title: Dice, golf balls, and CDs: assumptions about portion size measurement aids.
abstract: OBJECTIVE
  Portion size measurement aids (PSMAs) are used extensively by dietitians. In this cross-sectional, descriptive study, we explored the degree of consistency and concordance between measured and putative volumes of selected household and sport-related PSMAs that are commonly used for nutrition education and dietary assessment.
  
  
  METHODS
  An online search of portion size resources yielded several governmental and academic descriptions of household PMSAs (e.g., a compact disc, a nine-volt battery) and sport-related PMSAs (e.g., a golf ball) and their purported dimensions. The spherical items were purchased locally and measured using electronic digital calipers; measurements were then converted to volumes, in millilitres.
  
  
  RESULTS
  Overall, we observed a high degree of heterogeneity in how different educational resources related sport-related PSMAs to portion sizes of food. The mean percentage of error between the measured and putative volumes of PSMAs varied considerably.
  
  
  CONCLUSIONS
  Our findings indicate that the inaccurate use of PSMAs can lead to systematic bias in nutrition education and misreporting of dietary intake during dietary assessment. Dietitians should exercise caution when using PSMAs because these may not reflect the true portion size they are meant to represent.
authors.affiliation: Department of Pediatrics, University of Alberta, Edmonton, AB.
authors.forename: Geoff D C
authors.initials: GD
authors.lastname: Ball
authors.forename: Alinda
authors.initials: A
authors.lastname: Friedman
mesh_terms: D004032:Diet; D004046:Dietetics; D005502:Food; D006266:Health Education / Q000379:methods*; D006801:Humans; D015596:Nutrition Assessment; D018673:Nutrition Policy