Objectives: The objectives of this study were to examine variability of folate intake in order to estimate the number of days needed to accurately estimate intakes in women of childbearing age and to simulate the effect of folic acid fortification of cereals and grains on individual folate intake.
Design: Observational study of food intake over a 60-day period.
Sampling: A convenience sample of 21 women completed food records on randomly assigned days within a 60-day period.
Outcomes measured: Folate intake and variance ratios of folate intake.
Statistical analysis: Repeated measures analysis of variance.
Results: Six days of food records were needed to describe folate intake of these women of childbearing age (18 to 45 years) with 20% attenuation of a correlation coefficient between dietary folate intake and another biological variable. Seven days of records were needed with simulated folic acid fortification (assuming fortification of 140 micrograms folic acid per 100 g flour) and 5 days were needed with supplements containing 200 to 400 micrograms folic acid in addition to folic acid fortification. Food folate intake was 288 +/- 195 micrograms; only 2 of the participants consumed the recommended 400 micrograms. With fortification, folate intake increased to 550 +/- 279 micrograms without supplements and 609 +/- 327 micrograms with supplements.
Applications: Individual intakes of folate should be assessed with at least 7 days of dietary records (20% attenuation). In this sample, when folic acid fortification was added to dietary intake, routine supplementation was not necessary to achieve folate intakes of 400 micrograms in the majority of participants. The practice of routine folic acid supplementation should be considered carefully to ensure that individual intakes of folate do not exceed the upper limits of safety.