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Vitamin B12 (Cobalamin)

Vitamin B12 is also called cobalamin. We need vitamin B12 in our daily diet to help the cells in our bodies grow and maintain normal function. It is an especially important vitamin for healthy bone marrow (where blood cells are formed) and the nervous system. Not getting enough vitamin B12 leads to a disease called pernicious anemia, which results in red blood cells not getting enough oxygen and causing disorders of the nervous system. The elderly are at higher risk for developing pernicious anemia because aging causes a decrease in the amount of vitamin B12 that the body is able to absorb from food.

Uses

The most important use of vitamin B12 is to improve the symptoms of pernicious anemia. These symptoms include weakness, pallor, and neurologic symptoms such as burning or prickling of the hands and feet, loss of balance, confusion, loss of memory, and moodiness.

Recent studies suggest a role for vitamin B12 in the prevention of heart disease. Patients taking a combination of folic acid, vitamin B12, and vitamin B6 lowered their blood levels of homocysteine, a substance that seems to be associated with a higher risk of heart disease.

Dietary Sources

Vitamin B12 is present in foods containing animal protein. The richest sources of it are liver and kidney. Other good sources of vitamin B12 include milk, eggs, fish, and cheese.

Other Forms

Vitamin B12 can be found in vitamin form as cyanocobalamin. It is available as tablets, softgels, or lozenges in multivitamin form (including children's chewable and liquid drops), B-complex form, or by itself.

How to Take It

To avoid disorders of vitamin B12 deficiency, adults should get 2.0 mcg of vitamin B12 daily. People whose daily diet includes meat, milk, and other dairy products should be able to meet the 2.0 mcg recommended daily requirement without taking a vitamin supplement. Vegetarians who do not eat animal protein products should take a vitamin supplement with water, preferably after eating. Pregnant women should get 2.2 mcg of vitamin B12 daily and women who are breast-feeding should get 2.6 mcg of vitamin B12 daily. As with all medications and supplements, check with your health care provider before giving vitamin B12 supplements to a child. Elderly people may need more than 2.0 mcg of vitamin B12 daily because of decreasing ability to absorb vitamin B12 from our diet as we age. Elderly people should check with their health care provider to find out what dosage best fits their needs.

Precautions

Vitamin B12 is non-toxic, but there is no known benefit to healthy individuals of taking more than the 2.0 mcg recommended daily allowance.

Possible Interactions

The absorption of vitamin B12 is decreased when taking medications such as omeprazole, lansoprazole, ranitidine, cimetidine, or antacids that are often used to treat ulcers. This interference with vitamin B12 is most likely to result from prolonged use of more than a year.

Blood levels of vtamin B12 may also be reduced when taking metformin for diabetes or chemotherapeutic medications for cancer, particularly methotrexate.

Supporting Research

Ballal RS, Jacobsen DW, Robinson K. Homocysteine: update on a new risk factor. Cleve Clin J Med. 1997;64:543549.

Carmel R. Cobalamin, the stomach and aging. Am J Clin Nutr. 1997;66(4):750-759.

Committee on Dietary Allowances. Recommended Dietary Allowances. National Academy of Sciences. Accessed at www.nal.usda.gov/fnic/Dietary/rda.html on January 8, 1999.

Dorland Newman WA, ed. Dorland's Illustrated Medical Dictionary. 28th ed. Philadelphia, Pa: WB Saunders Co; 1994:73.

Ekhard ZE, Filer LJ, eds. Present Knowledge in Nutrition. 7th ed. Washington, DC: ILSI Press; 1996:191201.

Hardman JG, Limbird LE, eds. Goodman and Gillman's The Pharmacological Basis of Therapeutics. 9th ed. New York, NY: McGraw-Hill; 1996:13261333.

Howden CW. Vitamin B12 levels during prolonged treatment with proton pump inhibitors. J Clin Gastroenterol, 1999;30(1):29-33.

Hurter T, Reis HE, Borchard F. Disorders of intestinal absorption in patients treated with cytostatic chemotherapy [in German]. Z Gastroenterol. 1989;27(10):606-610.

Ingram CF, Fleming AF, Patel M, Galpin JS. The value of intrinsic factor antibody test in diagnosing pernicious anaemia. Cent Afr J Med. 1998;44:178181.

Lobo A, Naso A, Arheart K, et al. Reduction of homocysteine levels in coronary artery disease by low-dose folic acid combined with levels of vitamins B6 and B12. Am J Cardiol. 1999;83:821825.

Lee AJ. Metformin in noninsulin-dependent diabetes mellitis. Pharmacotherapy. 1996;16:327351.

Mahan LK, Arlin MT, eds. Krause's Food, Nutrition, and Diet Therapy. 8th ed. Philadelphia, Pa: WB Saunders Co; 1992:9697.

National Research Council. Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press; 1989:158165.

Nilsson-Ehle H. Age-related changes in cobalamin (vitamin B12) handling. Implications for therapy. Drugs Aging. 1998;12:277292.

Remacha AF, Cadafalch J. Cobalamin deficiency in patients infected with the human immunodeficiency virus. Semin Hematol. 1999;36:7587.

Schumann K. Interactions between drugs and vitamins in advanced age. Int J Vitam and Nutr Res, 1999;69(3):173-178.

Termanin B, Gibril F, Sutliff VE, Yu F, Venzon DJ, Jensen RT. Effect of long-term gastric acid suppressive therapy on serum vitamin B12 levels in patients with Zollinger-Ellison syndrome. Am J Med. 1998;104(5):422-430.

van Asselt DZ, van den Broek WJ, Lamers CB, et al. Free and protein-bound cobalamin absorption in healthy middle-aged and older subjects. J Am Geriatr Soc. 1996;44:949953.