Folate status response to controlled folate intake in pregnant women

A metabolic study (84-d) was conducted to investigate the folate status response of pregnant subjects (n = 12) during their second trimester and nonpregnant controls (n = 12) to folate intakes approximating the current (400 mu g/d) and former (800 mu g/d) recommended dietary allowance (RDA). The overall goal of the study was to provide metabolic data to assist in the interpretation of the current RDA for folate. Subjects were fed a controlled diet containing 120 +/- 15 mu g/d (mean +/- SD) folate and either 330 or 730 mu g/d synthetic folic acid. Outcome variables between and within supplementation groups were compared at steady state. Serum folate was higher (P less than or equal to 0.05) in pregnant women consuming 850 compared with 450 mu g/d (44.6 +/- 13.4, 26.3 +/- 11.3 nmol/L, respectively, mean +/- SD). No differences (P > 0.05) were detected in serum folate between pregnant and nonpregnant women within the same supplementation group. Urinary 5-methyl-tetrahydrofolate excretion was greater (P less than or equal to 0.05) in pregnant women consuming 850 compared with 450 mu g/d (198.0 +/- 100.4, 9.5 +/- 3.2 nmol/d, respectively). No differences (P > 0.05) in 5-methyl-tetrahydrofolate excretion were detected between pregnant and nonpregnant women within supplementation groups. Differences (P less than or equal to 0.05) were not detected in red cell folate between pregnant women consuming either 450 or 850 mu g/d (1452.5 +/- 251.8, 1733.5 +/- 208.5 nmol/L, respectively) or between pregnant and nonpregnant women consuming 450 mu g/d. Our data suggest that 450 mu g/d (dietary folate + synthetic folio acid) is sufficient to maintain folate status in pregnant women. This level of intake equates to similar to 600 mu g/d dietary equivalents, assuming 50 and 75% availability of dietary folate and synthetic folic acid consumed with meals, respectively.