Vitamin B12

Vitamin B12 (cobalamin) is involved in the metabolism of amino acids and folate and is essential for the normal metabolism of all cells, especially those of the GI tract, bone marrow, and nervous tissue. The vitamin also preserves DNA integrity and maintains the myelin sheaths that protect nerve fibers.

Vitamin B12 deficiency is uncommon in healthy individuals but can result in megaloblastic anemia that is characterized by large, immature red blood cells. Folate supplementation can alleviate the anemia, but other symptoms will progress. Cobalamin deficiency produces neurologic abnormalities, including irreversible paralysis of the nerves and muscles. A type of vitamin B12 deficiency called pernicious anemia can result from malabsorption related to inadequate production and secretion of gastric intrinsic factor. This is common in the elderly due to changes in their GI function.

Food sources of vitamin B12 are found exclusively in animal foods. Strict vegetarians need to find alternative sources such as vitamin B12-fortified soy beverages, fortified cereals, or B12 supplements. There are no adverse effects associated with large intakes of vitamin B12 from food or supplements in healthy people.

 
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