Nutrient intake variability in a pediatric population: implications for study design

Estimates of an individual's intake of specific nutrients is important in epidemiologic investigations of disease-diet relationships. The object of the present investigation was to determine the minimum number of daily food records required to estimate intake of specific nutrients in children. Both members of 70 pairs of twins (n = 140 children) completed a minimum of 3 and a maximum of 23 food records throughout a 2-y period. All subjects were white and range in age from 5 to 14 y. Assuming an attenuation of the correlation coefficient of 80%, the minimum number of daily food records required to estimate energy intake was seven for boys and eight for girls. As a group, the vitamin intakes were the most variable for both boys and girls, often requiring more than 20 records for either sex. Requirements for other nutrients generally fell between these two extremes. The results of the present investigation are particularly relevant to the interpretation and design of studies of associations with nutrient intake.