Validation of a food frequency questionnaire to measure intakes of inulin and oligofructose

Abstract

Background and objectives:Inulin and oligofructose are prebiotic carbohydrates associated with numerous health benefits. The aim of this study was to accurately measure inulin and oligofructose intakes and to develop and validate a food frequency questionnaire (FFQ).Subjects and methods:A 7-d semi-weighed food diary (FD) was used to measure intakes in 66 healthy subjects. A 23-item FFQ was developed to measure short-term inulin and oligofructose intakes over the same 7 days and was completed twice on 2 separate days.Results:There were no significant differences in inulin intake (4.0±1.3 vs 4.0±1.4 g/d, P=0.646) or oligofructose intake (3.8±1.2 vs 3.8±1.3 g/d, P=0.864) when measured using the 7-d FD or the FFQ. Bland-Altman analysis demonstrated low mean differences between the FD and FFQ in measuring intakes of inulin (-0.09 g/d) and oligofructose (-0.03 g/d). The FFQ categorised 89% of subjects into the same or adjacent tertiles of intakes as the 7-d FD. For the majority of food items, kappa values indicated substantial or almost perfect agreement for assignment of portion size and frequency of consumption between the FFQs completed on separate days.Conclusions:The FFQ is a valid and reliable method for measuring short-term inulin and oligofructose intakes for use in dietary surveys and clinical trials. © 2011 Macmillan Publishers Limited. All rights reserved.