The relative validity of reports of food intake of Dutch and Finnish boys aged 8 and 9 years.

Two studies were carried out to assess the relative validity of the techniques used in measuring the food intake during school lunch or home dinner of 30 Finnish and 68 Dutch boys aged 8 and 9 years. For each of the 30 Finnish boys, duplicate portions of three lunches provided to the boys were collected by a non-participating observer. Nutrient intakes were calculated with the use of a food composition table, and the results were compared with those from the records that were kept by the boys' mothers. For each of the 68 Dutch boys, duplicate portions of the hot meal, taken at home, were collected and analyzed chemically. The results were compared with those from the records that were kept by the boys' mothers. The mean values for the absolute intakes of energy and nutrients for the boys from both Finland and The Netherlands as reported by the boys themselves or their mothers were generally higher (15% to 35%) than those measured by chemical analysis of a duplicate portion or calculated from a weighed portion as collected by a non-participating observer. However, the results for the relative proportions of energy generally showed closer agreement (range of difference, +11% to -15%). The authors found in this study that collection of duplicate portions of food resulted in lower (3% to 15%) recorded food intakes in comparison with measurements recorded for meals consumed on other days.