Increasing prevalence of underreporting does not necessarily distort dietary surveys

To study the magnitude of and trends in energy underreporting and to compare food consumption, nutrient intake and socioeconomic characteristics of underreporters to those of other Finnish adults. Cardiovascular risk factor surveys in 1982 and 1992 using a 3 d food record. Underreporting was defined as energy intake lower than 1.27* BMR, since energy intake < 1.27* BMR is improbable. Four areas in Finland, both rural and urban. 1746 men and 1921 women, aged, 25-64 y. Proportion of underreporters has increased from 33% in 1982 to 46% in 1992 among women and from 27% in 1982 to 42% in 1992 among men. In a logistic regression model, BMI over 25 kg/m2, female gender, age over 45 y and high educational level predicted underreporting. Shares of energy intake from fat, carbohydrates, protein and alcohol remained the same whether or not underreporters were excluded. However, underreporters consumed significantly higher proportion of vegetables, fish, meat, potatoes, fruit and berries and less fat than others. In the 1992 data the absolute intake of most micronutrients increased and micronutrient densities decreased when underreporters were excluded. The proportion of underreporters has grown from 1982 to 1992. Results expressed as a percentage of energy intake are not affected by the exclusion of underreporters. In contrast, micronutrient intakes, both absolute and energy density values, were distorted by underreporting. Underreporting should be taken into account in future studies.