Folate Deficiency

Folate a.k.a folic acid is a water-soluble vitamin with an important role in DNA synthesis and repair. It is typically given during pregnancy to prevent neural tube defects in the embryo. Deficiency in folate or folic acid can also result in macrocytic anemia. Methotrexate, a drug that interferes with folate metabolism, inhibits the production of tetrahydrofolate (THF), an active form of folic acid, and can cause inflammation in the GI tract and marrow suppression. Therefore, folate supplement is usually given to reverse the toxic side effects of methotrexate. Folic acid, together with vitamin B12, is important in the conversion of homocysteine to methionine, therefore folate and/or vitamin B12 deficiency can lead to hyperhomocyteinemia (see vitamin B12). However, as opposed to B12 deficiency, MMA is not elevated in Folate deficiency since it is not involved in the conversion of methylmalonyl-CoA to succinyl-CoA in the Kreb cycle. Take home points: Folate deficiency may show hyperhomocyteinemia but no elevation in MMA (Methyl Malonic Acid). While B12 deficiency may show both hyperhomocyteinemia and an elevated MMA.