Findings of the effect of dietary glycemic index (GI) and glycemic load (GL) on the risk of incident diabetes are inconsistent.
We examined the associations of dietary GI and GL with clinical variables at baseline and the incidence of diabetes.
The 7321 white Whitehall II participants (71% men) attending screening in 1991-1993, free of diabetes at baseline, and with food-frequency questionnaire data were followed for 13 y.
At baseline, dietary GI and GL were associated inversely with HDL cholesterol, and GI was associated directly with triacylglycerols. Dietary GI and GL were related inversely to fasting glucose and directly to 2-h postload glucose, but only the association between GI and 2-h postload glucose was robust to statistical adjustments for employment grade, physical activity, smoking status, and intakes of alcohol, fiber, and carbohydrates. High-dietary GI was not associated with increased risk of incident diabetes. Hazard ratios (HRs) across sex-specific tertiles of dietary GI were 1.00, 0.95 (95% CI: 0.73, 1.24), and 0.94 (95% CI: 0.72, 1.22) (adjusted for sex, age, and energy misreporting; P for trend = 0.64). Corresponding HRs across tertiles of dietary GL were 1.00, 0.92 (95% CI: 0.71, 1.19), and 0.70 (95% CI: 0.54, 0.92) (P for trend = 0.01). The protective effect on diabetes risk remained significant after adjustment for employment grade, smoking, and alcohol intake but not after further adjustment for carbohydrate and fiber intakes.
The proposed protective effect of low-dietary GI and GL diets on diabetes risk could not be confirmed in this study.