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Vitamin B12 - cobalamin

Vitamin B12 or cobalamin is an essential water-soluble cobalt-containing nutrient with a key role in the normal functioning of the brain and nervous system, and for the formation of blood.

It is involved in the metabolism of every cell of the human body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production.

Vitamin B12 was discovered from its relationship to the disease pernicious anemia, which is an autoimmune disease in which the parietal cells of the stomach responsible for secreting intrinsic factor are destroyed leading to atrophic gastritis.

Intrinsic factor is necessary for the normal absorption of B12. Insufficient absorption of vitamin B12 causes a vitamin B12 deficiency, which may be severe.


Vitamin B12 is naturally found in animal products, including fish, meat plants and fruits are poor in vitamin B12 - cobalamin (especially liver), poultry, eggs, milk, and milk products.

Vitamin B12 is generally not present in plant foods. However, fortified breakfast cereals are a readily available source of vitamin B12 with high bioavailability for vegetarians. Here is a list of foods having the highest content of vitamin B12.

Daily intake

The recommended daily intake for adults is 2.4 micrograms for adults, 2.6 micrograms for pregnant women and 2.8 micrograms for lactating women.


A slight deficiency may be associated with unspecific symptoms such as fatigue, depression, and poor memory.

Severe vitamin B12 deficiency may be caused by a lack of intrinsic factor compromising the absorption of the vitamin leading to pernicious anemia.

A severe chronic vitamin B12 deficiency can cause marked and irreversible damage, especially to the brain and nervous system. Vitamin B12 deficiency can also cause symptoms of mania and psychosis.


Vitamin B12 has extremely low toxicity and even taking it in enormous doses appears not to be harmful to healthy individuals.

References: 1 , 2 , 3 , 4

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