Vitamin B12 Cobalamin

About Vitamin B12 Cobalamin

Vitamin B12, or cobalamin, is the only vitamin that contains a metal ion, cobalt, and has the most complex structure of all the vitamins, solved by Dorothy Hodgkin using X ray crystallography. It is made only by microorganisms and occurs naturally in animal foods. Absorption depends on intrinsic factor, secreted by gastric parietal cells, with the complex taken up in the terminal ileum. B12 is a cofactor for methylmalonyl CoA mutase and for methionine synthase, which converts homocysteine to methionine and links B12 to folate metabolism. Deficiency causes megaloblastic anemia indistinguishable from folate deficiency, plus neurological damage that can become permanent, including peripheral neuropathy, subacute combined degeneration of the spinal cord, cognitive decline and psychiatric symptoms. Causes include pernicious anemia, an autoimmune loss of intrinsic factor, gastric surgery, Crohn disease, unsupplemented vegan diets, and medicines such as metformin and acid suppressants. Deficiency is treated with injections or high dose oral B12.