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Vitamin B12

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, mecobalamin, 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.
  • Fever has been reported in patients with megaloblastic and pernicious anemia caused by vitamin B12 deficiency, which resolved when treated with vitamin B12 (4;5). However, research involving symptoms of "feeling hot" or "excessive sweating" with vitamin B12 deficiency is lacking.
  • The human body stores several years' worth of vitamin B12 in the liver (6); therefore, symptoms of vitamin B12 deficiency may take decades to manifest. 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 (7). 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 (8;9). According to a survey done in the United States and the United Kingdom, 6% of patients aged ≥60 years had vitamin B12 deficiency (10). 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 (11). Vitamin B12 deficiency is also common in HIV-infected patients, and in some cases, it may be asymptomatic (12). Additionally, strict vegetarians or lactovegetarians who are not taking in proper amounts of vitamin B12 (13;14) or those in developing countries where intake of animal-sourced foods are low (10) are also prone to a deficiency state. Another cause of vitamin B12 deficiency in adults may be due to food-cobalamin malabsorption, which may be considered the most common etiology (15). Vitamin B12 deficiency has become a severe problem due to diet in areas such as the Indian subcontinent, Mexico, Central and South America, and some areas in Africa (14).
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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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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.