Cobalamin, folic acid, and homocysteine.

Cobalamin deficiency can lead to several adverse health consequences: folate trapping in the methylation cycle and subsequent impaired DNA biosynthesis; pernicious anemia hematologically, similar to that caused by folate deficiency; elevated blood homocysteine (tHcy) (risk factor for cardiovascular disease and adverse pregnancy outcomes); and neural tube defects (NTDs). Population-wide folate status is expected to improve where folic acid fortification policies for reducing NTD occurrence are established. However, there is concern that cobalamin deficiency and its characteristic neuropathy could be masked when hematological abnormalities in risk groups such as the elderly and vegetarians are reversed through folic acid supplementation. Folate-cobalamin interactions and their impact on health are reviewed here.