The vitamins information pages - Vitamin B12 (cobalamin)
Description Vitamin B12
Vitamin B12 is also referred to as cobalamin, because it contains a metal ion (cobalt). This makes it the largest and most complex vitamin of all. The vitamin can only be synthesized by bacteria and therefore is mainly present in animal products. Two forms of vitamin B12 are used in the human body.
Functions of Vitamin B12
Vitamin B12 contributes to the formation of red blood cells and bone marrow, the metabolism of carbohydrates, fats and proteins and the production of genetic materials. It also assists nervous and cardiovascular mechanisms and plays a role in DNA synthesis. Deficiency of this vitamin may cause anaemia, exhaustion, irritation, depression, shortness of breath, difficulty walking, memory loss, mood swings, disorientation, dementia and constipation. This is estimated to affect 10-15% of individuals over the age of 60. This is a result of malfunction of either the stomach, pancreas or small intestine of elderly people, decreasing adsorption of the vitamin.
Vitamin B12 in food
Vitamin B12 is mainly present in animal products, such as meat, poultry, fish, eggs, seaweed, and to a lesser extent in milk and dairy products. Cereals may be fortified with this vitamin.
Vitamin B12 as a supplement
Vitamin B12 is recommended for people that experience digestive problems, anaemia, fatigue or mental and nervous problems. Because of its role in DNA synthesis, vitamin B12 may play a role in cancer prevention. This is currently still under investigation.
Vitamin B12, together with vitamin B6 and folate, plays an important role in homocysteine accumulation prevention, decreasing the risk of cardivascular disease. Medicinal gastric acid inhibitors may decrease vitamin B12 uptake from food. Medicine for treatment of high cholesterol may cause similar problems. Nitrous oxide used as an anaesthetic for elderly people may result in decreases of vitamin B12 adsorption. Large doses of folate may mask a B12 deficiency, leaving an individual at risk of developing irreversible neurological damage.
Vegetarians are likely to experience vitamin B12 deficit, as it is mainly found in animal products. The risk of vitamin B12 deficiency is higher for people suffering from AIDS and for alcoholics. Toxicity of vitamin B12 is rare, but one must carefully read the labels, because one form of the vitamin (e.g. cyanocobalamin) may enhance eye conditions.
Descriptions of vitamins on this website are based on information provided by BBC Health and The Linus Pauling Institute.