Methodological challenges in the application of the glycemic index in epidemiological studies using data from the European Prospective Investigation into Cancer and Nutrition.
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.
van Bakel
Marit M E
MM
Nutritional and Database Resource Team, International Agency for Research on Cancer, 63372 Lyon, France.
Slimani
Nadia
N
Feskens
Edith J M
EJ
Du
Huaidong
H
Beulens
Joline W J
JW
van der Schouw
Yvonne T
YT
Brighenti
Furio
F
Halkjaer
Jytte
J
Cust
Anne E
AE
Ferrari
Pietro
P
Brand-Miller
Jennie
J
Bueno-de-Mesquita
H Bas
HB
Peeters
Petra
P
Ardanaz
Eva
E
Dorronsoro
Miren
M
Crowe
Francesca L
FL
Bingham
Sheila
S
Rohrmann
Sabine
S
Boeing
Heiner
H
Johansson
Ingegerd
I
Manjer
Jonas
J
Tjonneland
Anne
A
Overvad
Kim
K
Lund
Eiliv
E
Skeie
Guri
G
Mattiello
Amalia
A
Salvini
Simonetta
S
Clavel-Chapelon
Françoise
F
Kaaks
Rudolf
R
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