title: Reproducibility and validity of dietary glycemic index, dietary glycemic load, and total carbohydrate intake in 141 Swedish men.
abstract: BACKGROUND
  Although the associations of dietary glycemic index (GI) and dietary glycemic load (GL) with many chronic diseases have been examined in epidemiologic studies, information regarding the reproducibility and validity of these measures assessed with the use of food-frequency questionnaires (FFQs) is lacking.
  
  
  OBJECTIVE
  We examined the reproducibility and validity of dietary GI and dietary GL and of carbohydrate intake as assessed by using an FFQ.
  
  
  METHODS
  Swedish men (n = 141) aged 40-74 y completed 2 FFQs 1 y apart and two 1-wk weighed diet records 6 mo apart. Dietary GI, dietary GL, and carbohydrate intake (starches and sugars) were calculated from both FFQs and diet records. We used intraclass correlations between the 2 FFQs to measure reproducibility and Pearson correlations between the diet records and the FFQs to assess the relative validity.
  
  
  RESULTS
  Reproducibility of the FFQs was 0.66 (95% CI: 0.56, 0.75) for dietary GI, 0.61 (95% CI: 0.50, 0.71) for dietary GL, and 0.61 (95% CI: 0.50, 0.71) for carbohydrate. The correlations between the FFQs and diet records were 0.62 (95% CI: 0.45, 0.74) for dietary GI, 0.77 (95% CI: 0.56, 0.88) for dietary GL, and 0.76 (95% CI: 0.55, 0.88) for carbohydrate after adjustment for within-person variation in the FFQs and diet records.
  
  
  CONCLUSIONS
  In this sample of men, an FFQ measured dietary GI, dietary GL, and carbohydrate with reproducibility and validity similar to other commonly studied nutritional factors.
authors.affiliation: Cardiovascular Epidemiology Research Unit, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA. elevitan@bidmc.harvard.edu
authors.forename: Emily B
authors.initials: EB
authors.lastname: Levitan
authors.forename: Camilla W
authors.initials: CW
authors.lastname: Westgren
authors.forename: Simin
authors.initials: S
authors.lastname: Liu
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
mesh_terms: D000328:Adult; D000368:Aged; D003625:Data Collection; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D005502:Food / Q000145:classification*; D038321:Glycemic Index; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013548:Sweden
chemical_list: D004040:Dietary Carbohydrates