Reproducibility and validity of a short food questionnaire for the assessment of dietary habits

Abstract

Background and aim: Dietary changes such as reducing the consumption of foods high in saturated fat, and increasing the daily intake of unsaturated fat, fibre and vitamins may have beneficial effects on long-term health. Accurate dietary information is essential for dietary counselling. Most of the methods used to examine an individual's diet (food records, diet interview, food frequency questionnaires) are too complicated and time-consuming for routine clinical use. There is a need for a fast and simple tool for food assessment. The aim of this study was to evaluate a short and simple food questionnaire for use in clinical practice that emphasises the intakes of fat, fibre, fruit and vegetables representative of the usual diet of an individual or group.

Methods and results: A 15-item questionnaire was completed twice on the same day by 111 participants in order to study reproducibility, and its validity was checked by comparing the results with those of a 7-day food record for 101 subjects. The participants reported a positive attitude to the questionnaire. The reproducibility and validity studies comparing the sum scores of the questionnaire and food record gave correlation coefficients of respectively 0.95 and 0.73, thus indicating good agreement. The reproducibility study showed weighted Kappa coefficients ranging from 0.97 for milk and snacks to 0.75 for vegetables. In the validity assessment, the weighted Kappa coefficients ranged from 0.73 for butter and margarine to 0.14-0.25 for vegetables, fish and snacks, which is a less satisfactory result. The correlation coefficient between the sum score of the questionnaire and the percentage of dietary saturated fat was-0.59.

Conclusions: This simple self-administered questionnaire allows for the rapid assessment of the constituents of the usual diet of an individual. It provides a good estimate of dietary fat and fibre but is less accurate in terms of the intake of vegetables, fish and snacks. It also offers an opportunity to discuss central points in the improvement of dietary habits and may be a useful health educational tool in clinical practice.