Controlled Dietary Folate Affects Folate Status in Nonpregnant Women

Abstract

In a study designed to estimate the requirement for dietary folate in nonpregnant women, 17 women (21–27 y) consumed 200, 300, or 400 µg/d of total folate for 70 d which was provided by low folate conventional foods (30 µg) plus supplemental folic acid. Group means for initial serum and erythrocyte folate and plasma homocysteine concentrations were not significantly different. Serum and erythrocyte folate decreased relative to the initial value in the 200 µg/d group (43.4 ± 12.1%, 13.6 ± 16.6%, respectively; mean ± SD), in contrast to an increase in the 400 µg/d group (16.8 ± 52.0%, 10.2 ± 18.5%, respectively). The final serum folate in the 200 and 300 µg/d groups (6.4 ± 0.8 nmol/L, 7.3 ± 1.1 nmol/L, respectively) was significantly lower than that of the 400 µg/d group (14.3 ± 2.0 nmol/L), with evidence in the 200 µg/d and 300 µg/d groups of low (<6.8 nmol/L) serum folate concentrations. Differences in final erythrocyte folate did not reach statistical significance, although low values (<362 nmol/L) were frequent in subjects with 200 µg/d intake. In the 200 µg/d group, plasma homocysteine was negatively correlated with serum and erythrocyte folate, and final mean plasma homocysteine (12.6 ± 1.7 µmol/L) was significantly higher than that of the 300 or 400 µg/d groups. Elevated plasma homocysteine levels (>16 µmol/L) were observed in the 200 µg/d group only. Data from this study indicate that 200 µg/d of folate was not sufficient to maintain folate status of these women and suggest that the current RDA of 180 µg/d may not be adequate to meet the dietary folate intake needs of nonpregnant women.