Nationally Representative Within-Person to Between-Person Variance Ratios of Nutrient Intakes and Their Application for Estimating Usual Nutrient Intake Distributions Using 1-Day Dietary Data in Japan.

BackgroundCollecting multiple-day dietary data is generally recommended to estimate usual intake distributions; however, in the National Health and Nutrition Survey (NHNS) in Japan, only 1-d dietary data are available.ObjectivesThis study aimed to calculate within-person to between-person variance ratios (WBVRs) of nutrient intake using multiple-day dietary data and to estimate usual nutrient intake distributions by applying the WBVRs to a 1-d dietary record (DR) of the National Health and Nutrition Survey (NHNS). Estimation robustness was also assessed.MethodsThe WBVRs were calculated from nonconsecutive 8-d paper-based DRs including 1375 males and 1422 females nationwide. Distributions of individual usual nutrient intake (food only; excluding supplements) were estimated from 1-d household-based DRs (paper-based) of 5053 males and 5652 females in the NHNS (2018-2019) by adapting the Best-Power method. We examined the influence of sex, age group, and sample size on WBVR values and the influence of WBVR values on estimated distributions.ResultsThe WBVRs did not vary substantially by sex or age group but did vary by nutrient, ranging from 0.71 for potassium to 3.08 for n-3 (ω-3) fatty acids in males and from 0.79 for potassium to 3.77 for vitamin D in females. The estimated usual intake distributions were narrower than 1-d intake; for example, the 90th percentiles of protein intake were 103 g/d for usual and 114 g/d for crude 1-d, whereas those for vitamin A were 738 and 875 μg retinol activity equivalents/d in males. Considerable variation in the calculated WBVR values was observed when a small number of participants and survey days were randomly selected from the multiple-day DRs. WBVR variation affected estimated distributions.ConclusionsThis study estimated nationally representative usual nutrient intake distributions in Japan. The WBVRs estimated in this study, derived from a large and nationwide dataset, may be the best presently available for use in future 1-d dietary surveys aimed at estimating usual nutrient intake distributions in Japan.