Variation in energy and nutrient intakes among pre-school children: implications for study design.

BACKGROUND: Within- and between-person variation in nutrient intakes has been characterized in adult populations, but little is known about variation in the diet of pre-school-aged children. The aim of this study was to describe dietary variations in Flemish pre-schoolers and to estimate the number of record days required for studying diet-disease associations among pre-school-aged children.
METHODS: Data from 3-day estimated diet records, collected in 2002-03, were used from 661 pre-school children (2.5-6.5 years) in Flanders, using parents/caregivers as a proxy. Age categories for studying differences in dietary variations between age groups were based on the age groups of the Belgian dietary recommendations (2.5-3 years and 4-6.5 years).
RESULTS: Overall, micronutrient intakes had smaller variance ratios than macronutrients. The largest variance ratios were found for cholesterol followed by fat, fatty acids and sodium intakes and would result in attenuated linear regression estimates of diet-disease associations in children. Within/between variance ratios were > or =1 for most nutrients in the oldest group (4-6.5 years) of pre-school children, while <1 for most micronutrients in the youngest age group (2.5-3 years), resulting in fewer days required for this youngest age group in comparison with the oldest group. No consistent differences in variance components were found between genders. Overall, 7-day dietary records were sufficient for accurately estimating 15 of the 23 nutrients in both age groups.
CONCLUSION: The number of record days required for reliably classifying pre-school children raises with increasing age category (from 2.5-3 years to 4-6.5 years) for most nutrients and varies from 3 or 4 days for some nutrients like carbohydrates to 2 or 3 weeks for others like dietary cholesterol or monounsaturated fatty acids.