Assessing dietary exposure or nutrient intakes requires detailed dietary data. These data are collected in France by the cross-sectional Individual and National Studies on Food Consumption (INCA). In 2014–2015, the third survey (INCA3) was launched in the framework of the European harmonization process which introduced major methodological changes. The present paper describes the design of the INCA3 survey, its participation rate and the quality of its dietary data, and discusses the lessons learned from the methodological adaptations.

Two representative samples of adults (18–79 years old) and children (0–17 years old) living in mainland France were selected following a three-stage stratified random sampling method using the national census database.

Food consumption was collected through three non-consecutive 24 h recalls (15–79 years old) or records (0–14 years old), supplemented by an FFQ. Information on food supplement use, eating habits, physical activity and sedentary behaviours, health status and sociodemographic characteristics were gathered by questionnaires. Height and body weight were measured.

In total, 4114 individuals (2121 adults, 1993 children) completed the whole protocol.

Participation rate was 41·5% for adults and 49·8% for children. Mean energy intake was estimated as 8795 kJ/d (2102 kcal/d) in adults and 7222 kJ/d (1726 kcal/d) in children and the rate of energy intake under-reporters was 17·8 and 13·9%, respectively.

Following the European guidelines, the INCA3 survey collected detailed dietary data useful for food-related and nutritional risk assessments at national and European level. The impact of the methodological changes on the participation rate should be further studied.

To investigate the frequency and the determinants of under-reporting in a semi-quantitative food frequency questionnaire used in the Greek segment of the European Prospective Study on Nutrition, Cancer and Health (EPIC study).

A food frequency questionnaire was completed by 9262 adult men and women. The questions included in this questionnaire covered the average intake of approximately 150 food items and beverages over 1 year. Evaluation of under-reporting was conducted on an individual basis taking into account the expected daily variation of nutritional intakes during the time period of recording. Individuals whose energy intake was lower than 1.14*BMR (basal metabolic rate) were defined as under-reporters.

Urban and rural population of Greece.

The data indicated underestimation of energy intake by 11.8% of individuals enrolled. Results from a logistic regression model indicated that body mass index (BMI), gender, age and educational level were significant predictors of under-reporting. The proportion of overweight participants (BMI>30) who tend to under-report energy intake was more than twice that of normal-weight individuals. Men were significantly more prone to under-reporting compared to women, while low education individuals under-report more often than others. Exclusion of under-reporters generated, as expected, mean nutrient values that were significantly higher (by about 6%) than those derived from the total number of participants. When the nutrient values were energy-adjusted, however, or were expressed as percentages of energy intake for macronutrients or as nutrient densities for micronutrients, the emerging differences were minimal and generally statistically not significant.

Under-reporting does exist and it is more extensive among men, those with low education levels and the overweight participants. Adjustment for energy intake minimizes the bias generated by under-reporting with respect to particular nutrients and their association with various disease outcomes in the cohort.