title: Methodological challenges in the application of the glycemic index in epidemiological studies using data from the European Prospective Investigation into Cancer and Nutrition.
abstract: Associations between the glycemic index (GI) or glycemic load (GL) and diseases are heterogeneous in epidemiological studies. Differences in assigning GI values to food items may contribute to this inconsistency. Our objective was to address methodological issues related to the use of current GI and GL values in epidemiological studies. We performed ecological comparison and correlation studies by calculating dietary GI and GL from country-specific dietary questionnaires (DQ) from 422,837 participants from 9 countries participating in the European Prospective Investigation into Cancer and Nutrition study and single standardized 24-h dietary recalls (24-HDR) obtained from a representative sample (n = 33,404) using mainly Foster Powell's international table as a reference source. Further, 2 inter-rater and 1 inter-method comparison were conducted, comparing DQ GI values assigned by independent groups with values linked by us. The ecological correlation between DQ and 24-HDR was good for GL (overall r = 0.76; P < 0.005) and moderate for GI (r = 0.57; P < 0.05). Mean GI/GL differences between DQ and 24-HDR were significant for most centers. GL but not GI from DQ was highly correlated with total carbohydrate (r = 0.98 and 0.15, respectively; P < 0.0001) and this was higher for starch (r = 0.72; P < 0.0001) than for sugars (r = 0.36; P < 0.0001). The inter-rater and inter-method variations were considerable for GI (weighted kappa coefficients of 0.49 and 0.65 for inter-rater and 0.25 for inter-method variation, respectively) but only mild for GL (weighted kappa coefficients > 0.80). A more consistent methodology to attribute GI values to foods and validated DQ is needed to derive meaningful GI/GL estimates for nutritional epidemiology.
authors.affiliation: Nutritional and Database Resource Team, International Agency for Research on Cancer, 63372 Lyon, France.
authors.forename: Marit M E
authors.initials: MM
authors.lastname: van Bakel
authors.forename: Nadia
authors.initials: N
authors.lastname: Slimani
authors.forename: Edith J M
authors.initials: EJ
authors.lastname: Feskens
authors.forename: Huaidong
authors.initials: H
authors.lastname: Du
authors.forename: Joline W J
authors.initials: JW
authors.lastname: Beulens
authors.forename: Yvonne T
authors.initials: YT
authors.lastname: van der Schouw
authors.forename: Furio
authors.initials: F
authors.lastname: Brighenti
authors.forename: Jytte
authors.initials: J
authors.lastname: Halkjaer
authors.forename: Anne E
authors.initials: AE
authors.lastname: Cust
authors.forename: Pietro
authors.initials: P
authors.lastname: Ferrari
authors.forename: Jennie
authors.initials: J
authors.lastname: Brand-Miller
authors.forename: H Bas
authors.initials: HB
authors.lastname: Bueno-de-Mesquita
authors.forename: Petra
authors.initials: P
authors.lastname: Peeters
authors.forename: Eva
authors.initials: E
authors.lastname: Ardanaz
authors.forename: Miren
authors.initials: M
authors.lastname: Dorronsoro
authors.forename: Francesca L
authors.initials: FL
authors.lastname: Crowe
authors.forename: Sheila
authors.initials: S
authors.lastname: Bingham
authors.forename: Sabine
authors.initials: S
authors.lastname: Rohrmann
authors.forename: Heiner
authors.initials: H
authors.lastname: Boeing
authors.forename: Ingegerd
authors.initials: I
authors.lastname: Johansson
authors.forename: Jonas
authors.initials: J
authors.lastname: Manjer
authors.forename: Anne
authors.initials: A
authors.lastname: Tjonneland
authors.forename: Kim
authors.initials: K
authors.lastname: Overvad
authors.forename: Eiliv
authors.initials: E
authors.lastname: Lund
authors.forename: Guri
authors.initials: G
authors.lastname: Skeie
authors.forename: Amalia
authors.initials: A
authors.lastname: Mattiello
authors.forename: Simonetta
authors.initials: S
authors.lastname: Salvini
authors.forename: Françoise
authors.initials: F
authors.lastname: Clavel-Chapelon
authors.forename: Rudolf
authors.initials: R
authors.lastname: Kaaks
mesh_terms: D015331:Cohort Studies; D004032:Diet; D004034:Diet Surveys; D005060:Europe / Q000453:epidemiology; D005247:Feeding Behavior; D005260:Female; D005504:Food Analysis / Q000379:methods; D038321:Glycemic Index; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000453:epidemiology*; D009747:Nutritional Physiological Phenomena; D009752:Nutritional Status; D015203:Reproducibility of Results; D012107:Research Design; D012727:Sex Characteristics; D013995:Time