Vitamin B12 is essential for normal metabolism of carbohydrates, fat and protein. As a cofactor for methylmalonyl-CoA mutase enzymes, vitamin B12 helps convert odd chain fatty acids and branched chain amino acids into succinyl-CoA, a common citric acid cycle intermediate. Vitamin B12 is also required for nucleic acid (DNA) synthesis, methionine synthesis from cysteine, and normal myelin synthesis in the nervous system. Along with vitamin B6 and folic acid, adequate levels of vitamin B12 are required to maintain normal plasma homocysteine levels. Certain populations, including the elderly and strict vegetarians are often at risk for vitamin B12 deficiency, either due to low dietary intake or impaired absorption. Studies indicate that methylcobalamin, a coenzyme form of B12, may be better utilized and better retained in the body. Other studies indicate that methylcobalamin itself may play important roles in supporting neurological and immune health.