Objectives: To investigate the frequency and the determinants of
under-reporting in a semiquantitative food frequency questionnaire used
in the Greek segment of the European Prospective Study on Nutrition,
Cancer and Health (EPIC study).
Design: 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.
Setting: Urban and rural population of Greece.
Results: 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.
Conclusions; 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
