Cobalamin

Vitamin B12 is a water-soluble vitamin, one of the eight-part B complex.

Physiology
Also known as cobalamin, B12 is involved in cellular metabolism and formation of red blood cells (RBCs). It has an integral role in brain and nervous system function. B12 is made from intrinsic factor in the human stomach.

Immune system
Vitamin B12 deficiency may be associated with decreased natural killer cell activity.