MONITORING DIETARY CHANGE IN POPULATIONS AND THE NEED FOR SPECIFIC FOOD TARGETS - LESSONS FROM THE NORTH-WEST THAMES REGIONAL HEALTH SURVEY

Dietary goals are usually expressed in the form of consumption of abso lute quantities of specific nutrients. Translating such information in to food patterns is difficult. Consequently it is not easy to convey t hese goals in the promotion of a healthy diet or to monitor dietary ch ange in populations. This paper explores the difficulties and advantag es of a food frequency questionnaire approach as used in a large regio nal health survey to describe food patterns and hence to monitor chang e in relation to dietary variables. There was considerable variation i n the frequency of consumption of individual foods between different s ub-groups in the population and these were as expected. To assess the overall diet a composite dietary index was proposed. The index score w as significantly associated with Various sacio-demographic and lifesty le variables. Unhealthy lifestyles were associated with low scores (i. e. an 'unhealthy' diet) on the index indicating a measure of validity. However there were several limitations in the food frequency question naire method used: neither the questionnaire nor simple global indices of a 'healthy' diet derived from the questions used had been validate d against a more robust quantifiable measure of diet; some of the ques tions were not specific for population groups of interest; some questi ons grouped foods in categories that masked differences in consumption and several did not correspond to recent food targets; and finally th ere was no energy adjustment, which meant that the obese appeared to h ave a healthy dietary pattern. The use of a valid set of food frequenc y questions as an efficient and practical way of monitoring a populati on's diet by survey is suggested. The questions must be validated agai nst reliable measures of nutrients, and be compatible with food target s based on nutritional recommendations.