Reproducibility and relative validity of a flavonoid-focused food frequency questionnaire for Chinese adults

Abstract

Abstract Background: In recent years, an increasing amount of evidence from nutritional epidemiological studies has revealed an association between flavonoid intake and noncommunicable diseases. The food frequency questionnaire (FFQ) is the most cost-effective method of assessing the dietaryflavonoidintake of both groups and individuals. However, only a few studies in China have developed tailored FFQs to describe dietary flavonoid intake. Therefore, this study aims to develop a flavonoid-focused FFQ for Chinese adults and to assess its relative validity and reproducibility. Method: We assessed the intake of representativefoods of the Chinese diet using the flavonoid-focused FFQ, which includes 12 food categories and 147 items. We invited 100 healthy adults to complete the flavonoid-focused FFQ twice (at a one-month interval) to assess the reproducibility of the tool. To assess the validity of the questionnaire, we asked 85 adults to complete the flavonoid-focused FFQ once and to complete three 24-hour dietary recall (24HDR) questionnaires for one week. Results: The reproducibility assessment showed that except for pelargonidin, there were no significant differences in flavonoid intakes between the two FFQ administrations. The Spearman correlation coefficients for nutrients, flavonoid subclasses, and their primary compounds ranged from 0.501 to 0.910, indicating excellent/moderate correlations. The energy-adjusted correlations were within the recommended range for all items. The ICCs ranged from 0.780 to 0.953, and the mean kappa coefficient (Kw) was 0.539. Validity assessment showed that 8 of 19 primary flavonoid compounds had higher intake levels on the FFQ than on the 24HDR. Spearman’s correlation analysis revealed that almost all flavonoid subclasses and primary flavonoid compounds had excellent/moderate correlation coefficients, with the exception of delphinidin, malvidin, pelargonidin, and apigenin. The energy-adjusted intakes showed slightly stronger agreement between the two tools, but this difference did not change the conclusions. The level of agreement (the same tertile) between the flavonoid-focused FFQ and the 24HDR ranged from 41.18% (pelargonidin and apigenin) to 77.65% (total flavonoids). Kw displayed substantial/moderate concordance of nutrients and flavonoid subclass intake and a fair to moderate concordance in almost all primary flavonoid compounds. Only malvidin, pelargonidin, and apigenin had weak concordance. Conclusion: The flavonoid-focused FFQ developed herein exhibited satisfactory reliability and validity for assessing the intake of most flavonoid subclasses and their primary compounds among Chinese adults. It can be used as a tool to investigate the relationship of flavonoid intake with health- and disease-related outcomes.