title: Daily, weekly, seasonal, within- and between-individual variation in nutrient intake according to four season consecutive 7 day weighed diet records in Japanese female dietitians.
abstract: OBJECTIVE
  To study daily, weekly, seasonal, within- and between-individual variance in intake of selected nutrients and minimal days necessary for assessing true intake with a specified degree of error based on four season consecutive 7 day weighed diet records (WDRs).
  
  
  METHODS
  We evaluated consumption of energy and 30 nutrients based on four season consecutive 7 day WDRs from 80 Japanese female dietitians in 1996-1997. We examined daily, weekly, seasonal, within- and between-individual variation in nutrient intake, relative contributions of their variances to total variance, and minimal days required to estimate a person's nutrient intake within 10% and 20% of their true mean with 95% confidence intervals.
  
  
  RESULTS
  The relative contributions of variation for all nutrients by person were larger than those by day, week and season. Within-individual variances were greater than the between-individual variances. The ratios of within- vs. between-individual variances thus ranged from 1.3-26.9. Minimal days necessary for estimating nutrient consumption per person within 10% (20%) of the true mean with 95% confidence intervals ranged from 10-35 (3-9) days for energy and major nutrients and 15-640 (4-160) days for micro-nutrients.
  
  
  CONCLUSIONS
  The relative contributions of variability by person were largest for all nutrients, followed by those due to sequence of days, season and day of week. Within-individual variation was greater than between-individual variation. Minimal days necessary for ascertaining major nutrients were in general fewer than micro-nutrients.
authors.affiliation: Nagoya-Bunri College, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tokudome
authors.forename: Nahomi
authors.initials: N
authors.lastname: Imaeda
authors.forename: Teruo
authors.initials: T
authors.lastname: Nagaya
authors.forename: Masato
authors.initials: M
authors.lastname: Ikeda
authors.forename: Nakako
authors.initials: N
authors.lastname: Fujiwara
authors.forename: Juichi
authors.initials: J
authors.lastname: Sato
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Kuriki
authors.forename: Shogo
authors.initials: S
authors.lastname: Kikuchi
authors.forename: Shinzo
authors.initials: S
authors.lastname: Maki
authors.forename: Shinkan
authors.initials: S
authors.lastname: Tokudome
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015930:Diet Records; D004046:Dietetics; D004435:Eating; D002149:Energy Intake; D005260:Female; D006801:Humans; D007564:Japan; D008875:Middle Aged; D012621:Seasons; D013997:Time Factors