Under-reporting in dietary surveys--implications for development of food-based dietary guidelines.

OBJECTIVE: To illustrate issues related to under-reporting in dietary surveys relevant for development of food-based dietary guidelines.
SETTING: Food and nutrient intakes in two national dietary surveys are analysed in relation to under-reporting using the concept of cut-off values for the ratio between energy intake and basal metabolic rate as well as biochemical markers of nutritional status.
RESULTS: Subjects with an implausibly low EI/BMR ratio had dietary patterns more close to recommended levels, e.g. lower fat intake and higher fibre intake, than those with acceptable energy intakes. Intakes of micronutrients were lower. This was due to both general and selective under-reporting of foods. Under-reporting was due to less frequent consumption, larger proportion of non-consumers and smaller portion sizes. Low EI/BMR ratios did not influence the characterisation of protein and micronutrient intake of low and high consumers of fruit and vegetable intake.
CONCLUSIONS: Under-reporting can influence the usefulness of dietary data as a tool for developing food-based dietary guidelines, and the extent of under-reporting should be assessed using appropriate methods.