A validation study on a method to estimate nutrient intake by family members through a household-based food-weighing survey.

The aim of the present study is to investigate the validity of a new method to estimate the food intake of individual subjects by a household-based dietary survey. The new method is based on the combination of household-based food weighing and approximating the proportions by which family members shared each dish or food in the household, which has been one of the components of the National Nutrition Survey, Japan, since 1995. We analyzed two sets of data from 64 volunteers (female students taking a dietitian course and their mothers) in 32 households by the approximated proportion method (method A) and the individual-based food weighing method (B) as a reference measurement. Energy and macronutrient intake by individual subjects estimated by method A was highly correlated to the corresponding values by method B (Pearson's correlation coefficients: r=0.90-0.92). Average energy intake was likely to be underestimated by method A compared with method B, being lower by 94 kcal (6.2% of the reference value in method B), at least in the young and middle-aged female adults that were the subjects of this study. When intake of boiled rice was separately analyzed, underestimation of energy intake by method A was 44 kcal, which contributed to approximately 50% of the total magnitude of the underestimation. The procedure manual for the National Nutrition Survey requests the participants to individually weigh the amount of boiled rice taken by family members in the household. However, this procedure is not observed in many actual settings. Therefore, following this procedure would be an effective measure to improve the accuracy of the dietary data.