-existing cervical lesions when compared with no treatment (109456).
Hypertension. It is unclear if oral zinc reduces blood pressure in normotensive or hypertensive patients. Details: A meta-analysis of small clinical trials shows that taking zinc reduces systolic blood pressure by about 1.5 mmHg, but does not reduce diastolic blood pressure, when compared with placebo. Response did not differ with the dosage of zinc or duration of supplementation. Only one study evaluated patients with hypertension; other patient populations included those with type 2 diabetes, diabetic retinopathy, pre-diabetes, obesity, polycystic ovary syndrome (PCOS), and patients on dialysis (104052). More research in patients with hypertension is needed to determine if zinc is beneficial in this population.
Impaired glucose tolerance (prediabetes). While some conflicting evidence exists, several small clinical studies suggest that oral zinc may improve glycemic control in patients with prediabetes. Details: A meta-analysis of three low-quality studies in patients with prediabetes suggests that taking zinc sulfate 20-30 mg, alone or in combination with lysine and vitamin C, for 6-12 months reduces fasting blood glucose and postprandial glucose when compared with control (105682). Furthermore, a small clinical study in patients with prediabetes shows that taking zinc gluconate 30 mg daily for 90 days improves glycemic parameters when compared with placebo. All study participants were also instructed to increase physical activity and start a calorie-restricted diet (105391). However, another small clinical study in patients with prediabetes shows that taking zinc gluconate 30 mg daily for 12 months does not improve glycemic parameters when compared with placebo (109454). The available research has been conducted in Sri Lanka, Bangladesh, Iran, and Australia; it is unclear if these findings are generalizable to other geographic locations.
Intestinal parasite infection. It is unclear if oral zinc is beneficial in patients with intestinal parasitic infections. Details: Zinc supplementation may help TREAT infection from Schistosoma mansoniin, but not other parasites, in children in developing countries. Results from one clinical study show that taking oral zinc sulfate 30-50 mg for 12 months reduces the intensity of Schistosoma mansoniin infection in children, as measured by number of eggs per gram in feces, when compared with placebo (87495). However, supplementation with zinc does not appear to reduce the intensity of Ascaris lumbricoides, Trichiuris trichura, nor Giardia lamblia infection in children (6586). Furthermore, preliminary clinical research suggests that supplementation with zinc may increase the duration of Entamoeba histolytica infection in children (87099). There are also inconsistent results regarding the effects of zinc in PREVENTING intestinal parasite infections. Some clinical research shows that taking zinc in combination with vitamin A reduces the incidence of Giardia lamblia infections when compared with placebo (87099). However, zinc supplementation does not appear to prevent intestinal infections by Ascaris lumbricoides, Schistosoma haematobium, nor Schistosoma mansoniin (87099,87495).
Kidney failure. It is unclear if oral zinc is beneficial for patients on hemodialysis who have resistance to erythropoiesis-stimulating agents (ESAs). Details: Zinc deficiency is thought to play a role in ESA-resistant anemia in patients with kidney failure. A small clinical trial in patients on hemodialysis with low zinc levels shows that taking zinc acetate hydrate, usually 25mg or 50 mg daily, for 12 months increases plasma levels of zinc and modestly reduces the required weekly dose of ESAs when compared with placebo. However, there was no effect on hemoglobin levels (109781).
Leukemia. It is unclear if oral zinc is beneficial for improving weight maintenance in children and adolescents with leukemia. Details: A small clinical study in children and adolescents with acute leukemia shows that taking zinc 2 mg/kg (as an amino acid salt) in two divided doses daily for 60 days doubles weight gain and reduces infection rate by approximately 60% when compared with placebo. However, zinc supplementation does not appear to improve nutritional status (90204).
Liver cancer. It is unclear if oral zinc is beneficial for preventing hepatocellular carcinoma (HCC). Details: In patients treated for hepatitis C, the presence of hepatic fibrosis increases the risk for development of HCC, and is also associated with low plasma zinc levels. In a retrospective analysis of patients with a sustained virological response to hepatitis C therapy, those taking oral zinc supplements for at least 6 months had approximately half the risk of developing HCC when compared with those not taking zinc. Maintaining a serum zinc level above 90 mcg/dL seems to reduce the risk for HCC (106904).
Lung cancer. It is unclear if increased dietary zinc intake is beneficial for reducing the risk of lung cancer. Details: Population research has found that the highest dietary intake of zinc is associated with a 32% reduced risk of lung cancer when compared with the lowest intake (106235).
Male infertility. It is unclear if oral zinc is beneficial for infertility in males. Details: Some preliminary clinical research shows that taking zinc sulfate 66 mg daily increases sperm count, testosterone levels, and the incidence of pregnancy in idiopathic infertile men with low testosterone levels (9334,87430). Another clinical study shows that taking zinc sulfate 66 mg daily can improve sperm morphology by approximately 33% when compared to baseline in men with a grade III varicocele (90194). However, not all research agrees. One clinical study shows that taking elemental zinc 30 mg with folic acid 5 mg daily for 6 months does not improve sperm morphology or pregnancy rates when compared with placebo in infertile men (102085). It is possible the lower dose used in this study was insufficient to produce the beneficial effects observed in earlier research. Zinc supplementation has also been studied as part of combination therapy. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, vitamin C 90 mg, coenzyme Q10 20 mg, folic acid 0.2 mg, selenium 0.05 mg, and vitamin B12 0.015 mg (Proxeed Plus, Sigma-Tau) orally twice daily for 6 months improves sperm count, sperm concentration, and sperm motility when compared with baseline. Improvements in semen parameters were greatest in subjects with more severe varicoceles. The validity of this study is limited by the lack of a comparator group (111296). There is also interest in using zinc to improve results of in vitro fertilization (IVF). A small clinical study in couples undergoing IVF suggests that infertile male partners who take a specific combination product (Menevit) containing zinc and other antioxidants seem to have an increased rate of viable pregnancies when compared with placebo (87087). However, it's unclear if the benefit can be attributed to zinc, other antioxidants, or the combination.
Melasma. It is unclear if topical zinc reduces melasma severity. Details: A small clinical study shows that applying a topical solution containing zinc sulfate 10% once daily for 2 months is less effective at reducing melasma severity when compared with hydroquinone 4% (90232).
Menopausal symptoms. It is unclear if oral zinc improves sexual function after menopause. Details: A single clinical trial shows that taking zinc sulfate 110 mg daily for 6 weeks modestly improves testosterone levels and sexual function, including desire, arousal, satisfaction, and pain, after menopause when compared with placebo (106228).
Migraine headache. It is unclear if oral zinc is beneficial in patients with migraine. Details: Two small clinical studies in patients with migraine show that taking zinc sulfate 200 mg or zinc gluconate 15 mg daily for 8-12 weeks modestly reduces migraine severity and frequency when compared with placebo (104040,105684). Both studies were conducted in Iran; it is unclear if these findings are generalizable to other geographic locations.
Nasopharyngeal cancer. It is unclear if oral zinc is beneficial in patients with this type of cancer. Details: A small clinical study in patients with locally advanced nasopharyngeal cancer shows that zinc supplementation 75 mg daily for 2 months may improve disease-free survival rates after 5 years when compared with placebo (87163).
Neonatal jaundice. It is unclear if oral zinc is beneficial for neonatal jaundice. Details: Two small clinical studies in infants with idiopathic neonatal hyperbilirubinemia show that receiving oral zinc sulfate 5 mg twice daily for 5-7 days does not affect levels of total bilirubin, the required duration of phototherapy, or the duration of hospitalization, when compared with placebo (90212,104814). A larger clinical trial suggests that this lack of effect may be due to the need for a longer treatment duration. In preterm infants receiving phototherapy and zinc 1.2 mg/kg daily as zinc sulfate heptahydrate, via either orogastric or nasogastric tube for 10 days, serum bilirubin levels were modestly decreased only on days 8-10 when compared with phototherapy alone (106242).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral zinc is beneficial in patients with NAFLD. Details: A small clinical study in patients with NAFLD shows that following a calorie-restricted diet and taking zinc 30 mg daily for 12 weeks reduces certain liver enzymes, but does not improve steatosis or reduce weight, when compared with taking placebo and following a calorie-restricted diet (104046).
Non-Hodgkin lymphoma. It is unclear if oral zinc is beneficial for non-Hodgkin lymphoma prevention. Details: Population research has found that higher dietary intake of zinc is associated with a 42% decreased odds of developing non-Hodgkin lymphoma (87048).
Obesity. Small studies suggest that oral zinc does not reduce weight or calorie intake in people with overweight or obesity. Details: A very small clinical study in adults with overweight or obesity shows that taking supplemental zinc 30 mg daily for 12 weeks does not reduce body weight, body mass index (BMI), calorie intake, or macronutrient intake when compared with placebo (112471). Additionally, clinical research in adults with overweight or obesity shows that taking zinc gluconate 25 mg and L-selenomethionine 200 mcg once daily for 8 weeks does not improve BMI, total body fat, or fat free mass when compared with placebo (111448).
Obsessive-compulsive disorder (OCD). It is unclear if oral zinc reduces symptoms in patients with OCD. Details: A small clinical study in patients with OCD shows that taking zinc sulfate 200 mg twice daily with fluoxetine 20 mg daily for 8 weeks modestly reduces the severity of OCD symptoms when compared with taking placebo with fluoxetine (90223).
Oral mucositis. It is unclear if oral or topical zinc prevents oral mucositis due to chemotherapy. Some small clinical studies suggest that oral zinc might prevent mucositis due to radiotherapy. Details: Two small clinical studies in adults with leukemia and other cancers shows that taking zinc sulfate 220 mg three times daily for 14 days or until the end of chemotherapy treatment reduces oral mucositis and pain intensity when compared with placebo (90191,98132). However, smaller doses have not shown benefit. A small clinical study in children and adolescents with leukemia shows that taking zinc 2 mg/kg daily (up to 60 mg daily) in two divided doses does not affect chemotherapy-induced mucositis when compared with placebo (90204). An unblinded clinical study in children and adolescents aged 8-16 years with recently diagnosed leukemia shows that taking zinc gluconate 50 mg (7 mg elemental zinc) daily does not significantly reduce the incidence or duration of oral mucositis when compared with a control group not receiving zinc (104816). Zinc also doesn't seem to be beneficial with high-dose chemotherapy. A small clinical study in adolescents and adults receiving high-dose chemotherapy prior to undergoing hematopoietic stem cell transplantation (HSCT) suggests that taking zinc sulfate 220 mg (50 mg elemental zinc) twice daily, beginning one day prior to the chemotherapy regimen and continuing for 3 weeks, does not affect the severity, duration, or onset of mucositis when compared with placebo (90215). Other preliminary clinical research in children aged 3-18 years receiving chemotherapy for leukemia or other cancer also shows that taking zinc 1 mg/kg orally daily for 14 days, beginning on the first day of chemotherapy, does not reduce the incidence or severity of mucositis when compared with placebo (111447). Topical zinc has also been investigated for radiation-induced or chemotherapy-induced oral mucositis. In two clinical studies, using 7.5 mL of a mouthwash containing zinc chloride 0.2% twice for 2 minutes every 8 hours for 3 weeks modestly reduces the incidence and severity of oral mucositis, and improves quality of life, when compared with a placebo mouthwash (106232,109690). In one study, the average patient weight was higher in the group using the mouthwash containing zinc (106232). Other preliminary clinical research in adults with head and neck cancer undergoing radiotherapy treatment, consisting of at least 30 Gy radiation exposure shows that using zinc sulfate 1% mouthwash, 5 mL three times daily for 6 weeks, beginning on the first day of radiation therapy, moderately improves oral mucositis severity and pain scores when compared with chlorhexidine 0.2% or placebo mouthwash (111291). Taking zinc orally might be beneficial in radiation-induced oral mucositis. A small clinical study in patients with head and neck tumors shows that taking zinc sulfate, providing 150 mg elemental zinc, daily starting at the first day of radiation therapy and ending at 6 weeks, reduces the severity of mucositis and prolongs the onset of mucositis when compared with placebo (86981). Another clinical study in patients with head and neck cancer shows that taking zinc sulfate 150 mg daily during and after chemoradiotherapy treatment, consisting of a total 69.5 Gy radiation exposure and cisplatin 40 mg/m2 weekly, is associated with less severe mucositis when compared with placebo (105677).
Osteoporosis. It is unclear if oral zinc improves bone density in patients with osteoporosis. Details: Population research has found that reduced zinc intake and lower zinc serum levels seem to be associated with lower bone mineral density (BMD) (6920,14410). In elderly patients with at least marginal zinc deficiency who are taking standard therapy for osteoporosis, preliminary clinical research shows that taking zinc acetate dihydrate (Nobelzin, Nobelpharma) providing elemental zinc 25 mg twice daily for 12 months increases BMD when compared with baseline. Increases in serum zinc were associated with improvements in BMD. However, it is unclear if increases in BMD were significant when compared with placebo (106230). It is also unclear if zinc improves BMD in patients without zinc deficiency. A small clinical study in healthy postmenopausal adults suggests that taking zinc in combination with copper, manganese, and calcium might slow bone loss when compared with placebo (1994). It is not clear if this effect is due to zinc, other ingredients, or the combination.
Overall mortality. It is unclear if oral zinc reduces overall mortality in young children. Details: A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc in daily doses of at least 10 mg reduces the risk of all-cause mortality by 16% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation. The risk of mortality was reduced by 54% when children took zinc for up to one year, but overall mortality was not reduced in studies lasting at least one year (106239).
Periodontitis. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a combination supplement containing zinc 3.75 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin C, and vitamin E twice daily for 8 weeks in addition to standard nonsurgical therapy does not reduce periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation when compared with placebo (111708).
Pharyngitis. There is limited evidence on the oral use of zinc for reducing the risk of postoperative sore throat. Details: Clinical research shows that dissolving a lozenge containing zinc 40 mg as zinc sulfate in the mouth in the 30 minutes before surgery involving endotracheal intubation reduces the incidence of postoperative sore throat by 58% when compared with placebo lozenges. It also seems to reduce the severity of postoperative sore throat that does occur (97138).
Polycystic ovary syndrome (PCOS). It is unclear if oral zinc is beneficial in patients with PCOS. Details: A small clinical study in adults taking metformin for PCOS shows that also taking zinc sulfate 220 mg (50 mg elemental zinc) daily for 8 weeks improves hair loss and facial growth, but not acne, when compared with placebo (96071).
Postpartum depression. It is unclear if oral zinc prevents postpartum depression after a Cesarean section (C-section). Details: A small observational study in pregnant patients with anemia who underwent C-section has found that taking zinc sulfate 100 mg daily for 4 days after surgery is associated with a 75% reduction in the odds of developing postpartum depression when compared with no supplementation (109452).
Premenstrual syndrome (PMS). It is unclear if oral zinc improves symptoms in patients with PMS. Details: A small clinical study in female college students shows that taking elemental zinc 30 mg daily for 3 months improves quality of life, but not quality of sleep, when compared with placebo (104049).
Preterm labor. It is unclear if oral zinc reduces the risk of preterm labor. Details: Observational research has found that low dietary intake of zinc during pregnancy is associated with an increased likelihood of preterm deliveries (87471). Also, most meta-analyses of clinical research show that taking zinc supplements during pregnancy modestly reduces the risk of preterm birth (106231). However, one large meta-analysis of 22 clinical studies shows that zinc supplementation during pregnancy seems to have little or no benefit for reducing the risk of preterm birth when compared with control (105679). Zinc supplementation also does not seem to reduce the risk of stillbirth, neonatal death, spontaneous abortion, or premature rupture of membranes (97142,105679,106231).
Prostatitis. It is unclear if oral zinc improves symptoms in men with chronic prostatitis. Details: A clinical study in men with chronic prostatitis shows that taking zinc sulfate 220 mg daily along with prazosin 2 mg daily for 12 weeks does not improve difficulty urinating or quality of life, but does seem to improve pain, when compared with prazosin alone (90210). The validity of this study was limited by a significant dropout rate.
Pruritus. There is limited evidence on the oral use of zinc for reducing pruritis in hemodialysis patients. Details: A small clinical study in end-stage renal disease patients with hemodialysis-associated pruritus shows that taking zinc sulfate 220 mg twice daily for 2 months reduces pruritus severity when compared with placebo (90218).
Psoriatic arthritis. It is unclear if oral zinc improves psoriatic arthritis symptoms. Details: Two small clinical trials in patients with psoriatic arthritis show that taking zinc orally, alone or in combination with nonsteroidal anti-inflammatory drugs (NSAIDs), does not seem to reduce pain or improve function when compared with control (6514,6515).
Respiratory tract infections. It is unclear if oral zinc reduces respiratory tract infections in children. Details: An open-label study in children aged 6 months to 5 years with zinc deficiency shows that taking zinc sulfate 20 mg orally once daily for 2 weeks reduces the number of episodes and the mean duration of upper and lower respiratory tract infections over 6 months of follow-up when compared with the 6 months prior to zinc supplementation (104815). The validity of this finding is limited by the lack of a comparator group.
Rosacea. It is unclear of oral zinc improves symptoms of rosacea or quality of life. Details: A small clinical trial shows that taking zinc sulfate 440 mg in two divided doses daily for 90 days does not improve quality of life or symptoms associated with rosacea when compared with placebo (90195).
Seizures. It is unclear if oral zinc reduces recurrent febrile seizures in children. Details: Although some individual preliminary clinical research disagrees (96069), a meta-analysis of generally low-quality research in children under 5 years of age with a previous febrile seizure shows that taking zinc sulfate 1-2 mg/kg or 20 mg daily for 6-12 months does not reduce febrile seizure recurrence when compared with placebo (106237). Also, a small clinical study shows that taking zinc does not increase the time to first febrile seizure recurrence (96069).
Sepsis. It is unclear if oral zinc is beneficial in sepsis of the newborn. Details: A meta-analysis of clinical research in children under the age of five years shows that supplementation with zinc reduces the risk of sepsis mortality by 57% when compared with either placebo, other vitamin and/or mineral supplementation, or no supplementation (106239). Also, a small clinical study in newborns with sepsis shows that giving zinc sulfate monohydrate 3 mg/kg twice daily for 10 days along with antibiotics reduces the likelihood of neurological abnormalities, such as those related to posture, behavior, and reflexes, by 70% when compared with antibiotics alone. Mortality and length of hospital stay were not improved, but the study may have been inadequately powered to detect a difference in these parameters (96077). Another study in preterm infants with late-onset sepsis (developing at least 72 hours after birth), shows that giving 1.4 mg/kg elemental zinc daily orally for 10 days in addition to antibiotics reduces the number of infants with unresolved sepsis at 10 days, and reduces C-reactive protein and procalcitonin levels, when compared with giving antibiotics alone (104819). A meta-analysis of small clinical studies in infants less than 4 months old shows that administering zinc 1-3 mg/kg daily for 1-18 weeks may reduce the rate of infant mortality and treatment failure when compared with placebo or control, but does not seem to prevent sepsis or improve sepsis-related mortality (108444).
Shigellosis. It is unclear if oral zinc is beneficial in patients with acute shigellosis from food poisoning. Details: A small clinical study in malnourished children with acute shigellosis (food poisoning) shows that administering a multivitamin syrup containing elemental zinc 20 mg daily for 2 weeks, in addition to standard treatment, can improve recovery time and reduce the number of diarrhea episodes when compared with multivitamin syrup without elemental zinc (87088).
Substance use disorder. It is unclear if oral zinc is beneficial for substance use disorder. Details: Preliminary clinical research in adults with opioid use disorder that were being treated with methadone shows that taking zinc sulfate, containing 12 mg zinc, orally daily for 3 months moderately improves relapse prevention scores, including drug use and drug craving scores, when compared with control. Taking zinc also modestly improved stress and anxiety scores (111293).
Traumatic brain injury (TBI). There is limited evidence on the parenteral use of zinc for closed head injury. Details: A small clinical study shows that administering zinc parenterally immediately following severe closed head injury seems to improve the rate of neurological recovery when compared with standard therapy (2696).
Tuberculosis. It is unclear if oral zinc can improve outcomes in patients receiving tuberculosis treatment. Details: Low levels of zinc are common in patients with tuberculosis. In patients newly diagnosed with tuberculosis and using anti-tuberculosis treatment, some clinical research shows that taking zinc 50 mg daily as zinc sulfate for 6 months increases the number of patients with negative sputum smears by 50% to 80% within the first 6 weeks of treatment when compared with placebo. However, there were no differences in the number of patients with negative smears after this time point. There were also improvements in some liver function enzyme levels after 2 months, but not 6 months, when compared with placebo (106238). However, other clinical research shows that taking zinc 15-90 mg daily for 2-6 months does not improve cure rates or sputum smear conversions when compared with placebo. However, when combined with vitamin A, serum levels of vitamin A, zinc, and hemoglobin were modestly improved and there was a modest increase in sputum smear conversions (109754).
Urinary tract infections (UTIs). It is unclear if oral zinc is beneficial in children with UTI. Details: A low-quality, clinical study in children aged 3-12 years hospitalized for a UTI and receiving intravenous antibiotic treatment shows that taking zinc 1 mg/kg daily for 14 days reduces the duration of dysuria, urinary frequency, and urgency when compared with intravenous antibiotics alone. Zinc does not improve fever or the time to negative urine culture (96081). However, this study did not demonstrate that treatment groups were equal at baseline.
Venous leg ulcers. It is unclear if oral or topical zinc is beneficial for leg ulcer healing. Details: Two small studies in elderly patients with leg ulcers suggest that using a zinc saline solution on a wound dressing or applying zinc oxide to a dressing might improve healing of leg ulcers (2694,6901). However, oral zinc supplementation does not seem to be beneficial. A meta-analysis of four small clinical trials in patients with venous leg ulcers shows that taking zinc orally does not improve healing when compared with placebo (104079).
Vertigo. Oral zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults with benign paroxysmal positional vertigo with serum 25-hydroxyvitamin D levels less than 20 ng/mL shows that taking a specific combination product containing zinc 7.5 mg, alpha-lipoic acid 600 mg, L-carnosine 165 mg, curcumin 100 mg, piperine 1 mg, cholecalciferol 800 units, vitamin B2 0.8 mg, and vitamin B6 1 mg (Vertistop D, Difass) orally daily for 6 months moderately reduces the number of vertigo relapse episodes when compared with control. However, in patients with serum 25-hydroxyvitamin D levels greater than 20 ng/mL that took a specific combination product containing zinc 7.5 mg, alanine 600 mg, L-carnosine 165 mg, curcumin 100 mg and piperine 1 mg (Vertistop L, Difass) orally daily for 6 months there was no difference in relapse episodes when compared with control (111294). It is unclear if this effect is due to zinc, other ingredients, or the combination.
Water warts. It is unclear if oral zinc is beneficial for the treatment of water warts in children. Details: In children with water warts, preliminary clinical research shows that taking zinc sulfate heptahydrate (as Zinco syrup) for 2 months results in lesion resolution in 70% of patients when compared with baseline. Lesion resolution occurred in an additional 13% of patients in the month after treatment completion, with no recurrence in any of these children over the next 9 months. Zinc 3 mg daily was used in children up to 3 years of age, and 5 mg daily was used in older children (106234). Due to the lack of a comparator group, it is unclear if these outcomes are due to zinc or the natural resolution of the condition.
Wound healing. Topical zinc might be beneficial for the healing of uncomplicated wounds. Details: A small clinical study shows that applying zinc chloride solution, standardized to contain zinc 20 mcg/mL, twice daily improves wound healing when compared with saline solution in patients with uncomplicated, skin wounds. However, when zinc is administered as a component of an insulin product (Humulin, Eli Lilly and Company), it seems to be more effective than zinc chloride alone (90192).
Wrinkled skin. Topical zinc has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A topical preparation containing 10% vitamin C as L-ascorbic acid and acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months seems to improve fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). More evidence is needed to rate zinc for these uses.

Safety view details

Below is general information about the safety of the known ingredients contained in the product Centrum Women Under 50. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

BIOTIN

LIKELY SAFE ...when used orally and appropriately. Biotin has been safely used in doses up to 300 mg daily for up to 6 months. A tolerable upper intake level (UL) has not been established (1900,6243,95662,102965). ...when applied topically as cosmetic products at concentrations of 0.0001% to 0.6% biotin (19344).

POSSIBLY SAFE ...when used intramuscularly and appropriately (8468,111366).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Biotin has been safely used at adequate intake doses of 5-25 mcg daily for up to 6 months (173,6243,19347,19348,111365). A tolerable upper intake level (UL) has not been established.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Biotin has been safely used at the adequate intake (AI) dose of 30 mcg daily during pregnancy and 35 mcg daily during lactation. It has also been used in supplemental doses of up to 300 mcg daily (6243,7878). A tolerable upper intake level (UL) has not been established.

BORON

LIKELY SAFE ...when used orally and appropriately. Boron is safe in amounts that do not exceed the tolerable upper intake level (UL) 20 mg daily (7135). ...when used vaginally. Boric acid, the most common form of boron, has been safely used for up to six months (15443,15444,15445,15446,15458,15449,15451,15453,15454). ...when used topically. Boron, in the form of sodium pentaborate pentahydrate 3% gel, has been applied to the skin with apparent safety up to four times daily for up to 5 weeks (95660,109557).

POSSIBLY UNSAFE ...when used orally in doses exceeding the UL of 20 mg daily. Higher doses might adversely affect the testes and male fertility (7135). Poisoning has occurred after ingestion of boron 2.12 grams daily for 3-4 weeks (17). Death has occurred after ingesting a single dose of 30 grams (36848,36863).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Boron is safe in amounts that do not exceed the tolerable upper intake level (UL). The UL by age is 3 mg daily at 1-3 years, 6 mg daily at 4-8 years, 11 mg daily at 9-13 years, and 17 mg daily at 14 years or older (7135). The UL for infants has not been determined (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in doses exceeding the age-based UL (7135). ...when applied topically in large quantities. Infant deaths have occurred after the use of topical boric acid powder to prevent diaper rash (36873,36874).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Boron is safe in amounts that do not exceed the UL during pregnancy or lactation, which is 20 mg daily in those 19-50 years of age or 17 mg daily for those 14-18 years of age (7135).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher doses might impair growth and cause adverse effects in the developing fetus (7135,102058). ...when used vaginally. Intravaginal boric acid has been associated with a 2.7- to 2.8-fold increased risk of birth defects when used during the first 4 months of pregnancy (15443,15645).

CALCIUM

LIKELY SAFE ...when used orally or intravenously and appropriately. Calcium is safe when used in appropriate doses (7555,12928,12946,95817). However, excessive doses should be avoided. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stone, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients not to consume more than the recommended daily intake of 1000-1200 mg per day and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (93533).

POSSIBLY UNSAFE ...when used orally in excessive doses. The National Academy of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 19-50 years, 2500 mg; 51 years and older, 2000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome. There has also been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these studies, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Advise patients to not consume more than the recommended daily intake of 1000-1200 mg per day and to consider total calcium intake from both dietary and supplemental sources (17484). Also, advise patients taking calcium supplements to take calcium along with vitamin D (93533).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Calcium is safe when used in appropriate doses (17506).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium according to age as follows: 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg (17506). Doses over these levels can increase the risk of side effects such as kidney stones, hypercalciuria, hypercalcemia, and milk-alkali syndrome.

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (945,1586,3263,3264,17506). The World Health Organization (WHO) recommends prescribing oral calcium supplementation 1.5-2 grams daily during pregnancy to those with low dietary calcium intake to prevent pre-eclampsia (97347).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. The Institute of Medicine sets the same daily tolerable upper intake level (UL) for calcium according to age independent of pregnancy status: 9-18 years, 3000 mg; 19-50 years, 2500 mg (17506). Doses over these amounts might increase the risk of neonatal hypocalcemia-induced seizures possibly caused by transient neonatal hypoparathyroidism in the setting of excessive calcium supplementation during pregnancy, especially during the third trimester. Neonatal hypocalcemia is a risk factor for neonatal seizures (97345).

CHROMIUM

LIKELY SAFE ...when used orally and appropriately in medicinal amounts, short-term. Chromium has been safely used in doses up to 1000 mcg daily for up to 6 months (1934,5039,5040,6858,6859,6860,6861,6862,6867,6868)(7135,7137,10309,13053,14325,14440,17224,90057,90061)(90063,94234,95095,95096,95097,98687); however, most of these studies have used chromium doses in a range of 150-600 mcg. The Food and Drug Administration (FDA) and Institute of Medicine (IOM) evaluations of the safety of chromium suggest that it is safe when used in doses of 200 mcg daily for up to 6 months (13241,13242).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts, long-term. Chromium has been safely used in a small number of studies at doses of 200-1000 mcg daily for up to 2 years (7060,7135,42618,42628,42666,110605,110607,110609). However, the Food and Drug Administration (FDA) and Institute of Medicine (IOM) evaluations of the safety of chromium suggest that it is safe when used in doses of 200 mcg daily for up to 6 months (13241,13242).

CHILDREN: LIKELY SAFE
when used orally and appropriately in amounts not exceeding the daily adequate intake (AI) levels by age: 0-6 months, 0. 2 mcg; 7-12 months, 5.5 mcg; 1-3 years, 11 mcg; 4-8 years, 15 mcg; males 9-13 years, 25 mcg; males 14-18 years, 35 mcg; females 9-13 years, 21 mcg; females 14-18 years, 24 mcg (7135). POSSIBLY SAFE...when used orally and appropriately in amounts exceeding AI levels. Chromium 400 mcg daily has been used safely for up to 6 weeks (42680).

PREGNANCY: LIKELY SAFE
when used orally and appropriately in amounts not exceeding adequate intake (AI) levels. The AI for pregnancy is 28 mcg daily for those 14-18 years of age and 30 mcg daily for those 19-50 years of age (7135).

PREGNANCY: POSSIBLY SAFE
when used orally in amounts exceeding the adequate intake (AI) levels. There is some evidence that patients with gestational diabetes can safely use chromium in doses of 4-8 mcg/kg (1953); however, patients should not take chromium supplements during pregnancy without medical supervision.

LACTATION: LIKELY SAFE
when used orally and appropriately in amounts not exceeding adequate intake (AI) levels. The AI for lactation is 44 mcg daily for those 14-18 years of age and 45 mcg daily for those 19-50 years of age (7135). Chromium supplements do not seem to increase normal chromium concentration in human breast milk (1937). There is insufficient reliable information available about the safety of chromium when used in higher amounts while breast-feeding.

COPPER

LIKELY SAFE ...when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 10 mg daily (7135).

POSSIBLY SAFE ...when copper oxide is used topically. A wound dressing impregnated with copper oxide in concentrations of 3% by weight has been used with apparent safety in one clinical trial (105363).

POSSIBLY UNSAFE ...when used orally in doses exceeding the UL of 10 mg daily. Higher intake can cause liver damage (7135,45865). Kidney failure and death can occur with ingestion of as little as 1 gram of copper sulfate (17).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 1 mg daily for 1-3 years of age, 3 mg daily for 4-8 years of age, 5 mg daily for 9-13 years of age, and 8 mg daily for 14-18 years of age (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in doses exceeding the UL (7135). Higher intake can cause liver damage (7135).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 8 mg daily for those 14-18 years of age or 10 mg daily for those 19 years and older (7135).

PREGNANCY: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher intake can cause liver damage (7135).

LACTATION: LIKELY SAFE
when used orally and appropriately. Copper is safe in amounts that do not exceed the tolerable upper intake level (UL) of 8 mg daily for those 14-18 years of age or 10 mg daily for those 19 years and older (7135).

LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher intake can cause liver damage (7135).

FOLIC ACID

LIKELY SAFE ...when used orally or parenterally and appropriately. Folic acid has been safely used in amounts below the tolerable upper intake level (UL). The UL for folic acid is based only on supplemental folic acid and is expressed in mcg folic acid. Dietary folate is not included in UL calculations, as dietary folate consumption has not been associated with adverse effects. The UL for folic acid in adults is 1000 mcg (6241). In cases of megaloblastic anemia resulting from folate deficiency or malabsorption disorders such as sprue, oral doses of 1-5 mg per day can also be used safely until hematologic recovery is documented, as long as vitamin B12 levels are routinely measured (6241,7725,8739).

POSSIBLY SAFE ...when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately, short-term. L-5-MTHF has been used with apparent safety at a dose of 416 mcg daily for 16 weeks (104913,104914) and a dose of 113 mcg daily for 24 weeks (104920). A specific L-5-MTHF product (Metafolin, Eprova) has been used with apparent safety at a dose of 1.3 mg daily for 12 weeks (104912).

POSSIBLY UNSAFE ...when used orally in large doses, long-term. Clinical research shows that taking folic acid daily in doses of 800 mcg to 1200 mcg for 3-10 years significantly increases the risk of developing cancer and adverse cardiovascular effects compared to placebo (12150,13482,16822,17041). Doses above 1 mg per day should also be avoided if possible to prevent precipitation or exacerbation of neuropathy related to vitamin B12 deficiency (6241,6242,6245). However, there is contradictory evidence suggesting that higher doses may not be harmful. There is some evidence that doses of 5 mg per day orally for up to 4 months can be used safely if vitamin B12 levels are routinely measured (7725). Also, other clinical research suggests that folic acid supplementation at doses up to 5 mg, usually in combination with vitamin B12, does not increase the risk of cancer when taken for 2-7 years (91312). Very high doses of 15 mg per day can cause significant central nervous system (CNS) and gastrointestinal side effects (505).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Folic acid has been safely used in children in amounts below the tolerable upper intake level (UL). The ULs for folic acid are based only on supplemental folic acid and are expressed in mcg folic acid. Dietary folate is not included in UL calculations, as dietary folate consumption has not been associated with adverse effects. The UL for children is: 1-3 years of age, 300 mcg; 4-8 years of age, 400 mcg; 9-13 years of age, 600 mcg; 14-18 years of age, 800 mcg (6241).

CHILDREN: POSSIBLY SAFE
when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately. One clinical study in infants aged 27 days and younger shows that consuming a formula containing L-5-MTHF (Metafolin, Merck & Cie) 10.4 mcg/100 mL daily has been used with apparent safety for up to 12 weeks (104918).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Folic acid 300-400 mcg is commonly used during pregnancy for prevention of neural tube defects (8739). Miscarriage rates and negative impacts on fetal growth have not been shown to increase with peri-conception supplemental folic acid intakes of 4 mg per day (91320,91322). However, other research shows that taking more than 5 mg per day during pregnancy may reduce development of cognitive, emotional, and motor skills in infants (91318). Also, the tolerable upper intake level (UL) of folic acid for pregnant or lactating women is 800 mcg daily for those 14-18 years of age and 1000 mcg daily for those 19 years and older (6241).

PREGNANCY AND LACTATION: POSSIBLY SAFE
when L-5-methyltetrahydrofolate (L-5-MTHF), the reduced form of folate, is used orally and appropriately, short-term. L-5-MTHF has been used with apparent safety at a dose of 416 mcg daily for 16 weeks during lactation. Compared to folic acid, this form seems to further increase the folate concentration of red blood cells, but not breast milk (104913,104914).

IODINE

LIKELY SAFE ...when used orally and appropriately. Iodine is safe in amounts that do not exceed the tolerable upper intake level (UL) of 1100 mcg daily (7135,103070). Higher doses can be safely used with appropriate medical monitoring (2197,7080). In some regions of the world, such as Japan, daily dietary intake is estimated to be as high as 5,280-13,800 mcg without adverse outcomes (16747). ...when used topically and appropriately, as a 2% solution. A 2% iodine solution is an FDA-approved prescription product (15).

POSSIBLY UNSAFE ...when used orally in high doses. Tell patients to avoid prolonged use of doses exceeding the UL of 1100 mcg daily without proper medical supervision. There is concern that higher intake can increase the risk of side effects such as thyroid dysfunction, as well as thyroiditis, thyroid papillary cancer, thyrotoxicosis, and atrial fibrillation (7135,55962,56013). However, in some regions of the world such as Japan, daily dietary intake is estimated to be as high as 5,280-13,800 mcg without adverse outcomes (16747).

CHILDREN: LIKELY SAFE
when used orally and appropriately (7135). Iodine is safe in amounts that do not exceed the tolerable upper intake level (UL) of 200 mcg daily for children 1-3 years, 300 mcg daily for children 4-8 years, 600 mcg daily for children 9-13 years, and 900 mcg daily for adolescents (7135). ...when used topically as a 2% solution (15). Iodine is an FDA-approved prescription product.

CHILDREN: POSSIBLY UNSAFE
when used orally in doses exceeding the UL (7135,108709). Higher intake can cause thyroid dysfunction (7135) and may be associated with a modest reduction in intelligence (108709).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Iodine is safe in amounts that do not exceed the tolerable upper intake level (UL) of 1100 mcg daily in those 18 years and older or 900 mcg daily in those 14-18 years of age (7135,103070). Iodine needs increase during pregnancy and lactation and adequate intakes should begin as soon as a patient is aware of the pregnancy, or earlier in areas of potential deficiency (17920). ...when used topically as a 2% solution (15). Iodine is an FDA-approved prescription product.

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher intake can cause thyroid dysfunction (7135). Also, higher intakes during pregnancy cause increased iodine levels in breast milk and infant blood samples. Higher iodine intake during pregnancy has also been associated with an increased risk of congenital hypothyroidism and reduced mental and physical development in the offspring (56089,91390,91394,91395).

IRON

LIKELY SAFE ...when used orally and appropriately. For people age 14 and older with adequate iron stores, iron supplements are safe when used in doses below the tolerable upper intake level (UL) of 45 mg per day of elemental iron. The UL is not meant to apply to those who receive iron under medical supervision (7135,96621). To treat iron deficiency, most people can safely take up to 300 mg elemental iron per day (15). ...when used intravenously and appropriately. Ferric carboxymaltose 200 mg and iron sucrose 200 mg have been given intravenously for up to 10 doses with no reported serious adverse effects (91179). A meta-analysis of clinical studies of hemodialysis patients shows that administering high-dose intravenous (IV) iron does not increase the risk of hospitalization, infection, cardiovascular events, or death when compared with low-dose IV iron, oral iron, or no iron treatment (102861). A more recent meta-analysis of clinical studies of all patient populations shows that administering IV iron does not increase the risk of hospital length of stay or mortality, although the risk of infection is increased by 16% when compared with oral iron or no iron (110186). Despite these findings, there are rare reports of hypophosphatemia and/or osteomalacia (112603,112608,112609,112610).

LIKELY UNSAFE ...when used orally in excessive doses. Doses of 30 mg/kg are associated with acute toxicity. Long-term use of high doses of iron can cause hemosiderosis and multiple organ damage. The estimated lethal dose of iron is 180-300 mg/kg; however, doses as low as 60 mg/kg have also been lethal (15).

CHILDREN: LIKELY SAFE
when used orally and appropriately (7135,91183,112601).

CHILDREN: LIKELY UNSAFE
when used orally in excessive amounts. Tell patients who are not iron-deficient not to use doses above the tolerable upper intake level (UL) of 40 mg per day of elemental iron for infants and children. Higher doses frequently cause gastrointestinal side effects such as constipation and nausea (7135,20097). Iron is the most common cause of pediatric poisoning deaths. Doses as low as 60 mg/kg can be fatal (15).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Iron is safe during pregnancy and breast-feeding in patients with adequate iron stores when used in doses below the tolerable upper intake level (UL) of 45 mg daily of elemental iron (7135,96625,110180).

PREGNANCY AND LACTATION: LIKELY UNSAFE
when used orally in high doses. Tell patients who are not iron deficient to avoid exceeding the tolerable upper intake level (UL) of 45 mg daily of elemental iron. Higher doses frequently cause gastrointestinal side effects such as nausea and vomiting (7135) and might increase the risk of preterm labor (100969). High hemoglobin concentrations at the time of delivery are associated with adverse pregnancy outcomes (7135,20109).

MAGNESIUM

LIKELY SAFE ...when used orally and appropriately. Oral magnesium is safe when used in doses below the tolerable upper intake level (UL) of 350 mg daily (7555). ...when used parenterally and appropriately. Parenteral magnesium sulfate is an FDA-approved prescription product (96484).

POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 350 mg daily frequently cause loose stools and diarrhea (7555).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Magnesium is safe when used in doses below the tolerable upper intake level (UL) of 65 mg daily for children 1 to 3 years, 110 mg daily for children 4 to 8 years, and 350 mg daily for children older than 8 years (7555,89396). ...when used parenterally and appropriately (96483).

CHILDREN: LIKELY UNSAFE
when used orally in excessive doses. Tell patients not to use doses above the tolerable upper intake level (UL). Higher doses can cause diarrhea and symptomatic hypermagnesemia including hypotension, nausea, vomiting, and bradycardia (7555,8095).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Magnesium is safe for those pregnant and breast-feeding when used in doses below the tolerable upper intake level (UL) of 350 mg daily (7555).

PREGNANCY AND LACTATION: POSSIBLY SAFE
when prescription magnesium sulfate is given intramuscularly and intravenously prior to delivery for up to 5 days (12592,89397,99354,99355). However, due to potential adverse effects associated with intravenous and intramuscular magnesium, use during pregnancy is limited to patients with specific conditions such as severe pre-eclampsia or eclampsia. There is some evidence that intravenous magnesium can increase fetal mortality and adversely affect neurological and skeletal development (12590,12593,60818,99354,99355). However, a more recent analysis of clinical research shows that increased risk of fetal mortality seems to occur only in the studies where antenatal magnesium is used for tocolysis and not for fetal neuroprotection or pre-eclampsia/eclampsia (102457). Furthermore, antenatal magnesium does not seem to be associated with increased risk of necrotizing enterocolitis in preterm infants (104396). There is also concern that magnesium increases the risk of maternal adverse events. A meta-analysis of clinical research shows that magnesium sulfate might increase the risk of maternal adverse events, especially in Hispanic mothers compared to other racial and ethnic groups (60971,99319).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Tell patients to avoid exceeding the tolerable upper intake level (UL) of 350 mg daily. Taking magnesium orally in higher doses can cause diarrhea (7555). ...when prescription magnesium sulfate is given intramuscularly and intravenously prior to delivery for longer than 5 days (12592,89397,99354,99355). Maternal exposure to magnesium for longer than 5-7 days is associated with an increase in neonatal bone abnormalities such as osteopenia and fractures. The U.S. Food and Drug Administration (FDA) recommends that magnesium injection not be given for longer than 5-7 days (12590,12593,60818,99354,99355).

MANGANESE

LIKELY SAFE ...when used orally and appropriately. Oral manganese is safe when used in doses below the tolerable upper intake level (UL) of 11 mg daily for adults 19 years and older (1994,7135). ...when used parenterally and appropriately. Parenteral manganese chloride and manganese sulfate are FDA-approved prescription products.

POSSIBLY UNSAFE ...when used orally in high doses. Doses exceeding 11 mg daily can cause significant adverse effects (7135). ...when used parenterally in moderate or high doses, long-term. Reports of neurotoxicity and Parkinson-like symptoms have been reported with parenteral nutrition manganese doses above 60 mcg daily. It is recommended that adults on long-term parenteral nutrition receive manganese in doses of no more than 55 mcg daily (99302).

LIKELY UNSAFE ...when inhaled in moderate doses, long-term. According to the US Occupational Safety and Health Administration (OSHA), the permissible exposure limit (PEL) for manganese is 5 mg/m3. Exposure to higher amounts of manganese dust or fumes has been associated with central nervous system toxicity, Parkinson-like symptoms, and poor bone health (61296,102516).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Manganese is safe in children when used in daily doses less than the tolerable upper intake level (UL) of 2 mg in children 1-3 years, 3 mg in children 4-8 years, 6 mg in children 9-13 years, and 9 mg in children 14-18 years (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses. Daily doses greater than the UL are associated with a greater risk of toxicity (7135).

CHILDREN: LIKELY UNSAFE
when inhaled at moderate doses, long-term. Exposure to high amounts of manganese dust has been associated with central nervous system toxicity and Parkinson-like symptoms (61296).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Manganese is safe when used in doses below the tolerable upper intake level (UL) of 11 mg daily during pregnancy or lactation in those aged 19 or older. However, those under 19 years of age should limit doses to less than 9 mg daily (7135).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Doses over the UL are associated with a greater risk of toxicity (7135). Additionally, observational research shows that adults with higher blood manganese levels have greater odds of delivering low birth weight or small for gestational age (SGA) male, but not female, infants (102515).

PREGNANCY AND LACTATION: LIKELY UNSAFE
when inhaled at moderate doses, long-term. Manganese salts can cross the placenta, and animal research suggests that large amounts of manganese may be teratogenic (61296).

MOLYBDENUM

LIKELY SAFE ...when used orally and appropriately. Molybdenum is safe in amounts that do not exceed 2 mg/day, the Tolerable Upper Intake Level (UL) (7135).

POSSIBLY UNSAFE ...when used orally in high doses. Use of molybdenum in doses exceeding the Tolerable Upper Intake Level (UL) of 2 mg/day might not be safe (7135).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Molybdenum is safe in amounts that do not exceed the Tolerable Upper Intake Level (UL) of 0.3 mg/day for children 1 to 3 years, 0.6 mg/day for children 4 to 8 years, 1.1 mg/day for children 9 to 13 years, and 1.7 mg/day for adolescents (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Molybdenum might not be safe when used in doses exceeding the UL of 0.3 mg/day for children 1 to 3 years, 0.6 mg/day for children 4 to 8 years, 1.1 mg/day for children 9 to 13 years, and 1.7 mg/day for adolescents (7135).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Molybdenum crosses the placenta by passive diffusion and is exchanged freely between the mother and fetus (16482). However, molybdenum is safe when used in amounts that do not exceed the Tolerable Upper Intake Level (UL) of 1.7 mg/day for women 14 to 18 years, or 2 mg/day for women 19 years of age and older (7135).

PREGNANCY: POSSIBLY UNSAFE
when used orally in high doses. Molybdenum might not be safe during pregnancy when used in doses exceeding the UL of 1.7 mg/day for women 14 to 18 years, or 2 mg/day for women 19 and older (7135).

LACTATION: LIKELY SAFE
when used orally and appropriately. Molybdenum is safe when used in amounts that do not exceed the Tolerable Upper Intake Level (UL) of 2 mg/day for breast-feeding women 19 years of age or older, or 1.7 mg/day for breast-feeding women ages 14 to 18 years (7135).

LACTATION: POSSIBLY UNSAFE
when used orally in high doses. Molybdenum might not be safe when used in doses exceeding the UL of 2 mg/day for breast-feeding women 19 or older, or 1.7 mg/day for breast-feeding women ages 14 to 18 years (7135).

NIACIN

LIKELY SAFE ...when niacin is taken in food or as a supplement in amounts below the tolerable upper intake level (UL) of 30 mg daily for adults 18 years of age and 35 mg daily for adults 19 years and older (6243). ...when prescription products are used orally and appropriately in doses of up to 2 grams daily (12033). CHILDREN:

LIKELY SAFE ...when used orally in amounts that do not exceed the tolerable upper intake level (UL). The ULs of niacin for children are: 1-3 years of age, 10 mg daily; 4-8 years of age, 15 mg daily; 9-13 years of age, 20 mg daily; 14-18 years of age, 30 mg daily (6243).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the tolerable upper intake level (UL). The UL of niacin during pregnancy and lactation is 30 mg daily for 14-18 years of age and 35 mg daily for 19 years and older (6243). There is insufficient reliable information available about the safety of larger oral doses of niacin during pregnancy or lactation; avoid using.

NICKEL

LIKELY SAFE ...when used orally and appropriately. Nickel is safe for most adults when used in doses less than the tolerable upper intake level (UL) of 1 mg daily (7135).

POSSIBLY UNSAFE ...when used in high doses and for prolonged periods. Taking nickel in doses above the tolerable upper intake level (UL) of 1 mg daily increases the chance of adverse effects (7135). Taking high doses of nickel is associated with acute toxicity. Prolonged industrial exposure to nickel is also associated with hypersensitivity disorders, lung disorders, and cancer (7135,16307,16311).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Nickel is safe in children when used in daily doses less than the tolerable upper intake level (UL) of 0.2 mg daily in children 1-3 years, 0.3 mg daily in children 4-8 years, and 0.6 mg daily in children 9-13 years (7135).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Taking nickel in doses above the UL might not be safe (7135).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately. Nickel is safe to use during pregnancy and lactation in doses below the tolerable upper intake level (UL) of 1 mg daily (7135). There is insufficient reliable information available about the safety of nickel when taken in doses above the UL during pregnancy and lactation.

LIKELY SAFE ...when used orally and appropriately. The pantothenic acid derivative calcium pantothenate has a generally recognized as safe (GRAS) status for use in food products (111258). While a tolerable upper intake level (UL) has not been established, pantothenic has been used in doses of 10-20 grams daily with apparent safety (15,6243,111258) ...when applied topically and appropriately, short-term. The Cosmetic Ingredient Review Expert Panel has concluded that pantothenic acid and its derivatives are safe for use in cosmetic products in concentrations up to 5.3% (111258). Gels or ointments containing a derivative of pantothenic acid, dexpanthenol, at concentrations of up to 5%, have been used safely for up to 30 days (67802,67806,67817).

POSSIBLY SAFE ...when applied intranasally and appropriately, short-term. A dexpanthenol nasal spray has been used with apparent safety up to four times daily for 4 weeks (67826). ...when applied in the eyes appropriately, short-term. Dexpanthenol 5% eyedrops have been used with apparent safety for up to 28 days (67783). ...when injected intramuscularly and appropriately, short-term. Intramuscular injections of dexpanthenol 500 mg daily for up to 5 days or 250 mg weekly for up to 6 weeks have been used with apparent safety (67822,111366).

CHILDREN: LIKELY SAFE
when used orally and appropriately (15,6243). Calcium pantothenate is generally recognized as safe (GRAS) when used as a food additive and in infant formula (111258). However, a tolerable upper intake level (UL) has not been established (15,6243). ...when applied topically and appropriately (67795,105190,111262). Infant products containing pantothenic acid and its derivatives have been used safely in concentrations of up to 5% for infant shampoos and 2.5% for infant lotions and oils. The Cosmetic Ingredient Review Expert Panel has concluded that pantothenic acid and derivatives are safe for use in topical infant products. (111258).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. The daily adequate intake (AI) during pregnancy is 6 mg (3094).

LACTATION: LIKELY SAFE
when used orally and appropriately. The daily adequate intake (AI) during lactation is 7 mg (3094).

LIKELY SAFE ...when used orally and appropriately short-term (15). ...when sodium phosphate is used rectally and appropriately, no more than once every 24 hours, short-term (104471). Long-term use or high doses used orally or rectally require monitoring of serum electrolytes (2494,2495,2496,2497,2498,3092,112922). ...when used intravenously. Potassium phosphate is an FDA-approved prescription drug (15).

POSSIBLY UNSAFE ...when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL) of 4 grams daily for adults under 70 years and 3 grams daily for adults older than 70. Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur (7555). ...when used rectally more frequently than once every 24 hours, in excessive doses, with longer retention enema time, or in older patients with comorbidity or renal impairment (112922). The US Food and Drug Administration (FDA) warns that this may increase the risk of hyperphosphatemia, dehydration, and electrolyte imbalances leading to kidney and heart damage (104471).

CHILDREN: LIKELY SAFE
when used orally and appropriately at recommended dietary allowances (RDAs). The daily RDAs are: children 1-3 years, 460 mg; children 4-8 years, 500 mg; males and females 9-18 years, 1250 mg (7555). ...when sodium phosphate is used rectally and appropriately, no more than once every 24 hours, short-term in children 2 years and older (104471). ...when used intravenously. Intravenous potassium phosphate is an FDA-approved prescription drug (15).

CHILDREN: POSSIBLY UNSAFE
when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL) of 3 grams daily for children 1-8 years of age and 4 grams daily for children 9 years and older. Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur (7555). ...when sodium phosphate is used rectally more frequently than once every 24 hours, or in children under 2 years of age or with Hirchsprung disease (112922). The US Food and Drug Administration (FDA) warns that these uses may increase the risk of hyperphosphatemia, dehydration, and electrolyte imbalances leading to kidney and heart damage (104471).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately at the recommended dietary allowance (RDA) of 1250 mg daily for individuals 14-18 years of age and 700 mg daily for those over 18 years of age (7555). ...when sodium phosphate is used rectally and appropriately short-term (15). ...when used intravenously. Intravenous potassium phosphate is an FDA-approved prescription drug (15).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL). Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur. The UL during pregnancy is 3.5 grams daily. During lactation, the UL is 4 grams daily (7555).

POTASSIUM

LIKELY SAFE ...when used orally in doses up to 100 mEq total potassium daily, not to exceed 200 mEq in a 24-hour period (95010,107989). Oral potassium chloride and potassium citrate are FDA-approved prescription products (95010,107989). Larger doses increase the risk of hyperkalemia (15). ...when administered intravenously (IV) at appropriate infusion rates (95011). Parenteral potassium is an FDA-approved prescription product (15,95011). A tolerable upper intake level (UL) for potassium has not been established; however, potassium levels should be monitored in individuals at increased risk for hyperkalemia, such as those with kidney disease, heart failure, and adrenal insufficiency (100310,107966).

CHILDREN: LIKELY SAFE
when used orally and appropriately in dietary amounts. A tolerable upper intake level (UL) has not been established for healthy individuals (6243,100310).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in dietary amounts of 40-80 mEq daily (15). A tolerable upper intake level (UL) has not been established for healthy individuals (100310).

RIBOFLAVIN

LIKELY SAFE ...when used orally and appropriately. Riboflavin 400 mg daily has been taken for up to 3 months, and 10 mg daily has been taken safely for up to 6 months (4912,91752,105480). A tolerable upper intake level (UL) has not been established (3094,91752,94089).

CHILDREN: LIKELY SAFE
when used orally and appropriately in dietary amounts. A tolerable upper intake level (UL) has not been established (3094,94089). ...when used orally in higher doses for up to 1 year. Doses of 100-200 mg daily have been used safely for 4-12 months in children ages 9-13 years (71483,105484).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately in dietary amounts. A tolerable upper intake level (UL) has not been established (3094,94089).

SELENIUM

LIKELY SAFE ...when used orally and appropriately. Selenium appears to be safe when taken short-term in amounts below the tolerable upper intake level (UL) of 400 mcg daily (4844,7830,7831,7836,7841,9724,9797,14447,17510,17511)(17512,17513,17515,17516,97087,97943,109085); however, there is concern that taking selenium long-term might not be safe. Some evidence shows that consuming a diet containing more than the recommended dietary allowance (RDA) of selenium, which is 55 mcg daily for most adults, is associated with an increased risk for developing type 2 diabetes (99661). Some evidence also shows that taking a selenium supplement 200 mcg daily for an average of 3-8 years increases the risk of developing type 2 diabetes (97091,99661). Higher serum levels of selenium are also associated with an increased risk of developing diabetes and increased mortality (16710,99661). ...when used intravenously. Selenium, as selenious acid, is an FDA-approved drug. Sodium selenite intravenous infusions up to 1000 mcg daily have been safely used for up to 28 days (90347,92910).

POSSIBLY UNSAFE ...when used orally in high doses or long-term. Doses above 400 mcg daily can increase the risk of developing selenium toxicity (4844,7825). Additionally, some evidence shows that consuming a diet containing more than the recommended dietary allowance (RDA) of selenium, which is 55 mcg daily for most adults, is associated with an increased risk for developing type 2 diabetes (99661). There is also concern that taking a selenium supplement 200 mcg daily long-term, for an average of 3-8 years, increases the risk of developing type 2 diabetes (99661). Higher serum levels of selenium are also associated with an increased risk of developing diabetes and increased mortality (16710,99661).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately. Selenium seems to be safe when used short-term in doses below the tolerable upper intake level (UL) of 45 mcg daily for infants up to age 6 months, 60 mcg daily for infants 7 to 12 months, 40-90 mcg daily for children 1 to 3 years, 100-150 mcg daily for children 4 to 8 years, 200-280 mcg daily for children 9 to 13 years, and 400 mcg daily for children age 14 years and older (4844,86095); however, there is some concern that long-term use might not be safe. ...when used via a nasogastric tube in premature infants (7835,9764).

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately. Selenium appears to be safe when used short-term in amounts that do not exceed the tolerable upper intake level (UL) of 400 mcg daily (4844,17507,74419,74481,74391); however, there is concern that long-term use might not be safe.

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses. Doses above 400 mcg daily may cause significant toxicity (4844).

LACTATION: POSSIBLY SAFE
when used orally and appropriately. Selenium appears to be safe when used short-term in amounts that do not exceed the tolerable upper intake level (UL) of 400 mcg daily when taken short-term (4844,74467); however, there is concern that long-term use might not be safe.

LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Doses above 400 mcg daily may cause significant toxicity (4844,7838). ...when used orally in HIV-positive women. Selenium supplementation in HIV-positive women not taking highly active antiretroviral therapy may increase HIV-1 levels in breast milk (90358).

SILICON

LIKELY SAFE ...when used orally and appropriately in amounts commonly found in foods (7135,10470,92135). It is estimated that the average dietary intake of silicon is 20-50 mg daily (110029); however, there is currently no established recommended dietary allowance or tolerable upper intake level for silicon (7135,92136,95009,110029).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts commonly found in foods (7135,10470). It is estimated that the average dietary intake of silicon is 20-50 mg daily (110029). There is insufficient reliable information available about the safety of silicon when used in larger, medicinal amounts; avoid using.

THIAMINE

LIKELY SAFE ...when used orally and appropriately. A tolerable upper intake level (UL) has not been established for thiamine, and doses up to 50 mg daily have been used without adverse effects (15,6243). ...when used intravenously or intramuscularly and appropriately. Injectable thiamine is an FDA-approved prescription product (15,105445).

CHILDREN: LIKELY SAFE
when used orally and appropriately in dietary amounts. A tolerable upper intake level (UL) has not been established for healthy individuals (6243).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in dietary amounts of 1. 4 mg daily. A tolerable upper intake level (UL) has not been established for healthy individuals (3094,6243).

TIN

LIKELY SAFE ...when tin in the form of stannous fluoride is used topically and appropriately. Stannous fluoride is approved for use by the US Food and Drug Administration (FDA) as an ingredient in dentifrices, gels, and other dental hygiene products. The concentration of stannous fluoride in dentifrices in the US is 0.454% (98554). There is insufficient reliable information available about the safety of tin when used orally in medicinal amounts.

CHILDREN: LIKELY SAFE
when tin in the form of stannous fluoride is used topically and appropriately in children aged 6 years and older. Stannous fluoride is approved for use by the US Food and Drug Administration (FDA) as an ingredient in dentifrices, gels, and other dental hygiene products. The concentration of stannous fluoride in dentifrices in the US is 0.454% (98554). There is insufficient reliable information available about the safety of tin when used orally in medicinal amounts.

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

VANADIUM

LIKELY SAFE ...when used orally and appropriately. Vanadium is safe when taken in amounts below the tolerable upper intake level (UL) of 1.8 mg daily (7135).

POSSIBLY UNSAFE ...when used orally in high doses. Taking more than the tolerable upper intake level (UL) of 1.8 mg daily can increase the risk of gastrointestinal side effects and theoretically, kidney toxicity (7135). In some cases, patients with diabetes have used very high doses (100 mg daily) safely for up to 4 weeks (3055,3056,3057). However, there is concern that prolonged use of high doses might cause serious side effects including kidney damage (7135). Doses of 22.5 mg daily for five months can cause cramps and diarrhea (3012).

CHILDREN: LIKELY SAFE
when used orally in amounts found in foods (7135). There is insufficient reliable information available about the safety of vanadium when used in amounts greater than those typically found in foods.

PREGNANCY: LIKELY SAFE
when used orally in amounts found in foods (7135).

PREGNANCY: POSSIBLY UNSAFE
when used orally in medicinal amounts. Epidemiological research has found that increased urinary levels of vanadium are associated with an increased risk of both term and preterm premature rupture of membranes (PROM). When comparing tertiles of urinary vanadium levels, patients in the middle tertile had 1.66 times the risk of term PROM when compared with the lowest tertile, and those in the highest tertile had 3.75 times the risk. For preterm PROM (rupture prior to 37 weeks' gestation), those in the highest tertile had an 8.14 times increased risk when compared with those in the lowest tertile (99052). Epidemiological research has also found that higher prenatal serum levels of vanadium are associated with impaired fetal growth, particularly in male newborns. The risk appears greatest with vanadium exposure in the second trimester (102096).

LACTATION: LIKELY SAFE
when used orally in amounts found in foods (7135). There is insufficient reliable information available about the safety of vanadium when used in amounts greater than those typically found in foods; avoid using.

VITAMIN A

LIKELY SAFE ...when used orally or intramuscularly and appropriately. Vitamin A, as pre-formed vitamin A (retinol or retinyl ester), is safe in adults when taken in doses below the tolerable upper intake level (UL) of 10,000 IU (3000 mcg) per day (7135). Higher doses increase the risk of side effects. There is also growing concern that taking high doses of antioxidants such as vitamin A might do more harm than good. In an analysis of studies, taking vitamin A supplements alone or in combination with other antioxidants is associated with an increased risk of mortality from all causes (15305,90775). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

POSSIBLY SAFE ...when used topically and appropriately, short-term. Retinol 0.5% has been used on the skin daily for up to 12 weeks with apparent safety. No serious adverse effects have been reported in clinical trials (103671,103680).

POSSIBLY UNSAFE ...when used orally in high doses. Doses higher than the UL of 10,000 IU (3000 mcg) per day of pre-formed vitamin A (retinol or retinyl ester) might increase the risk of side effects (7135). While vitamin A 25,000 IU (as retinyl palmitate) daily for 6 months followed by 10,000 IU daily for 6 months has been used with apparent safety in one clinical trial (95052), prolonged use of excessive doses of vitamin A can cause significant side effects such as hypervitaminosis A. The risk for developing hypervitaminosis A is related to total cumulative dose of vitamin A rather than a specific daily dose (1467,1469). There is also concern that taking high doses of antioxidants such as vitamin A might do more harm than good. In an analysis of studies, taking vitamin A supplements alone or in combination with other antioxidants is associated with an increased risk of mortality from all causes (15305,90775). There is insufficient reliable information available about the safety of using sublingual formulations of vitamin A.

CHILDREN: LIKELY SAFE
when used orally or intramuscularly and appropriately. The amount of pre-formed vitamin A (retinol or retinyl ester) that is safe depends on age. For children up to 3 years of age, doses less than 2000 IU (600 mcg) per day seem to be safe. For children ages 4 to 8, doses less than 3000 IU (900 mcg) per day seem to be safe. For children ages 9 to 13, doses less than 5667 IU (1700 mcg) per day seem to be safe. For children 14 to 18, doses less than 9333 IU (2800 mcg) per day seem to be safe (7135). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

CHILDREN: POSSIBLY UNSAFE
when pre-formed vitamin A (retinol or retinyl ester) is used orally in excessive doses. For children up to 3 years of age, avoid doses greater than 2000 IU (600 mcg) per day. For children ages 4 to 8, avoid doses greater than 3000 IU (900 mcg) per day. For children ages 9 to 13, avoid doses greater than 5667 IU (1700 mcg) per day. For children ages 14 to 18, avoid doses greater than 9333 IU (2800 mcg) per day (7135). Higher doses of vitamin A supplementation have been associated with increased risk of side effects such as pneumonia, bone pain, and diarrhea (319,95051). Long-term supplementation with low to moderate doses on a regular basis can cause severe, but usually reversible, liver damage (11978).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally or intramuscularly and appropriately. Vitamin A, as pre-formed vitamin A (retinol or retinyl ester), is safe during pregnancy and lactation when used in doses less than 10,000 IU (3000 mcg) per day (7135,16823,107293). Keep in mind that vitamin A is available in two different forms: pre-formed vitamin A (retinol or retinyl ester) and provitamin A (carotenoids). The safety concerns associated with high vitamin A intake occur with pre-formed vitamin A only. Some supplements contain vitamin A in both pre-formed and provitamin A forms. For these supplements, the amount of pre-formed vitamin A should be used to determine if the amount of vitamin A is safe.

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally or intramuscularly in excessive doses. Daily intake of greater than 10,000 IU (3000 mcg) can cause fetal malformations (3066,7135). Excessive dietary intake of vitamin A has also been associated with teratogenicity (11978). The first trimester of pregnancy seems to be the critical period for susceptibility to vitamin A-associated birth defects such as craniofacial abnormalities and abnormalities of the central nervous system (7135). Pregnant patients should monitor their intake of pre-formed vitamin A (retinol or retinyl ester). This form of vitamin A is found in several foods including animal products, some fortified breakfast cereals, and dietary supplements (3066).

VITAMIN B12

LIKELY SAFE ...when used orally, topically, intravenously, intramuscularly, or intranasally and appropriately. Vitamin B12 is generally considered safe, even in large doses (15,1344,1345,1346,1347,1348,2909,6243,7289,7881)(9414,9416,10126,14392,15765,82832,82949,82860,82864,90386)(111551,111554).

PREGNANCY: LIKELY SAFE
when used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA for vitamin B12 during pregnancy is 2.6 mcg daily (6243). There is insufficient reliable information available about the safety of larger amounts of vitamin B12 during pregnancy.

LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the recommended dietary allowance (RDA). The RDA of vitamin B12 during lactation is 2.8 mcg daily (6243). There is insufficient reliable information available about the safety of larger amounts of vitamin B12 while breastfeeding.

VITAMIN B6

LIKELY SAFE ...when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of 100 mg daily for adults (15). ...when used parenterally and appropriately. Injectable vitamin B6 (pyridoxine) is an FDA-approved prescription product (15).

POSSIBLY SAFE ...when used orally and appropriately in doses of 101-200 mg daily (6243,8558).

POSSIBLY UNSAFE ...when used orally in doses at or above 500 mg daily. High doses, especially those exceeding 1000 mg daily or total doses of 1000 grams or more, pose the most risk. However, neuropathy can occur with lower daily or total doses (6243,8195). ...when used intramuscularly in high doses and frequency due to potential for rhabdomyolysis (90795).

CHILDREN: LIKELY SAFE
when used orally and appropriately (3094).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in amounts exceeding the recommended dietary allowance (5049,8579,107124,107125,107135).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses, long-term (3094).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. A special sustained-release product providing vitamin B6 (pyridoxine) 75 mg daily is FDA-approved for use in pregnancy. Vitamin B6 (pyridoxine) is also considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology (111601). However, it should not be used long-term or without medical supervision and close monitoring.

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses. There is some concern that high-dose maternal vitamin B6 (pyridoxine) can cause neonatal seizures (4609,6397,8197).

LACTATION: LIKELY SAFE
when used orally in doses not exceeding the recommended dietary allowance (RDA) (3094). The RDA in lactating women is 2 mg daily. There is insufficient reliable information available about the safety of vitamin B6 when used in higher doses in breast-feeding women.

VITAMIN C

LIKELY SAFE ...when used orally, topically, intramuscularly, or intravenously and appropriately. Vitamin C is safe when taken orally in doses below the tolerable upper intake level (UL). Tell patients not to exceed the UL of 2000 mg daily (1959,4713,4714,4844). ...when used intravenously or intramuscularly and appropriately. Injectable vitamin C is an FDA-approved prescription product (15).

POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 2000 mg daily can significantly increase the risk of adverse effects such as osmotic diarrhea and gastrointestinal upset (4844).

CHILDREN: LIKELY SAFE
when used orally and appropriately (4844,10352,14443).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 400 mg daily for children ages 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years. Higher doses can cause osmotic diarrhea and gastrointestinal upset (4844).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (4844).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Tell patients over age 19 not to use doses exceeding the UL of 2000 mg daily when pregnant or breast-feeding and for those 14-18 years of age not to use doses exceeding 1800 mg daily when pregnant or breast-feeding. Higher doses can cause osmotic diarrhea and gastrointestinal upset. Large doses of vitamin C during pregnancy can also cause newborn scurvy (4844); avoid using.

VITAMIN D

LIKELY SAFE ...when used orally or intramuscularly and appropriately. Vitamin D has been safely used in a wide range of doses (7555,16888,16891,17476,95913,98186,104619,105209,109059). When used orally long-term, doses should not exceed the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily for adults (17506,99773); however, much higher doses such as 50,000 IU (1250 mcg) weekly orally for 6-12 weeks are often needed for the short-term treatment of vitamin D deficiency (16891,17476). Monthly oral doses of up to 60,000 IU (1500 mcg) have also been safely used for up to 5 years (105726). Toxicity usually does not occur until plasma levels exceed 150 ng/mL (17476).

POSSIBLY UNSAFE ...when used orally in excessive doses, long-term. Taking doses greater than the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily for long periods can increase the risk of hypercalcemia (17506); however, much higher doses are often needed for short-term treatment of vitamin D deficiency. Toxicity typically occurs when levels exceed 150 ng/mL (17476).

CHILDREN: LIKELY SAFE
when used orally and appropriately. When used long-term, doses should not exceed the tolerable upper intake level (UL) of 1000 IU (25 mcg) daily for those 0-6 months of age, 1500 IU (37.5 mcg) daily for those 6-12 months of age, 2500 IU (62.5 mcg) daily for those 1-3 years of age, 3000 IU (75 mcg) daily for those 4-8 years of age, and 4000 IU (100 mcg) daily for those 9 years and older (17506); however, much higher doses are often needed for the short-term treatment of vitamin D deficiency. Some research shows that giving vitamin D 14,000 IU (350 mcg) weekly for a year in children aged 10-17 years is safe (16875). A meta-analysis of clinical studies shows that 1000 IU (25 mcg) daily in those up to a year of age and greater than 2000 IU (50 mcg) daily in those aged 1-6 years does not increase the risk of serious adverse events (108424).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses for longer than one year. Taking doses greater than the tolerable upper intake level (UL) long-term can increase the risk of hypercalcemia (17506).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Vitamin D is safe when used in doses below the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily (17506,95910).

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily. Hypercalcemia during pregnancy due to excessive vitamin D intake can lead to several fetal adverse effects, including suppression of parathyroid hormone, hypocalcemia, tetany, seizures, aortic valve stenosis, retinopathy, and mental and/or physical developmental delay (17506).

LACTATION: LIKELY SAFE
when used orally and appropriately. Vitamin D is safe when used in doses below the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily (17506).

LACTATION: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 4000 IU (100 mcg) daily (17506).

VITAMIN E

LIKELY SAFE ...when used orally or topically and appropriately. Vitamin E is generally considered safe, even at doses exceeding the recommended dietary allowance (RDA); however, adverse effects are more likely to occur with higher doses. The tolerable upper intake level (UL) in healthy people is 1000 mg daily, equivalent to 1100 IU of synthetic vitamin E (all-rac-alpha-tocopherol) or 1500 IU of natural vitamin E (RRR-alpha-tocopherol) (4668,4681,4713,4714,4844,89234,90067,90069,90072,19206)(63244,97075). Although there is some concern that taking vitamin E in doses of 400 IU (form unspecified) per day or higher might increase the risk of adverse outcomes and mortality from all causes (12212,13036,15305,16709,83339), most of this evidence comes from studies that included middle-aged or older patients with chronic diseases or patients from developing countries in which nutritional deficiencies are prevalent.

POSSIBLY UNSAFE ...when used orally in high doses. Repeated doses exceeding the tolerable upper intake level (UL) of 1000 mg daily are associated with significant side effects in otherwise healthy people (4844). ...when used intravenously in large doses. Large repeated intravenous doses of all-rac-alpha-tocopherol (synthetic vitamin E) were associated with decreased activity of clotting factors and bleeding in one report (3074). ...when inhaled. E-cigarette, or vaping, product-use associated lung injury (EVALI) has occurred among adults who use e-cigarette, or vaping, products, which often contain vitamin E acetate. In some cases, this has resulted in death. The majority of patients with EVALI reported using tetrahydrocannabinol (THC)-containing products in the 3 months prior to the development of symptoms. Vitamin E acetate has been detected in most bronchoalveolar lavage samples taken from patients with EVALI. Other ingredients, including THC or nicotine, were also commonly found in samples. However, priority toxicants including medium chain triglyceride (MCT) oil, plant oil, petroleum distillate, or terpenes, were undetectable in almost all samples. While this association shows a correlation between vitamin E acetate inhalation and lung injury, a causal link has not yet been determined, and it is not clear if other toxic compounds are also involved (101061,101062,102970).

CHILDREN: LIKELY SAFE
when used orally and appropriately. Vitamin E has been safely used in children in amounts below the tolerable upper intake level (UL). The UL for healthy children is: 200 mg in children aged 1-3 years, 300 mg in children aged 4-8 years, 600 mg in children aged 9-13 years, and 800 mg in children aged 14-18 years. A UL has not been established for infants up to 12 months of age (23388).

CHILDREN: POSSIBLY UNSAFE
when used orally in doses above the UL due to increased risk of adverse effects (23388). ...when alpha-tocopherol is used intravenously in large doses in premature infants. Large intravenous doses of vitamin E are associated with an increased risk of necrotizing enterocolitis and sepsis in this population (85062,85083). ...when inhaled. E-cigarette, or vaping, product-use associated lung injury (EVALI) has occurred among adolescents and teenagers who use e-cigarette, or vaping, products. In some cases, this has resulted in death. The majority of patients with EVALI reported using tetrahydrocannabinol (THC)-containing products in the 3 months prior to the development of symptoms. Constituents in E-cigarette or vaping products with the potential to cause lung injury or impaired lung function include lipids, such as vitamin E acetate. Vitamin E acetate has been detected in all bronchoalveolar lavage samples taken from patients with EVALI. No other ingredient, including THC or nicotine, was found in all samples, and other ingredients, including medium chain triglyceride (MCT) oil, plant oil, petroleum distillate, or terpenes, were undetectable This shows that vitamin E acetate is at the primary site of lung injury. A causal link has not yet been described and it is not clear if other compounds are also involved (101061,101062).

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately. The tolerable upper intake level (UL) during pregnancy is 800 mg for those 14-18 years of age and 1000 mg for those 19 years and older. However, maternal supplementation is not generally recommended unless dietary vitamin E falls below the RDA (4260). No serious adverse effects were reported with oral intake of 400 IU per day starting at weeks 9-22 of pregnancy in healthy patients or those at high risk for pre-eclampsia (3236,97075), or with 600-900 IU daily during the last two months of pregnancy (4260). However, some preliminary evidence suggests that taking vitamin E supplements might be harmful when taken in early pregnancy. A case-control study found that taking a vitamin E supplement during the first 8 weeks of pregnancy is associated with a 1.7-9-fold increase in odds of congenital heart defects (16823). However, the exact amount of vitamin E consumed during pregnancy in this study is unclear. Until more is known, advise patients to avoid taking a vitamin E supplement in early pregnancy unless needed for an appropriate medical indication.

LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the tolerable upper intake level (UL). The UL during lactation is 800 mg for those 14-18 years of age and 1000 mg for those 19 years and older (4844).

LACTATION: POSSIBLY UNSAFE
when used orally in amounts that exceed the UL due to increased risk of adverse effects (4844).

VITAMIN K

LIKELY SAFE ...when vitamin K1 (phytonadione) or vitamin K2 (menaquinone) is used orally and appropriately. Vitamin K1 up to 10 mg daily and vitamin K2 up to 45 mg daily have been safely used in clinical trials lasting up to 2 years. A tolerable upper intake level for vitamin K in adults has not been set (54,55,58,6799,7135,14364). ...when vitamin K1 (phytonadione) is used parenterally and appropriately. Vitamin K1 (phytonadione) in oral and injectable form is an FDA-approved drug (7135).

POSSIBLY SAFE ...when vitamin K1 (phytonadione) 0. 1% is used topically in a cream or ointment for up to 12 weeks (91455,103919).

CHILDREN: LIKELY SAFE
when vitamin K1 (phytonadione) is used orally or parenterally and appropriately. Vitamin K1 (phytonadione) in oral and injectable form is FDA approved for use in children. A tolerable upper intake level for vitamin K in children has not been set (7135).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts that do not exceed the daily adequate intake level (AI). A tolerable upper intake level for vitamin K in pregnancy and lactation has not been set (7135).

ZINC

LIKELY SAFE ...when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 40 mg daily (7135). ...when used topically and appropriately (2688,6538,6539,7135,8623,11051,111291).

POSSIBLY SAFE ...when used orally and appropriately in doses higher than the tolerable upper intake level (UL). Because the UL of zinc is based on regular daily intake, short-term excursions above 40 mg daily are not likely to be harmful. In fact, there is some evidence that doses of elemental zinc as high as 80 mg daily in combination with copper 2 mg can be used safely for approximately 6 years without significant adverse effects (7303,8622,92212). However, there is some concern that doses higher than the UL of 40 mg daily might decrease copper absorption and result in anemia (7135).

POSSIBLY UNSAFE ...when used intranasally. Case reports and animal research suggest that intranasal zinc might cause permanent anosmia or loss of sense of smell (11155,11156,11703,11704,11705,11706,11707,16800,16801,17083). Several hundred reports of anosmia have been submitted to the US Food and Drug Administration (FDA) and the manufacturer of some intranasal zinc products (Zicam) (16800,16801). Advise patients not to use intranasal zinc products.

LIKELY UNSAFE ...when taken orally in excessive amounts. Ingestion of 10-30 grams of zinc sulfate can be lethal in adults (7135). Chronic intake of 450-1600 mg daily can cause multiple forms of anemia, copper deficiency, and myeloneuropathies (7135,17092,17093,112473). This has been reported with use of zinc-containing denture adhesives in amounts exceeding the labeled directions, such as several times a day for several years (17092,17093). Advise patients to follow the label directions on denture adhesives that contain zinc.

CHILDREN: LIKELY SAFE
when used orally and appropriately (7135). Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL). The UL for children is based on age: 4 mg daily for 0-6 months, 5 mg daily for 7-12 months, 7 mg daily for 1-3 years, 12 mg daily for 4-8 years, 23 mg daily for 9-13 years, and 34 mg daily for 14-18 years (7135,97140).

CHILDREN: POSSIBLY UNSAFE
when used orally in high doses. Taking amounts greater than the UL can cause sideroblastic anemia and copper deficiency (7135). ...when used topically on damaged skin. An infant treated with 10% zinc oxide ointment for severe diaper rash with perianal erosions developed hyperzincemia. Absorption seemed to occur mainly via the erosions; plasma levels dropped after the erosions healed despite continued use of the ointment (106905).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 34 mg daily during pregnancy in those 14-18 years of age and 40 mg daily in those 19-50 years of age (7135).

PREGNANCY: LIKELY UNSAFE
when used orally in doses exceeding the UL (7135).

LACTATION: LIKELY SAFE
when used orally and appropriately. Zinc is safe in amounts that do not exceed the tolerable upper intake level (UL) of 34 mg daily during lactation in those 14-18 years of age, and 40 mg daily for those 19-50 years of age (7135).

LACTATION: POSSIBLY UNSAFE
when used orally in doses exceeding the UL. Higher doses can cause zinc-induced copper deficiency in nursing infants (7135).

Interactions with Drugs view details

Below is general information about the interactions of the known ingredients contained in the product Centrum Women Under 50. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

BIOTIN

None known.

BORON

None known.

CALCIUM

ALUMINUM

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Calcium citrate might increase aluminum absorption and toxicity. Other types of calcium do not increase aluminum absorption.

Details

Calcium citrate can increase the absorption of aluminum when taken with aluminum hydroxide. The increase in aluminum levels may become toxic, particularly in individuals with kidney disease (21631). However, the effect of calcium citrate on aluminum absorption is due to the citrate anion rather than calcium cation. Calcium acetate does not appear to increase aluminum absorption (93006).

BISPHOSPHONATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Calcium reduces the absorption of bisphosphonates.

Details

Advise patients to take bisphosphonates at least 30 minutes before calcium, but preferably at a different time of day. Calcium supplements decrease absorption of bisphosphonates (12937).

CALCIPOTRIENE (Dovonex)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Taking calcipotriene with calcium might increase the risk for hypercalcemia.

Details

Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia (12938). Theoretically, combining calcipotriene with calcium supplements might increase the risk of hypercalcemia.

CALCIUM CHANNEL BLOCKERS

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Intravenous calcium may decrease the effects of calcium channel blockers; oral calcium is unlikely to have this effect.

Details

Intravenous calcium is used to decrease the effects of calcium channel blockers in the management of overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects (6124). But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers (12939,12947).

CEFTRIAXONE (Rocephin)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = D

Co-administration of intravenous calcium and ceftriaxone can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys.

Details

Avoid administering intravenous calcium in any form, such as parenteral nutrition or Lactated Ringers, within 48 hours of intravenous ceftriaxone. Case reports in neonates show that administering intravenous ceftriaxone and calcium can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys. In several cases, neonates have died as a result of this interaction (15794,21632). So far there are no reports in adults; however, there is still concern that this interaction might occur in adults.

DIGOXIN (Lanoxin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Using intravenous calcium with digoxin might increase the risk of fatal cardiac arrhythmias.

Details

Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin (12940). However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin (38960).

DILTIAZEM (Cardizem, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, calcium may reduce the therapeutic effects of diltiazem.

Details

Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, calcium might increase this risk of hypercalcemia and reduce the effectiveness of diltiazem.

DOLUTEGRAVIR (Tivicay)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = B

Calcium seems to reduce levels of dolutegravir.

Details

Advise patients to take dolutegravir either 2 hours before or 6 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium carbonate 1200 mg concomitantly with dolutegravir 50 mg reduces plasma levels of dolutegravir by almost 40%. Calcium appears to decrease levels of dolutegravir through chelation (93578).

ELVITEGRAVIR (Vitekta)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = B

Calcium seems to reduce levels of elvitegravir.

Details

Advise patients to take elvitegravir either 2 hours before or 2 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium along with elvitegravir can reduce blood levels of elvitegravir through chelation (94166).

LEVOTHYROXINE (Synthroid, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Calcium seems to reduce the absorption and effectiveness of levothyroxine.

Details

Advise patients to take levothyroxine and calcium supplements at least 4 hours apart. Calcium reduces levothyroxine absorption, probably by forming insoluble complexes (5082). Calcium carbonate supplements reduce effectiveness of levothyroxine in patients with hypothyroidism (5081,5082,6137).

LITHIUM

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, concomitant use of calcium and lithium may increase this risk of hypercalcemia.

Details

Clinical research suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients (38953). Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

QUINOLONE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Calcium seems to reduce the absorption of quinolone antibiotics.

Details

Advise patients to take oral quinolones at least 2 hours before or 4-6 hours after calcium supplements or calcium-fortified foods. Taking calcium at the same time as oral quinolones can reduce quinolone absorption. Calcium binds to quinolones in the gut (4412,10339,21638,38570).

RALTEGRAVIR (Isentress)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Calcium may reduce levels of raltegravir.

Details

Pharmacokinetic research shows that taking a single dose of calcium carbonate 3000 mg along with raltegravir 400 mg twice daily modestly decreases the mean area under the curve of raltegravir, but the decrease does not necessitate a dose adjustment of raltegravir (94164). However, a case of elevated HIV-1 RNA levels and documented resistance to raltegravir has been reported for a patient taking calcium carbonate 1 gram three times daily plus vitamin D3 (cholecalciferol) 400 IU three times daily in combination with raltegravir 400 mg twice daily for 11 months. It is thought that calcium reduced raltegravir levels by chelation, leading to treatment failure (94165).

SOTALOL (Betapace)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Calcium seems to reduce the absorption of sotalol.

Details

Advise patients to separate doses by at least 2 hours before or 4-6 hours after calcium. Calcium appears to reduce the absorption of sotalol, probably by forming insoluble complexes (10018).

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Calcium seems to reduce the absorption of tetracycline antibiotics.

Details

Advise patients to take oral tetracyclines at least 2 hours before, or 4-6 hours after calcium supplements. Taking calcium at the same time as oral tetracyclines can reduce tetracycline absorption. Calcium binds to tetracyclines in the gut (1843).

THIAZIDE DIURETICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Taking calcium along with thiazides might increase the risk of hypercalcemia and renal failure.

Details

Thiazides reduce calcium excretion by the kidneys (1902). Using thiazides along with moderately large amounts of calcium carbonate increases the risk of milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure). Patients may need to have their serum calcium levels and/or parathyroid function monitored regularly.

VERAPAMIL (Calan, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, calcium may reduce the therapeutic effects of verapamil.

Details

Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically, use of calcium supplements may increase this risk of hypercalcemia and reduce the effectiveness of verapamil.

CHROMIUM

ANTIDIABETES DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = A

Theoretically, chromium may have additive effects with antidiabetic agents and increase the risk of hypoglycemia.

Details

Some research shows that taking chromium might lower blood glucose levels, especially in patients with poorly controlled type 2 diabetes (7137,14440,15169,94234,95097,95098,98687).

ASPIRIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = D

Theoretically, aspirin might increase chromium absorption.

Details

Animal research suggests that aspirin may increase chromium absorption and chromium levels in the blood (21055).

INSULIN

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, concomitant use of chromium and insulin might increase the risk of hypoglycemia.

Details

In clinical research, chromium has been shown to increase insulin sensitivity (1952,14440,95095),

LEVOTHYROXINE (Synthroid, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Chromium might bind levothyroxine in the intestinal tract and decrease levothyroxine absorption.

Details

Clinical research in healthy volunteers shows that taking chromium picolinate 1000 mcg with levothyroxine 1 mg decreases serum levels of levothyroxine by 17% when compared to taking levothyroxine alone (16012). Advise patients to take levothyroxine at least 30 minutes before or 3-4 hours after taking chromium.

NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDs)

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

NSAIDs might increase chromium levels in the body.

Details

Drugs that are prostaglandin inhibitors, such as NSAIDs, seem to increase chromium absorption and retention (7135).

COPPER

CONTRACEPTIVE DRUGS

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

Theoretically, taking copper with contraceptive drugs might increase the levels and toxic effects of copper.

Details

A meta-analysis of clinical studies suggests that chronic use of oral contraceptives increases serum copper levels by a mean of 57 mcg/dL. In most people, this resulted in levels above the normal reference range for copper (92395).

PENICILLAMINE (Cuprimine, Depen)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, taking copper with penicillamine might decrease the absorption of penicillamine; separate dosing by at least 2 hours.

Details

Copper chelates penicillamine, which decreases its absorption and may reduce its clinical effects (4412,4453,4531,4535,9630).

FOLIC ACID

5-FLUOROURACIL

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, high doses of folic acid might increase the toxicity of 5-fluorouracil.

Details

Increases in gastrointestinal side effects of 5-fluorouracil, such as stomatitis and diarrhea, have been described in two clinical studies when leucovorin, a form of folic acid, was administered with 5-fluorouracil (16845).

CAPECITABINE (Xeloda)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Use of high-dose folic acid might contribute to capecitabine toxicity.

Details

Clinical research suggests that higher serum folate levels are associated with an increased risk for moderate or severe toxicity during capecitabine-based treatment for colorectal cancer (105402). Additionally, in one case report, taking folic acid 15 mg daily might have contributed to increased toxicity, including severe diarrhea, vomiting, edema, hand-foot syndrome, and eventually death, in a patient prescribed capecitabine (16837).

METHOTREXATE (Trexall, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Folic acid might reduce the efficacy of methotrexate as a cancer treatment when given concurrently.

Details

Methotrexate exerts its cytotoxic effects by preventing conversion of folic acid to the active form needed by cells. There is some evidence that folic acid supplements reduce the efficacy of methotrexate in the treatment of acute lymphoblastic leukemia, and theoretically they could reduce its efficacy in the treatment of other cancers (9420). Advise cancer patients to consult their oncologist before using folic acid supplements. In patients treated with long-term, low-dose methotrexate for rheumatoid arthritis (RA) or psoriasis, folic acid supplements can reduce the incidence of side effects, without reducing efficacy (768,2162,4492,4493,4494,4546,9369).

PHENOBARBITAL (Luminal)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Folic acid might have antagonistic effects on phenobarbital and increase the risk for seizures.

Details

Folic acid can have direct convulsant activity in some people, reversing the effects of phenobarbital and worsening seizure control (4427,9357,9358). Monitor closely for increased seizure activity.

PHENYTOIN (Dilantin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Folic acid might reduce serum levels of phenytoin in some patients.

Details

Folic acid may be a cofactor in phenytoin metabolism (4471). Folic acid, in doses of 1 mg daily or more, can reduce serum levels of phenytoin in some patients (4471,4477,4531,4536). Increases in seizure frequency have been reported. If folic acid supplements are added to established phenytoin therapy, monitor serum phenytoin levels closely. If phenytoin and folic acid are started at the same time and continued together, adverse changes in phenytoin pharmacokinetics are avoided (4471,4472,4473,4531). Note that phenytoin also reduces serum folate levels.

PRIMIDONE (Mysoline)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Folic acid might have antagonistic effects on primidone and increase the risk for seizures.

Details

Folic acid can have direct convulsant activity in some people, reversing the effects of primidone and worsening seizure control (4427,9357,9358). Monitor closely for increased seizure activity. Note that primidone also reduces serum folate levels.

PYRIMETHAMINE (Daraprim)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Folic acid might antagonize the effects of pyrimethamine.

Details

Folic acid can antagonize the antiparasitic effects of pyrimethamine against toxoplasmosis and Pneumocystis carinii pneumonia. Folic acid doesn't antagonize the effects of pyrimethamine in the treatment of malaria, because malarial parasites cannot use exogenous folic acid. Use folinic acid as an alternative to folic acid when indicated (9380).

IODINE

AMIODARONE (Cordarone)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Combining iodine with amiodarone might cause excessively high iodine levels.

Details

Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use with iodine might increase the risk of having excessive iodine levels and adversely affecting thyroid function (7135,17574). Monitor thyroid function.

ANTITHYROID DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Iodine might alter the effects of antithyroid drugs.

Details

Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking iodine while using antithyroid drugs could alter the effects of the antithyroid drugs (2138,17574).

LITHIUM

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Combining iodine with lithium might have additive hypothyroid effects.

Details

Lithium can inhibit thyroid function. Several case reports suggest that concomitant use of lithium and potassium iodide can reduce thyroid function in otherwise healthy adults (17574). Monitor thyroid function.

IRON

BISPHOSPHONATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Iron reduces the absorption of bisphosphonates.

Details

Advise patients that doses of bisphosphonates should be separated by at least two hours from doses of all other medications, including supplements such as iron. Divalent cations, including iron, can decrease absorption of bisphosphonates by forming insoluble complexes in the gastrointestinal tract (15).

CHLORAMPHENICOL

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Theoretically, taking chloramphenicol with iron might reduce the response to iron therapy in iron deficiency anemia.

Details

Chloramphenicol interferes with erythrocyte maturation (15,3046). However, since chloramphenicol isn't usually taken for prolonged periods, this isn't likely to be clinically significant.

DOLUTEGRAVIR (Tivicay)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Iron might decrease dolutegravir levels by reducing its absorption.

Details

Advise patients to take dolutegravir at least 2 hours before or 6 hours after taking iron. Pharmacokinetic research shows that iron can decrease the absorption of dolutegravir from the gastrointestinal tract through chelation (93578). When taken under fasting conditions, a single dose of ferrous fumarate 324 mg orally along with dolutegravir 50 mg reduces overall exposure to dolutegravir by 54% (94190).

INTEGRASE INHIBITORS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, taking iron along with integrase inhibitors might decrease the levels and clinical effects of these drugs.

Details

Iron is a divalent cation. There is concern that iron may decrease the absorption of integrase inhibitors from the gastrointestinal tract through chelation (93578). One pharmacokinetic study shows that iron can decrease blood levels of the specific integrase inhibitor dolutegravir through chelation (94190). Also, other pharmacokinetic research shows that other divalent cations such as calcium can decrease the absorption and levels of some integrase inhibitors through chelation (93578,93579).

LEVODOPA

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Iron might decrease levodopa levels by reducing its absorption.

Details

Advise patients to separate doses of levodopa and iron as much as possible. There is some evidence in healthy people that iron forms chelates with levodopa, reducing the amount of levodopa absorbed by around 50% (9567). The clinical significance of this hasn't been determined.

LEVOTHYROXINE (Synthroid, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Iron might decrease levothyroxine levels by reducing its absorption.

Details

Advise patients to separate levothyroxine and iron doses by at least 2 hours. Iron can decrease the absorption and efficacy of levothyroxine by forming insoluble complexes in the gastrointestinal tract (9568).

METHYLDOPA (Aldomet)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Iron might decrease methyldopa levels by reducing its absorption.

Details

Advise patients to separate methyldopa and iron doses by at least 2 hours. Iron can decrease the absorption of methyldopa from the gastrointestinal tract through chelation, resulting in increases in blood pressure (7900,20151).

MYCOPHENOLATE MOFETIL (CellCept)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Unlikely • Level of Evidence = D

Theoretically, iron might decrease mycophenolate mofetil levels by reducing its absorption.

Details

Advise patients to take iron 4-6 hours before, or 2 hours after, mycophenolate mofetil. It has been suggested that a decrease of absorption is possible, probably by forming nonabsorbable chelates. However, mycophenolate pharmacokinetics are not affected by iron supplementation in available clinical research (3046,20152,20153,20154,20155).

PENICILLAMINE (Cuprimine, Depen)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Iron might decrease penicillamine levels by reducing its absorption.

Details

Advise patients to separate penicillamine and iron doses by at least 2 hours. Oral iron supplements can reduce absorption of penicillamine by 30% to 70%, probably due to chelate formation. In people with Wilson's disease, this interaction has led to reduced efficacy of penicillamine (3046,3072,20156).

QUINOLONE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Iron might decrease levels of quinolone antibiotics by reducing their absorption.

Details

Advise patients to separate quinolone antibiotics and iron doses by at least 2 hours. Iron decreases the absorption of quinolones due to formation of insoluble complexes in the gastrointestinal tract (15,3072).

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Iron might decrease levels of tetracycline antibiotics by reducing their absorption.

Details

Advise patients to take iron at least 2 hours before or 4 hours after tetracycline antibiotics. Concomitant use can decrease absorption of tetracycline antibiotics from the gastrointestinal tract by 50% to 90% (15).

MAGNESIUM

AMINOGLYCOSIDE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Concomitant use of aminoglycoside antibiotics and magnesium can increase the risk for neuromuscular weakness.

Details

Both aminoglycosides and magnesium reduce presynaptic acetylcholine release, which can lead to neuromuscular blockade and possible paralysis. This is most likely to occur with high doses of magnesium given intravenously (13362).

ANTACIDS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Use of acid reducers may reduce the laxative effect of magnesium oxide.

Details

A retrospective analysis shows that, in the presence of H2 receptor antagonists (H2RAs) or proton pump inhibitors (PPIs), a higher dose of magnesium oxide is needed for a laxative effect (90033). This may also occur with antacids. Under acidic conditions, magnesium oxide is converted to magnesium chloride and then to magnesium bicarbonate, which has an osmotic laxative effect. By reducing acidity, antacids may reduce the conversion of magnesium oxide to the active bicarbonate salt.

ANTICOAGULANT/ANTIPLATELET DRUGS

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = B

Theoretically, magnesium may have antiplatelet effects, but the evidence is conflicting.

Details

In vitro evidence shows that magnesium sulfate inhibits platelet aggregation, even at low concentrations (20304,20305). Some preliminary clinical evidence shows that infusion of magnesium sulfate increases bleeding time by 48% and reduces platelet activity (20306). However, other clinical research shows that magnesium does not affect platelet aggregation, although inhibition of platelet-dependent thrombosis can occur (60759).

BISPHOSPHONATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Magnesium can decrease absorption of bisphosphonates.

Details

Cations, including magnesium, can decrease bisphosphonate absorption. Advise patients to separate doses of magnesium and these drugs by at least 2 hours (13363).

CALCIUM CHANNEL BLOCKERS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Magnesium can have additive effects with calcium channel blockers, although evidence is conflicting.

Details

Magnesium inhibits calcium entry into smooth muscle cells and may therefore have additive effects with calcium channel blockers. Severe hypotension and neuromuscular blockades may occur when nifedipine is used with intravenous magnesium (3046,20264,20265,20266), although some contradictory evidence suggests that concurrent use of magnesium with nifedipine does not increase the risk of neuromuscular weakness (60831). High doses of magnesium could theoretically have additive effects with other calcium channel blockers.

DIGOXIN

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Magnesium salts may reduce absorption of digoxin.

Details

Clinical evidence suggests that treatment with oral magnesium hydroxide or magnesium trisilicate reduces absorption of digoxin from the intestines (198,20268,20270). This may reduce the blood levels of digoxin and decrease its therapeutic effects.

GABAPENTIN (Neurontin)

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Unlikely • Level of Evidence = B

Gabapentin absorption can be decreased by magnesium.

Details

Clinical research shows that giving magnesium oxide orally along with gabapentin decreases the maximum plasma concentration of gabapentin by 33%, time to maximum concentration by 36%, and area under the curve by 43% (90032). Advise patients to take gabapentin at least 2 hours before, or 4 to 6 hours after, magnesium supplements.

KETAMINE (Ketalar)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Magnesium might precipitate ketamine toxicity.

Details

In one case report, a 62-year-old hospice patient with terminal cancer who had been stabilized on sublingual ketamine 150 mg four times daily experienced severe ketamine toxicity lasting for 2 hours after taking a maintenance dose of ketamine following an infusion of magnesium sulfate 2 grams (105078). Since both magnesium and ketamine block the NMDA receptor, magnesium is thought to have potentiated the effects of ketamine.

LEVODOPA/CARBIDOPA (Sinemet)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = B

Magnesium can reduce the bioavailability of levodopa/carbidopa.

Details

Clinical research in healthy volunteers shows that taking magnesium oxide 1000 mg with levodopa 100 mg/carbidopa 10 mg reduces the area under the curve (AUC) of levodopa by 35% and of carbidopa by 81%. In vitro and animal research shows that magnesium produces an alkaline environment in the digestive tract, which might lead to degradation and reduced bioavailability of levodopa/carbidopa (100265).

POTASSIUM-SPARING DIURETICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Potassium-sparing diuretics decrease excretion of magnesium, possibly increasing magnesium levels.

Details

Potassium-sparing diuretics also have magnesium-sparing properties, which can counteract the magnesium losses associated with loop and thiazide diuretics (9613,9614,9622). Theoretically, increased magnesium levels could result from concomitant use of potassium-sparing diuretics and magnesium supplements.

QUINOLONE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Magnesium decreases absorption of quinolones.

Details

Magnesium can form insoluble complexes with quinolones and decrease their absorption (3046). Advise patients to take these drugs at least 2 hours before, or 4 to 6 hours after, magnesium supplements.

SEVELAMER (Renagel, Renvela)

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = B

Sevelamer may increase serum magnesium levels.

Details

In patients on hemodialysis, sevelamer use was associated with a 0.28 mg/dL increase in serum magnesium. The mechanism of this interaction remains unclear (96486).

SKELETAL MUSCLE RELAXANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = A

Parenteral magnesium alters the pharmacokinetics of skeletal muscle relaxants, increasing their effects and accelerating the onset of effect.

Details

Parenteral magnesium shortens the time to onset of skeletal muscle relaxants by about 1 minute and prolongs the duration of action by about 2 minutes. Magnesium potentiates the effects of skeletal muscle relaxants by decreasing calcium-mediated release of acetylcholine from presynaptic nerve terminals, reducing postsynaptic sensitivity to acetylcholine, and having a direct effect on the membrane potential of myocytes (3046,97492,107364). Magnesium also has vasodilatory actions and increases cardiac output, allowing a greater amount of muscle relaxant to reach the motor end plate (107364). A clinical study found that low-dose rocuronium (0.45 mg/kg), when given after administration of magnesium 30 mg/kg over 10 minutes, has an accelerated onset of effect, which matches the onset of effect seen with a full-dose rocuronium regimen (0.6 mg/kg) (96485). In another clinical study, onset times for rocuronium doses of 0.3, 0.6, and 1.2 mg/kg were 86, 76, and 50 seconds, respectively, when given alone, but were reduced to 66, 44, and 38 seconds, respectively, when the doses were given after a 15-minute infusion of magnesium sulfate 60 mg/kg (107364). Giving intraoperative intravenous magnesium sulfate, 50 mg/kg loading dose followed by 15 mg/kg/hour, reduces the onset time of rocuronium, enhances its clinical effects, reduces the dose of intraoperative opiates, and prolongs the spontaneous recovery time (112781,112782). It does not affect the activity of subsequently administered neostigmine (112782).

SULFONYLUREAS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Magnesium increases the systemic absorption of sulfonylureas, increasing their effects and side effects.

Details

Clinical research shows that administration of magnesium hydroxide with glyburide increases glyburide absorption, increases maximal insulin response by 35-fold, and increases the risk of hypoglycemia, when compared with glyburide alone (20307). A similar interaction occurs between magnesium hydroxide and glipizide (20308). The mechanism of this effect appears to be related to the elevation of gastrointestinal pH by magnesium-based antacids, increasing solubility and enhancing absorption of sulfonylureas (22364).

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Magnesium decreases absorption of tetracyclines.

Details

Magnesium can form insoluble complexes with tetracyclines in the gut and decrease their absorption and antibacterial activity (12586). Advise patients to take these drugs 1 hour before or 2 hours after magnesium supplements.

MANGANESE

ANTIPSYCHOTIC DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, the risk for manganese toxicity might increase when taken with antipsychotic drugs.

Details

Hallucinations and behavioral changes have been reported in a patient with liver disease who was taking haloperidol and manganese. Researchers speculate that taking manganese along with haloperidol, phenothiazine-derivatives, or other antipsychotic medications might increase the risk of manganese toxicity in some patients (61493).

QUINOLONE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, manganese might reduce the absorption of quinolone antibiotics.

Details

Manganese is a multivalent cation. Interactions resulting in reduced quinolone absorption have been reported between quinolones and other multivalent cations, such as calcium and iron (488).

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, manganese might reduce the absorption of tetracycline antibiotics.

Details

Manganese is a multivalent cation. Interactions resulting in reduced tetracycline absorption have been reported between tetracyclines and other multivalent cations, such as calcium and iron (488).

MOLYBDENUM

None known.

NIACIN

ALCOHOL (Ethanol)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Concomitant use of alcohol and niacin might increase the risk of flushing and hepatotoxicity.

Details

Alcohol can exacerbate the flushing and pruritus associated with niacin (4458,11689). Large doses of niacin might also exacerbate liver dysfunction associated with chronic alcohol use. A case report describes delirium and lactic acidosis in a patient taking niacin 3 grams daily who ingested 1 liter of wine (14510). Advise patients to avoid large amounts of alcohol while taking niacin.

ALLOPURINOL (Zyloprim)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as allopurinol.

Details

Large doses of niacin can reduce urinary excretion of uric acid, potentially resulting in hyperuricemia (4860,4863,12033). Doses of uricosurics such as allopurinol might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

ANTICOAGULANT/ANTIPLATELET DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, niacin may have additive effects when used with anticoagulant or antiplatelet drugs.

Details

Several cases of clotting factor synthesis deficiency and coagulopathy have been reported in patients taking sustained-release niacin (25915). Also, thrombocytopenia has been reported in patients treated with niacin or niacin plus lovastatin (25916).

ANTIDIABETES DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.

Details

Niacin impairs glucose tolerance in a dose-dependent manner, probably by causing or aggravating insulin resistance and increasing hepatic production of glucose (4860,4863,11692,11693). In diabetes patients, niacin 4.5 grams daily for 5 weeks can increase plasma glucose by an average of 16% and glycated hemoglobin (HbA1c) by 21% (4860). However, lower doses of 1.5 grams daily or less appear to have minimal effects on blood glucose (12033). In some patients, glucose levels increase when niacin is started, but then return to baseline when a stable dose is reached (12033,93344). Up to 35% of patients with diabetes may need adjustments in hypoglycemic therapy when niacin is added (4458,4860,4863,11689,12033).

ANTIHYPERTENSIVE DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, niacin may increase the risk of hypotension when used with antihypertensive drugs.

Details

The vasodilating effects of niacin can cause hypotension (4863,12033,93341). Furthermore, some clinical evidence suggests that a one-hour infusion of niacin can reduce systolic, diastolic, and mean blood pressure in hypertensive patients. This effect is not observed in normotensive patients (25917).

ASPIRIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Likely • Level of Evidence = B

Large doses of aspirin might alter the clearance of niacin.

Details

Aspirin is often used with niacin to reduce niacin-induced flushing (4458,11689). Doses of 80-975 mg aspirin have been used, but 325 mg appears to be optimal (4458,4852,4853,11689). Aspirin also seems to reduce the clearance of niacin by competing for glycine conjugation. Taking aspirin 1 gram seems to reduce niacin clearance by 45% (14524). This is probably a dose-related effect and not clinically significant with the more common aspirin dose of 325 mg (11689,14524).

BILE ACID SEQUESTRANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Bile acid sequestrants can bind niacin and decrease absorption. Separate administration by 4-6 hours to avoid an interaction.

Details

In vitro studies show that colestipol (Colestid) binds about 98% of available niacin and cholestyramine (Questran) binds 10% to 30% (14511).

GEMFIBROZIL (Lopid)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of niacin and gemfibrozil might increase the risk of myopathy in some patients.

Details

A case of myopathy from concomitant use of niacin and gemfibrozil has been reported (25920). Niacin alone has also been associated with cases of myopathy (26100,26111). Using gemfibrozil with niacin might further increase the risk of developing myopathy.

HEPATOTOXIC DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.

Details

Niacin has been associated with cases of liver toxicity, especially when used in pharmacologic doses (4863,11689,11691,25929,25930,25931). Sustained-release niacin preparations appear to be associated with a higher risk of hepatotoxicity than immediate-release niacin (11691,25930,25931,93342).

HMG-CoA REDUCTASE INHIBITORS ("Statins")

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of niacin and statins might increase the risk of myopathy and rhabdomyolysis in some patients.

Details

Some case reports have raised concerns that niacin might increase the risk of myopathy and rhabdomyolysis when combined with statins (14508,25918). However, a significantly increased risk of myopathy has not been demonstrated in clinical trials, including those using an FDA-approved combination of lovastatin and niacin (Advicor) (7388,11689,12033,14509).

PROBENECID (Benemid)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as probenecid.

Details

Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia (4863,12033). Doses of uricosurics such as probenecid might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

SULFINPYRAZONE (Anturane)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = C

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as sulfinpyrazone.

Details

Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia (4863,12033). Doses of uricosurics such as sulfinpyrazone might need to be increased to maintain control of gout in patients who start taking niacin (4458). People who have frequent attacks of gout despite uricosuric therapy should avoid niacin (4863).

THYROID HORMONE

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, niacin might antagonize the therapeutic effects of thyroid hormones.

Details

Clinical research and case reports suggests that taking niacin can reduce serum levels of thyroxine-binding globulin by up to 25% and moderately reduce levels of thyroxine (T4) (25916,25925,25926,25928). Patients taking thyroid hormone for hypothyroidism might need dose adjustments when using niacin.

TRANSDERMAL NICOTINE (Nicoderm)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of niacin and transdermal nicotine might increase the risk of flushing and dizziness.

Details

Niacin and nicotine can both cause flushing and dizziness (496,96211).

NICKEL

DISULFIRAM (Antabuse)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Disulfiram can reduce the absorption and clinical effects of nickel.

Details

Disulfiram can chelate nickel, preventing its absorption. This interaction has been used therapeutically to reduce eczema in people with severe nickel hypersensitivity (16322).

None known.

BISPHOSPHONATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, taking phosphate salts with bisphosphonates might increase the risk of hypocalcemia.

Details

Combining bisphosphonates and phosphate can cause hypocalcemia. In one report, hypocalcemic tetany developed in a patient taking alendronate (Fosamax) who received a large dose of phosphate salts as a pre-operative laxative (14589).

ERDAFITINIB (Balversa)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = A

Taking erdafitinib with phosphate salts increases the risk of hyperphosphatemia.

Details

Erdafitinib increases phosphate levels. It is recommended that patients taking erdafitinib restrict phosphate intake to no more than 600-800 mg daily (104470).

FUTIBATINIB (Lytgobi)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Likely • Level of Evidence = A

Taking futibatinib with phosphate salts increases the risk of hyperphosphatemia.

Details

Futibatinib can cause hyperphosphatemia, as reported in 88% of patients in clinical studies. In addition, 77% of patients in clinical studies required use of a phosphate binder to manage hyperphosphatemia. Phosphate salts should generally be avoided by people taking this medication (112912).

POTASSIUM

ACE INHIBITORS (ACEIs)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Likely • Level of Evidence = C

Using ACEIs with high doses of potassium increases the risk of hyperkalemia.

Details

ACEIs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion (95628). Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia (15,23207). However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels (95628).

ANGIOTENSIN RECEPTOR BLOCKERS (ARBs)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Likely • Level of Evidence = C

Using ARBs with high doses of potassium increases the risk of hyperkalemia.

Details

ARBs block the actions of the renin-angiotensin-aldosterone system and reduce potassium excretion (95628). Concomitant use of these drugs with potassium supplements increases the risk of hyperkalemia (15,23207). However, concomitant use of these drugs with moderate dietary potassium intake (about 3775-5200 mg daily) does not increase serum potassium levels (95628).

POTASSIUM-SPARING DIURETICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Likely • Level of Evidence = C

Concomitant use increases the risk of hyperkalemia.

Details

Using potassium-sparing diuretics with potassium supplements increases the risk of hyperkalemia (15).

RIBOFLAVIN

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, taking riboflavin with tetracycline antibiotics may decrease the potency of these antibiotics.

Details

In vitro research suggests that riboflavin may inhibit the potency of tetracycline antibiotics (23372). It is not clear if this effect is clinically significant, as this interaction has not been reported in humans.

SELENIUM

ANTICOAGULANT/ANTIPLATELET DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Selenium may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

Details

Clinical research suggests that taking selenium 10 mcg/kg/day can increase bleeding times by increasing prostacyclin production, which inhibits platelet activity (14540). Other clinical research suggests that taking selenium 75 mcg daily, in combination with ascorbic acid 600 mg, alpha-tocopherol 300 mg, and beta-carotene 27 mg, reduces platelet aggregation (74406).

BARBITURATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, selenium might prolong the sedating effects of barbiturates.

Details

Laboratory research suggests that selenium can inhibit the hepatic metabolism of barbiturates (14601,14602). Selenium seems to prolong the sedative effect of pentobarbital in animal models (14601).

CONTRACEPTIVE DRUGS

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = B

Contraceptive drugs might increase levels of selenium, although the clinical significance of this effect is unclear.

Details

Some research suggests that oral contraceptives increase serum selenium levels in women taking oral contraceptives; however, other research shows no change in selenium levels (14544,14545,14546,101343). It is suggested that an increase could be due to increased carrier proteins, indicating a redistribution of selenium rather than a change in total body selenium (14545).

GOLD SALTS

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

Gold salts might interfere with selenium activity in tissues.

Details

Gold forms complexes with selenium, altering its tissue distribution. Theoretically, this might prevent the normal activity of selenium and produce effects equivalent to deficiency (14547,14548).

IMMUNOSUPPRESSANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, selenium supplementation may reduce the effectiveness of immunosuppressant therapy.

Details

In vitro research and preliminary clinical evidence suggests that selenium may stimulate the immune system (74483,74445).

NIACIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = A

Selenium might reduce the beneficial effects of niacin on high-density lipoprotein (HDL) levels.

Details

A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as selenium, or to the combination. It also is not known whether it will occur in other patient populations.

WARFARIN (Coumadin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, selenium might interfere with warfarin activity.

Details

Animal research suggests that selenium can increase warfarin activity. Selenium might interact with warfarin by displacing it from albumin binding sites, reducing its metabolism in the liver, or by decreasing production of vitamin K-dependent clotting factors (14541). Selenium can also prolong bleeding times in humans by increasing prostacyclin production, which inhibits platelet activity (14540).

SILICON

None known.

THIAMINE

TRIMETHOPRIM (Proloprim)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Probable • Level of Evidence = B

Trimethoprim might increase blood levels of thiamine.

Details

In vitro, animal, and clinical research suggest that trimethoprim inhibits intestinal thiamine transporter ThTR-2, hepatic transporter OCT1, and renal transporters OCT2, MATE1, and MATE2, resulting in paradoxically increased thiamine plasma concentrations (111678).

TIN

None known.

VANADIUM

ANTICOAGULANT/ANTIPLATELET DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, vanadium might increase the risk of bleeding when taken with anticoagulant/antiplatelet drugs.

Details

In vitro research shows that the sodium orthovanadate form of vanadium prolongs clotting time, likely through inhibition of thrombin and factor Xa (3054).

ANTIDIABETES DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Theoretically, vanadium might increase the risk of hypoglycemia when taken with antidiabetes drugs.

Details

A few very small clinical studies in patients with type 2 diabetes show that the vanadyl sulfate form of vanadium increases insulin sensitivity (3055,3056,3057) and might lower blood glucose levels (3057).

VITAMIN A

HEPATOTOXIC DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = C

Theoretically, taking high doses of vitamin A in combination with other potentially hepatotoxic drugs might increase the risk of liver disease.

Details

The tolerable upper intake level (UL) is the highest level of intake that is likely to pose no risk of adverse effects. Doses of vitamin A above the UL can cause hepatotoxicity, ranging from elevated liver enzymes to liver failure (7135,82554).

RETINOIDS

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Probable • Level of Evidence = D

Concomitant use of retinoids with vitamin A supplements might produce supratherapeutic vitamin A levels.

Details

Retinoids, which are vitamin A derivatives, could have additive toxic effects when taken with vitamin A supplements (3046).

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, taking tetracycline antibiotics with high doses of vitamin A can increase the risk of pseudotumor cerebri.

Details

Benign intracranial hypertension (pseudotumor cerebri) can occur with tetracyclines and with acute or chronic vitamin A toxicity. Case reports suggest that taking tetracyclines and vitamin A concurrently can increase the risk of this condition (10545,10546,10547). Avoid high doses of vitamin A in people taking tetracyclines chronically.

WARFARIN (Coumadin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, high doses of vitamin A could increase the risk of bleeding with warfarin.

Details

Vitamin A toxicity is associated with hemorrhage and hypoprothrombinemia, possibly due to vitamin K antagonism (505). Advise patients taking warfarin to avoid doses of vitamin A above the tolerable upper intake level of 10,000 IU/day for adults.

VITAMIN B12

None known.

VITAMIN B6

AMIODARONE (Cordarone)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, vitamin B6 might increase the photosensitivity caused by amiodarone.

Details

Despite initial case reports suggesting that pyridoxine may have a protective effect against amiodarone-induced photosensitivity, preliminary clinical research suggests that pyridoxine may actually exacerbate this adverse effect (8892,8893).

ANTIHYPERTENSIVE DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, vitamin B6 may have additive effects when used with antihypertensive drugs.

Details

Research in hypertensive rats shows that vitamin B6 can decrease systolic blood pressure (30859,82959,83093). Similarly, clinical research in patients with hypertension shows that taking high doses of vitamin B6 may reduce systolic and diastolic blood pressure, possibly by reducing plasma levels of epinephrine and norepinephrine (83091).

LEVODOPA

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Vitamin B6 may increase the metabolism of levodopa when taken alone, but not when taken in conjunction with carbidopa.

Details

Vitamin B6 (pyridoxine) enhances the metabolism of levodopa, reducing its clinical effects. However, this interaction does not occur when carbidopa is used concurrently with levodopa (Sinemet). Therefore, it is not likely to be a problem in most people (3046).

PHENOBARBITAL (Luminal)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

High doses of vitamin B6 may reduce the levels and clinical effects of phenobarbital.

Details

Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenobarbital, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenobarbital to avoid high doses of vitamin B6 (3046,10801).

PHENYTOIN (Dilantin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

High doses of vitamin B6 may reduce the levels and clinical effects of phenytoin.

Details

Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenytoin, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenytoin to avoid high doses of vitamin B6 (3046,10801).

VITAMIN C

ACETAMINOPHEN (Tylenol, others)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Probable • Level of Evidence = B

High-dose vitamin C might slightly prolong the clearance of acetaminophen.

Details

A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases (6451). This effect is not likely to be clinically significant.

ALKYLATING AGENTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.

Details

The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

ALUMINUM

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.

Details

Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption (10549,10550,10551,21556). In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely (10549). Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

ANTITUMOR ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.

Details

The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

ASPIRIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = B

Acidification of the urine by vitamin C might increase aspirin levels.

Details

It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction is not clinically significant.

CHOLINE MAGNESIUM TRISALICYLATE (Trilisate)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = B

Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.

Details

It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046,4531). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

ESTROGENS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Vitamin C might increase blood levels of estrogens.

Details

Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products (129,130,11161). It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall (129,11161). When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements (11161). Monitor these patients for estrogen-related side effects.

FLUPHENAZINE (Prolixin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, vitamin C might decrease levels of fluphenazine.

Details

In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started (11017). The mechanism is not known, and there is no further data to confirm this interaction.

INDINAVIR (Crixivan)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Vitamin C can modestly reduce indinavir levels.

Details

One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown (11300,93578).

LEVOTHYROXINE (Synthroid, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Vitamin C can increase levothyroxine absorption.

Details

Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH (102978).

NIACIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = A

Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.

Details

A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

SALSALATE (Disalcid)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = B

Acidification of the urine by vitamin C might increase salsalate levels.

Details

It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

WARFARIN (Coumadin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

High-dose vitamin C might reduce the levels and effectiveness of warfarin.

Details

Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption (11566). There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time (9804,9806). Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant (9805,9806,11566,11567). However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR) (90942). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

VITAMIN D

ALUMINUM

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Vitamin D might increase aluminum absorption and toxicity, but this has only been reported in people with renal failure.

Details

The protein that transports calcium across the intestinal wall can also bind and transport aluminum. This protein is stimulated by vitamin D, which may therefore increase aluminum absorption (11595,11597,22916). This mechanism may contribute to increased aluminum levels and toxicity in people with renal failure, when they take vitamin D and aluminum-containing phosphate binders chronically (11529,11596,11597).

ATORVASTATIN (Lipitor)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Vitamin D might reduce absorption of atorvastatin.

Details

A small, low-quality clinical study shows that taking vitamin D reduces levels of atorvastatin and its active metabolites by up to 55%. However, while atorvastatin levels decreased, total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol levels did not substantially change (16828). Atorvastatin is metabolized in the gut by CYP3A4 enzymes, and researchers theorized that vitamin D might induce CYP3A4, causing reduced levels of atorvastatin. However, this proposed mechanism was not specifically studied.

CALCIPOTRIENE (Dovonex)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Taking calcipotriene with vitamin D increases the risk for hypercalcemia.

Details

Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia (15). Theoretically, combining calcipotriene with vitamin D supplements might increase the risk of hypercalcemia.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

Vitamin D might induce CYP3A4 enzymes and reduce the bioavailability of CYP3A4 substrates.

Details

There is some concern that vitamin D might induce CYP3A4. In vitro research suggests that vitamin D induces CYP3A4 transcription. Additionally, observational research has found that increased UV light exposure and serum vitamin D levels are associated with decreased serum levels of CYP3A4 substrates such as tacrolimus and sirolimus, while no association between UV light exposure or vitamin D levels and levels of mycophenolic acid, a non-CYP3A4 substrate, was found (110539). A small, low-quality clinical study shows that taking vitamin D reduces levels of the CYP3A4 substrate atorvastatin and its active metabolites by up to 55%; however, the clinical effects of atorvastatin were not reduced (16828). While researchers theorized that vitamin D might induce CYP3A4, this proposed mechanism was not specifically studied.

DIGOXIN (Lanoxin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, hypercalcemia induced by high-dose vitamin D can increase the risk of arrhythmia from digoxin.

Details

High doses of vitamin D can cause hypercalcemia. Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin (15). Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and digoxin concurrently.

DILTIAZEM (Cardizem, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Theoretically, hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of diltiazem for arrhythmia.

Details

High doses of vitamin D can cause hypercalcemia. Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation (10574). Theoretically this could also occur with diltiazem. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and diltiazem concurrently.

THIAZIDE DIURETICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = D

Theoretically, taking thiazide diuretics and high-dose vitamin D can increase the risk of hypercalcemia.

Details

Thiazide diuretics decrease urinary calcium excretion, which could lead to hypercalcemia if vitamin D supplements are taken concurrently (3072,11541,69580). This has been reported in people being treated with vitamin D for hypoparathyroidism, and also in elderly people with normal parathyroid function who were taking a thiazide, vitamin D, and calcium-containing antacids daily (11539,11540).

VERAPAMIL (Calan, others)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of verapamil for arrhythmia.

Details

Hypercalcemia due to high doses of vitamin D can reduce the effectiveness of verapamil in atrial fibrillation (10574). Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and verapamil concurrently.

VITAMIN E

ALKYLATING AGENTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, antioxidant effects of vitamin E might reduce the effectiveness of alkylating agents.

Details

There's concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). However, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that might interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin E have on chemotherapy. Advise patients to consult their oncologist before using vitamin E supplements, especially in high doses.

ANTICOAGULANT/ANTIPLATELET DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Concomitant use of vitamin E and anticoagulant or antiplatelet agents might increase the risk of bleeding.

Details

Vitamin E seems to inhibit of platelet aggregation and antagonize the effects of vitamin K-dependent clotting factors (4733,4844,11580,11582,11583,11584,11586,112162). These effects appear to be dose-dependent, and are probably only likely to be clinically significant with doses of at least 800 units daily (11582,11585). Mixed tocopherols, such as those found in food, might have a greater antiplatelet effect than alpha-tocopherol (10364). RRR alpha-tocopherol (natural vitamin E) 1000 IU daily antagonizes vitamin K-dependent clotting factors (11999). Advise patients to avoid high doses of vitamin E, especially in people with low vitamin K intake or other risk factors for bleeding.

ANTITUMOR ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, antioxidant effects of vitamin E might reduce the effectiveness of antitumor antibiotics.

Details

There's concern that antioxidants could reduce the activity of antitumor antibiotic drugs such as doxorubicin, which generate free radicals (391). However, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that might interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin E have on chemotherapy involving antitumor antibiotics. Advise patients to consult their oncologist before using vitamin E supplements, especially in high doses.

CYCLOSPORINE (Neoral, Sandimmune)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Unlikely • Level of Evidence = B

A specific form of vitamin E might increase absorption and levels of cyclosporine.

Details

There is some evidence that one specific formulation of vitamin E (D-alpha-tocopheryl-polyethylene glycol-1000 succinate, TPGS, tocophersolan, Liqui-E) might increase absorption of cyclosporine. This vitamin E formulation forms micelles which seems to increase absorption of cyclosporine by 40% to 72% in some patients (624,625,10368). However, this interaction is unlikely to occur with the usual forms of vitamin E.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.

Details

Vitamin E appears to bind with the nuclear receptor, pregnane X receptor (PXR), which results in increased expression of CYP3A4 (13499,13500). Although the clinical significance of this is not known, use caution when considering concomitant use of vitamin E and other drugs affected by these enzymes.

NIACIN

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = A

Vitamin E might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.

Details

A combination of niacin and simvastatin (Zocor) effectively raises high-density lipoprotein (HDL) cholesterol levels in people with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% (7388,11537). Vitamin E alone combined with a statin does not seem to decrease HDL levels (11286,11287). It is not known whether the adverse effect on HDL is due to one of the other antioxidants or to the combination. It also is not known whether it will occur in other patient populations.

SELUMETINIB (Koselugo)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Taking selumetinib with vitamin E can result in a total daily dose of vitamin E that exceeds safe limits and therefore might increase the risk of bleeding.

Details

Selumetinib contains 48-54 IU vitamin E per capsule (102971). The increased risk of bleeding with vitamin E appears to be dose-dependent (11582,11585,34577). Be cautious when using selumetinib in combination with supplemental vitamin E, especially in patients at higher risk of bleed, such as those with chronic conditions and those taking antiplatelet drugs (102971).

WARFARIN (Coumadin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Using vitamin E with warfarin might increase the risk of bleeding.

Details

Due to interference with production of vitamin K-dependent clotting factors, use of more than 400 IU of vitamin E daily with warfarin might increase prothrombin time (PT), INR, and the risk of bleeding, (91,92,93). At a dose of 1000 IU per day, vitamin E can antagonize vitamin K-dependent clotting factors even in people not taking warfarin (11999). Limited clinical evidence suggests that doses up to 1200 IU daily may be used safely by patients taking warfarin, but this may not be applicable in all patient populations (90).

VITAMIN K

WARFARIN (Coumadin)

Interaction Rating = Major Do not take this combination.

Severity = High • Occurrence = Likely • Level of Evidence = C

Vitamin K can antagonize and reverse the therapeutic effects of warfarin.

Details

Vitamin K antagonizes the effects of warfarin (15,23380,25507,25508,85425,85429). Excessive vitamin K intake, either from supplements or from changes in the diet, can reduce the anticoagulant effect of warfarin (15).

ZINC

AMILORIDE (Midamor)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Probable • Level of Evidence = B

Amiloride can modestly reduce zinc excretion and increase zinc levels.

Details

Clinical research shows that amiloride can reduce urinary zinc excretion, especially at doses of 10 mg per day or more. This zinc-sparing effect can help to counteract zinc losses caused by thiazide diuretics, but it is unlikely to cause zinc toxicity at usual amiloride doses (830,11626,11627,11634). The other potassium-sparing diuretics, spironolactone (Aldactone) and triamterene (Dyrenium), do not seem to have a zinc-sparing effect.

ATAZANAVIR (Reyataz)

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Probable • Level of Evidence = B

Zinc modestly reduces levels of atazanavir, although this effect does not seem to be clinically significant.

Details

Clinical research shows that zinc might decrease serum atazanavir levels by chelating with atazanavir in the gut and preventing its absorption (93578). Although a single dose of zinc sulfate (Solvazinc tablets) 125 mg orally does not affect atazanavir concentrations in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate 125 mg daily for 2 weeks reduces plasma levels of atazanavir by about 22% in these patients. However, despite this decrease, atazanavir levels still remain at high enough concentrations for the prevention of HIV virus replication (90216).

CEPHALEXIN (Keflex)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Zinc might decrease cephalexin levels by chelating with cephalexin in the gut and preventing its absorption.

Details

A pharmacokinetic study shows that zinc sulfate 250 mg taken concomitantly with cephalexin 500 mg decreases peak levels of cephalexin by 31% and reduces the exposure to cephalexin by 27%. Also, taking zinc sulfate 3 hours before cephalexin decreases peak levels of cephalexin by 11% and reduces the exposure to cephalexin by 18%. By decreasing cephalexin levels, zinc might increase the risk of treatment failure. This effect does not occur when zinc is taken 3 hours after the cephalexin dose (94163). To avoid an interaction, advise patients take zinc sulfate 3 hours after taking cephalexin.

CISPLATIN (Platinol-AQ)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, zinc might interfere with the therapeutic effects of cisplatin.

Details

Animal research suggests that zinc stimulates tumor cell production of the protein metallothionein, which binds and inactivates cisplatin (11624,11625). It is not known whether zinc supplements or high dietary zinc intake can cause clinically significant interference with cisplatin therapy. Cisplatin might also increase zinc excretion.

INTEGRASE INHIBITORS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Theoretically, taking zinc along with integrase inhibitors might decrease the levels and clinical effects of these drugs.

Details

Zinc is a divalent cation. Pharmacokinetic studies have shown that other divalent cations such as calcium and iron can decrease blood levels of the integrase inhibitor dolutegravir through chelation (93578,93579).

PENICILLAMINE (Cuprimine, Depen)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Zinc might reduce the levels and clinical effects of penicillamine.

Details

By forming an insoluble complex with penicillamine, zinc interferes with penicillamine absorption and activity. Zinc supplements reduce the efficacy of low-dose penicillamine (0.5-1 gram/day), but do not seem to affect higher doses (1-2.75 gram/day), provided dosing times are separated (2678,4534,11605). Advise patients to take zinc and penicillamine at least 2 hours apart.

QUINOLONE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Zinc can decrease the levels and clinical effects of quinolones antibiotics.

Details

Quinolones form complexes with zinc in the gastrointestinal tract, reducing absorption of both the quinolone and zinc if taken at the same time (828,2682,3046,11600). Advise patients to take these drugs at least 2 hours before, or 4-6 hours after, zinc supplements.

RITONAVIR (Norvir)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Mild • Occurrence = Probable • Level of Evidence = B

Zinc modestly reduces levels of ritonavir.

Details

Clinical research shows that zinc might reduce serum ritonavir levels by chelating with ritonavir in the gut and preventing its absorption (93578). In patients with HIV, ritonavir is taken with atazanavir to prevent the metabolism and increase the effects of atazanavir. A pharmacokinetic study shows that, in patients being treated with atazanavir/ritonavir, co-administration of zinc sulfate (Solvazinc tablets) 125 mg as a single dose or as multiple daily doses for 2 weeks reduces plasma levels of ritonavir by about 16% (90216). However, atazanavir levels still remains high enough to prevent HIV virus replication. Therefore, the decrease in ritonavir levels is not likely to be clinically significant.

TETRACYCLINE ANTIBIOTICS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Probable • Level of Evidence = B

Zinc might reduce levels of tetracycline antibiotics.

Details

Tetracyclines form complexes with zinc in the gastrointestinal tract, which can reduce absorption of both the tetracycline and zinc when taken at the same time (3046,4945). Taking zinc sulfate 200 mg with tetracycline reduces absorption of the antibiotic by 30% to 40% (11615). Demeclocycline and minocycline cause a similar interaction (4945). However, doxycycline does not seem to interact significantly with zinc (11615). Advise patients to take tetracyclines at least 2 hours before, or 4-6 hours after, zinc supplements to avoid any interactions.

Report an Adverse Reaction to Centrum Women Under 50

Adverse Effects view details

Below is general information about the adverse effects of the known ingredients contained in the product Centrum Women Under 50. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

BIOTIN

General ...Orally and topically, biotin is generally well tolerated.
Most Common Adverse Effects: None.

Gastrointestinal ...Orally, high-dose biotin has been rarely associated with mild diarrhea. Transient mild diarrhea was reported by 2 patients taking biotin 300 mg daily (95662).

Pulmonary/Respiratory ...In one case report in France, a 76-year-old female frequent traveler developed eosinophilic pleuropericarditis after taking biotin 10 mg and pantothenic acid 300 mg daily for 2 months. She had also been taking trimetazidine for 6 years (3914). Whether eosinophilia in this case was related to biotin, pantothenic acid, other substances, or patient-specific conditions is unknown. There have been no other similar reports.

BORON

General ...Orally, boron is generally well tolerated when used in doses below the tolerable upper intake level (UL) of 20 mg. Vaginally, boron is well tolerated.
Most Common Adverse Effects:
Orally: Anorexia, dermatitis, erythema, indigestion.
Vaginally: Burning and pain.

Dermatologic ...Orally, chronic use of 1 gram daily of boric acid or 25 grams daily of boric tartrate can cause dermatitis and alopecia (7135).
Larger doses can result in acute poisoning. Symptoms of poisoning in adults and children may include skin erythema, desquamation, and exfoliation (17).

Gastrointestinal ...Orally, chronic use of 1 gram daily of boric acid or 25 grams daily of boric tartrate can cause anorexia and indigestion (7135).
Larger doses can result in acute poisoning. Children who have ingested 5 grams or more of borates can have persistent nausea, vomiting, and diarrhea leading to acute dehydration, shock, and coma. Adults who have ingested 15-20 grams of borate can exhibit nausea, vomiting, diarrhea, epigastric pain, hematemesis, and a blue-green discoloration of feces and vomit (17).

Genitourinary ...Vaginally, boric acid can cause vulvovaginal burning and dyspareunia in males if intercourse occurs shortly after vaginal treatment (15447).

Neurologic/CNS ...Orally, large doses can result in acute poisoning. Poisoning with boron can cause hyperexcitability, irritability, tremors, convulsions, weakness, lethargy, and headaches (17).

Ocular/Otic ...Exposure to boric acid or boron oxide dust has been reported to cause eye irritation (36852).

Pulmonary/Respiratory ...Exposure to boric acid and boron oxide dust has been reported to cause mouth and nasal passage irritation, sore throat, and productive cough (36852).

CALCIUM

General ...Orally and intravenously, calcium is well-tolerated when used appropriately.
Most Common Adverse Effects:
Orally: Belching, constipation, diarrhea, flatulence, and stomach upset.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about calciphylaxis and kidney stones.

Cardiovascular ...There has been concern that calcium intake may be associated with an increased risk of cardiovascular disease (CVD) and coronary heart disease (CHD), including myocardial infarction (MI). Some clinical research suggests that calcium intake, often in amounts over the recommended daily intake level of 1000-1300 mg daily for adults, is associated with an increased risk of CVD, CHD, and MI (16118,17482,91350,107233). However, these results, particularly meta-analyses, have been criticized for excluding trials in which calcium was administered with vitamin D (94137). Many of these trials also only included postmenopausal females. Other analyses report conflicting results, and have not shown that calcium intake affects the risk of CVD, CHD, or MI (92994,93533,97308,107231). Reasons for these discrepancies are not entirely clear. It may relate to whether calcium is taken as monotherapy or in combination with vitamin D. When taken with vitamin D, which is commonly recommended, calcium supplementation does not appear to be associated with an increased risk of CVD, CHD, or MI (93533,107231). Also, the association between calcium supplementation and CVD, CHD, or MI risk may be influenced by the amount of calcium consumed as part of the diet. Supplementation with calcium may be associated with an increased risk of MI in people with dietary calcium intake above 805 mg daily, but not in those with dietary calcium intake below 805 mg daily (17482). To minimize the possible risk of CVD, CHD, or MI, advise patients not to consume more than the recommended daily intake of 1000-1200 mg and to consider total calcium intake from both dietary and supplemental sources (17484). While dietary intake of calcium is preferred over supplemental intake, advise patients who require calcium supplements to take calcium along with vitamin D, as this combination does not appear to be associated with an increased risk of MI (93533).
Rarely, calcium intake can increase the risk of calciphylaxis, which usually occurs in patients with kidney failure. Calciphylaxis is the deposition of calcium phosphate in arterioles, which causes skin ulcers and skin necrosis. In a case report, a 64-year-old female with a history of neck fracture, sepsis, and ischemic colitis presented with painful leg ulcers due to calciphylaxis. She discontinued calcium and vitamin D supplementation and was treated with sodium thiosulfate and supportive care (95816).

Gastrointestinal ...Orally, calcium can cause belching, flatulence, nausea, gastrointestinal discomfort, and diarrhea (1824,1843,12950,38803). Although constipation is frequently cited as an adverse effect of calcium, there is no scientific substantiation of this side effect (1824,1843,1844,1845,12950,38978). Calcium carbonate has been reported to cause acid rebound, but this is controversial (12935,12936).

Oncologic ...There is some concern that very high doses of calcium might increase the risk of prostate cancer. Some epidemiological evidence suggests that consuming over 2000 mg/day of dietary calcium might increase the risk for prostate cancer (4825,12949). Additional research suggests that calcium intake over 1500 mg/day might increase the risk of advanced prostate cancer and prostate cancer mortality (14132). Consumption of dairy products has also been weakly linked to a small increase in prostate cancer risk (98894). However, contradictory research suggests no association between dietary intake of calcium and overall prostate cancer risk (14131,14132,104630). More evidence is needed to determine the effect of calcium, if any, on prostate cancer risk.

Renal ...Kidney stones have been reported in individuals taking calcium carbonate 1500 mg daily in combination with vitamin D 2000 IU daily for 4 years (93943).

CHROMIUM

General ...Orally, chromium is generally well tolerated.
Most Common Adverse Effects:
Orally: Gastrointestinal irritation, headaches, insomnia, irritability, mood changes.
Serious Adverse Effects (Rare):
Orally: Rare cases of kidney and liver damage, rhabdomyolysis, and thrombocytopenia have been reported.

Dermatologic ...Orally, chromium-containing supplements may cause acute generalized exanthematous pustulosis (42561), skin rashes (42679), and urticaria (17224). Also, chromium picolinate or chromium chloride may cause systemic contact dermatitis when taken orally, especially in patients with contact allergy to chromium (6624,90058). In one clinical study, a patient taking chromium nicotinate 50 mcg daily reported itchy palms that improved after the intervention was discontinued. It is unclear of this effect was due to the chromium or another factor (95096).
Topically, hexavalent chromium, which can be present in some cement, leather products, or contaminated soil, may cause allergic contact dermatitis (42645,42789,90060,90064,110606).
A case of lichen planus has been reported for a patient following long-term occupational exposure to chromium (42688).

Endocrine ...Orally, cases of hypoglycemia have been reported for patients taking chromium picolinate 200-1000 mcg daily alone or 200-300 mcg two or three times weekly in combination with insulin (42672,42783). Chromium picolinate has also been associated with weight gain in young females who do not exercise and in those following a weight-lifting program (1938).

Gastrointestinal ...Orally, chromium in the form of chromium picolinate, chromium polynicotinate, chromium-containing brewer's yeast, or chromium-containing milk powder may cause nausea, vomiting, diarrhea, decreased appetite, constipation, flatulence, or gastrointestinal upset (14325,42594,42607,42622,42643,42679).
Long-term exposure to heavy metals, including chromium, has been associated with increased risk of gallbladder disease and cancer (42682,42704).

Genitourinary ...Orally, chromium polynicotinate has been associated with disrupted menstrual cycles in patients taking the supplement to prevent weight gain during smoking cessation (42643).

Hematologic ...Anemia, hemolysis, and thrombocytopenia were reported in a 33 year-old female taking chromium picolinate 1200-2400 mcg daily for 4-5 months (554). The patient received supportive care, blood product transfusions, and hemodialysis and was stabilized and discharged a few days later. Lab values were normal at a one-year follow-up.

Hepatic ...Liver damage has been reported for a 33-year-old female taking chromium picolinate 1200 mcg daily for 4-5 months (554). Also, acute hepatitis has been reported in a patient taking chromium polynicotinate 200 mcg daily for 5 months (9141). Symptoms resolved when the product was discontinued. Two cases of hepatotoxicity have been reported in patients who took a specific combination product (Hydroxycut), which also contained chromium polynicotinate in addition to several herbs (13037).

Musculoskeletal ...Acute rhabdomyolysis has been reported for a previously healthy 24-year-old female who ingested chromium picolinate 1200 mcg over a 48-hour time period (42786). Also, chromium polynicotinate has been associated with leg pain and paresthesia in patients taking the supplement to prevent weight gain during smoking cessation (42643).

Neurologic/CNS ...Orally, chromium picolinate may cause headache, paresthesia, insomnia, dizziness, and vertigo (6860,10309,14325,42594). Vague cognitive symptoms, slowed thought processes, and difficulty driving occurred on three separate occasions in a healthy 35-year-old male after oral intake of chromium picolinate 200-400 mcg (42751). Transient increases in dreaming have been reported in three patients with dysthymia treated with chromium picolinate in combination with sertraline (2659). A specific combination product (Hydroxycut) containing chromium, caffeine, and ephedra has been associated with seizures (10307). But the most likely causative agent in this case is ephedra.

Psychiatric ...Orally, chromium picolinate has been associated with irritability and mood changes in patients taking the supplement to lose weight, while chromium polynicotinate has been associated with agitation and mood changes in patients taking the supplement to prevent weight gain during smoking cessation (6860,42643).

Renal ...Orally, chromium picolinate has been associated with at least one report of chronic interstitial nephritis and two reports of acute tubular necrosis (554,1951,14312). Laboratory evidence suggests that chromium does not cause kidney tissue damage even after long-term, high-dose exposure (7135); however, patient- or product-specific factors could potentially increase the risk of chromium-related kidney damage. More evidence is needed to determine what role, if any, chromium has in potentially causing kidney damage.
Intravenously, chromium is associated with decreased glomerular filtration rate (GFR) in children who receive long-term chromium-containing total parenteral nutrition - TPN (11787). Topically, burns caused by chromic acid, a hexavalent form of chromium, have been associated with acute chromium poisoning with acute renal failure (42699). Early excision of affected skin and dialysis are performed to prevent systemic toxicity.

Other ...Another form of chromium, called hexavalent chromium, is unsafe. This type of chromium is a by-product of some manufacturing processes. Chronic exposure can cause liver, kidney, or cardiac failure, pulmonary complications, anemia, and hemolysis (9141,11786,42572,42573,42699). Occupational inhalation of hexavalent chromium can cause ulceration of the nasal mucosa and perforation of the nasal septum, and has been associated with pneumoconiosis, allergic asthma, cough, shortness of breath, wheezing, and increased susceptibility to respiratory tract cancer and even stomach and germ cell cancers (42572,42573,42601,42610,42636,42667,42648,42601,42788,90056,90066). Although rare, cases of interstitial pneumonia associated with chromium inhalation have been reported. Symptoms resolved with corticosteroid treatment (42614).

COPPER

General ...Orally, copper is generally well tolerated when consumed in doses below the tolerable upper intake level (UL).

Dermatologic ...Contact dermatitis caused by copper has been reported rarely. A case report describes a 5-year-old male who developed recurrent fingertip dermatitis and a positive skin test to copper after playing with toy cars made with a copper-containing alloy (95538). Also, in a small clinical trial in children 1-3 months of age with umbilical granuloma, 3 of 33 children receiving a single topical application of copper sulfate developed superficial burns, whereas no superficial burns occurred in those receiving topical sodium chloride (109403).
In one case report, a 68-year-old male with type 2 diabetes and peripheral neuropathy developed second- and third-degree burns after wearing a copper-containing compression sock on the right leg for 3 hours while sitting in the sun. The patient received treatment with topical silver sulfadiazine and oral clindamycin. After 6 weeks, the patient was found to have multiple persistent wounds containing necrotic tissue which required debridement, daily dressing changes, and tubular compression. It is thought that the heat conductance of copper magnified the effects of sun exposure in this case (109402).

Endocrine ...There is evidence from observational studies that people with diabetes (type 1 or type 2) have higher copper levels in their blood than people without diabetes, although not all studies have shown this (95537). It is not known if elevated copper levels contribute to development or worsening of diabetes.

Hematologic ...A case report of copper overdose in a 28-year-old male resulted in hemolysis exacerbated by glucose-6-phosphate dehydrogenase deficiency. The patient was hospitalized, received D-penicillamine chelation, blood transfusion, and ultimately, 4 cycles of plasmapheresis which led to clinical recovery (112378).

FOLIC ACID

General ...Orally, folic acid is generally well-tolerated in amounts found in fortified foods, as well as in supplemental doses of less than 1 mg daily.
Most Common Adverse Effects:
Orally: At doses of 5 mg daily - abdominal cramps, diarrhea, and rash. At doses of 15 mg daily - bitter taste, confusion, hyperactivity, impaired judgment, irritability, nausea, sleep disturbances.
Serious Adverse Effects (Rare):
Orally: Cancer (long-term use), cardiovascular complications, liver injury, seizures.
All ROAs: Allergic reactions such as bronchospasm and anaphylactic shock.

Cardiovascular ...There is some concern that high oral doses of folic acid might increase the risk of adverse cardiovascular outcomes. Clinical research shows that taking doses of 800 mcg to 1.2 mg/day might increase the risk of adverse cardiovascular events in patients with cardiovascular disease (12150,13482). High doses of folic acid might promote cell growth by providing large amounts of the biochemical precursors needed for cell replication. Overgrowth of cells in the vascular wall might increase the risk of occlusion (12150). Although some research suggests that use of folic acid might increase the need for coronary revascularization, analysis of multiple studies suggests that taking folic acid up to 5 mg/day for up to 24 months does not appear to affect coronary revascularization risk (90798).

Dermatologic ...Orally, folic acid 1-5 mg daily can cause rash (7225,90375,91319). Folic acid 15 mg daily can sometimes cause allergic skin reactions (15).

Gastrointestinal ...Orally, folic acid 5 mg daily can cause abdominal cramps and diarrhea (7225). Folic acid 15 mg daily can sometimes cause nausea, abdominal distention, flatulence, and bitter taste in the mouth (15). In children aged 6-30 months at risk of malnourishment, taking a nutritional supplement (Nutriset Ltd) enriched in folic acid 75-150 mcg daily, with or without vitamin B 12 0.9-1.8 mcg daily, for 6 months increases the likelihood of having persistent diarrhea (90391).

Hepatic ...Liver dysfunction, with jaundice and very high liver enzymes, occurred in a 30-year-old pregnant patient with severe nausea and vomiting taking a folic acid supplement (Folic acid, Nature Made) 400 mcg daily. Based on the timing of ingestion, the lack of other etiological factors, a positive drug-induced lymphocyte stimulation test, and liver function normalization once the folic acid had been stopped, the authors suggest the folic acid supplement was the cause. However, the authors did not determine which substance in the folic acid supplement was responsible and therefore it cannot be determined that folic acid itself was the cause (91309).

Neurologic/CNS ...Orally, folic acid 15 mg daily can sometimes cause altered sleep patterns, vivid dreaming, irritability, excitability, hyperactivity, confusion, and impaired judgment (15). Large doses of folic acid can also precipitate or exacerbate neuropathy in people deficient in vitamin B12 (6243). Use of folic acid for undiagnosed anemia has masked the symptoms of pernicious anemia, resulting in lack of treatment and eventual neurological damage (15). Patients should be warned not to self-treat suspected anemia. There is also some concern that consuming high amounts of folic acid from the diet and/or supplements might worsen cognitive decline in older people. A large-scale study suggests that people over 65 years of age, who consume large amounts of folic acid (median of 742 mcg/day), have cognitive decline at a rate twice as fast as those consuming smaller amounts (median of 186 mcg/day). It's not known if this is directly attributable to folic acid. It is theorized that it could be due to folic acid masking a vitamin B12 deficiency. Vitamin B12 deficiency is associated with cognitive decline (13068). More evidence is needed to determine the significance of this finding. For now, suggest that most patients aim for the recommended folic acid intake of 400 mcg/day.

Oncologic ...There is some concern that high dose folic acid might increase the risk of cancer, although research is unclear and conflicting. A large-scale population study suggests that taking a multivitamin more than 7 times per week with a separate folic acid supplement significantly increased the risk of prostate cancer (15607). Clinical research also shows that taking folic acid 1 mg daily increase the absolute risk of prostate cancer by 6.4% over a 10-year period when compared with placebo. However, those with a higher baseline dietary intake of folic acid had a lower rate of prostate cancer, but this was not statistically significant. Also, folate and folic acid intake in patients with prostate cancer is not associated with the risk of prostate cancer recurrence after radical prostatectomy (91317). However, it is possible that discrepancies are due to dietary folate versus folic acid intake. Large analyses of population studies suggest that while dietary folate/folic acid is not associated with prostate cancer, high blood folate/folic acid increases the risk of prostate cancer (50411,91316).
Additional clinical research shows that taking folic acid 800 mcg daily, in combination with vitamin B12 400 mcg, significantly increases the risk of developing cancer, especially lung cancer, and all-cause mortality in patients with cardiovascular disease (17041). However, this may be due to vitamin B12, as other observational research found that higher vitamin B12 levels are linked with an increased risk for lung cancer (102383). Meta-analyses of large supplementation trials of folic acid at levels between 0.5-2.5 mg daily also suggest an increased risk of cancer (50497,110318). Also, in elderly individuals, taking folic acid 400 mcg daily with vitamin B12 500 mcg daily increased the risk of cancer. The risk was highest in individuals over 80 years of age and in females and mainly involved gastrointestinal and colorectal cancers (90393).
Not all researchers suspect that high intake of folic acid supplements might be harmful. Some research suggests that increased dietary intake of folic acid, along with other nutrients, might be protective against cancer (16822). A meta-analysis of multiple clinical trials suggests that folic acid supplementation studies with folic acid levels between 500 mcg to 50 mg/day does not increase the risk of general or site-specific cancer for up to 7 years (91312,91321). Also, a post-hoc subgroup analysis of results from clinical research in adults with a history of recent stroke or ischemic attack suggests that taking folic acid, vitamin B12, and vitamin B6 does not increase cancer risk overall, although it was associated with an increased risk of cancer in patients who also had diabetes (90378).

Psychiatric ...Orally, folic acid 15 mg daily can sometimes cause exacerbation of seizure frequency and psychotic behavior (15).

Pulmonary/Respiratory ...Folic acid use in late pregnancy has been associated with an increased risk of persistent and childhood asthma at 3. 5 years in population research (50380). When taken pre-pregnancy or early in pregnancy, population research has not found an association with increased risk of asthma or allergies in childhood (90799,103979). Folic acid use in pregnancy has been associated with a slightly increased risk of wheeze and lower respiratory tract infections up to 18 months of age in population research (50328).

IODINE

General ...Orally, iodine is well tolerated when taken in amounts that do not exceed the tolerable upper intake level (UL) or when used therapeutically with appropriate medical monitoring (2197,7080,7135).
Most Common Adverse Effects:
Orally: Abdominal upset, diarrhea, goiter, headache, hyperthyroidism, hypothyroidism, metallic taste, nausea, rhinorrhea, thyroid adenoma.
Topically: Burns, dermatitis, irritation.
Serious Adverse Effects (Rare):
All ROAs: Hypersensitivity reactions such as anaphylaxis and angioedema.

Dermatologic ...Orally, taking iodine chronically or in large amounts has been reported to cause acneform skin lesions called iododerma (2138). In one case, a patient developed iododerma after consuming a specific product (Hoxsey's Brown Tonic) containing an unspecified quantity of potassium iodide. After several months of consumption, the patient developed acneform skin lesions on the nose, cheeks, and upper back and presented with a urine iodine level of 7,455,647 ug/L (reference range: 34-523 ug/L). After discontinuation of potassium iodide, the lesions resolved gradually over the course of several weeks (95431).
Topically, iodine may stain skin, irritate tissues, and cause sensitization in some individuals (15,56106). Iodine burns are associated with application of 7% hydroalcoholic solution (15). Povidone-iodine may cause contact dermatitis or irritant reactions in some people. However, patch testing with potassium iodide is usually negative in these patients, indicating that contact dermatitis caused by topical iodine does not indicate a propensity for reaction to oral potassium iodide (93001).

Endocrine ...Prolonged use and/or large oral doses of iodine intake can cause thyroid gland hyperplasia, thyroid adenoma, goiter, and hypothyroidism (15,56013,56089,91397,91398,99793,99795). In another case report, an infant presented with reversible hypothyroidism at birth because the mother had consumed excessive seaweed soup during and after pregnancy, which resulted in excessive iodine consumption (99795). Iodine has also been linked to rare cases of adverse events. In one case report, a 56-year-old male developed thyrotoxic hypokalemic paralysis thought to be related to excessive intake of iodine (91401).
Topically, using povidone-iodine (PI) 1% solution as a gargle and nasal spray, in addition to intranasal application of PI 10% ointment over 5 days, can precipitate subclinical hypothyroidism, with elevated thyroid stimulating hormone (TSH) and normal thyroid hormone levels. TSH levels seem to normalize about 7-12 days after stopping topical PI application (105877).

Gastrointestinal ...Orally, the commonly reported adverse effects of a saturated solution of potassium iodide (SSKI) are nausea (14%), abdominal pain (14%), metallic taste (4%), and diarrhea (4%) (17561). These side effects can be minimized by avoiding quick dosage increases (17574). Taking iodine chronically or in large amounts has also been reported to cause soreness in teeth and gums, burning in mouth and throat, increased salivation, swelling of parotid and submaxillary glands, inflammation of the respiratory tract, gastric upset, and diarrhea (15,2138).
Intranasally, applying povidone-iodine 1% solution along with a 10% ointment can cause unpleasant nasal tingling (105877).

Immunologic ...People who are allergic to iodine-containing foods or drugs are sometimes stated to have "iodine allergy", but the actual allergen is another agent such as seafood proteins or radiocontrast media (93001). However, some people can be hypersensitive to iodine when used orally. Symptoms of hypersensitivity can include angioedema, cutaneous and mucosal hemorrhage, fever, arthralgia, lymph node enlargement, eosinophilia, urticaria, erythema, and thrombotic thrombocytopenic purpura (15,17561). Other reported side effects include potassium toxicity, metabolic acidosis, pustular psoriasis, and vasculitis (17574). However, such sensitivity is very rare (93001). Orally, iodine hypersensitivity can cause fatal periarteritis (15).

Neurologic/CNS ...Orally, common side effects of a saturated solution of potassium iodide (SSKI) have included headache (7%) (17561). Side effects can be minimized by avoiding quick dosage increases (17574).
High intake of iodine may be associated with adverse cognitive outcomes in children. Observational research in children aged 7-14 years has found that those consuming drinking water with iodine concentrations above 900 mcg/L daily, which exceeds the tolerable upper intake level, is associated with a 1.6-point reduction in intelligence level when compared with those consuming water with iodine concentrations below 300 mcg/L (108709).

Ocular/Otic ...Orally, taking iodine chronically or in large amounts has been reported to cause eye irritation and eyelid swelling (15,2138).

Pulmonary/Respiratory ...Orally, common side effects of a saturated solution of potassium iodide (SSKI) included rhinorrhea (11%) (17561). Side effects can be minimized by avoiding quick dosage increases (17574). Taking iodine chronically or in large amounts has also been reported to cause coryza, sneezing, cough, and pulmonary edema (15,2138). Ophthalmically, povidone-iodine 5% solution 3 drops administered in each eye has been reported to slow respiration by about 18 seconds (range 4 to 96 seconds) when compared with saline control in children ages 2-17 years undergoing strabismus surgery (103077).

Renal ...When povidone-iodine was used in renal pelvic instillation sclerotherapy, one patient (2%) had significant flank pain during treatment (55970).

IRON

General ...Orally or intravenously, iron is generally well tolerated when used appropriately.
Most Common Adverse Effects:
Orally: Abdominal pain, constipation, diarrhea, gastrointestinal irritation, nausea, and vomiting.
Serious Adverse Effects (Rare):
Orally: Case reports have raised concerns about oral or gastric ulcerations.
Intravenously: Case reports have raised concerns about hypophosphatemia and osteomalacia.

Cardiovascular ...There is debate regarding the association between coronary heart disease (CHD) or myocardial infarction (MI) and high iron intake or high body iron stores. Some observational studies have reported that high body iron stores are associated with increased risk of MI and CHD (1492,9542,9544,9545,15175). Some observational studies reported that only high heme iron intake from dietary sources such as red meat are associated with increased risk of MI and CHD (1492,9546,15174,15205,15206,91180). However, the majority of research has found no association between serum iron levels and cardiovascular disease (1097,1099,9543,9547,9548,9549,9550,56469,56683).
There is one case of Kounis syndrome, also referred to as allergic angina or allergic myocardial infarction, in a 39-year-old female patient without previous coronary artery disease given intravenous ferric carboxymaltose. The patient experienced anaphylactic symptoms, including headache, abdominal pain, and breathing difficulties, 3 minutes after starting the infusion. She was further diagnosed with non-ST-elevation myocardial infarction (112607).

Dermatologic ...Cutaneous hemosiderosis, or skin staining, has been reported following intravenous iron infusion in various case reports. Most of these cases are due to extravasation following iron infusion (112605,112611). In one case, extravasation has occurred following iron derisomaltose infusion in a 41-year-old female with chronic kidney disease (112605). Rarely, diffuse cutaneous hermosiderosis has occurred. In one case, a 31-year-old female with excessive sweating developed cutaneous hemosiderosis in the armpits following an intravenous iron polymaltose infusion (112611).

Endocrine ...Population research in females shows that higher ferritin levels are associated with an approximately 1. 5-fold higher odds of developing gestational diabetes. Increased dietary intake of heme-iron, but not non-heme iron, is also associated with an increased risk for gestational diabetes. The effects of iron supplementation could not be determined from the evaluated research (96618). However, in a sub-analysis of a large clinical trial in pregnant adults, daily supplementation with iron 100 mg from 14 weeks gestation until delivery did not affect the frequency or severity of glucose intolerance or gestational weight gain (96619).

Gastrointestinal ...Orally, iron can cause dry mouth, gastrointestinal irritation, heartburn, abdominal pain, constipation, diarrhea, nausea, or vomiting (96621,102864,104680,104684,110179,110185,110188,110189,110192). These adverse effects are uncommon at doses below the tolerable upper intake level (UL) of 45 mg per day of elemental iron in adults with normal iron stores (7135). Higher doses can be taken safely in adults with iron deficiency, but gastrointestinal side effects may occur (1095,20118,20119,56698,102864). Taking iron supplements with food seems to reduce gastrointestinal side effects (7135). However, food can also significantly reduce iron absorption. Iron should be taken on an empty stomach, unless it cannot be tolerated.
There are several formulations of iron products such as ferrous sulfate, ferrous gluconate, ferrous fumarate, and others. Manufacturers of some formulations, such as polysaccharide-iron complex products (Niferex-150, etc), claim to be better tolerated than other formulations; however, there is no reliable evidence to support this claim. Gastrointestinal tolerability relates mostly to the elemental iron dose rather than the formulation (17500).
Enteric-coated or controlled-release iron formulations might reduce nausea for some patients, however, these products also have lower absorption rates (17500).
Liquid oral preparations can blacken and stain teeth (20118).
Iron can also cause oral ulcerations and ulcerations of the gastric mucosa (56684,91182,96622,110179). In one case report, an 87-year-old female with Alzheimer disease experienced a mucosal ulceration, possibly due to holding a crushed ferrous sulfate 80 mg tablet in the mouth for too long prior to swallowing (91182). The ulceration was resolved after discontinuing iron supplementation. In another case report, a 76-year old male suffered gastric mucosal injury after taking a ferrous sulfate tablet daily for 4 years (56684). In a third case report, a 14-year-old female developed gastritis involving symptoms of upper digestive hemorrhage, nausea, melena, and stomach pain. The hemorrhage was attributed to supplementation with ferrous sulfate 2 hours after meals for the prior 2 weeks (96622). In one case report, a 43-year old female developed atrophic gastritis with non-bleeding ulcerations five days after starting oral ferrous sulfate 325 mg twice daily (110179).
Intravenously, iron can cause gastrointestinal symptoms sch as nausea (104684,110192).

Immunologic ...Although there is some clinical research associating iron supplementation with an increased rate of malaria infection (56796,95432), the strongest evidence to date does not support this association, at least for areas where antimalarial treatment is available (95433,96623). In an analysis of 14 trials, iron supplementation was not associated with an increased risk of malaria (96623). In a sub-analysis of 7 preliminary clinical studies, the effect of iron supplementation was dependent upon the access to services for antimalarial treatment. In areas where anemia is common and services are available, iron supplementation is associated with a 9% reduced risk of clinical malaria. In an area where services are unavailable, iron supplementation was associated with a 16% increased risk in malaria incidence (96623). The difference in these findings is likely associated with the use of malaria prevention methods.
A meta-analysis of clinical studies of all patient populations shows that administering IV iron, usually iron sucrose and ferric carboxymaltose, increases the risk of infection by 16% when compared with oral iron or no iron. However, sub-analyses suggest this increased risk is limited to patients with inflammatory bowel disease (IBD) (110186).
Intravenously, iron has rarely resulted in allergic reactions, including anaphylactoid reactions (110185,110192,112606,112607). There is one case of Kounis syndrome, also referred to as allergic angina or allergic myocardial infarction, in a 39-year-old female patient without previous coronary artery disease given intravenous ferric carboxymaltose. The patient experienced anaphylactic symptoms, including headache, abdominal pain, and breathing difficulties, 3 minutes after starting the infusion. She was further diagnosed with non-ST-elevation myocardial infarction (112607).

Musculoskeletal ...Intravenously, iron rarely results in osteomalacia related to hypophosphatemia (112609). At least 2 cases exist of hypophosphatemic osteomalacia. In one case, a 70-year-old male with a genetic hemorrhagic disorder infused with ferric carboxymaltose developed lower limb pain with hypophosphatemia and diffuse bone demineralization in the feet (112609). In a second case, a 61-year-old male developed femoral neck insufficiency fractures following repeated ferric carboxymaltose transfusions for anemia related to vascular malformation in the bowel (112603). Severe hypophosphatemia requiring intravenous phosphate in the absence of osteomalacia has also occurred following intravenous ferric carboxymaltose (112608,112610).

Oncologic ...There is a debate regarding the association between high levels of iron stores and cancer. Data are conflicting and inconclusive (1098,1099,1100,1102). Epidemiological studies suggest that increased body iron stores may increase the risk of cancer or general mortality (56703).
Occupational exposure to iron may be carcinogenic (56691). Oral exposure to iron may also be carcinogenic. Pooled analyses of population studies suggest that increasing the intake of heme iron increases the risk of colorectal cancer. For example, increasing heme iron intake by 1 mg/day is associated with an 11% increase in risk (56699,91185).

Other ...Intravenously, sodium ferric gluconate complex (SFGC) caused drug intolerance reactions in 0. 4% of hemodialysis patients including 2 patients with pruritus and one patient each with anaphylactoid reaction, hypotension, chills, back pain, dyspnea/chest pain, facial flushing, rash and cutaneous symptoms of porphyria (56527).

MAGNESIUM

General ...Magnesium is generally well tolerated. Some clinical research shows no differences in adverse effects between placebo and magnesium groups.
Most Common Adverse Effects:
Orally: Diarrhea, gastrointestinal irritation, nausea, and vomiting.
Intravenously: Bradycardia, dizziness, flushing sensation, hypotension, and localized pain and irritation. In pregnancy, may cause blurry vision, dizziness, lethargy, nausea, nystagmus, and perception of warmth.
Serious Adverse Effects (Rare):
All ROAs: With toxic doses, loss of reflexes and respiratory depression can occur. High doses in pregnancy can increase risk of neonatal mortality and neurological defects.

Cardiovascular ...Intravenously, magnesium can cause bradycardia, tachycardia, and hypotension (13356,60795,60838,60872,60960,60973,60982,61001,61031). Magnesium sulfate may cause rapid heartbeat when administered antenatally (60915).
In one case report, a 99-year-old male who took oral magnesium oxide 3000 mg daily for chronic constipation was hospitalized with hypermagnesemia, hypotension, bradycardia, heart failure, cardiomegaly, second-degree sinoatrial block, and complete bundle branch block. The patient recovered after discontinuing the magnesium oxide (108966).

Dermatologic ...Intravenously, magnesium may cause flushing, sweating, and problems at the injection site (including burning pain) (60960,60982,111696). In a case study, two patients who received intravenous magnesium sulfate for suppression of preterm labor developed a rapid and sudden onset of an urticarial eruption (a skin eruption of itching welts). The eruption cleared when magnesium sulfate was discontinued (61045). Orally, magnesium oxide may cause allergic skin rash, but this is rare. In one case report, a patient developed a rash after taking 600 mg magnesium oxide (Maglax) (98291).

Gastrointestinal ...Orally, magnesium can cause gastrointestinal irritation, nausea, vomiting, and diarrhea (1194,4891,10661,10663,18111,60951,61016,98290). In rare cases, taking magnesium orally might cause a bezoar, an indigestible mass of material which gets lodged in the gastrointestinal tract. In a case report, a 75-year-old female with advanced rectal cancer taking magnesium 1500 mg daily presented with nausea and anorexia from magnesium oxide bezoars in her stomach (99314). Magnesium can cause nausea, vomiting, or dry mouth when administered intravenously or by nebulization (60818,60960,60982,104400). Antenatal magnesium sulfate may also cause nausea and vomiting (60915). Two case reports suggest that giving magnesium 50 grams orally for bowel preparation for colonoscopy in patients with colorectal cancer may lead to intestinal perforation and possibly death (90006).
Delayed meconium passage and obstruction have been reported rarely in neonates after intravenous magnesium sulfate was given to the mother during pregnancy (60818). In a retrospective study of 200 neonates born prematurely before 32 weeks of gestation, administration of prenatal IV magnesium sulfate, as a 4-gram loading dose and then 1-2 grams hourly, was not associated with the rate of meconium bowel obstruction when compared with neonates whose mothers had not received magnesium sulfate (108728).

Genitourinary ...Intravenously, magnesium sulfate may cause renal toxicity or acute urinary retention, although these events are rare (60818,61012). A case of slowed cervical dilation at delivery has been reported for a patient administered intravenous magnesium sulfate for eclampsia (12592). Intravenous magnesium might also cause solute diuresis. In a case report, a pregnant patient experienced polyuria and diuresis after having received intravenous magnesium sulfate in Ringer's lactate solution for preterm uterine contractions (98284).

Hematologic ...Intravenously, magnesium may cause increased blood loss at delivery when administered for eclampsia or pre-eclampsia (12592). However, research on the effect of intravenous magnesium on postpartum hemorrhage is mixed. Some research shows that it does not affect risk of postpartum hemorrhage (60982), while other research shows that intrapartum magnesium administration is associated with increased odds of postpartum hemorrhage, increased odds of uterine atony (a condition that increases the risk for postpartum hemorrhage) and increased need for red blood cell transfusions (97489).

Musculoskeletal ...Intravenously, magnesium may cause decreased skeletal muscle tone, muscle weakness, or hypocalcemic tetany (60818,60960,60973).
Although magnesium is important for normal bone structure and maintenance (272), there is concern that very high doses of magnesium may be detrimental. In a case series of 9 patients receiving long-term tocolysis for 11-97 days, resulting in cumulative magnesium sulfate doses of 168-3756 grams, a lower bone mass was noted in 4 cases receiving doses above 1000 grams. There was one case of pregnancy- and lactation-associated osteoporosis and one fracture (108731). The validity and clinical significance of this data is unclear.

Neurologic/CNS ...Intravenously, magnesium may cause slurred speech, dizziness, drowsiness, confusion, or headaches (60818,60960). With toxic doses, loss of reflexes, neurological defects, drowsiness, confusion, and coma can occur (8095,12589,12590).
A case report describes cerebral cortical and subcortical edema consistent with posterior reversible encephalopathy syndrome (PRES), eclampsia, somnolence, seizures, absent deep tendon reflexes, hard to control hypertension, acute renal failure and hypermagnesemia (serum level 11.5 mg/dL), after treatment with intravenous magnesium sulfate for preeclampsia in a 24-year-old primigravida at 39 weeks gestation with a previously uncomplicated pregnancy. The symptoms resolved after 4 days of symptomatic treatment in an intensive care unit, and emergency cesarian delivery of a healthy infant (112785).

Ocular/Otic ...Cases of visual impairment or nystagmus have been reported following magnesium supplementation, but these events are rare (18111,60818).

Psychiatric ...A case of delirium due to hypermagnesemia has been reported for a patient receiving intravenous magnesium sulfate for pre-eclampsia (60780).

Pulmonary/Respiratory ...Intravenously, magnesium may cause respiratory depression and tachypnea when used in toxic doses (12589,61028,61180).

Other ...Hypothermia from magnesium used as a tocolytic has been reported (60818).

MANGANESE

General ...Orally and parenterally, manganese is generally well tolerated when used in appropriate doses. High doses might be unsafe.
Serious Adverse Effects (Rare):
All routes of administration: Neurotoxicity, including Parkinson-like extrapyramidal symptoms, when used in high doses.

Cardiovascular ...Chronic occupational exposure to manganese dust or fumes can cause orthostatic hypotension, and heart rate and rhythm disturbances (61363).

Endocrine ...Chronic occupational exposure to manganese dust or fumes can cause elevations in thyrotropin-releasing hormone (TRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels (61378).

Hepatic ...Manganese intoxication may cause cirrhosis and hepatic steatosis. In one case, a 13-year-old female with manganese intoxication developed severe, life-threatening neurological symptoms, with liver biopsy indicating incomplete cirrhosis and microvesicular steatosis. Chelation therapy and multiple rounds of therapeutic plasma exchange were required before symptoms resolved. The source of manganese exposure was not identified, and it is not clear if the impaired liver function contributed to the manganese accumulation or if elevated manganese exposure led to the liver damage.

Musculoskeletal ...Chronic occupational exposure to manganese dust or fumes has been associated with lower bone quality in females, but not males, suggesting that prolonged manganese exposure might increase the risk of osteoporosis in females (102516). A meta-analysis of 11 observational studies in adults also suggests that increased environmental exposure to airborne manganese sources is associated with lower motor function scores (108537).

Neurologic/CNS ...Orally, there is concern that higher doses of manganese might increase the risk of neurotoxicity, including Parkinson-like extrapyramidal symptoms (7135,10665,10666). One severe case of irreversible Parkinson disease possibly related to taking manganese 100 mg daily for 2-4 years has been reported (96418). In another case, a 13-year-old female with manganese intoxication (diagnosed from blood manganese levels and cranial MRI evidence) developed severe neurological symptoms including loss of consciousness, decorticate posture, clonus, increased reflexes in the extremities, isochoric pupils, and no painful stimulus response. Liver biopsy also showed incomplete cirrhosis and microvesicular steatosis. The patient was intubated, and chelation therapy and multiple rounds of therapeutic plasma exchange were required before symptoms resolved. The source of the child's manganese exposure was not identified (112137). Individuals with impaired manganese excretion can also experience these effects even with very low manganese intake. Manganese accumulation due to chronic liver disease seems to cause Parkinson-like extrapyramidal symptoms, encephalopathy, and psychosis (1992,7135). One review recommends stopping supplementation if aminotransferase or alkaline phosphatase levels rise beyond twice normal (99302).
Chronic occupational exposure to manganese dust or fumes can also cause extrapyramidal reactions (1990,7135). In 1837, Couper observed that exposure to manganese dust particles produces a neurological syndrome characterized by muscle weakness, tremor, bent posture, whispered speech, and excess salivation (61264). Additionally, observational research in children has found that elevated manganese levels detected in the hair and fingernails due to environmental exposure may be associated with impaired neurocognitive function or development (108535). A meta-analysis of 11 observational studies in adults also suggests that increased environmental exposure to airborne manganese sources is associated with lower cognitive function scores (108537).
Intravenously, manganese might increase the risk of neurotoxicity when administered at high doses or for an extended duration. Cases of Parkinson-like symptoms have been reported in patients receiving parenteral nutrition containing more than 60 mcg of manganese daily. Moderate MRI intensity uptake for manganese in the globus pallidus and basal ganglion areas of the brain has been shown in patients receiving parenteral manganese (96416,99302).

Psychiatric ...Chronic occupational exposure to manganese dust or fumes can cause mood disturbance and dementia (1990,7135). A case report describes a man who presented with confusion, psychosis, dystonic limb movements, and cognitive impairment after chronic industrial manganese exposure (99415). Symptoms of manganese toxicity from inhalational exposure develop slowly with initial fatigue and personality changes, progressing to hallucinations, delusions, hyperexcitability, Parkinson-like symptoms, dystonia, and dementia (99415). Additionally, observational research has found that chronic environmental exposure to manganese sources such as mining operations and various industrial processes may be associated with a greater risk for developing symptoms of depression (108536).

Pulmonary/Respiratory ...Chronic occupational exposure to manganese dust or fumes can cause acute chemical pneumonitis, pulmonary edema, or acute tracheobronchitis (61495).

MOLYBDENUM

General ...Orally, molybdenum is well tolerated when used appropriately in amounts that do not exceed the Tolerable Upper Intake Level (UL) of 2 mg/day (7135). People living in an area of Armenia with a very high dietary molybdenum intake of 10 to 15 mg/day due to high local soil levels have reported an increased incidence of hyperuricemia, gout, and arthralgias (7135,16478,16487). Environmental exposure to molybdenum has been reported to cause pneumoconiosis (63365,63547,63510) and to reduce testosterone levels and sperm concentration in men (63482,63484).
Molybdenum is present in some stainless steel angioplasty stents. In some case reports, patients with these stents can develop a contact allergy to molybdenum, which might increase the risk for restenosis of the stented artery (16485).

Genitourinary ...Environmental exposure to molybdenum has been reported to be a reproductive toxicant in men. Circulating levels of molybdenum are inversely associated with testosterone levels and sperm concentration (63482,63484).

Hematologic ...Orally, in an area of Armenia, a very high dietary molybdenum intake of 10 to 15 mg/day due to high local soil levels has resulted in an increased incidence of hyperuricemia (7135,16478,16487). The mechanism likely involves increased xanthine oxidase activity, leading to increased uric acid production (2663).

Immunologic ...Molybdenum is present in some stainless steel angioplasty stents. Multiple cases report on patients with these stents who have developed a contact allergy to molybdenum, as indicated by positive skin patch tests. It is suggested that this increases the risk for restenosis of the stented artery (16485).

Musculoskeletal ...Orally, in an area of Armenia, a very high dietary molybdenum intake of 10 to 15 mg/day due to high local soil levels has resulted in an increased incidence of hyperuricemia, gout, and arthralgias (7135,16478,16487). There is also a case report of gout in a man with industrial exposure to molybdenum metal dust (16480). The mechanism likely involves increased xanthine oxidase activity, leading to increased uric acid production (2663).

Neurologic/CNS ...In one case report of a man in his late thirties, dietary supplementation with molybdenum 300-800 micrograms daily for a cumulative dose of 13. 5 mg over 18 days resulted in acute psychosis with visual and auditory hallucinations, petit mal seizures, and a life-threatening grand mal attack, related to frontal cortical damage. Chelation therapy with calcium ethylene diamine tetraacetic acid (CaEDTA) was required. A year later, the man was diagnosed with toxic encephalopathy with executive deficiencies, learning disability, major depression, and post-traumatic stress disorder (63368).

Psychiatric ...In one case report of a man in his late thirties, dietary supplementation with molybdenum 300-800 micrograms daily for a cumulative dose of 13. 5 mg over 18 days resulted in acute psychosis with visual and auditory hallucinations, petit mal seizures, and a life-threatening grand mal attack, related to frontal cortical damage. Chelation therapy with calcium ethylene diamine tetraacetic acid (CaEDTA) was required. A year later, the man was diagnosed with toxic encephalopathy with executive deficiencies, learning disability, major depression, and post-traumatic stress disorder (63368).

Pulmonary/Respiratory ...Pneumoconiosis has been reported with excessive intake of molybdenum or exposure in the workplace (63365,63547,63510).

NIACIN

General ...Orally, niacin is well tolerated in the amounts found in foods. It is also generally well tolerated in prescription doses when monitored by a healthcare provider.
Most Common Adverse Effects:
Orally: Flushing, gastrointestinal complaints (abdominal pain, constipation, diarrhea, heartburn, nausea, vomiting), and elevated liver enzymes.
Serious Adverse Effects (Rare):
Orally: Hepatotoxicity, myopathy, thrombocytopenia, and vision changes.

Cardiovascular ...Orally, flushing is a common dose-related adverse reaction to niacin. A large meta-analysis of clinical studies shows that up to 70% of patients may experience flushing (96211). Although flushing can occur with doses of niacin as low as 30 mg daily, it is more common with the larger doses used for treatment of dyslipidemia. The flushing reaction is due to prostaglandin-induced blood vessel dilation and can also include symptoms of burning, tingling, urticaria, erythema, pain, and itching of the face, arms, and chest. There may also be increased intracranial blood flow and headache (4889,26089,93341,104933). Onset is highly variable and ranges from within 30 minutes to as long as 6 weeks after the initial dose (6243). Flushing can be minimized via various strategies, including taking doses with meals, slow dose titration, using extended release formulations, pretreating with non-steroidal anti-inflammatory drugs, taking regular-release niacin with meals, or taking the sustained-release product at bedtime (4852,4853,4854,4857,4858,25922,26073,26084). Flushing often diminishes with continued use but can recur when niacin is restarted after missed doses (4863,6243,26081). The vasodilating effects of niacin can also cause hypotension, dizziness, tachycardia, arrhythmias, syncope, and vasovagal attacks, especially in patients who are already taking antihypertensive drugs (4863,12033,93341,110494).
High doses of niacin can raise homocysteine levels. A 17% increase has been reported with 1 gram daily and a 55% increased has been reported with 3 grams daily. Elevated homocysteine levels are an independent risk factor for cardiovascular disease (490); however, the clinical significance of this effect is unknown. A large-scale study (AIM-HIGH) found that patients receiving extended-release niacin (Niaspan) 1500-2000 mg daily with a statin had an over two-fold increased risk of ischemic stroke (1.6%) when compared with those receiving only simvastatin (0.7%). However, when the risk was adjusted for confounding factors, niacin was not found to be associated with increased stroke risk (17627,93354). A meta-analysis of three clinical trials conducted in approximately 29,000 patients showed a higher risk of mortality in patients taking niacin in addition to a statin when compared with a statin alone. However, with a p-value of 0.05 and confidence interval including 1, the validity of this finding remains unclear (97308).

Endocrine ...Orally, niacin can impair glucose tolerance in a dose-dependent manner. Dosages of 3-4 grams daily appear to increase blood glucose in patients with or without diabetes, while dosages of 1.5 grams daily or less have minimal effects (12033). Niacin is thought to impair glucose tolerance by increasing insulin resistance or increasing hepatic output of glucose (4863,11692,11693). In patients with diabetes, niacin 4.5 grams daily for 5 weeks has been associated with an average 16% increase in plasma glucose and 21% increase in glycated hemoglobin (HbA1C) (4860). Up to 35% of patients with diabetes may need to increase the dose or number of hypoglycemic agents when niacin is started (4458,4860,4863,11689,12033). Occasionally, severe hyperglycemia requiring hospitalization can occur (11693). In patients with impaired fasting glucose levels, niacin may also increase fasting blood glucose, and adding colesevelam might attenuate this effect (93343).
Although patients without diabetes seem to only experience small and clinically insignificant increases in glucose (4458), niacin might increase their risk of developing diabetes. A meta-analysis of clinical research involving over 26,000 patients shows that using niacin over 5 years is associated with increased prevalence of new onset type 2 diabetes at a rate of 1 additional case of diabetes for every 43 patients treated with niacin (96207). This finding is limited because the individual trials were not designed to assess diabetes risk and the analysis could not be adjusted for confounding factors like obesity. One small clinical study shows that taking extended-release niacin with ezetimibe/simvastatin does not increase the risk of a new diagnosis of diabetes or need for antidiabetic medication when compared with ezetimibe/simvastatin alone after 16 months (93344). This may indicate that the increased risk of developing diabetes is associated with niacin use for more than 16 months.
Niacin therapy has also been linked with hypothyroidism and its associated alterations in thyroid hormone and binding globulin tests (such as decreased total serum thyroxine, increased triiodothyronine, decreased thyroxine-binding globulin levels, and increased triiodothyronine uptake) (25916,25925,25926,25928).

Gastrointestinal ...Orally, large doses of niacin can cause gastrointestinal disturbances including nausea, vomiting, bloating, heartburn, abdominal pain, anorexia, diarrhea, constipation, and activation of peptic ulcers (4458,4863,12033,26083,93341,96211). These effects may be reduced by taking the drug with meals or antacid, and usually disappear within two weeks of continued therapy (4851,26094). Gastrointestinal effects may be more common with time-release preparations of niacin (11691).

Hematologic ...Orally, sustained-release niacin has been associated with cases of reversible coagulopathy, mild eosinophilia, and decreased platelet counts (4818,25915,26097,93340). Also, there have been reports of patients who developed leukopenia while taking niacin for the treatment of hypercholesterolemia (25916).

Hepatic ...Orally, niacin is associated with elevated liver function tests and jaundice, especially with doses of 3 grams/day or more, and when doses are rapidly increased (4458,4863,6243). The risk of hepatotoxicity appears to be higher with slow-release and extended-release products (4855,4856,4863,6243,11691,12026,12033,93342). Niacin should be discontinued if liver function tests rise to three times the upper limit of normal (4863). There are rare cases of severe hepatotoxicity with fulminant hepatitis and encephalopathy due to niacin (4863,6243,11691). Also, there is at least one case of niacin-induced coagulopathy resulting from liver injury without liver enzyme changes (93340).

Musculoskeletal ...Orally, niacin has been associated with elevated creatine kinase levels (4818,4888). Also, several cases of niacin-induced myopathy have been reported (26100,26111). Concomitant administration of niacin and HMG-CoA reductase inhibitors may increase the risk of myopathy and rhabdomyolysis (14508,25918,26111); patients should be monitored closely.

Neurologic/CNS ...Orally, high-dose niacin has been associated with cases of neuropsychiatric adverse events such as extreme pain and psychosis. Two 65-year-old males taking niacin orally for 5 months for the treatment of dyslipidemias developed severe dental and gingival pain. The pain was relieved by the discontinuation of niacin. The pain was thought to be due to inflammation and pain referral to the teeth (4862). In one case report, a 52-year-old male with no history of psychiatric illness who initially complained of hot flushes when taking niacin 500 mg daily, presented with an acute psychotic episode involving mania after niacin was increased to 1000 mg daily (93350).

Ocular/Otic ...Orally, chronic use of large amounts of niacin has been associated with dry eyes, toxic amblyopia, blurred vision, eyelid swelling, eyelid discoloration, loss of eyebrows and eyelashes, proptosis, keratitis, macular edema, and cystic maculopathy, which appear to be dose-dependent and reversible (4863,6243,26112).

NICKEL

General ...Orally, nickel is well tolerated when taken in amounts found in foods, which are typically below the tolerable upper intake level (UL). However, doses above the UL can cause serious adverse effects.
Most Common Adverse Effects:
All routes of administration: Contact dermatitis.
Serious Adverse Effects (Rare):
Orally: Chronic consumption of large quantities of nickel might increase the risk of cancers of the lung, nose, larynx, and prostate.

Cardiovascular ...Particulate matter-associated nickel exposures have been associated with cardiopulmonary diseases (65021). Nickel exposure may also cause variable degrees of cardiovascular system poisoning (16333). In one case report, a 45-year-old male developed leukocytosis, low-grade fevers, dyspnea, and fatigue after implantation of a cardioverter-defibrillator (ICD). The patient eventually developed fulminant hypereosinophilia and eosinophilic myocarditis, resulting in cardiogenic shock and multiorgan failure. After the patient had been medically stabilized, the ICD was removed, leading to symptom resolution (99670).

Dermatologic ...Orally and topically, nickel can cause dermatitis and other hypersensitivity reactions in sensitized individuals (65045). Nickel exposure may cause systemic contact dermatitis (65017). Orally, nickel sulfate has been associated with classic systemic allergic contact eczema (64916). Topical exposure can occur from the use of common equipment containing nickel. There are at least four case reports of allergic contact dermatitis of the hand due to the use of a nickel-containing electronic cigarette device. Patients with nickel allergy should be advised to avoid devices that contain nickel (99665,99669). There is also a case report of a 21-year-old female who developed recurrent rash on her upper chest and thighs due to exposure to nickel via weightlifting equipment at her gym (99671).
"Nickel itch" may occur up to seven days before skin eruption occurs. The primary skin eruption is follicular, which may be followed by skin ulceration. Nickel may cause Baboon syndrome, characterized by a clinical presentation of systemic contact dermatitis with a pruritic and confluent maculopapular, light red eruption, localized in the gluteal area and the major flexures and developing several hours or days after nickel contact (64963,65092).
Individuals with mutations in the filaggrin gene may be especially susceptible to hand eczema caused by additive effects from irritants and nickel exposure (65012). Nickel exposure may lead to cross-sensitivity dermatitis reaction in individuals who are allergic to other metals, especially palladium, cobalt, and aluminum (65023,64939,65099,65028,64968,65026).

Gastrointestinal ...Orally, consuming high doses of nickel 0. 5-2.5 grams has been reported to cause nausea, vomiting, abdominal pain, and diarrhea. Patients with systemic nickel allergy syndrome (SNAS) can experience colic and diarrhea after consumption of nickel-rich foods (99663).

Genitourinary ...Nickel has been shown to cross the placenta and to have embryotoxic and teratogenic properties (65068,65091). Nickel may upset the hormonal balance of the mother and may impair development of the preimplantation embryo (65061).

Hepatic ...Orally, nickel has been reported to cause hepatotoxicity (65009).

Immunologic ...Orally and topically, nickel can cause hypersensitivity reactions in sensitized individuals (64916,65017,65045). Nickel sensitivity, which can cause dermatologic and gastrointestinal symptoms, has an estimated prevalence of 11% in the general population, with a higher overall incidence in females than in males (99668). About 10% of nickel-sensitive people react to ingestion of 550-1300 mcg. Nickel sensitivity, once acquired, may persist indefinitely (64994). Some clinical research suggests that daily consumption of nickel 30 ng, 0.3 mcg, or 1.5 mcg for one year can hyposensitize individuals and reduce symptoms of nickel sensitivity (99663).
In sensitive individuals, dermal or systemic exposure to nickel can induce a type I immediate (anaphylactic) reaction and a type IV delayed hypersensitivity reaction, mediated by secreted cytokines and allergen-specific T lymphocytes (64989,65002). Nickel exposure may cause a cross-sensitivity reaction in individuals who are allergic to other metals, especially palladium, cobalt, and aluminum (65023,64939,65099,65028,64968,65026).
Implantation of devices containing nickel have been reported to cause localized and systemic reactions. A 59-year-old male with a hip arthroplasty, who later tested positive for nickel allergy, experienced hip pain, aseptic implant loosening, and contact allergic dermatitis in the inguinal regions, necessitating multiple surgeries (99664). In another case, a 45-year-old male developed leukocytosis, low-grade fevers, dyspnea, fatigue, and edema immediately and during the two months after implantation of a cardioverter-defibrillator (ICD). The patient eventually developed fulminant hypereosinophilia and eosinophilic myocarditis, resulting in cardiogenic shock and multiorgan failure. Once the patient was stabilized, the ICD was removed and all symptoms resolved. The patient tested positive for nickel allergy (99670).
There have been at least two case reports of hypersensitivity reactions to the nickel contained in implanted cardiac rings. One 57-year-old male experienced severe urticaria and angioedema two weeks after implantation of a mitral valve annuloplasty ring. The patient tested positive for nickel allergy and, although there was no evidence of nickel in his blood, symptoms resolved upon removal of the nickel-containing ring (99667). A 56-year-old male experienced persistent urticarial rash and multiple episodes of anaphylactic shock within the first month after implantation of a mitral ring. The patient tested positive to nickel upon skin prick testing; symptoms resolved after removal of the mitral ring (99666).

Neurologic/CNS ...Orally, consuming large quantities of nickel can lead to acute nickel toxicity, which may cause cerebral edema (16334).

Oncologic ...The International Agency for Research on Cancer has classified nickel compounds as carcinogenic to humans (65046). Occupational exposure to nickel and nickel compounds in nickel refining, cutlery factories, and alkaline battery manufacturing plants is associated with an increased incidence of lung, bronchial, and nasal cancers (39918,65029,16334,65056,64962,65075,64912,65006,64974). It is unclear if one specific lung cancer cell type is associated with nickel exposure (65054). Nickel fumes present in nickel and some steel refineries are associated with undifferentiated and squamous histologies of the nose and paranasal sinuses (65040,65050,65101,64898,65093,64909,64984,65031,64969). Occupational changes in industrial processes that have eliminated or reduced exposures to nickel compounds have reduced the risk of lung cancer (64966); however, experts believe that further preventive measures are needed to decrease or eliminate occupational nickel exposure time (65010). Exposure to nickel concentrate or metallic nickel through the metallurgical refining process has not been associated with an increase in respiratory cancer risk (64918).
Although clinical and epidemiologic research show that sparingly soluble nickel compounds, and possibly also soluble nickel compounds, may be linked to an increased risk for lung and nasal cancers, there is conflicting evidence as to whether inhalation exposure to soluble nickel alone is carcinogenic (42782,64940). According to some researchers, these opposing positions may be resolved by the hypothesis that high concentrations of inhaled nickel may induce chronic lung inflammation, enhancing carcinogenic risks associated with inhalation exposure to other substances (64938). Therefore, it has been suggested that if exposures are kept below levels that cause chronic respiratory toxicity, carcinogenic effects may be avoided.
There is concern that exposure to nickel in conjunction with another metal might increase the risk for certain forms of cancer. In the art glass industry, an association was found between an increased risk for stomach cancer and the use of a mixture of arsenic, copper, nickel, and manganese (65086). Based on epidemiological data and genotoxicity testing, the combination of nickel and chromium in the fumes from the welding of stainless and high alloy steels may contribute to an additive risk of respiratory tract cancer (65064). Additionally, co-exposure to nickel and cadmium may increase the risk of lung cancer (64945).
Epidemiological studies that have found an association between nickel and an increased risk for cancer might be confounded by the presence of cigarette smoking and asbestos exposure (65087,65106). Nickel occurs in mainstream cigarette smoke in the range of 0-0.51 mg per cigarette (65096). The high prevalence of prostate cancer in smokers may be related to the nickel in cigarettes (65109).
Implantation of nickel-containing hardware has also been reported to induce the development of cancer (64913,65032,65039). In one case, a 65-year-old female developed osteogenic sarcoma at the site of a nail that had been implanted for nine years for fixation of a femoral neck fracture. A concentration of 14 ppm of nickel was detected within the tumor tissue, indicating neoplastic induction by nickel (65032). In a different case, a malignant fibrous histiocytoma of the bone developed 20 years after a femoral fracture treated by plate-screw fixation. Nickel was present in the tumor tissue, indicating the metabolism of corrosion products (64913).

Pulmonary/Respiratory ...Inhalation of nickel carbonyl has been reported to cause nickel toxicity, including pulmonary edema, acute tracheobronchitis, or diffuse interstitial pneumonitis (16334,64905,61495).
Occupational exposure to nickel has been reported to cause chronic rhinitis, sinusitis, airway narrowing, asthma, bronchitis, reduced lung function, lung fibrosis, nasal polyposis, perforation of the nasal septum, and cancer of the lungs and nasal sinuses (65045,64933,65077). Bronchiolitis induced by nickel and nitric acid have also been reported (64948).

Renal ...Orally, nickel has been reported to cause nephrotoxicity (16333,65009), especially when consumed in excessive amounts (65104).

Other ...Orally, nickel toxicity can occur after the consumption of large quantities of nickel. The level of toxicity caused by nickel exposure seems to depend on its chemical form. Insoluble nickel compounds, including metallic nickel, nickel sulfides, and nickel oxides, seem to have a higher carcinogenic potential than water-soluble nickel salts (chloride, nitrate, sulfate) (64902). Conversely, it has been reported that nickel compounds, other than nickel carbonyl, are essentially nontoxic after ingestion due to their low absorption from the gastrointestinal tract (65052).
The treatment of nickel toxicity is not well studied. In some reports, antioxidants, such as ascorbic acid, may protect against nickel toxicity (65009,64991). Chelating drugs have been used as an antidote in nickel poisoning (65045,64979). Sodium diethyldithiocarbamate and disulfiram have also been proposed as effective nickel chelators in the treatment of acute nickel carbonyl poisoning; however, adequate clinical studies are not available to assess the effectiveness of these options (65003).

General ...Orally, pantothenic acid is generally well tolerated. Topically and intramuscularly, dexpanthenol, a synthetic form of pantothenic acid, seems to be well tolerated.
Most Common Adverse Effects:
Topically: Burning, contact dermatitis, eczema, irritation, and itching related to dexpanthenol.

Cardiovascular ...There is one case of eosinophilic pleuropericardial effusion in a patient taking pantothenic acid 300 mg per day in combination with biotin 10 mg per day for 2 months (3914).

Dermatologic ...Topically, dexpanthenol has been associated with itching, burning, skin irritation, contact dermatitis, and eczema (67779,67781,67788,111258,111262). Three cases of allergic contact dermatitis have been reported (111260,111261).

Gastrointestinal ...Orally, pantothenic acid has been associated with diarrhea (67822,111258).

General ...Orally, intravenously, and rectally, phosphate salts are generally well tolerated when used appropriately and/or as prescribed.
Most Common Adverse Effects:
Orally: Abdominal pain, anal irritation, bloating, diarrhea, headache, gastrointestinal irritation, hyperphosphatemia, hypocalcemia, malaise, nausea, sleep disturbance, and vomiting.
Rectally: Hyperphosphatemia and hypocalcemia.
Serious Adverse Effects (Rare):
Orally: Extraskeletal calcification.

Cardiovascular ...Orally, a case of allergic acute coronary syndrome e., Kounis syndrome) is reported in a 43-year-old female after ingesting a specific sodium phosphate laxative product (Travad oral). She presented with maculopapular rash that progressed to anaphylaxis and a non-ST elevation acute coronary syndrome. The patient recovered after hospitalization for 3 days with medical management (112894).

Gastrointestinal ...Orally, phosphate salts can cause gastrointestinal irritation, nausea, abdominal pain, bloating, anal irritation, and vomiting (15,2494,2495,2496,2497,93846,93848,93850,93851,93853,107008). Sodium and potassium phosphates can cause diarrhea (15). Aluminum phosphate can cause constipation (15). A large comparative study shows that, when taken orally as a bowel preparation for colonoscopy, sodium phosphate is associated with gastric mucosal lesions in about 4% of patients (93868).

Neurologic/CNS ...Orally, phosphate salts can commonly cause malaise (93846). Headaches and sleep disturbance may also occur (93848,93851).

Renal ...Orally, use of sodium phosphate for bowel cleansing has been associated with an increased risk of acute kidney injury in some patients (93863). However, a pooled analysis of clinical research suggests that results are not consistent for all patients (93864). Some evidence suggests that female gender, probably due to lower body weight, iron-deficiency anemia, dehydration, and chronic kidney disease are all associated with an increased risk of sodium phosphate-induced kidney dysfunction (93865).

Other ...Orally, phosphate salts can cause fluid and electrolyte disturbances including hyperphosphatemia and hypocalcemia, and extraskeletal calcification. Potassium phosphates can cause hyperkalemia. Sodium phosphates can cause hypernatremia and hypokalemia (15,2494,2495,2496,2497,107008).
Rectally, phosphate salts can cause fluid and electrolyte disturbances including hyperphosphatemia and hypocalcemia (15,112922).
Deaths related to intake of oral or rectal phosphate salts are rare and most have occurred in infants and are related to overdose (93866). However, death has also been reported in elderly patients using sodium phosphate enemas, mainly at standard doses of 250 mL (93867).

POTASSIUM

General ...Orally or intravenously, potassium is generally well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, belching, diarrhea, flatulence, nausea, and vomiting.
Serious Adverse Effects (Rare):
All ROAs: High potassium levels can cause arrhythmia, heart block, hypotension, and mental confusion.

Cardiovascular ...Orally or intravenously, high potassium levels can cause hypotension, cardiac arrhythmias, heart block, or cardiac arrest (15,16,3385,95011,95626,95630).

Gastrointestinal ...Orally or intravenously, high doses of potassium can cause, nausea, vomiting, abdominal pain, diarrhea, and flatulence (95010,95011). Bleeding duodenal ulcers have also been associated with ingestion of slow-release potassium tablets (69625,69672).

Neurologic/CNS ...Orally or intravenously, high potassium levels can cause paresthesia, generalized weakness, flaccid paralysis, listlessness, vertigo, or mental confusion (15,16,3385,95011).

RIBOFLAVIN

General ...Orally, riboflavin is generally well tolerated.
Most Common Adverse Effects:
Orally: Dose-related nausea and urine discoloration.

Gastrointestinal ...Orally, riboflavin has been associated with rare diarrhea and dose-related nausea (1398,71483). In one clinical study, one subject out of 28 reported having diarrhea two weeks after starting riboflavin 400 mg daily (1398).

Genitourinary ...Orally, high doses of riboflavin can cause bright yellow urine. Furthermore, in one clinical study, one subject out of 28 reported polyuria two weeks after starting riboflavin 400 mg daily (1398,3094).

SELENIUM

General ...Orally, selenium is generally well-tolerated when used in doses that do not exceed the tolerable upper intake level (UL) of 400 mcg daily. Intravenously, selenium is generally well-tolerated.
Most Common Adverse Effects:
Orally: Gastric discomfort, headache, and rash. Excessive amounts can cause alopecia, dermatitis, fatigue, nail changes, nausea and vomiting, and weight loss.
Serious Adverse Effects (Rare):
Orally: Excessive ingestion has led to cases of multi-organ failure and death.

Dermatologic ...Excess selenium can produce selenosis in humans, affecting liver, skin, nails, and hair (74304,74326,74397,74495,90360) as well as dermatitis (74304). Results from the Nutritional Prevention of Cancer Trial conducted among individuals at high risk of nonmelanoma skin cancer demonstrate that selenium supplementation is ineffective at preventing basal cell carcinoma and that it increases the risk of squamous cell carcinoma and total nonmelanoma skin cancer (10687). Mild skin rash has been reported in patients taking up to 200 mcg of selenium daily for up to 12 months (97943).

Endocrine ...Multiple clinical studies have found an association between increased intake of selenium, either in the diet or as a supplement, and the risk for type 2 diabetes (97091,99661). One meta-analysis shows that a selenium plasma level of 90 mcg/L or 140 mcg/L is associated with a 50% or 260% increased risk for developing type 2 diabetes, respectively, when compared with plasma levels below 90 mcg/L. Additionally, consuming selenium in amounts exceeding the recommended dietary allowance (RDA) is associated with an increased risk of developing diabetes when compared with consuming less than the RDA daily. Also, taking selenium 200 mcg daily as a supplement is associated with an 11% increased risk for diabetes when compared with a placebo supplement (99661).
Hypothyroidism, secondary to iodine deficiency, has been reported as a result of selenium intravenous administration (14563,14565). One large human clinical trial suggested a possible increased risk of type 2 diabetes mellitus in the selenium group (16707).

Gastrointestinal ...In human research, nausea, vomiting, and liver dysfunction has been reported as a result of high selenium exposure (74439,74376). Mild gastric discomfort has been reported in patients taking up to 200 mcg of selenium daily for up to 12 months (97943).

Genitourinary ...The effect of selenium supplementation on semen parameters is unclear. In human research, selenium supplementation may reduce sperm motility (9729); however, follow-up research reported no effect on sperm motility or any other semen quality parameter (74441).

Neurologic/CNS ...Chronic exposure to organic and inorganic selenium may cause neurotoxicity, particularly motor neuron degeneration, leading to an increased risk of amyotrophic lateral sclerosis (ALS) (74304). Mild headache has been reported in patients taking up to 200 mcg of selenium daily for up to 12 months (97943).

SILICON

General ...Orally, silicon in the amounts found in food and water is not associated with adverse effects.
Serious Adverse Effects (Rare):
Inhaled: Crystalline silicon dioxide in the form of quartz dust found in industrial and occupational settings is associated with an increased risk of diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD), lung cancer, glomerulonephritis, vasculitis, and rheumatoid arthritis.

Cardiovascular ...Case control studies have shown that occupational exposure to silicon dioxide-containing compounds may cause vasculitis (75114). Patients with occupational pulmonary silicosis may develop microscopic polyangiitis (inflammation of the blood vessels in the nose, sinuses, throat, lungs, and kidneys, also known as Wegener's granulomatosis).

Dermatologic ...Occupational silica exposure may be a risk factor for scleroderma, particularly in males (75099).

Genitourinary ...Limited reports in humans indicate that long-term use of large amounts of antacids containing magnesium trisilicate may be associated with urolithiasis and silicon-containing stones (11760,11861,75075,75103). However, fewer than 30 cases associated with antacids containing silicates have been reported, despite these products being commercially available since the 1930s. Although exceptionally rare, silicon dioxide kidney stones can also occur without magnesium trisilicate ingestion (11556). Their formation is caused by an acidic urinary pH. In at least one case, urine alkalinization resulted in resolution of the symptoms (75075).
Case-control studies have shown that occupational exposure to silicon dioxide is related to antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (75114). High silicon levels in patients undergoing chronic hemodialysis have been associated with nephropathy (75089).

Hepatic ...High silicon levels in patients undergoing chronic hemodialysis have been associated with liver disease (75089).

Musculoskeletal ...High silicon levels in patients undergoing chronic hemodialysis have been associated with bone disease (75089). A meta-analysis suggests that the risk of rheumatoid arthritis is elevated with occupational exposure to silicon dioxide (75078).

Neurologic/CNS ...High silicon levels in patients undergoing chronic hemodialysis have been associated with neuropathy (75089).

Pulmonary/Respiratory ...Occupational exposure to crystalline silicon dioxide dust is associated with an increased risk of pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD), and lung cancer (75076,75081,75084,75114). Patients with occupational pulmonary silicosis may develop microscopic polyangiitis (inflammation of the blood vessels in the nose, sinuses, throat, lungs, and kidneys, also known as Wegener's granulomatosis). Meta-analyses suggest that occupational exposure to silicon dioxide increases the risk of lung cancer (75085,75095,75115). An analysis of 19 studies shows that lung cancer risk is approximately 2 times higher for those with silicosis (75115). It is not clear whether silicon dioxide is carcinogenic in the absence of silicosis (75083).

THIAMINE

General ...Orally and parenterally, thiamine is generally well tolerated.
Serious Adverse Effects (Rare):
Parenterally: Hypersensitivity reactions including angioedema and anaphylaxis.

Immunologic ...Orally, thiamine might rarely cause dermatitis and other allergic reactions. Parenterally, thiamine can cause anaphylactoid and hypersensitivity reactions, but this is also rare (<0.1%). Reported symptoms and events include feelings of warmth, tingling, pruritus, urticaria, tightness of the throat, cyanosis, respiratory distress, gastrointestinal bleeding, pulmonary edema, angioedema, hypotension, and death (15,35585,105445).
In one case report, a 46-year-old female presented with systemic allergic dermatitis after applying a specific product (Inzitan, containing lidocaine, dexamethasone, cyanocobalamin and thiamine) topically by iontophoresis; the allergic reaction was attributed to thiamine (91170).

TIN

General ...Orally, intake of food contaminated with large amounts of tin may cause gastrointestinal effects, including diarrhea, stomach pain, nausea, and anemia (28635).
Topically, dentifrices and mouthwashes containing tin as stannous fluoride or stannous chloride may cause teeth staining or tongue discoloration (28648,94409,101106,106016).
When inhaled long-term, tin may cause stannosis (28635).

Dermatologic ...When used topically on the teeth, stannous fluoride or stannous chloride dentifrice gels or pastes can cause teeth staining or tongue discoloration (28648,94409,101106,106016).

Gastrointestinal ...Orally, intake of food contaminated with large amounts of tin may cause gastrointestinal effects. Several cases of gastrointestinal events, including diarrhea, stomach pain, nausea, and/or gastroenteritis have been reported for patients who ingested foods contaminated with tin from tin cans. The dose of tin contained in these foods ranged from 250-1000 mg/kg body weight (28635). Consumption of food containing lower amounts of inorganic tin (100-200 ppm) has not been associated with adverse gastrointestinal effects (28650).

Hematologic ...Orally, intake of food contaminated with large amounts of tin has caused anemia (28635).

Pulmonary/Respiratory ...Multiple cases of stannosis, a benign form of pneumoconiosis, have been reported for patients exposed to inhalable tin dust, long-term (15 to 20 years). The exposure levels for these cases have not been reported (28635).

VANADIUM

General ...Orally, vanadium is well tolerated when taken in amounts below the tolerable upper intake level (UL) of 1. 8 mg daily. Higher doses may cause adverse effects.
Most Common Adverse Effects:
Orally: Gastrointestinal adverse effects, including abdominal discomfort, diarrhea, flatulence, and nausea, when taken at doses above the UL.
Serious Adverse Effects (Rare):
Orally: Kidney damage, when taken long-term at high doses.
Topically: Contact dermatitis and other allergic reactions in sensitive individuals.

Cardiovascular ...Higher levels of vanadium in the body have been associated with a greater risk for hypertension (107923). However, it is unclear if oral supplementation with vanadium causes elevated blood pressure.

Dermatologic ...Allergic reactions to vanadium metal have been reported (99051,102095). A 68-year-old female developed an itchy, erythematous rash, ocular pruritus, and a positive skin test to vanadium after implantation of a vanadium-containing knee prosthesis (99051). Contact dermatitis, presenting as pruritic eczema of the hand, and a positive skin patch test to vanadium was reported in a 39-year-old male who worked with vanadium-containing tools (102095).

Endocrine ...In some cases, patients with diabetes have used very high doses (100 mg daily) safely for up to 4 weeks (3055,3056,3057). However, high body levels of vanadium have been associated with an increased incidence malnutrition-related diabetes mellitus (3020).

Gastrointestinal ...Orally, vanadium most commonly causes mild gastrointestinal upset (7135). There is concern that taking doses exceeding the tolerable upper intake level (UL) of 1.8 mg per day can increase the risk of gastrointestinal side effects and possibly lead to more severe toxicity. At higher doses, vanadium frequently causes gastrointestinal effects including abdominal discomfort, diarrhea, nausea, and flatulence (3012,3055,3056,3057,12557,12558). Doses of 22.5 mg daily can also cause cramps (3012). Vanadium has also been associated with green discoloration of the tongue, which is unrelated to dose (7135).

Immunologic ...Allergic reactions to vanadium metal have been reported (99051,102095). A 68-year-old female developed an itchy, erythematous rash, ocular pruritus, and a positive skin test to vanadium after implantation of a vanadium-containing knee prosthesis (99051). Contact dermatitis, presenting as pruritic eczema of the hand, and a positive skin patch test to vanadium was reported in a 39-year-old male who worked with vanadium-containing tools (102095).
Higher levels of vanadium in the body have been associated with a weakened immune system in children, as measured by reductions in CD3+ and CD4+ cell counts (107924). However, it is unclear if oral supplementation with vanadium causes a weakened immune system or increases the risk of infection.

Neurologic/CNS ...Orally, vanadium has been rarely associated with fatigue, lethargy, and focal neurological lesions, which are unrelated to dose (7135).

Pulmonary/Respiratory ...Severe and chronic respiratory tract disorders have been reported from occupational exposure to vanadium dusts (17).

Renal ...In some cases, patients with diabetes have used very high doses (100 mg daily) of vanadium safely for up to 4 weeks (3055,3056,3057). However, there is concern based on animal research that prolonged use of high doses might cause serious side effects including kidney damage (7135). High body levels of vanadium have also been associated with an increased incidence of kidney stones, distal renal tubular acidosis, hypokalemic periodic paralysis, and sudden unexplained nocturnal death (3020).

VITAMIN A

General ...Orally, vitamin A is generally well-tolerated at doses below the tolerable upper intake level (UL).
Serious Adverse Effects (Rare):
Orally: In very high doses, vitamin A can cause pseudotumor cerebri, pain, liver toxicity, coma, and even death.

Dermatologic ...Chronic oral use of large amounts of vitamin A causes symptoms of vitamin A toxicity including dry skin and lips; cracking, scaling, and itchy skin; skin redness and rash; hyperpigmentation; shiny skin, and massive skin peeling (7135,95051). Hypervitaminosis A can cause brittle nails, cheilitis, gingivitis, and hair loss (15,95051). Adverse effects from a single ingestion of a large dose of vitamin A is more common in young children than adults (15). In children, approximately 25,000 IU/kg can cause skin redness and generalized peeling of the skin a few days later and may last for several weeks (15).

Gastrointestinal ...There is some evidence that oral vitamin A supplementation might increase the risk of diarrhea in children. Although vitamin A can prevent diarrhea and reduce mortality in malnourished children, doses as low as 10,000 IU weekly for 40 weeks have been associated with diarrhea in well-nourished children (319). Diarrhea (82326,82389), nausea (7135,100329), abdominal pain (95051), abdominal fullness (100329), and vomiting (7135,82559,95051,95055,109755) have been reported following use of large doses of oral vitamin A. Adverse effects from a single ingestion of a large dose of vitamin A is more common in young children than adults (15). In children, approximately 25,000 IU/kg can cause vomiting and diarrhea (15). Chronic use of large amounts of vitamin A causes symptoms of vitamin A toxicity including anorexia, abdominal discomfort, and nausea and vomiting (7135).

Genitourinary ...Hypervitaminosis A can cause reduced menstrual flow (15). Intravaginally, all-trans retinoic acid can cause vaginal discharge, itching, irritation, and burning (9199).

Hematologic ...Hypervitaminosis A can cause spider angiomas, anemia, leukopenia, leukocytosis, and thrombocytopenia (15,95051).

Hepatic ...Since the liver is the main storage site for vitamin A, hypervitaminosis A can cause hepatotoxicity, with elevated liver enzymes such as alanine aminotransferase (ALT, formerly SGPT) and aspartate aminotransferase (AST, formerly SGOT), as well as fibrosis, cirrhosis, hepatomegaly, portal hypertension, and death (6377,7135,95051).

Musculoskeletal ...Vitamin A can increase the risk for osteoporosis and fractures. Observational research has found that chronic, high intake of vitamin A 10,000 IU or more per day is associated with an increased risk of osteoporosis and hip fracture in postmenopausal adults, as well as overall risk of fracture in middle-aged males (7712,7713,9190). A meta-analysis of these and other large observational studies shows that high dietary intake of vitamin A or retinol is associated with a 23% to 29% greater risk of hip fracture when compared with low dietary intake (107294). High serum levels of vitamin A as retinol also increase the risk of fracture in males. Males with high serum retinol levels are seven times more likely to fracture a hip than those with lower serum retinol levels (9190). Vitamin A damage to bone can occur subclinically, without signs or symptoms of hypervitaminosis A. Some researchers are concerned that consumption of vitamin A fortified foods such as margarine and low-fat dairy products in addition to vitamin A or multivitamin supplements might cause excessive serum retinol levels. Older people have higher levels of vitamin A and might be at increased risk for vitamin A-induced osteoporosis.
Vitamin A's effects on bone resorption could lead to hypercalcemia (95051).
Hypervitaminosis can cause slow growth, premature epiphyseal closure, painful hyperostosis of the long bones, general joint pain, osteosclerosis, muscle pain, and calcium loss from the bones (15,95051). One child experienced severe bone pain after taking vitamin A 600,000 IU daily for more than 3 months (95051). Vitamin A was discontinued and symptoms lessened over a period of 2 weeks. The patient made a full recovery 2 months later.

Neurologic/CNS ...Orally, adverse effects from a single large dose of vitamin A are more common in young children than adults (15). Headache, increased cerebrospinal fluid pressure, vertigo, and blurred vision have been reported following an acute oral dose of vitamin A 500,000 IU (7135). In children, approximately 25,000 IU/kg can cause headache, irritability, drowsiness, dizziness, delirium, and coma (15). Chronic use of large amounts of vitamin A causes symptoms of vitamin A toxicity including fatigue, malaise, lethargy, and irritability (7135).
There are reports of bulging of the anterior fontanelle associated with an acute high oral dose of vitamin A in infants (7135,90784,95053,95054). In children, approximately 25,000 IU/kg can cause increased intracranial pressure with bulging fontanelles in infants (15). Also, muscular incoordination has been reported following short-term high doses of vitamin A (7135).
A case of intracranial hypertension involving diffuse headaches and brief loss of vision has been reported secondary to topical use of vitamin A. The patient was using over-the-counter vitamin A preparations twice daily including Avotin 0.05% cream, Retin-A gel 0.01%, and Isotrexin gel containing isotretinoin 0.05% and erythromycin 2%, for treatment of facial acne. Upon exam, the patient was noted to have bilateral optic disc edema. The patient discontinued use of topical vitamin A products. Two months later, the patient reported decreased headaches and an improvement in bilateral optic disc edema was seen (95056).

Ocular/Otic ...In children, oral vitamin A approximately 25,000 IU/kg can cause swelling of the optic disk, bulging eyeballs, and visual disturbances (15). Adverse effects from a single ingestion of a large dose of vitamin A are more common in young children than adults (15).

Oncologic ...There is concern that high intake of vitamin A might increase some forms of cancer. Population research suggests high vitamin A intake might increase the risk of gastric carcinoma (9194).

Psychiatric ...Chronic oral use of large amounts of vitamin A causes symptoms of vitamin A toxicity, which can include symptoms that mimic severe depression or schizophrenic disorder (7135).

Pulmonary/Respiratory ...There is some evidence that oral vitamin A supplementation might increase the risk of pneumonia and diarrhea in children. Although vitamin A can prevent diarrhea and reduce mortality in malnourished children, doses as low as 10,000 IU weekly for 40 weeks have been associated with pneumonia and diarrhea in well-nourished children (319). In preschool children, high-dose vitamin A also increases the risk of respiratory infection (82288).

Other ...Chronic use of large amounts of vitamin A (>25,000 IU daily for more than 6 years or 100,000 IU daily for more than 6 months) can cause symptoms of vitamin A toxicity including mild fever and excessive sweating (7135). High intakes of vitamin A may result in a failure to gain weight normally in children and weight loss in adults (15).

VITAMIN B12

General ...Orally, intramuscularly, and topically, vitamin B12 is generally well-tolerated.
Most Common Adverse Effects:
Intramuscular: Injection site reactions.
Serious Adverse Effects (Rare):
Intramuscularly: Severe hypokalemia has been rarely linked with correction of megaloblastic anemia with vitamin B12.

Cardiovascular ...In human clinical research, an intravenous loading dose of folic acid, vitamin B6, and vitamin B12, followed by daily oral administration after coronary stenting, increased restenosis rates (12150). Hypertension following intravenous administration of hydroxocobalamin has been reported in human research (82870,82864).

Dermatologic ...Orally or intramuscularly, vitamin B12 can cause allergic reaction such as rash, pruritus, erythema, and urticaria. Theoretically, allergic reactions might be caused by the cobalt within the vitamin B12 molecule (82864,90373,90381,103974). In one case report, oral methylcobalamin resulted in contact dermatitis in a 59-year-old Japanese woman with a cobalt allergy (103974). Vitamin B12 (intramuscular or oral) has also been associated with at least 19 cases of acneiform eruptions which resolved upon discontinuation of vitamin B12 (90365,90369,90388). High-dose vitamin B12 (20 mcg daily) and vitamin B6 (80 mg daily) have been associated with cases of rosacea fulminans characterized by intense erythema with nodules, papules, and pustules. Symptoms may last up to four months after the supplement is stopped and can be treated with systemic corticosteroids and topical therapy (10998,82870,82871).

Gastrointestinal ...Intravenously, vitamin B12 (hydroxocobalamin) 2. 5-10 grams can cause nausea and dysphagia (82864).

Genitourinary ...Intravenously, vitamin B12 (hydroxocobalamin) 5-15 grams has been associated with chromaturia in clinical research (82870,82871).

Hematologic ...According to case report data, the correction of megaloblastic anemia with vitamin B12 may result in fatal hypokalemia (82914).

Musculoskeletal ...According to case report data, correction of megaloblastic anemia with vitamin B12 has precipitated gout in susceptible individuals (82879).

Neurologic/CNS ...Treatment with vitamin B12 has been rarely associated with involuntary movements in infants with vitamin B12 deficiency (90370,90385,90397). In some cases these adverse reactions were misdiagnosed as seizures or infantile tremor syndrome (90370,90385). These adverse reactions presented 2-5 days after treatment with vitamin B12 and resolved once vitamin B12 was discontinued (90370,90385,90397).

Oncologic ...Although some epidemiological research disagrees (9454), most research has found that elevated plasma levels of vitamin B12 are associated with an increased risk of various types of cancer, including lung and prostate cancers and solid tumors (50411,102383,107743). One study found, when compared with blood levels of vitamin B12 less than 1000 ng/mL, plasma vitamin B12 levels of at least 1000 ng/mL was strongly associated with the occurrence of solid cancer (107743). It is unclear if increased intake of vitamin B12, either through the diet or supplementation, directly affects the risk of cancer. It is possible that having cancer increases the risk of vitamin B12 elevation. However, one observational study has found that the highest quintile of dietary intake of vitamin B12 is associated with a 75% increased incidence of developing esophageal cancer when compared with the lowest quintile in never drinkers, but not drinkers (107147).

Renal ...There is a case report of oxalate nephropathy in a 54-year-old male which was determined to be related to the use of intravenous hydroxocobalamin as treatment for cyanide poisoning. Intermittent hemodialysis was started 5 days after admission, along with a low-oxalate diet, oral calcium acetate, and pyridoxine 5 mg/kg daily (107148). A review of the use of intravenous hydroxocobalamin for suspected cyanide poisoning in 21 intensive care units in France between 2011 and 2017 resulted in a 60% increased odds of acute kidney injury and a 77% increased odds of severe acute kidney injury in the first week. However, biopsies were not conducted and a direct link with use of hydroxocobalamin could not be made (107139).

Other ...Several studies have found that higher vitamin B12 levels may be associated with increased mortality or decreased survival rates in hospitalized elderly patients (82889,82812,82857,82895). Human research has also found a positive correlation between vitamin B12 status and all-cause mortality in Pima Indians with diabetes (82863).

VITAMIN B6

General ...Orally or by injection, vitamin B6 is well tolerated in doses less than 100 mg daily.
Most Common Adverse Effects:
Orally or by injection: Abdominal pain, allergic reactions, headache, heartburn, loss of appetite, nausea, somnolence, vomiting.
Serious Adverse Effects (Rare):
Orally or by injection: Sensory neuropathy (high doses).

Dermatologic ...Orally, vitamin B6 (pyridoxine) has been linked to reports of skin and other allergic reactions and photosensitivity (8195,9479,90375). High-dose vitamin B6 (80 mg daily as pyridoxine) and vitamin B12 (20 mcg daily) have been associated with cases of rosacea fulminans characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy (10998).

Gastrointestinal ...Orally or by injection, vitamin B6 (pyridoxine) can cause nausea, vomiting, heartburn, abdominal pain, mild diarrhea, and loss of appetite (8195,9479,16306,83064,83103,107124,107127,107135). In a clinical trial, one patient experienced infectious gastroenteritis that was deemed possibly related to taking vitamin B6 (pyridoxine) orally up to 20 mg/kg daily (90796). One small case-control study has raised concern that long-term dietary vitamin B6 intake in amounts ranging from 3.56-6.59 mg daily can increase the risk of ulcerative colitis (3350).

Hematologic ...Orally or by injection, vitamin B6 (pyridoxine) can cause decreased serum folic acid concentrations (8195,9479). One case of persistent bleeding of unknown origin has been reported in a clinical trial for a patient who used vitamin B6 (pyridoxine) 100 mg twice daily on days 16 to 35 of the menstrual cycle (83103). It is unclear if this effect was due to vitamin B6 intake.

Musculoskeletal ...Orally or by injection, vitamin B6 (pyridoxine) can cause breast soreness or enlargement (8195).

Neurologic/CNS ...Orally or by injection, vitamin B6 (pyridoxine) can cause headache, paresthesia, and somnolence (8195,9479,16306). Vitamin B6 (pyridoxine) can also cause sensory neuropathy, which is related to daily dose and duration of intake. Doses exceeding 1000 mg daily or total doses of 1000 grams or more pose the most risk, although neuropathy can occur with lower daily or total doses as well (8195). The mechanism of the neurotoxicity is unknown, but is thought to occur when the liver's capacity to phosphorylate pyridoxine via the active coenzyme pyridoxal phosphate is exceeded (8204). Some researchers recommend taking vitamin B6 as pyridoxal phosphate to avoid pyridoxine neuropathy, but its safety is unknown (8204). Vitamin B6 (pyridoxine) neuropathy is characterized by numbness and impairment of the sense of position and vibration of the distal limbs, and a gradual progressive sensory ataxia (8196,10439). The syndrome is usually reversible with discontinuation of pyridoxine at the first appearance of neurologic symptoms. Residual symptoms have been reported in patients taking more than 2 grams daily for extended periods (8195,8196). Tell patients daily doses of 100 mg or less are unlikely to cause problems (3094).

Oncologic ...In females, population research has found that a median intake of vitamin B6 1. 63 mg daily is associated with a 3.6-fold increased risk of rectal cancer when compared with a median intake of 1.05 mg daily (83024). A post-hoc subgroup analysis of results from clinical research in adults with a history of recent stroke or ischemic attack suggests that taking folic acid, vitamin B12, and vitamin B6 does not increase cancer risk overall, although it was associated with an increased risk of cancer in patients who also had diabetes (90378). Also, in patients with nasopharyngeal carcinoma, population research has found that consuming at least 8.6 mg daily of supplemental vitamin B6 during treatment was associated with a lower overall survival rate over 5 years, as well as a reduced progression-free survival, when compared with non-users and those with intakes of up to 8.6 mg daily (107134).

VITAMIN C

General ...Orally, intravenously, and topically, vitamin C is well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, esophagitis, heartburn, headache, osmotic diarrhea, nausea, vomiting. Kidney stones have been reported in those prone to kidney stones. Adverse effects are more likely to occur at doses above the tolerable upper intake level of 2 grams daily.
Topically: Irritation and tingling.
Serious Adverse Effects (Rare):
Orally: There have been rare case reports of carotid inner wall thickening after large doses of vitamin C.
Intravenously: There have been case reports of hyperoxalosis and oxalate nephropathy following high-dose infusions of vitamin C.

Cardiovascular ...Evidence from population research has found that high doses of supplemental vitamin C might not be safe for some people. In postmenopausal adults with diabetes, supplemental vitamin C intake in doses greater than 300 mg per day is associated with increased risk of cardiovascular mortality. However, dietary intake of vitamin C is not associated with this risk. Also, vitamin C intake is not associated with an increased risk of cardiovascular mortality in patients without diabetes (12498).
Oral supplementation with vitamin C has also been associated with an increased rate of carotid inner wall thickening in men. There is preliminary evidence that supplemental intake of vitamin C 500 mg daily for 18 months can cause a 2.5-fold increased rate of carotid inner wall thickening in non-smoking men and a 5-fold increased rate in men who smoked. The men in this study were 40-60 years old (1355). This effect was not associated with vitamin C from dietary sources (1355).
There is also some concern that vitamin C may increase the risk of hypertension in some patients. A meta-analysis of clinical research suggests that, in pregnant patients at risk of pre-eclampsia, oral intake of vitamin C along with vitamin E increases the risk of gestational hypertension (83450). Other clinical research shows that oral intake of vitamin C along with grape seed polyphenols can increase both systolic and diastolic blood pressure in hypertensive patients (13162).

Dental ...Orally, vitamin C, particularly chewable tablets, has been associated with dental erosion (83484).

Dermatologic ...Topically, vitamin C might cause tingling or irritation at the site of application (6166). A liquid containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) has been reported to cause mild tingling and skin tightness (102355). It is unclear if these effects are due to vitamin C, the other ingredients, or the combination.

Gastrointestinal ...Orally, the adverse effects of vitamin C are dose-related and include nausea, vomiting, esophagitis, heartburn, abdominal cramps, gastrointestinal obstruction, and diarrhea. Doses greater than the tolerable upper intake level (UL) of 2000 mg per day can increase the risk of adverse effects such as osmotic diarrhea and severe gastrointestinal upset (3042,4844,96707,104450). Mineral forms of vitamin C, such as calcium ascorbate (Ester-C), seem to cause fewer gastrointestinal adverse effects than regular vitamin C (83358). In a case report, high dose intravenous vitamin C was associated with increased thirst (96709).

Genitourinary ...Orally, vitamin C may cause precipitation of urate, oxalate, or cysteine stones or drugs in the urinary tract (10356). Hyperoxaluria, hyperuricosuria, hematuria, and crystalluria have occurred in people taking 1 gram or more per day (3042,90943). Supplemental vitamin C over 250 mg daily has been associated with higher risk for kidney stones in males. There was no clear association found in females, but the analysis might not have been adequately powered to evaluate this outcome (104029). In people with a history of oxalate kidney stones, supplemental vitamin C 1 gram per day appears to increase kidney stone risk by 40% (12653). A case of hematuria, high urine oxalate excretion, and the presence of a ureteral stone has been reported for a 9-year-old male who had taken about 3 grams of vitamin C daily since 3 years of age. The condition resolved with cessation of vitamin C intake (90936).

Hematologic ...Prolonged use of large amounts of vitamin C can result in increased metabolism of vitamin C; subsequent reduction in vitamin C intake may precipitate the development of scurvy (15). In one case, a patient with septic shock and a large intraperitoneal hematoma developed moderate hemolysis and increased methemoglobin 12 hours after a high-dose vitamin C infusion. The patient received a blood transfusion and the hemolysis resolved spontaneously over 48 hours (112479).

Neurologic/CNS ...Orally, the adverse effects of vitamin C are dose-related and include fatigue, headache, insomnia, and sleepiness (3042,4844,83475,83476).

Renal ...Hyperoxalosis and oxalate nephropathy have been reported following high-dose infusions of vitamin C. Hyperoxalosis and acute kidney failure contributed to the death of a 76-year-old patient with metastatic adenocarcinoma of the lung who received 10 courses of intravenous infusions containing vitamins, including vitamin C and other supplements over a period of 1 month. Dosages of vitamin C were not specified but were presumed to be high-dose (106618). In another case, a 34-year-old patient with a history of kidney transplant and cerebral palsy was found unresponsive during outpatient treatment for a respiratory tract infection. The patient was intubated for acute hypoxemic respiratory failure, initiated on vasopressors, hydrocortisone, and antibacterial therapy, and received 16 doses of vitamin C 1.5 grams. Serum creatinine level peaked at greater than 3 times baseline and the patient required hemodialysis for oliguria and uncontrolled acidosis. Kidney biopsy revealed oxalate nephropathy with concomitant drug-induced interstitial nephritis (106625). In another case, a 41-year-old patient with a history of kidney transplant presented with fever, nausea, and decreased urine output 4 days after receiving intravenous vitamin C 7 grams for urothelial carcinoma. Serum creatinine levels increased from 1.7 mg/dL to 7.3 mg/dL over those 4 days, and hemodialysis was initiated 3 days after admission due to anuria. Renal biopsy confirmed the diagnosis of acute oxalate nephropathy (109962).

Other ...Intravenously, hypernatremia and falsely elevated ketone levels is reported in a patient with septic shock and chronic kidney disease after a high-dose vitamin C infusion. The hypernatremia resolved over 24 hours after cessation of the infusion (112479).

VITAMIN D

General ...Orally or intramuscularly, vitamin D is well tolerated.
Serious Adverse Effects (Rare):
Orally or intramuscularly: Excessive doses can lead to vitamin D toxicity with symptoms of hypercalcemia, and also sometimes azotemia and anemia.

Cardiovascular ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses. Rarely, people develop hypertension (10142). An analysis of clinical research suggests that, when taken orally, vitamin D might modestly increase levels of low-density lipoprotein (LDL)-cholesterol. However, it is not clear if this increase is clinically significant (84642).

Gastrointestinal ...Orally, vitamin D may cause dry mouth. In clinical research, intake of vitamin D 50,000 IU weekly for 4 weeks followed by 50,000 IU monthly for 5 months thereafter was associated with a 3.7-fold increase in reports of dry mouth compared with placebo (91348).Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses. Symptoms of vitamin D toxicity include pancreatitis (10142,84433). Vomiting occurred in one patient given a single dose of 200,000 IU (104624).

Genitourinary ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses. Advanced symptoms may include decreased libido (10142). Vaginal discharge and itching have been reported in a clinical trial following oral use (91348).

Hematologic ...Lab values of urinary and blood calcium, phosphate, albumin, blood urea nitrogen, serum cholesterol, aspartate aminotransferase, and alanine aminotransferase concentrations might increase with vitamin D use, especially with high doses (10142,91349,93943).
A case of elevated international normalized ration (INR) has been reported for an 84 year-old patient who took vitamin D 50,000 IU daily for 2 months. The patient's serum levels of vitamin D increased from <7 ng/mL to 100 ng/mL over 6 months. To resolve symptoms, vitamin D supplementation was discontinued (84433).

Musculoskeletal ...Vitamin D intoxication can occur when vitamin D supplements are taken in excessive doses (10142,17506). Symptoms of vitamin D toxicity include osteoporosis in adults and decreased growth in children (10142).

Ocular/Otic ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses (10142,17506). Symptoms of vitamin D toxicity include calcific conjunctivitis and photophobia (10142).

Psychiatric ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses (10142,17506). In rare cases, symptoms of vitamin D toxicity include psychosis (10142,93002).

Pulmonary/Respiratory ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses. Advanced symptoms of vitamin D toxicity may include runny nose (10142,17506,93002).

Renal ...Vitamin D intoxication can occur when vitamin D supplements are taken orally in excessive doses. Symptoms of vitamin D toxicity include azotemia. Vitamin D may also cause hypercalcemia, with advanced symptoms including kidney stones or kidney insufficiency due to precipitation of calcium phosphate in the tubules. Symptoms of renal impairment include frequency, nighttime awakening to urinate, thirst, inability to concentrate urine, and proteinuria. Renal impairment is usually reversible with discontinuation of vitamin D supplements (10142,93002,93943,110831,110833).

VITAMIN E

General ...Orally and topically, vitamin E is generally well-tolerated.
Serious Adverse Effects (Rare):
Orally: Bleeding, hemorrhagic stroke, cardiovascular complications.
Inhaled: Vitamin E acetate is thought to be responsible for e-cigarette, or vaping, product-use associated lung injury (EVALI).

Cardiovascular ...Some evidence suggests that taking vitamin E supplements, especially greater than or equal to 400 IU taken by mouth daily for over one year, might also increase the risk of mortality in non-healthy patients (12212,13036,15305,16709,83339). A population study shows that vitamin E use is associated with a significantly increased risk of mortality in people with a history of severe cardiovascular disease such as stroke or myocardial infarction (16709). In an analysis of clinical trials, patients who took either all-rac-alpha-tocopherol (synthetic vitamin E) or RRR-alpha-tocopherol (natural vitamin E) in doses of 400 IU/day or higher had an increased risk of mortality from all causes. The risk of mortality seems to increase when higher doses are used (12212). A large-scale study also suggests that patients with diabetes or cardiovascular disease who take RRR-alpha-tocopherol (natural vitamin E) 400 IU daily have an increased risk of heart failure and heart failure-related hospitalization (13036). However, in another large scale study, taking 600 IU vitamin E every other day for 10 years did not increase the risk of heart failure in healthy females over 45 years of age (90068). There is speculation that high-dose vitamin E might disrupt the normal antioxidant balance and result in pro-oxidant rather than antioxidant effects.
There is some evidence that vitamin E in combination with simvastatin (Zocor), niacin, selenium, vitamin C, and beta-carotene might lower high density lipoprotein-2 (HDL-2) by 15%. HDL-2 is considered to be the most cardioprotective component of HDL (7388). However, vitamin E and a statin alone don't seem to negatively affect HDL (11286,11287). In addition, vitamin E has been associated with increased triglycerides (85215). Although only certain isomers of vitamin E are included for determination of dietary requirements, all isomers are considered for determining safe intake levels. All the isomers are thought to potentially contribute to toxicity.

Dermatologic ...Topically, vitamin E has been associated with contact dermatitis, inflammatory reactions, and eczematous lesions (11998,85066,85285). Dermatitis, often associated with moisturizers containing vitamin E, has a scattered generalized distribution, is more common on the face than the hands, and is more common in females with a history of atopic dermatitis. In a retrospective analysis of results of patch tests for DL-alpha-tocopherol sensitivity, 0.9% of patients had a definite positive reaction, while over 50% had a weakly positive, non-vesicular erythematous reaction (107869).
Orally, vitamin E has been associated with pruritus in one clinical trial (34596).
Subcutaneously, vitamin E has been associated with reports of lipogranuloma (85188,112331). In one case, subcutaneous injection of a specific supplement (1Super Extenze), containing mineral oil and tocopherol acetate, into the penile tissue resulted in penile disfigurement due to sclerosing lipogranuloma (85188). In another case, a 50-year-old Iranian female presented with lipogranuloma of the face, characterized by severe facial erythema, edema, and tenderness, 3 months after receiving subcutaneous injections of vitamin E to the cheeks for "facial rejuvenation." The patient had noticed initial symptoms within 3 days, and her symptoms progressively worsened over time (112331).

Gastrointestinal ...Orally, vitamin E supplementation has been associated with abdominal pain, nausea, diarrhea, or flu-like symptoms (85040,85323). Intravenously, large doses of vitamin E in premature infants are associated with an increased risk of necrotizing enterocolitis and sepsis (85083,85231).

Genitourinary ...There is contradictory evidence about the effect of vitamin E on prostate cancer risk. One large-scale population study shows that males who take a multivitamin more than 7 times per week and who also take a separate vitamin E supplement have a significantly increased risk of developing prostate cancer (15607). In a large-scale clinical trial (The SELECT trial) in males over the age of 50 years, taking all-rac-alpha-tocopherol (synthetic vitamin E) 400 IU daily increased the risk of developing prostate cancer by 17% when compared with placebo. However, the difference in prostate cancer risk between vitamin E and placebo became significant only 3 years after patients stopped taking supplementation and were followed in an unblinded fashion. Interestingly, patients taking vitamin E plus selenium did not have a significantly increased risk of prostate cancer (17688).

Hematologic ...High doses of vitamin E might increase the risk of bleeding due to antagonism of vitamin K-dependent clotting factors and platelet aggregation. Patients with vitamin K deficiencies or taking anticoagulant or antiplatelet drugs are at a greater risk for bleeding (4098,4844,11999,34596,34538,34626,34594,112162).

Neurologic/CNS ...There is concern that vitamin E might increase the risk of hemorrhagic stroke (16708,34594,34596,108641). In one clinical study, there was a higher incidence of hemorrhagic stroke in male smokers taking all-rac-alpha-tocopherol (synthetic vitamin E) for 5-8 years compared to those not taking vitamin E (3949). Other studies lasting from 1.4-4.5 years and using either all-rac-alpha-tocopherol (synthetic vitamin E) or RRR-alpha-tocopherol (natural vitamin E) showed no significantly increased risk for stroke (2307,3896,3936). A meta-analysis of studies shows that vitamin E in doses of 300-800 IU daily, including both natural and synthetic forms, does not significantly affect total stroke risk. However, it significantly increases the risk of hemorrhagic stroke by 22%. This means that there will be one additional hemorrhagic stroke for every 1250 patients taking vitamin E. In contrast to this finding, the analysis also found that vitamin E significantly reduces the risk of ischemic stroke by 10%. This means that one ischemic stroke will be prevented for every 476 patients taking vitamin E (14621). In patients with moderately severe Alzheimer disease, taking vitamin E 2000 IU for 2 years has been associated with a modest, but significant, increase in falls and episodes of syncope when compared to placebo (4635).

Pulmonary/Respiratory ...When inhaled, vitamin E acetate is thought to play a role in the development of e-cigarette, or vaping, product-use associated lung injury (EVALI). Although a causal link has not yet been determined, in two case series, vitamin E acetate has been found in most bronchoalveolar lavage samples taken from the primary site of lung injury in patients with EVALI, whereas no vitamin E was found in healthy control samples. Other ingredients, including THC or nicotine, were also commonly found in samples. However, priority toxicants including medium chain triglyceride (MCT) oil, plant oil, petroleum distillate, or terpenes, were undetectable in almost all samples. EVALI has resulted in death in some patients (101062,102970).

Other ...In an analysis of 3 trials, taking vitamin E 400 IU with vitamin C 1000 mg daily for 14-22 weeks during gestation appears to increase the risk of gestational hypertension by 30% compared to placebo in patients at risk of pre-eclampsia. However, the risk of pre-eclampsia itself was not increased (83450).

VITAMIN K

General ...Orally, vitamin K is generally well tolerated.
Most Common Adverse Effects:
Orally: Diarrhea, nausea, and stomach upset.
Serious Adverse Effects (Rare):
Intravenously: There have been rare cases of anaphylaxis and hyperbilirubinemia (in infants).

Dermatologic ...Orally, intake of vitamin K2 (menaquinone) along with calcium and vitamin D3 can cause an increased incidence of skin and skin appendage lesions compared to taking calcium and vitamin D3 alone. However, the risk of this adverse event is low, with 0.5 incidences per 100 patient-years occurring for patients treated with vitamin K, calcium, and vitamin D3 and 0.1 incidences per 100 patient-years occurring for patients treated with calcium and vitamin D3 alone (85467).

Gastrointestinal ...Orally, vitamin K can cause mild to moderate gastrointestinal side effects (91450,91451). The most common effects include nausea, abdominal pain, and diarrhea (91450,91451).

Hepatic ...Orally, vitamin K3 (menadione) has been linked to hepatotoxicity. Vitamin K3 is no longer used therapeutically in North America because it has been linked to hepatic toxicity and jaundice in animal research (7135).

Other ...Intravenously, vitamin K can cause reactions that resemble hypersensitivity or anaphylaxis (85389). These reactions are rare. It is unclear whether the adverse effect is caused by the drug or a component of the solution. There have been very rare cases of hyperbilirubinemia, particularly in premature neonates, following large doses of vitamin K (15).

ZINC

General ...Orally, zinc is well tolerated in doses below the tolerable upper intake level (UL), which is 40 mg daily for adults. Topically, zinc is well tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, diarrhea, metallic taste, nausea and vomiting (dose-related).
Topically: Burning, discoloration, itching, stinging, and tingling when applied to irritated tissue.
Intranasally: Bad taste, dry mouth, headache, irritation, reduced sense of smell.
Serious Adverse Effects (Rare):
Orally: There have been cases of acute renal tubular necrosis, interstitial nephritis, neurological complications, severe vomiting, and sideroblastic anemia after zinc overdose.
Intranasally: There have been cases where intranasal zinc caused permanent loss of smell (anosmia).

Dermatologic ...Topically, zinc can cause burning, stinging, itching, and tingling when applied to inflamed tissue (6911,8623,87297). Zinc oxide can be deposited in the submucosal tissue and cause dark discoloration of the skin. This can occur with prolonged topical application to intact skin, application to eroded or ulcerated skin, or penetrating traumatic exposure, and also parenteral administration (8618).
In rare cases, oral zinc has resulted in worsened acne (104056), skin sensitivity (6592), a leishmanial reaction with a macular rash that occurred on exposed parts of the body (86935), eczema (104055), systemic contact dermatitis (109457), and the development of severe seborrheic dermatitis (86946).

Gastrointestinal ...Orally, zinc can cause nausea (338,2663,2681,6592,6700,18216,106230,106233,106227), vomiting (2663,2681,6519,6592,96069,96074), a metallic or objectionable taste in the mouth (336,338,6700,11350,18216,106902), abdominal cramping (6592,96069), indigestion (87227), heartburn (96069), dry mouth (87533), and mouth irritation (336,2619). When used orally in amounts above the tolerable upper intake level, zinc may cause irritation and corrosion of the gastrointestinal tract (331,86982,87315,106902), watery diarrhea (1352), epigastric pain (2663,2681), and severe vomiting (2663,2681).
Intranasally, zinc can cause bad taste, dry mouth, and burning and irritation of the throat (8628,8629).
When used topically as a mouth rinse, zinc may cause tooth staining (90206).

Hematologic ...There is concern that high daily doses of zinc, above the tolerable upper intake level (UL) of 40 mg per day, might increase the risk of copper deficiency, potentially leading to anemia and leukopenia (7135,112473). To prevent copper deficiency, some clinicians give a small dose of copper when zinc is used in high doses, long-term (7303).

Hepatic ...There are two cases of liver deterioration in patients with Wilson disease following initiation of treatment with zinc 50-200 mg three times daily. The mechanism of action is not understood, and the event is extremely uncommon (86927,87470).

Immunologic ...Daily doses of 300 mg of supplemental zinc for 6 weeks appear to impair immune response (7135). A case of erythematosus-like syndrome, including symptoms such as fever, leg ulcers, and rash, has been reported following intake of effervescent tablets (Solvezink) containing zinc 45 mg (87506). In another case, severe neutropenia was reported after taking supplemental zinc 900 mg daily for an unknown duration (112473).

Neurologic/CNS ...Zinc-containing denture adhesives can cause toxicity if used more frequently than recommended for several years. Case reports describe hyperzincemia, low copper levels, blood dyscrasias, and neurological problems, including sensory disturbances, numbness, tingling, limb weakness, and difficulty walking in patients applying denture adhesive multiple times daily for several years (17092,17093,90205,90233). Due to reports of zinc toxicity associated with use of excessive amounts of zinc-containing denture adhesives for several years, GlaxoSmithKline has reformulated Polygrip products to remove their zinc content (17092,17093).
Intranasally (8628) and orally (87534), zinc can cause headache. When used orally in amounts above the tolerable upper intake level (UL), zinc may cause central nervous system (CNS) symptoms including lethargy, fatigue, neuropathy, dizziness, and paresthesia (2663,2681,87369,87470,87533,87534,112473).

Oncologic ...There is concern that zinc might worsen prostate disease. For example, some preliminary evidence suggests that higher dietary zinc intake increases the risk for benign prostatic hyperplasia (6908). Epidemiological evidence suggests that taking more than 100 mg of supplemental zinc daily or taking supplemental zinc for 10 or more years doubles the risk of developing prostate cancer (10306). Another large-scale population study also suggests that men who take a multivitamin more than 7 times per week and who also take a separate zinc supplement have a significantly increased risk of prostate cancer-related mortality (15607). However, a large analysis of population research suggests that there is no association between zinc intake and the risk of prostate cancer (96075).

Pulmonary/Respiratory ...There are several hundred reports of complete loss of sense of smell (anosmia) that may be permanent with use of zinc gluconate nasal gel, such as Zicam (11306,11155,11707,16800,16801,17083,86999,87535). Loss of sense of smell is thought to be dose related but has also been reported following a single application (11306,11155,11707,16800). Patients often report having sniffed deeply when applying the gel, then experiencing an immediate burning sensation, and noticing anosmia within 48 hours (17083). On June 16, 2009, the US Food and Drug Administration (FDA) advised patients not to use a specific line of commercial zinc nasal products (Zicam) after receiving 130 reports of loss of smell (16800). The manufacturer of these products had also received several hundred reports of loss of smell related to its intranasal zinc products (16801). Zinc sulfate nasal spray was used unsuccessfully for polio prophylaxis before the polio vaccine was developed. It caused loss of smell and/or taste, which was sometimes permanent (11713). Animal studies suggest that zinc sulfate negatively affects smell, possibly by damaging the olfactory epithelium and neurons (11156,11703,11704,11705,11706). Zinc gluconate nasal spray has not been tested for safety in animals or humans. The clinical studies of intranasal zinc have not described anosmia as an adverse effect, but testing was not done to see if zinc use adversely affected sense of smell (6471,8628,8629,10247). Also, these clinical studies reported tingling or burning sensation in the nostril, dry nose, nose pain, and nosebleeds.
When used in amounts above the tolerable upper intake level (UL), zinc may cause flu-like symptoms including coughing (2663).

Renal ...In overdose, zinc can cause acute renal tubular necrosis and interstitial nephritis (331,1352,87338).

Other ...Occupational inhalation of zinc oxide fumes can cause metal fume fever with symptoms including fatigue, chills, fever, myalgias, cough, dyspnea, leukocytosis, thirst, metallic taste, and salivation (331).

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