An optimal folate nutritional status is important in minimizing developmental and degenerative disease.Therefore, constant monitoring of folate intake and of biomarkers of folate nutritional status is essential.The objective of this research was to compare two folate intake instruments and validate each oneagainst RBC folate measured by a high-throughput liquid chromatography tandem mass spectrometry(HT LC-MS/MS) method described in the companion paper (Owens, J. E.; Holstege, D. M.; Clifford,A. J.
J. Agric. Food Chem. 2007,
55, 3292-3297). A
food frequency questionnaire (FFQ) and afolate-targeted semiquantitative Block dietary folate equivalents (DFE) screener were compared andindividually validated against an HT LC-MS/MS method. RBC folate was 1178 ± 259 nmol/L (mean± SD) in a population of 337 normal adult subjects. Folate intakes were 556 ± 265
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g/day by theFFQ and 524 ± 276
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g/day by the DFE screener. Folate intakes by the DFE screener wereapproximately 34
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g less than by the FFQ (paired
t test,
p < 0.01), but the intake instruments werehighly correlated for total folate intake (
r = 0.608,
p < 0.01). Correlations between instruments andRBC folate were low (
r < 0.35) but strong (
p < 0.01). ROC curve analysis indicates that themeasurement of RBC folate by the HT LC-MS/MS method is a better predictive tool than are intakeinstruments for the evaluation of marginal folate status.