Chapter 17 – Folate

Folate is the generic descriptor for folic acid (pteroylmonoglutamic acid) and related compounds exhibiting the biological activity of folic acid. Folate has a role in the etiology of homocysteinemia, which is a risk factor for neural tube defects (NTDs). Folates are found in a wide variety of foods; best sources include leafy green vegetables and organ meats. Absorption of folate, a water-soluble vitamin, typically occurs following deconjugation to mono- or diglutamate forms followed by active uptake or passive diffusion by the enterocyte. Folates function as enzyme cosubstrates in a network of reactions in the metabolism of amino acids and nucleotides, as well as the formation of the primary methyl donor for biological methylations, S-adenosylmethionine. In each of these functions, tetrahydrofolic acid serves as an acceptor or donor of a single-carbon unit and is regenerated with the transfer such that continuous cycling can occur. Folate fortification programs began in the United States in 1993 and have resulted in increased folate intakes and reduced the incidence of NTDs. Folate deficiency is uncommon in areas with fortification programs; signs include anemia, depression, and polyneuropathy.