Prospective study of dietary carbohydrates, glycemic index, glycemic load, and incidence of type 2 diabetes mellitus in middle-aged Chinese women

BACKGROUND: Much uncertainty exists about the role of dietary glycemic index and glycemic load in the development of type 2 diabetes mellitus, especially in populations that traditionally subsist on a diet high in carbohydrates. METHODS: We observed a cohort of 64,227 Chinese women with no history of diabetes or other chronic disease at baseline for 4.6 years. In-person interviews were conducted to collect data on dietary habits, physical activity, and other relevant information using a validated questionnaire. Incident diabetes cases were identified via in-person follow-up. Associations between dietary carbohydrate intake, glycemic index, and glycemic load and diabetes incidence were evaluated using multivariable Cox proportional hazards models. RESULTS: We identified 1,608 incident cases of type 2 diabetes mellitus in 297,755 person-years of follow-up. Dietary carbohydrate intake and consumption of rice were positively associated with risk of developing type 2 diabetes mellitus. The multivariable-adjusted estimates of relative risk comparing the highest vs the lowest quintiles of intake were 1.28 (95% confidence interval, 1.09-1.50) for carbohydrates and 1.78 (95% confidence interval, 1.48-2.15) for rice. The relative risk for increasing quintiles of intake was 1.00, 1.04, 1.02, 1.09, and 1.21 (95% confidence interval, 1.03-1.43) for dietary glycemic index and 1.00, 1.06, 0.97, 1.23, and 1.34 (95% confidence interval, 1.13-1.58) for dietary glycemic load. CONCLUSION: High intake of foods with a high glycemic index and glycemic load, especially rice, the main carbohydrate-contributing food in this population, may increase the risk of type 2 diabetes mellitus in Chinese women.