Abstract
BackgroundNo validated dietary questionnaire for assessing folate and vitamin B12 intakes during pregnancy is available in Japan. We evaluated the validity and reproducibility of intakes of folate and vitamin B12 estimated from a self-administered diet history questionnaire (DHQ) in Japanese pregnant women.MethodsA 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 B12 were assessed using the DHQ. The serum concentrations of folate and vitamin B12 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.ResultsSignificantly positive correlations were found between energy-adjusted intakes and serum concentrations of folate and vitamin B12 (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 B12 increased to 0.313 (p = 0.001). When participants were classified into quintiles based on intakes and serum concentrations of folate and vitamin B12 , 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 B12 .ConclusionThe present study indicated that the DHQ had acceptable validity and reproducibility for assessing folate and vitamin B12 intakes in Japanese pregnant women.
Highlights
No validated dietary questionnaire for assessing folate and vitamin B12 intakes during pregnancy is available in Japan
When participants were classified into quintiles based on intakes and serum concentrations of folate and vitamin B12, approximately 60% fell into the same or adjacent quintiles
The Bland-Altman plots of folate and vitamin B12 showed that most participants were in the accepted range of agreement, but a few women showed differences between the intakes estimated from the two-time diet history questionnaire (DHQ) beyond the accepted ranges (Figure 1 and 2). To our knowledge, this is the first study to validate the dietary intake of folate and vitamin B12 in Japanese pregnant women using quantitative biological markers
Summary
No validated dietary questionnaire for assessing folate and vitamin B12 intakes during pregnancy is available in Japan. The methods used for assessment of dietary intake often include weighed food records, measurement of certain blood markers, and 24-hour urine analysis [9]. These methods may be costly and can impose a significant burden on participants. Easier and less onerous methods are needed for screening and large-scale research studies, such as the dietary assessment questionnaire This convenient method is used commonly in epidemiological studies to identify individuals with low and high nutrient intake [9]. No validated dietary assessment questionnaire exists in Japan for pregnant women, making it difficult to implement large interventional studies and epidemiologic studies regarding prenatal nutrition
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