Vitamin B12 is one of the
water-soluble B vitamins. Vitamin B12 is the collective name for
a family of compounds which contain cobalt, known as corrinoids.
Vitamin B12's primary roles are aiding in the
production of red blood cells, and in helping to maintain the health
of the central nervous system. It also functions as a component
involved in producing DNA and RNA - genetic material. Nerves are
encased in an insulating sheath which is made of a protein known
as myelin. Cobalamin is critical for maintaining this myelin sheath
around nerves. A deficiency of vitamin B12 can be a contribute to
wide range of health problems and disorders. Extended periods of
deficiency can eventually result in degenerations of nerves and
even irrepairable neurological damage. Read more about the benefits
and functions of vitamin B12 and signs of vitamin
Vitamin B12 can be obtained only from foods
that come from animal sources, or from some fermented foods in which
bacteria create cobalamin. This means that vegans may require supplementation.
The richest sources of vitamin B12 are organ meats such as liver,
kidneys, and hearts. Other good food sources are shellfish (clams
and oysters), lean beef, poultry, various types of seafood, eggs,
and dairy. Miso, a type of fermented soy product, is also a good
source. Read more about sources
of vitamin B12 and the daily
requirement of vitamin B12.
Vitamin B12 is not known to be toxic. Even
large doses of cobalamin have not been known to cause any adverse
effects. Read more about vitamin
Vitamin B12 is a the umbrella name term for
a family of compounds called corrinoids. Corrinoid compounds contain
cobalt. The primary forms of cobalamin are cyanocobalamin, hydroxocobalamin,
as well as the two coenzyme forms of cobalamin, methylcobalamin
and 5-deoxyadenosylcobalamin, or adenosylcobalamin. Cyanocobalamin
is the main type of vitamin B12 that is used for enriching or fortifying
foods, and used in vitamin supplements.
Vitamin B12 is tied to proteins in food. In
the stomach, pepsin and hydrochloric acid release the vitamin from
proteins in foods. The vitamin is bound by an R-protein and then
gets transported to the small intestine. R-proteins are hydrolyzed,
releasing free vitamin B12, in the duodenum. This free vitamin B12
is then tied to another protein known as the gastric intrinsic factor,
which is needed for the vitamin to be absorbed in the intestines.
Taken at low doses (about 0.1 micrograms),
nearly eighty percent vitamin B12 is absorbed by a person who has
a normally functioning digestive system. When doses are increased,
the absorption rate of vitamin B12 drops to as low as three percent.
Unlike the other water-soluble vitamins, including
the other B vitamins, vitamin B12 can be stored by the body. The
body can store about 5-12 milligrams of vitamin B12, mostly in the
kidneys and the liver. Excess quantities are disposed of via the
kidneys or in bile.