Vitamin B12 contains the mineral cobalt which gives its characteristic dark red colour. Cyanocobalamin and hydroxyl cobalt are the two forms of B12.
  1. B12 is essential for the maturation of red blood corpuscles and it combines with globulin
  2. B12takes part in the enzymatic reaction. Especially co-enzyme B12 is very prominent in the body. Niacin, riboflavin and magnesium are essential for this conversion of B12 to co-enzyme B12.
  3. Co-enzyme is required for the action of dehydrase enzyme
  4. Vitamin B12 acts as a necessary substance for the lipoprotein action in the nervous tissues. It is also necessary for the synthesis of myelin. Within the bone marrow B12 co-enzyme participates in the synthesis of DNA
  5. Co-enzyme B12 is essential for carbohydrate, protein and fat metabolism. In experimental animals vitamin B12 has been found to stimulate growth.
  6. B12 co-enzyme is also essential for the synthesis and transfer of single carbon units such as the methyl group. eg. Methionine and choline synthesis
  • Due to the deficiency of vitamin B12, pernicious anaemia occurs.
  • To prevent anaemia two factors are required.
  • An intrinsic factor produced by the gastric parietal cells and the extrinsic factor of vitamin B12.
  • If due to any cause enough intrinsic factor is not secreted, B12 is not absorbed and utilized properly.
  • B12 is otherwise known as extrinsic factor.
  • Congenital intrinsic factor deficiency and low absorption of B12 or its deficiency leads to pernicious anaemia.
  • In pernicious anaemia the life span of red blood cells is reduced to 60 days instead of the normal 120 days and their size and shape also is changed. Skin changes show a yellowish pallor.
  • Soreness and shine on the tongue are other manifestations of skin lesions. Gastric secretion is reduced.
  • Stomach mucosa shows atrophic changes.
  • Nervous tissues are degenerated, especially the posterior column of the spinal cord is affected. Peripheral neuropathy and later on mental changes are common.
  • Tingling, numbness, loss of sensation in the limbs, exaggerated knee jerks and ankle jerks are the other symptoms.
  • Depression and other psychosis symptoms are common in later stages.
  • Good sources: Organ meats like kidney, liver, brain, meat, poultry, egg, fish and milk
RDA of Vitamin B12 for Indians
Group Recommended intake μg/d
Adult male 1.0
Adult female 1.0
Pregnancy 1.2
Lactation 1.5
Infant 0.2
1-9 y 0.2-1.0
10-12 y 0.2-1.0
13-17y 0.2-1.0

Last modified: Monday, 4 June 2012, 7:10 AM