Vitamin B12

DEFINITION

Vitamin B12 or Cobalamin is a member of the B group vitamins that are essential for the growth and replication of cells in the body.

DESCRIPTION

Vitamin B12 is a water-soluble vitamin that is stored in the liver. Vitamin B12 is absorbed from the stomach using a special 'carrier'-like substance called intrinsic factor. Intrinsic factor is secreted by the stomach lining and it tightly binds Vitamin B12 and helps it pass through the intestinal lining and into the blood. Any abnormal production of this intrinsic factor can result in Vitamin B12 deficiency. Vitamin B12 is important for the activity of certain enzymes within calls that control fat, amino acid and carbohydrate metabolism (enzymes are special substances that speed up reactions in the body). Both Vitamin B12 and the vitamin folate are essential for the production of genetic material in the body (DNA and RNA). Vitamin B12 deficiency prevents the body from using folate properly, which causes abnormal red blood cells to be produced that are too large, few in number and unable to carry oxygen very effectively. There is little evidence that very large doses of Vitamin B12 cause any ill health effec s (i.e. Vitamin B12 toxicity), as some people are given very high doses of Vitamin B12 on a monthly basis because they cannot absorb this vitamin from the food they eat.

MEDICAL USE

Always consult your Health Professional to advise you on dosages and any possible medical interactions.

Vitamin B12 is used medically both as oral supplements and in injection form to treat a number of diseases and conditions. Oral supplements may sometimes be given to people who do not eat animal products (e.g. vegans) or those whose dietary intake is inadequate (e.g. alcoholics) to prevent or treat Vitamin B12 deficiency. People who have had part of their intestines removed during a surgical procedure may also be at risk of Vitamin B12 deficiency because they cannot absorb this nutrient. Certain people do not produce adequate amounts of the intrinsic factor that is essential for absorption of Vitamin B12. These people may be given Vitamin B12 injections to prevent deficiency and anaemia.

Poor dietary intake in some older people may result in mild deficiency of Vitamin B12 that may be managed using injection of this vitamin. Certain medications, such as the proton pump inhibitor drug omeprazole, can reduce the amount of Vitamin B12 absorbed by the body. People taking these medications may also require Vitamin B12 injections.

DEFICIENCY

Vitamin B12 deficiency can take some time to appear after a person stops receiving adequate amounts of this nutrient, because the liver stores a supply of about 5 years worth of Vitamin B12. Vitamin B12 deficiency affects the blood and the nervous system. The cells in the blood divide rapidly and need to copy their genetic material frequently, but Vitamin B12 deficiency prevents them from doing this normally. This causes abnormally large red blood cells to be produced, a condition called macrocytic (or megaloblastic) anaemia. Vitamin B12 deficiency also causes irreversible damage to the nervous system. A thick, protective sheath surrounds the nerves in the brain and body that helps the nerves to conduct messages. Vitamin B12 deficiency causes damage to this thick sheath as well as the death of nerve cells. This results in numbness and loss of feeling in the hands and feet, unsteadiness and uncoordination, confusion, moodiness, loss of memory and even loss of central vision. Vitamin B12 deficiencies in pregnan women increases the risks of their developing child having a malformations called neural tube defect. The neural tube is a foetal structure that develops into the spine and spinal cord. One type of neural tube defect is spina bifida.

SOURCES

Vitamin B12 is found only in animal products. High levels are found in foods such as organ meats (liver, kidney etc.), bivalve molluscs such as clams and oysters, and at moderate levels in egg yolks, muscle meat, poultry, fish, fermented cheeses and dry milk.

DOSAGE

The recommended dietary intake for Vitamin B12 is 2 micrograms per day for adults, but women who are pregnant require 3 micrograms per day and who are lactating require 2.5 micrograms per day. Much larger dosages may be recommended by a Doctor to prevent or treat Vitamin B12 deficiency.