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.