An investigation of the face validity of a food intake questionnaire: lessons for dietary advice
Aim: To assess the face validity of a food intake questionnaire (FIQ) by comparison to current dietetic practice exemplified by State Registered Dietitians (SRD) working in the North West of England.
Methods: 228 questionnaires were posted to 38 dietetic departments in the North West & North Wales branch of the British Dietetic Association. Dietitians were asked to name foods they considered most important when advising clients on four aspects of healthy eating: lowering sugar intake, lowering fat intake, increasing fibre intake and decreasing salt intake; the foods mentioned by most respondents in each category were ranked 1–10. If an FIQ item appeared in the list of ranked foods and was selected by more than 50% of the sample its inclusion in the FIQ was considered face valid.
Results: 56 foods out of the 80 ranked 1–10 in the eight categories appeared in the FIQ. Thirty-one of these 56 foods were mentioned by more than 50% of dietitians when considering the four aspects of healthy eating; 27 (87%) of these were included in FIQ items. The study also revealed a surprisingly large number of foods to be mentioned by dietitians for each of the four categories. The list of foods mentioned was extensive; for example, 120 foods were mentioned when considering lowering fat intake.
Conclusions: The items chosen for the FIQ can be seen to agree closely with the opinions of practising SRDs, confirming its face validity. The results also suggest there is a need to debate the nature of dietary advice which is given to the public. The findings of the study suggest that translating nutritional guidelines into advice about which foods should be eaten is far from simple. The results may provide one reason for public confusion about healthy eating.
Document Type: Research Article
Affiliations: 1: Department of Community Nutrition & Dietetics, Abercromby Health Centre, Grove Street, Liverpool L7 7HG, UK 2: Reader in Community Nutrition, School of Education & Community Studies, Liverpool John Moores University, IM Marsh Campus, Barkhill Road, Aigburth, Liverpool L7 6BD, UK 3: Department of Dietetics,Burnley General Hospital, Casterton Avenue, Burnley BB10 2PQ, UK 4: Department of Dietetics, Whiston General Hospital, Warrington Road, Prescot, Liverpool L35, UK
Publication date: August 1, 1999