Cobalt is best known for its structural role in vitamin B12; recall that B12 is actually named cobalamin because of the presence of cobalt. In humans, cobalt also acts as a cofactor for methylmalonyl-CoA mutase and methionine synthase. Other cobalt-dependent enzymes and proteins have been found in bacteria, but the role of cobalt in humans, at present, appears to be limited to just these few enzymes.
A Recommended Dietary Allowance (RDA) for cobalt hasn’t been established, but 5 to 8 mcg per day appears to be adequate intake. However, there is an RDA for B12 which is 2.4 μg/day. Trace amounts of cobalt are found in most foods, but foods high in vitamin B12 are the only source of cobalt used by the body. Some foods rich in B12 include eggs, milk, soymilk, clams, chicken, tuna, apples, bananas, alfalfa, potatoes, and mushrooms.
Like chromium, cobalt alloys are used in the manufacturing of some artificial joint prosthetics. Industrial uses of cobalt include the coloring of glass and the manufacturing or use of dyes.
Absorption and Transport:
Hydrochloric acid and enzymes dissociate vitamin B12 into its free form in the stomach. Once free, B12 combines with intrinsic factor. Intrinsic factor is a glycoprotein produced by the parietal cells in the stomach. Intrinsic factor is needed for the absorption of B12 in the small intestine. Once in the small intestine, the B12-intrinsic factor complex can be absorbed by enterocytes. Once inside these enteric epithelial cells, vitamin B12 dissociates and binds to transcobalamin II which exits the cells and is carried to the liver.
