What Is B12 or Cobalamin?

Vitamin B12, or cobalamin, is one of the water-soluble vitamins that is part of the vitamin B complex. Although most water-soluble vitamins are usually not stored in the body, vitamin B12 can be stored for years in the liver, according to Medline Plus. Vitamin B12 plays many important roles, and deficiencies are often seen in vegetarians and the elderly.

Food Sources

Vitamin B12 is mostly present in foods from animal origin, which explains why vegetarians often present deficiencies. Cobalamin is found in eggs, poultry, seafood, meat, milk, cheese and fortified breakfast cereals, according to Medline Plus. Yeast itself does not provide vitamin B12. However, if it is grown on a vitamin B12-enriched medium and mixed with that medium, it will be a source of vitamin B12, according to "Understanding Normal and Clinical Nutrition." Moreover, fermented soy products and algae, such as spirulina, are not reliable sources of vitamin B12. Although vitamin B12 may appear on the label of these foods, it is present in its inactive form.

Absorption

Hydrochloric acid and pepsin in the stomach release vitamin B12 that is bound to protein in foods. Then, vitamin B12 requires the presence of the intrinsic factor, and secreted in the stomach, to which it binds in order to be recognized by the receptors of the intestines, as explained in "Understanding Normal and Clinical Nutrition." People taking acid-lowering medications and people over 50 years of age do not absorb vitamin B12 as well as others and may be recommended a supplement by their health care provider.

Roles

Vitamin B12 is required to activate folate, and folate is also necessary to activate vitamin B12. Moreover, cobalamin is involved in many metabolic reactions allowing the release of energy from carbohydrates, fat and protein, in addition to participating in nervous system maintenance, blood cell formation and bone metabolism, according to Medline Plus.

Pernicious Anemia

Anemia can be caused by iron, folate or vitamin B12 deficiencies. Pernicious anemia however is only associated with a deficit of vitamin B12 and is characterized by large immature blood cells, according to Health Castle. Often seen in vegetarians, this type of anemia leads to fatigue and muscle weakness, in addition to potentially causing irreversible neurological damages.

Recommendations

The adequate intake for healthy adults established by the Institute of Medicine Food and Nutrition Board corresponds to 2.4 mcg of vitamin B12 a day. The requirements for cobalamin are slightly increased in pregnant and lactating women. No adverse effects related to an excessive vitamin B12 intake from foods or supplements have been observed to date.