title: Within- and between-individual variation in energy and nutrient intake in Japanese adults: effect of age and sex differences on group size and number of records required for adequate dietary assessment.
abstract: BACKGROUND
  Information on within- and between-individual variation in energy and nutrient intake is critical for precisely estimating usual dietary intake; however, data from Japanese populations are limited.
  
  
  METHODS
  We used dietary records to examine within- and between-individual variation by age and sex in the intake of energy and 31 selected nutrients among Japanese adults. We also calculated the group size required to estimate mean intake for a group and number of days required both to rank individuals within a group and to assess an individual's usual intake, all with appropriate arbitrary precision. A group of Japanese women (younger: 30-49 years, n = 58; older: 50-69 years, n = 63) and men (younger: 30-49 years, n = 54; older: 50-76 years, n = 67) completed dietary records for 4 nonconsecutive days in each season (16 days in total).
  
  
  RESULTS
  Coefficients of within-individual variation and between-individual variation were generally larger in the younger group than in the older group and in men as compared with women. The group size required to estimate a group's mean intake, and number of days required to assess an individual's usual intake, were generally larger for the younger group and for men. In general, a longer period was required to rank women and older adults.
  
  
  CONCLUSIONS
  In a group of Japanese adults, coefficients of within-individual variation and between-individual variation, which were used to estimate the group size and number of records required for adequate dietary assessment, differed by age, sex, and nutrient.
authors.affiliation: Department of Social and Preventive Epidemiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Fukumoto
authors.forename: Keiko
authors.initials: K
authors.lastname: Asakura
authors.forename: Kentaro
authors.initials: K
authors.lastname: Murakami
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sasaki
authors.forename: Hitomi
authors.initials: H
authors.lastname: Okubo
authors.forename: Naoko
authors.initials: N
authors.lastname: Hirota
authors.forename: Akiko
authors.initials: A
authors.lastname: Notsu
authors.forename: Hidemi
authors.initials: H
authors.lastname: Todoriki
authors.forename: Ayako
authors.initials: A
authors.lastname: Miura
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Fukui
authors.forename: Chigusa
authors.initials: C
authors.lastname: Date
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D004032:Diet / Q000706:statistics & numerical data*; D015930:Diet Records; D002149:Energy Intake; D005260:Female; D006801:Humans; D007206:Individuality; D007564:Japan; D008297:Male; D008875:Middle Aged; D012737:Sex Factors