Vitamin B12 (Cobalamin)

What is it?

Vitamin B12 (Cobalamin) is a water soluble vitamin obtained mostly from animal protein products in the diet.

Food sources.

Lambs, liver, sardines, oysters, egg yolk, fish, beef, kidney, cheese, milk. For vegetarians, nori seaweed appears to be a good source. Up to 10% is lost through cooking.

Deficiency signs.

Manifest mainly as haematological and neurological signs - anaemia, lethargy, weight loss, pallor, numbness, poor memory, irritability, mood swings, depression and in severe cases, psychosis.

Main actions.

It is an important co-factor in many biochemical reactions and is essential for the normal function of all cells.

It is involved in the production of red blood cells in the bone marrow.

Vitamin B12 in conjunction with folic acid and vitamin B6 reduce homocysteine levels.

It supports the myelination of nerve tissue.

Immunomodulator of cellular immunity.

Clinical use.

The treatment and prevention of pernicious anaemia.

Lowering homocysteine levels which is a risk factor for cardiovascular disease.

Depression.

Cognitive impairment.

Sleep disorders and tinnitus.

Recurrent mouth ulcers.

Important interactions.

Phenobarbitone and phenytoin increase levels of Vitamin B12.

Carbemazepine, oral contraceptives and gastric acid inhibitors lower levels of Vitamin B12.

Vitamin B12 may affect the bioavailability of tetracycline antibiotics.