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Vitamin B12

Vitamin B12, or cobalamin, is essential for human health and survival.

Vitamin B12 is an essential nutrient which has to be consumed in animal source foods, fortified foods or supplements. Its key roles in the body include synthesis of red blood cells, nerve and brain function, prevention of neural tube defects, and prevention of growth and cognitive impairment in infants and young children. Date of preparation: February 2019

Contribution:


Importance of vitamin B12 for health

Vitamin B12, or cobalamin, is essential for human health and survival. It consists of a corrin ring with a cobalt atom in the center. The cobalt atom is bound to cyano or hydroxyl groups forming cyanocobalamin or hydroxocobalamin, the forms commonly used as supplements. In cells the usual forms are methylcobalamin and 5’-deoxyadenosyl cobalamin.

The Biomarkers of Nutrition for Development (BOND) review on vitamin B12 provides a major review of B12’s metabolism, function and requirements, and provides useful information relevant to each page of this OpeN-Global fact-sheet (1). The European Food Safety Authority (EFSA) also has a recent review focused on B12 requirements (2).
Both of these publications are open-access.

Vitamin B12 serves as a cofactor for two enzymes:

I. Methylmalonyl CoA mutase, which converts methylmalonyl CoA to succinyl CoA, an intermediate in the oxidation of fatty acids and the breakdown of some amino acids and

II. Methionine synthase, which converts homocysteine to methionine in a reaction with folate as a cofactor.

Metabolic functions of vitamin B12 include:

  • Synthesis of red blood cells
  • Nerve function
  • Brain function
  • Prevention of neural tube defects
  • Prevention of growth and cognitive impairment in infants and young children

Vitamin B12 is an essential nutrient which has to be consumed in animal source foods, fortified foods or supplements.

 

Key info

Keywords: vitamin B12, cobalamin, holotranscobalamin, methylmalonic acid, requirements, animal source foods.

Related nutrients/biomarkers:

  • cobalt
  • folate deficiency also produces megaloblastic anaemia and elevated serum total homocysteine but the two deficiencies can be distinguished using biomarker assays.
  • There is controversial evidence that high folic acid intake from supplements can exacerbate B12 deficiency.
  • Vitamin B6 and riboflavin are cofactors in the same metabolic pathways as vitamin B12.

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