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. Vitamin B12 is frequently used in combination with other B vitamins in a vitamin B complex formulation. Vitamin B12 plays an important role in supplying essential methyl groups for protein and DNA synthesis. Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases B12 from protein during digestion. Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream.
• The human body stores several years' worth of vitamin B12 in the liver, so nutritional deficiency of this vitamin is extremely rare. However, deficiency can result from being unable to use vitamin B12. Inability to absorb vitamin B12 from the intestinal tract can be caused by pernicious anemia. Vitamin B12 deficiency is common in the elderly. HIV-infected persons and vegetarians who are not taking in proper amounts of B12 are also prone to deficiency.

References

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