Mechanisms of Folic Acid Deficiency in Nontropical Sprue

Abstract

THE ANEMIA seen in nontropical sprue is commonly associated with folic (pteroylglutamic) acid deficiency which seems to be due to unknown interferences with absorption of this vitamin. In nontropical sprue there is impaired absorption of orally-administered folic acid as measured by urinary excretion or circulating levels after saturating the tissues with folic acid.^1,2 This malabsorption may be related to an enzyme defect in the intestinal mucosal cells.³ The latter supposition initiated the studies reported here. We have developed an oral folic acid tolerance test using a microbial method which directly correlates serum folate activity with folate absorption and hemopoietic activity. This enabled us to study the absorption of folic acid and two folylglutamate conjugates, pteroyldiglutamic acid (pteroylglutamyl-α-glutamic acid) (Diopterin) and sodium pteroyl triglutamate (pteroylglutamyl-γ-glutamyl-γ-glutamic acid) (Teropterin), in normal subjects, patients with nontropical sprue, and patients with nutritional folate-deficiency anemia. Materials and Methods Absorption of a synthetic glutamyl conjugate,