Cobalamin of vitamin B12

Cobalamin is a water soluble vitamin consisting of corrin-ring with wide-chain components bound to central cobalt atom. It is the only molecule in the body to contain cobalt.

This vitamin is required for the normal development of red blood cells, and a deficiency in it causes acute pernicious anemia and a variety of other disorders.

The exact requirement of vitamin B12 is yet unknown, since some B12 is synthesized by bacteria in the intestine.

Neither humans nor animals are able to synthesize this vitamin.  Foods or animals source are the only natural source of cobalamin in human diet. The organs of animals are excellent sources of vitamin B12 and the muscles of warm-blooded animals and fish are good sources.

Because large amount of cobalamin (2.0-2.5 mg) are stored in the body, especially in the liver the lack of adequate dietary vitamin B12 may take years to cause cobalamin deficiency.
Cobalamin of vitamin B12