title: Sources of variation of energy and nutrient intake among adolescents in São Paulo, Brazil.
abstract: The aim of the current study was to describe the sources of variation of energy and nutrient intake and to calculate the number of repetitions of diet measurements to estimate usual intake in adolescents from São Paulo, Brazil. Data was collected using 24-hour dietary recalls (24hR) in 273 adolescents between 2007 and 2008. Individuals completed a repeat 24hR around two months later. The sources of variation were estimated using the random effect model. Variance ratios (within-person to between-person variance ratio) and the number of repetitions of 24hR to estimate usual intake were calculated. The principal source of variation was due to within-person variance. The contribution of day of week and month of year was less than 8%. Variations ranged from 1.15 for calcium to 7.31 for vitamin E. The number of 24hR repeats required to estimate usual intake varied according to nutrient and gender, numbering 15 for males and 8 for females.
authors.affiliation: Universidade de São Paulo, Brasil.
authors.forename: Eliseu
authors.initials: E
authors.lastname: Verly Junior
authors.forename: Regina Mara
authors.initials: RM
authors.lastname: Fisberg
authors.forename: Chester Luis Galvão
authors.initials: CL
authors.lastname: Cesar
authors.forename: Dirce Maria Lobo
authors.initials: DM
authors.lastname: Marchioni
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001938:Brazil; D002136:Calcium, Dietary / Q000008:administration & dosage; D004034:Diet Surveys / Q000706:statistics & numerical data*; D002149:Energy Intake; D005260:Female; D006801:Humans; D008297:Male; D009752:Nutritional Status; D013997:Time Factors; D014810:Vitamin E / Q000008:administration & dosage
chemical_list: D002136:Calcium, Dietary; D014810:Vitamin E