ABSORPTION DIETARY AND SUPPLEMENTAL FOLATE IN WOMEN WITH PRIOR PREGNANCIES WITH NEURAL-TUBE DEFECTS AND CONTROLS

Background: The Public Health Service of the United States recommends that all women capable of childbearing consume .4 mg (400 mu g) folic acid per day to decrease the risk of having a pregnancy affected by a neural tube defect such as spina bifida or anencephaly. Three strategi es are available to women to achieve this goal: use of dietary supplem ents; use of fortified foods; and/or increased intake of naturally occ urring folate from foods. Identification of the most effective vehicle for delivery of folate to all women is critical in order to prevent t hese devastating congenital defects. Objective: To investigate the dif ference in response to an oral load of folate both from naturally occu rring food sources and synthetic supplements among women with prior pr egnancies affected by neural tube defects and controls. Methods: We co mpared the absorption of test doses of 400 mu g pteroylglutamic acid ( unconjugated or synthetic folic acid found in supplements) and 400 mu g pteroylpolyglutamic acid (conjugated or food folate) in 10 women wit h a history of neural tube defect affected pregnancies and eight contr ols with normal birth outcomes. The folate test dose was given as eith er 32 fluid ounces of orange juice or a folic acid single supplement p ill. All participants received each test dose at separate clinic visit s. The response to each test dose was measured by constructing an area under the curve (AUC) from the serum folate levels at, 1, 2 and 3 hou rs post dose and applying a t-test to compare within and between cases and controls. We also compared red cell folate, vitamin B-12, zinc an d homocysteine between cases and controls. Results: Within group compa risons showed that the area under the curve was significantly greater for the pteroylglutamic acid dose compared to the pteroylpolyglutamic acid dose for both cases and controls (p=0.02 and p=0.03, respectively ). In a between group comparison, control women had a greater serum fo late response to both forms of the vitamin compared to the case women, but the difference reached statistical significance only for the pter oylglutamic acid dose (p=0.02). Other measured nutrients differed betw een cases and controls, but did not reach statistical significance. Co nclusion: We conclude that for all women synthetic folic acid as suppl ements or fortified foods may be the best way to increase acute folate levels in the blood, and thus delivery to the developing embryo. Furt her, since case women had a diminished response to both forms of the v itamin, and some case women had almost no response, we speculate that women with prior affected pregnancies may need a larger dose of folate to elicit a plasma response equivalent to the general population.