ASSESSMENT OF FOOD INTAKES - ARE WE MEASURING WHAT PEOPLE EAT

Accurate assessments of dietary intake are a pre-requisite for assessi ng the relationships between diet and health. However, the quantificat ion of errors in dietary data has remained largely undetected because of the absence of techniques to verify dietary survey methodology. Rec ent studies using doubly-labelled water estimates of total energy expe nditure to validate self-reported energy intakes have demonstrated tha t the majority of these are systematically biased towards under-estima tion of usual requirements. Bias is unlikely to be consistent in popul ation studies. Subjects who report the highest energy intake tend to e stimate their requirements more accurately than these who report low i ntakes. Mechanisms for cross-checking energy intake data against estim ated energy requirements have been developed and provide limited guida nce for checking the physiological plausibility of reported intakes, w ith special emphasis on under-reporting. In the absence of independent validation the evaluation of dietary survey data should be approached with caution.