Development and Validation of a Food Frequency Questionnaire to Assess Fermented Food Consumption in Adults

ABSTRACT Background Fermented foods can confer benefits to human health and modulate the microbiota–gut–brain axis. Fermented foods are gaining popularity in Western cultures, with increasing calls for their inclusion in national dietary guidelines. As no specific validated measure to capture fermented food intake exists, this study aimed to develop and validate a fermented food intake questionnaire (FFIQ) to assess habitual intake in adults from the United States, Canada, the United Kingdom, Ireland, Australia and New Zealand, aged 18−60 years. Methods A 32‐item self‐administered FFIQ, informed by available international food consumption data for adults, was developed and subsequently validated in an online sample of 167 adults using six online 24‐h automated dietary recalls (intake24.com) as the reference method. Correlation and Bland–Altman analyses were used to assess agreement and bias between the FFIQ and the 24‐h dietary recalls. Results The most frequently consumed fermented foods were cheeses, yoghurt, kefir and kombucha. Median (Interquartile range) intake of total fermented food was 85.4 (42.3, 143.0) g/day for the FFIQ and 54.9 (20.8, 112.1) g/day for the average of the 24‐h dietary recalls, respectively and showed good agreement for total fermented food consumption ( r = 0.56, p < 0.001) and for most individual fermented foods and food categories. The FFIQ classified 93.4% of participants in the same or adjacent tertile of total fermented food intake. Bland–Altman plots for total intake of fermented food demonstrated good agreement between the FFIQ and the 24 h recalls. The FFIQ also showed good to excellent reliability upon re‐administration for most fermented foods as indicated by the intraclass correlation coefficients. Conclusions The FFIQ provides a robust estimate of fermented food consumption among adults from English‐first language countries. This will be a valuable resource with potential applications in clinical and epidemiological research aimed at exploring associations between fermented foods and health outcomes.