What is "vitamin b12"

vitamin B12 \vitamin B12\ n. a B vitamin that is used to treat pernicious anemia.

Syn: cobalamin, cyanocobalamin.

n. (context vitamin English) The compound cobalamin or cyanocobalamin.

n. a B vitamin that is used to treat pernicious anemia [syn: cobalamin, cyanocobalamin, antipernicious anemia factor]

Vitamin B, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin that has a key role in the normal functioning of the brain and nervous system, and the formation of red blood cells. It is one of eight B vitamins. It is involved in the metabolism of every cell of the human body, especially affecting DNA synthesis, fatty acid and amino acid metabolism. No fungi, plants, nor animals (including humans) are capable of producing vitamin B. Only bacteria and archaea have the enzymes needed for its synthesis. Proved food sources of B are animal products (meat, fish, dairy products). Some research states that certain non-animal products possibly can be a natural source of B because of bacterial symbiosis. B is the largest and most structurally complicated vitamin and can be produced industrially only through a bacterial fermentation-synthesis. This synthetic B is used to fortify foods and sold as a dietary supplement.

Vitamin B consists of a class of chemically related compounds ( vitamers), all of which show pharmacological activity. It contains the biochemically rare element cobalt (chemical symbol Co) positioned in the center of a planar tetra- pyrrole ring called a corrin ring. The vitamer is produced by bacteria as hydroxocobalamin, but conversion between different forms of the vitamin occurs in the body after consumption.

A common synthetic form of the vitamin is cyanocobalamin, produced by chemically modifying bacterial hydroxocobalamin. Because of superior stability and low cost this form is used in many pharmaceuticals and supplements as well as for fortification of foods. In the body, it is converted into the human physiological forms methylcobalamin and 5'-deoxyadenosylcobalamin. In this process a cyanide ion, (CN), is produced, but the amount is very, very small (20 μg from 1,000 μg of cyanocobalamin) compared to what would cause a toxicity risk, and is in fact less than the amount of cyanide consumed daily from food (primarily fruit, nuts, seeds, and legumes). Cyanide-free synthetic forms of the vitamin—hydroxocobalamin, methylcobalamin, and adenosylcobalamin—are being used in some pharmacological products and supplements, but their claimed superiority to cyanocobalamin is debatable.

Vitamin B was discovered from its relationship to the disease pernicious anemia, an autoimmune disease in which parietal cells of the stomach responsible for secreting intrinsic factor are destroyed; these cells are also responsible for secreting acid in the stomach. Because intrinsic factor is crucial for the normal absorption of B, its lack in the presence of pernicious anemia causes a vitamin B deficiency. Many other subtler kinds of vitamin B deficiency and their biochemical effects have since been elucidated.