title: Underreporting of energy, protein and potassium intake in relation to body mass index.
abstract: BACKGROUND
  Differential underreporting of dietary intake by subgroups of body mass index (BMI) will confound associations between dietary intake and BMI-related diseases. We estimated the magnitude of BMI-related underreporting for energy, protein, and potassium intake for the Dutch cohorts of the European Prospective Investigation into Cancer and Nutrition (EPIC).
  
  
  METHODS
  The study population consisted of 134 Dutch men and women, aged 21-71 years, who participated in a pilot of EPIC. Ratios of reported dietary intakes to biomarkers were used as measures for underreporting. Dietary intake was assessed by a food frequency questionnaire (FFQ) and repeated 24-hour dietary recalls. Biomarker for energy intake was calculated basal metabolic rate; for protein and potassium intake the biomarker was 24-hour urinary nitrogen and potassium excretion, respectively. The measures of underreporting were linearly regressed on BMI (in kg/m2).
  
  
  RESULTS
  Significant negative regression coefficients were observed when regressing energy ratio on BMI with adjustment for physical activity (FFQ: beta = -0.04 for men, beta = -0.02 for women; 24-hour recalls: beta = -0.03 for men, beta = -0.04 for women). In men, a significant negative regression coefficient (beta = -0.03) was observed when regressing protein ratio on BMI; for the recalls however only after adjustment for age and education (beta = -0.02). In women, negative regression coefficients were also obtained, but for the FFQ only after exclusion of dieting women (both FFQ and 24-hour recalls: beta = -0.02). According to the recalls, but not the FFQ, a significant negative regression coefficient (beta = -0.02) was observed among women when regressing potassium ratio on BMI.
  
  
  CONCLUSIONS
  In this Dutch population, BMI-dependent underreporting of 20-25% over the observed range of BMI is present for protein and energy, Further study on BMI-dependent underreporting of dietary intake in EPIC cohorts is warranted.
authors.affiliation: Department of Chronic Disease and Environmental Epidemiology, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: D W
authors.initials: DW
authors.lastname: Heerstrass
authors.forename: M C
authors.initials: MC
authors.lastname: Ocké
authors.forename: H B
authors.initials: HB
authors.lastname: Bueno-de-Mesquita
authors.forename: P H
authors.initials: PH
authors.lastname: Peeters
authors.forename: J C
authors.initials: JC
authors.lastname: Seidell
mesh_terms: D000328:Adult; D000368:Aged; D001481:Basal Metabolism; D015992:Body Mass Index; D004044:Dietary Proteins / Q000008:administration & dosage*; D018563:Disease Notification / Q000706:statistics & numerical data*; D002149:Energy Intake; D015991:Epidemiologic Measurements; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D015596:Nutrition Assessment; D017419:Potassium, Dietary / Q000008:administration & dosage*
chemical_list: D004044:Dietary Proteins; D017419:Potassium, Dietary