Validity and reproducibility of folate and vitamin B(12 )intakes estimated from a self-administered diet history questionnaire in Japanese pregnant women

BACKGROUND: No validated dietary questionnaire for assessing folate and vitamin B(12 )intakes during pregnancy is available in Japan. We evaluated the validity and reproducibility of intakes of folate and vitamin B(12 )estimated from a self-administered diet history questionnaire (DHQ) in Japanese pregnant women. METHODS: A sample of 167 healthy subjects with singleton pregnancies in the second trimester was recruited at a private obstetric hospital in metropolitan Tokyo from June to October 2008 (n = 76), and at a university hospital in Tokyo from June 2010 to June 2011 (n = 91). The dietary intakes of folate and vitamin B(12 )were assessed using the DHQ. The serum concentrations of folate and vitamin B(12 )were measured as reference values in the validation study. To assess the reproducibility of the results, 58 pregnant women completed the DHQ twice within 4-5 week interval. RESULTS: Significantly positive correlations were found between energy-adjusted intakes and serum concentrations of folate and vitamin B(12 )(r = 0.286, p < 0.001 and r = 0.222, p = 0.004, respectively). After excluding the participants with nausea (n = 121), the correlation coefficient for vitamin B(12 )increased to 0.313 (p = 0.001). When participants were classified into quintiles based on intakes and serum concentrations of folate and vitamin B(12 ), approximately 60% were classified in the same or adjacent quintile. The intraclass correlation coefficients of the two-time DHQ were 0.725 for folate and 0.512 for vitamin B(12 ). CONCLUSION: The present study indicated that the DHQ had acceptable validity and reproducibility for assessing folate and vitamin B(12 )intakes in Japanese pregnant women.