title: The Malmö Food Study: the relative validity of a modified diet history method and an extensive food frequency questionnaire for measuring food intake.
abstract: OBJECTIVE
  To assess the relative validity of two diet assessment methods, an extensive quantitative food frequency questionnaire (method A) and a novel shorter quantitative food frequency questionnaire with a 14 day food record (method B).
  
  
  METHODS
  A randomized prospective cohort study.
  
  
  METHODS
  General community.
  
  
  METHODS
  206 residents of the town of Malmö, aged between 50-69 years, 101 men and 105 women who completed the methods during one year.
  
  
  METHODS
  Both diet methods were designed to cover the whole diet and portion sizes were estimated using a booklet with 120 photographs; method A comprised 250 items and method B combined a two-week food record measuring lunch and dinner meals and a shorter 130 item quantitative food frequency questionnaire for average consumption of foods, snacks and beverages during the past year. An 18 day dietary record comprising six 3-day weighed records evenly distributed over one year served as a reference method.
  
  
  RESULTS
  Pearson's correlation coefficients varied from 0.25 for fat intake to 0.84 for milk products for method A and from 0.32 for fish to 0.88 for meat for method B. Correlations for most food groups ranged between 0.50-0.80, and were higher for method B. Only small changes were noted after adjustment for energy intake. On average for most food groups categorization of subjects into quartiles, 55% of subjects belonging to the lowest quartile, and 57-59% of those belonging to the highest quartile for method A and B were correctly classified.
  
  
  CONCLUSIONS
  A combined food record with a quantitative food frequency questionnaire is a better tool for food assessment than an extensive food frequency questionnaire.
authors.affiliation: Department of Community Medicine, Lund University, Malmö, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Elmståhl
authors.forename: E
authors.initials: E
authors.lastname: Riboli
authors.forename: F
authors.initials: F
authors.lastname: Lindgärde
authors.forename: B
authors.initials: B
authors.lastname: Gullberg
authors.forename: R
authors.initials: R
authors.lastname: Saracci
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D004032:Diet; D015930:Diet Records; D004034:Diet Surveys; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D013548:Sweden