Vitamin B12 (Cobalamin) – Chemistry, Functions, Food Sources, Deficiency

Chemistry and Characteristics

This vitamin is the only cobalt containing substance essential for health. It occurs as deep red needle like crystal which is slightly soluble in water. This vitamin is absorbed from the ileum only. Its absorption depends on the presence of an intrinsic factor (a muco-protein produced by the parietal cells of gastric mucosa).


  1. It helps in the synthesis of nucleic acid and nucleoproteins.
  2. It is essential for the maturation of red blood cells in bone marrow.
  3. It is also required for the maintenance of nervous tissues.

Food Sources

It is present only in the foods of animal origin. Liver, meat, egg and milk are good sources.It is not found in the foods of vegetable origin.


Deficiency of this vitamin occurs due to inability to absorb sufficient B12 (due to lack of intrinsic factor) leading to Pernicious anaemia. Macrocytic anaemia and degenerative changes of the nervous system may results from deficiency of this vitamin.

Other deficiency symptoms includes: weakness, weight loss, anorexia, indigestion, diarrhoea, memory loss and lack of concentration.

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