Synonyms/Common Names/Related Substances:

• Adenosylcobalamin, AdoB12, B complex, B complex vitamin, B-12, bedumil, cobalamin, cobalamins, cobamin, cyanocobalamin, cyanocobalamine, cyanocobalaminum, cycobemin, hydroxocobalamin, hydroxocobalaminum, hydroxocobemine, idrossocobalamina, methylcobalamin, vitadurin, vitamin B-12, vitamina B12 (Spanish), vitamine B12 (French).

Clinical Bottom Line/Effectiveness

Brief Background:

• Vitamin B12 is an essential water-soluble vitamin that is commonly found in a variety of foods, such as fish, shellfish, meat, eggs, and dairy products (1). It is frequently used in combination with other B vitamins in vitamin B complex formulations. Vitamin B12 plays an important role in supplying essential methyl groups for protein and DNA synthesis (2).
• Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, vitamin B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream (3). According to secondary sources, vitamin B12 is the largest and most structurally complicated vitamin, and it can only be produced industrially through bacterial fermentation-synthesis. Cyanocobalamin is a common synthetic form of vitamin B12 that is widely used in pharmaceuticals and supplements, and as a food additive.
• The human body stores several years' worth of vitamin B12 in the liver, so nutritional deficiency of this vitamin has been found to be extremely rare (4). However, deficiency may result from being unable to use vitamin B12. The inability to absorb vitamin B12 from the intestinal tract can be caused by pernicious anemia, a type of megaloblastic anemia, characterized by a lack of gastric intrinsic factor (5). Vitamin B12 deficiency is common in the elderly due to an increasing prevalence of atrophic gastritis type B, which occurs in 20-50% of elderly subjects (6). Atrophic gastritis is characterized by decreased gastric acid and pepsinogen secretion, therefore reducing intestinal digestion and absorption of vitamin B12 and folic acid. In patients who have undergone restorative proctocolectomy, vitamin B12 deficiency anemia is commonly seen (7). Vitamin B12 deficiency is also common in HIV-infected patients, and in some cases, it may be asymptomatic (8). Additionally, strict vegetarians or even lactovegetarians who are not taking in proper amounts of vitamin B12 are also prone to a deficiency state (9). Vitamin B12 deficiency may be indicated by elevated methylmalonic acid (MMA) or homocysteine (Hcy) concentrations (2). One study concluded that mean corpuscular volume (MCV) should not be used as the only parameter in the detection of vitamin B12 deficiency, as the diagnostic accuracy is low and could fail to detect up to 84% of vitamin B12-deficient cases (10).
• Current available human data suggest that low maternal vitamin B12 status may increase the risk of fetal neural tube defects (11;​12;​13). One study concluded that a marginal maternal vitamin B12 status increases the risk of spina bifida in offspring (14). Vitamin B12 deficiency has also been associated with hearing loss; however, short-term vitamin B12 supplementation was not shown to improve hearing status in vitamin B12-deficient elderly (15).
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Dosing/Toxicology

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Precautions/Contraindications

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Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Mechanism of Action

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History

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Evidence Table

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Evidence Discussion

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Products Studied

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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