Dietary glycemic index and glycemic load are associated with high-density-lipoprotein cholesterol at baseline but not with increased risk of diabetes in the Whitehall II study

Background: Findings of the effect of dietary glycemic index (GI) and glycemic load (GL) on the risk of incident diabetes are inconsistent. Objective: We examined the associations of dietary GI and GL with clinical variables at baseline and the incidence of diabetes. Design: 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. Results: 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. Conclusion: The proposed protective effect of low-dietary GI and GL diets on diabetes risk could not be confirmed in this study. KEY WORDS Glycemic index, carbohydrate, diabetes, glycemia, lipids