Folate intake assessment: Validation of a new approach

Abstract

Objective To describe the performance characteristics and validate a folate-specific focused recall approach to estimating folate intake. Design In a cross-sectional study, folate-specific recalls were used to estimate subjects' average daily folate intake from seven days of dietary recall over a one-month period. This estimate was compared to an estimate of the average daily folate intake obtained using the Fred Hutchinson Cancer Research Center Food Frequency Questionnaire (FFQ) and to plasma folate and homocysteine concentrations. Subjects Subjects were women aged 21 to 47 years and were recruited from the university community. Thirty-three subjects were recruited, and 28 subjects completed the study. Intervention After an initial clinic visit, during which a baseline blood sample was collected for measurement of plasma folate and total homocysteine concentrations, subjects participated in focused dietary recall interviews by telephone and/or Internet (e-mail). At the end of the month, subjects completed the FFQ. Main outcome measures The main outcome measures were to describe how well the focused recalls were able to describe relative dietary folate intake as compared to the FFQ and if the focused recall method estimate correlated with plasma folate and homocysteine concentrations. Statistical analyses Estimated folate intakes were ranked by tertiles using the two dietary assessment approaches and the rankings were compared. The Spearman correlation test was used to compare the focused recall and the FFQ dietary data to plasma folate and homocysteine concentrations. Results Estimated folate intake inclusive of supplements was 411.4±192.8 (mean±SD) μg/day based on focused recalls and 458.5±221.5 μg/day based on the FFQ. Exclusive of supplements, estimated folate intake from the diet was 327.8±30.2 μg/day based on focused recalls and 373.5±155.6 μg/day based on the FFQ. The ranking comparison of focused recalls vs the FFQ demonstrated a concordance of 44% without supplements and 67% with supplements for the highest tertile, and 56% without supplements and 67% with supplements for the lowest tertile. Estimated folate intake based on focused recalls was correlated significantly with plasma homocysteine ( r=−0.443, P<.02) and was marginally significantly correlated with plasma folate ( r=0.354; P=.06) concentrations. Applications A focused dietary recall approach is a useful method for collecting information on folate intake in women. Estimated folate intake based on the focused recall approach is reasonably correlated with plasma folate and total homocysteine concentrations even in this small sample of women. Accurate data on folate intake can form the basis of dietary counseling to increase intake of this important micronutrient in the target population of young women. J Am Diet Assoc. 2003;103:991-1000.