Vitamin B12 is a water-soluble vitamin, so it cannot be stored in the body and is one of the vitamins most often needing supplementation, especially by women in various stages of their reproductive life. It is involved in all cell metabolism throughout the body, in particular in the synthesis of DNA, and the metabolism of amino and fatty acids.
It also, plays a crucial role in forming red blood cells, and in ensuring that the brain and the central nervous system function correctly. It can only be produced by bacteria and single-celled organisms, which possess the enzymes required to make it, but it can be found in many animal-based food sources, especially fish and shellfish, meat and dairy products.
Vitamin B12 can also be made industrially; this is the source of food additives and the dietary supplements most commonly available. There is also some research in progress to confirm that an active form of B12 can be found in some seaweeds.
A deficiency is closely associated with the auto-immune disease, pernicious anaemia, as well as causing varying degrees of damage to the brain and nervous system ranging from fatigue to depression, mania and psychosis.