The Importance Of Vitamin B12 For Your Health.
By Sam Cyrus

Vitamin B12 is a vitamin which is important for the normal functioning of the brain and nervous system. This vitamin is required for a number of vital biological reactions. Two of its most important roles are in the production of components of DNA and the proper functioning of different parts of the neurological system. Tissues in which cells are constantly dividing, such as bone marrow and the lining of the entire gastrointestinal and respiratory tracts, require a constant supply of vitamin B12.

A deficiency often manifests itself first in the development of neurological dysfunction. Several surveys have shown that most strict, long-term vegetarians are vitamin B12 deficient. Many elderly people are also deficient because their production of the intrinsic factor needed to absorb the vitamin from the small intestine decline rapidly with age. Their symptoms are totally reversible through effective supplementation. A low level of vitamin B12 has also been associated with asthma, depression, AIDS, multiple sclerosis, tinnitus, diabetic neuropathy and low sperm counts. Clearly, it is very important to maintain adequate body stores of the vitamin B12.

Vitamin B12 comes from animal products and bacteria.  The stomach produces a factor that binds to the vitamin in food and allows it to be absorbed in the small intestine.  Diseases of the stomach and small intestine can cause problems with absorption and consequent vitamin B12 deficiency. Therefore, the primary causes of vitamin B12 deficiency are dietary deficiency and malabsorption.

The richest dietary sources of vitamin B12 are liver, especially lamb's liver, and kidneys. Eggs, cheese and some species of fish also supply small amounts, but vegetables and fruits are very poor sources. 

The amount of vitamin B12 actually needed by the body is very small, probably only about 2 micrograms or 2 millionth of a gram/day. Unfortunately, vitamin B12 is not absorbed very well so much larger amounts need to be supplied through the diet or supplementation. Recent studies have highlighted the value of screening for B12 deficiency in older people with mild dementia.  B12 deficiency in older individuals is probably related to changes in the gastrointestinal tract with aging and fairly limited diets, both problems that appear to be more common with advancing age.  Pernicious anemia is most common in older women. For this reason, the 2005 Dietary Guidelines for Americans recommends that people over age 50 consume vitamin B12 in its crystalline form (i.e., fortified foods or supplement pills).