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Vitamin B12

Vitamin B12 – the most chemically complex of all vitamins, 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). Beside cyanocobalamin and methylcobalamin there are two further vitamers of Vitamin B12 called hydroxycobalamin and adenosylcobalamin.

Authored by Dr Peter Engel in 2010, reviewed and revised by Angelika Friedel on 29.06.2017

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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. Read More

  • Deficiency

    Symptoms of vitamin B12 deficiency (or cobalamin deficiency) include numbness and tingling, difficulty walking, memory loss, disorientation, and dementia. Read More

  • Sources

    Foods high in vitamin B12 (cobalamin) include mostly animal products like meat, poultry, fish, and shellfish, and to a lesser extent milk. Read More

  • Safety

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

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