Estimates of the effects of folic-acid fortification and folic-acid bioavailability for women.

OBJECTIVE

With the recent implementation of the folic-acid-fortification program, our objective was to estimate its benefits in adult women and account for the higher bioavailability of synthetic folic acid in fortification programs and supplements.

METHODS

The study used a cross-sectional design. Dietary assessment data were collected with a quantitative food-frequency questionnaire, the Nutrition DISCovery program. Fortification was simulated with the use of fortification standards (140 microg/100 g of flour) and new bioavailability standards for synthetic folic acid. Data were collected from 289 women 18 to 89 y old. Subjects were recruited from participants in two health-screening events in autumn of 1997. Chi-square tests were used to estimate the differences between categoric variables, and F tests were used in analysis of variance for continuous outcome measures. Results were considered significant at P < 0.05.

RESULTS

Estimated mean dietary intake of folate increased considerably with simulation of fortification (320 to 608 microg of dietary folate equivalents). Women in the lower quartiles for age (18 to 39 and 40 to 46 y) consumed more servings from the bread group than women did in the upper quartile (55 to 89 y). Thus, the improvement in folate intake with fortification was significantly greater for the younger than for the older women (P < 0.05). Despite the limitations of estimating folate intakes, these data suggest that most women met the new estimated average requirement. However, 61% of women of childbearing age had intakes of synthetic folic acid below the recommended level of 400 microg/d, and only those using supplements containing folic acid met the guideline.

CONCLUSIONS

Based on this sample of well-educated, adult women, the current level of folic-acid fortification should improve the intakes of a large proportion of women, especially when accompanied by supplements containing folic acid. These improvements in folate intake might not be seen in groups with limited resources, however. Further, under existing standards and practices, many women will not meet current recommendations for prevention of neural-tube defects.