Vitamin B12

Vitamin B12, found only in foods of animal origin, is unique among vitamins as it contains the metal ion cobalt. For this reason compounds having vitamin B12 activity are called ‘cobalamin’.

In the human body, the vitamin B12 forms ‘methylcobalamin’ and ‘5-deoxyadenosyl cobalamin’ are used. Most supplements contain the form ‘cyanocobalamin’, which is converted in the body (1).

Health functions

The vitamin B12 form methylcobalamin is required as cofactor for the function of the vitamin B9 (folate)-dependent enzyme that catalyzes the synthesis of the amino acid methionine from homocysteine.

Disease risk reduction

Even slightly raised levels of the amino acid homocysteine in the blood can result in an increased risk of cardiovascular diseases, as shown in over 80 studies (3).

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Things to know about Vitamin B12

  • Other applications

    Pernicious anemia occurs when stomach cells are not able to produce a certain protein (‘intrinsic factor’), needed by the body to absorb vitamin B12. Symptoms include weakness, pale skin, diarrhea, weight loss, fever, numbness or a tingling sensation in the hands and feet, loss of balance, confusion, memory loss, and irritability.

  • Intake recommendations

    In 1993, the European Scientific Committee for Food set population reference intakes (PRI) for vitamin B12 in micrograms (mcg) per day (26).

  • Supply situation

    Detailed intake data on vitamin B12 in European countries are scarce.

  • Deficiency

    Absorption of vitamin B12 from food requires normal function of the stomach, pancreas, and the digestive tract (‘intestine’).

  • Sources

    Vitamin B12, which can only be synthesized by bacteria, is present in animal products such as meat, poultry, fish (including shellfish), mussels, and to a lesser extent milk, but it is not generally present in plant products or yeast (1).

  • Safety

    No toxic or adverse effects have been associated with large intakes of vitamin B12 from food or supplements in healthy people.

  • References

    Consult the full list of scientific references.