Issue 97 Item 7 Dietary Fiber, Glycemic Load, and Risk of Type 2 Diabetes

Fiber reduces the incidence of a large glycemic response OBJECTIVE: Intake of carbohydrates that provide a large glycemic response has been hypothesized to increase the risk of TYPE 2 DIABETES, whereas dietary fiber is suspected to reduce incidence. These hypotheses have not been evaluated prospectively.

RESEARCH DESIGN AND METHODS: We examined the relationship between diet and risk of TYPE 2 DIABETES in a cohort of 42,759 men without TYPE 2 DIABETES or cardiovascular disease, who were 40-75 years of age in 1986. Diet was assessed at baseline by a validated semiquantitative food frequency questionnaire. During 6-years of follow-up, 523 incident cases of TYPE 2 DIABETES were documented.

RESULTS: The dietary glycemic index (an indicator of carbohydrate’s ability to raise blood glucose levels) was positively associated with risk of Type 2 diabetes after adjustment for age, BMI, smoking, physical activity, family history of diabetes, alcohol consumption, cereal fiber, and total energy intake. Comparing the highest and lowest quintiles, the relative risk (RR) of TYPE 2 DIABETES was 1.37 (95% CI, 1.02-1.83, P trend = 0.03). Cereal fiber was inversely associated with risk of TYPE 2 DIABETES (RR = 0.70; 95% CI, 0.51-0.96, P trend = 0.007; for > 8.1 g/day vs. < 3.2 g/day). The combination of a high glycemic load and a low cereal fiber intake further increased the risk of Type 2 diabetes (RR = 2.17, 95% CI, 1.04-4.54) when compared with a low glycemic load and high cereal fiber intake.

CONCLUSIONS: These findings support the hypothesis that diets with a high glycemic load and a low fiber content increase risk of TYPE 2 DIABETES in men. Further, they suggest that grains should be consumed in a minimally refined form to reduce the incidence of Type 2 diabetes.
Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts

Diabetes Care, Vol 20, Issue 4 545-550