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You are here : 3-RX.com > Medical Encyclopedia > Diet and Nutrition > Vitamin B12
      Category : Health Centers > Food, Nutrition, and Metabolism

Vitamin B12

Alternate Names : Cobalamin, Cyanocobalamin

Overview & Description | Functions and Sources

Vitamin B12 is a water-soluble vitamin. It can dissolve in water. It is one of the B-complex vitamins. The B complex includes:

  • B1
  • B2
  • B6
  • pantothenic acid
  • folic acid
  • niacin
  • biotin
  • Cobalamin is the general name for vitamin B12.


    The recommended dietary allowance for adults, called RDA, for vitamin B12 is 2 micrograms (mcg) per day. For pregnant women, the RDA is 2.2 mcg; for nursing women, it is 2.6 mcg. A microgram is a very small amount. Since the only dietary sources of B12 are animal products, strict vegetarians may need to take supplements. They may also eat foods that have had the vitamin added.

    Not getting enough vitamin B12 can cause:

  • anemia
  • fatigue
  • nerve damage, with symptoms such as tingling sensations and numbness
  • smooth tongue
  • very sensitive skin
  • muscle and nerve paralysis
  • Some people have trouble absorbing B12. Other people may just have poor dietary intake. Anemia can be treated with injections of B12. Strict vegetarians who eat no animal products, their infants, and older people are at the highest risk for vitamin B12 deficiency. For these people, eating fortified foods and/or taking dietary supplements can help prevent a deficiency. High intakes of folic acid can hide this type of anemia.

    Getting too much vitamin B12 has no known symptoms or toxicity. Since it is water-soluble, any extra leaves the body in the urine. There is no proof that taking extra B12 boosts energy. Vitamins do not provide calories or create energy. Vitamins can help break down nutrients that yield energy. These nutrients include carbohydrate, protein, and fat.

    Calcium is needed to help the body absorb vitamin B12. A deficiency of either iron or vitamin B6 can decrease the amount of B12 the body is able to absorb.


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    Vitamin B12: Functions and Sources

    Author: Kimberly Tessmer, RD, LD
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 09/28/02

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