Methylcobalamin B-12 is a form of the water-soluble vitamin B-12 used in the human body. The name stems from its cofactor, a cobalt ion. Vitamin B-12 is usually bound to proteins in food. During digestion, stomach acid releases the bound vitamin, which then combines with intrinsic factor. This factor helps our bodies absorb the vitamin into our bloodstream for use.
Function
Once in the body, vitamin B-12 is a vital player in human metabolism. It is required for the reaction that synthesizes the amino acid methionine from homocysteine. It also helps maintain the central nervous system by keeping nerve cells healthy and plays a role in the formation of red blood cells and DNA.
Recommended Intake
The Food and Nutrition Board of the Institute of Medicine recommends that adult males and females consume 2.4 mcg per day of vitamin B-12. Specific recommendations exist for certain subgroups -- infants and children require less vitamin B-12, while pregnant women and nursing mothers require 2.6 and 2.8 mcg per day, respectively.
Food Sources
Methylcobalamin B-12 is mainly found in animal products like eggs, meat, poultry, shellfish and dairy products. The best source is braised beef liver, which contains 48 mcg per slice. Other good sources are cooked clams, rainbow trout, salmon, haddock, tuna, sirloin beef, yogurt and milk. Fortified breakfast cereals also contain vitamin B-12.
Deficiency
While most water-soluble vitamins are excreted in urine, vitamin B-12 has the potential to be stored in the liver. However, deficiencies do occur when the body is unable to properly use or absorb the vitamin, which can be caused by a condition known as pernicious anemia. Additionally, vegans and vegetarians who do not consume animal products may be deficient in vitamin B-12. Side effects of a deficiency include numbness or tingling in the extremities, muscle weakness, loss of balance, low blood pressure, vision problems, psychiatric problems and another type of anemia -- megaloblastic anemia -- where red blood cells are larger than normal. Treatment of vitamin B-12 deficiency consists of supplements or injections.
Significance
According to MayoClinic.com, a deficiency of vitamin B-12 may be involved in the development of Alzheimer's disease and breast cancer, and supplementation may help prevent heart disease and fatigue and lower cholesterol levels. More evidence is needed to make definitive associations and conclusions.
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