Dietary fiber intake and glycemic index and incidence of diabetes in African-American and white adults: the ARIC study.

OBJECTIVE To determine the association of dietary fiber and glycemic index with incident type 2 diabetes in African-Americans and whites. RESEARCH DESIGN AND METHODS We studied 12,251 adults aged 45-64 years and free of diabetes at baseline (1987-1989). A total of 1,447 cases of diabetes were reported between baseline and 9 years of follow-up. Diabetes status was determined by fasting glucose level > or =126 mg/dl (7.0 mmol/l), nonfasting glucose level > or =200 mg/dl (11.1 mmol/l), self-report of physician diagnosis, or use of diabetes medication. Usual dietary intake over the previous year was obtained at baseline using a 66-item food-frequency questionnaire. Nutrients were energy-adjusted using the residuals method. Proportional hazard regression analysis was used to examine dietary fiber intake and glycemic index as predictors of type 2 diabetes in both ethnic groups. RESULTS After adjustment for age, BMI, education, smoking status, physical activity, sex, and field center, there were no statistically significant associations of intake of total dietary fiber, fruit fiber, legume fiber, glycemic index, or glycemic load with incident diabetes. The hazard ratio for the fifth compared with the first quintile of cereal fiber was 0.75 (95% CI 0.60-0.92) in whites and 0.86 (0.65-1.15) in African-Americans. CONCLUSIONS This finding supports a protective role for cereal fiber in the development of diabetes in whites. More studies are needed to determine the role of dietary fiber and glycemic index in diabetes in African-Americans.