Abstract 20: Carbohydrate Quality, Measured Using Multiple Carbohydrate Quality Metrics, is Negatively Associated with Risk of Type 2 Diabetes in US Women

Background: Carbohydrate quality may be an important determinant of type 2 diabetes (T2D), however, the relationships between various carbohydrate quality metrics and T2D risk have not been systematically investigated. Objective: To prospectively examine the association between carbohydrate, starch, fiber, and different combinations of these nutrients in relation to the risk of T2D in US women. Methods: We prospectively collected information on diet and lifestyle behaviors among 70,041 women from the Nurses Health Study every 2-4 years, after baseline in 1984. These participants were free of diagnosed cardiovascular disease, cancer, or diabetes at baseline. We used Cox proportional hazards regression models to assess the association between dietary factors of interest and incidence of T2D. Results: With 24 years of follow-up we ascertained 6,934 incident cases of T2D during 1,484, 213 person years of follow-up. After adjusting for age, lifestyle and dietary variables, total carbohydrate intake was not associated with T2D (RR=0.98, 95% CI: 0.89 - 1.08, p for trend=0.84), while starch was positively associated with T2D (RR=1.23, 95%CI: 1.12 - 1.35), p for trend <0.0001), comparing the highest to lowest quintile. Total fiber (RR= 0.80, 95%CI: 0.72 - 0.89, p for trend < 0.0001), cereal fiber (RR= 0.71, 95%CI: 0.65 - 0.78, p for trend < 0.0001) and fruit fiber (RR= 0.80, 95%CI: 0.73 - 0.88, p for trend < 0.0001) were all inversely associated with T2D, comparing extreme quintiles. . There was a borderline significant positive association between the ratio of carbohydrate to total fiber intake and risk of T2D (RR= 1.09, 95%CI: 1.00 - 1.20, p for trend = 0.039), and stronger positive associations between the ratios of carbohydrate to cereal fiber (RR= 1.28, 95%CI: 1.17 - 1.39, p for trend < 0.0001), starch to total fiber (RR= 1.12, 95%CI: 1.02 - 1.23, p for trend = 0.030) and starch to cereal fiber (RR= 1.39, 95%CI: 1.27 - 1.53, p for trend < 0.0001) with T2D, comparing extreme quintiles.. Conclusion: Diets with high starch, low fiber and high starch to cereal fiber ratio were associated with increased risk of T2D. Using the starch to cereal fiber ratio of the overall diet is a potentially useful way of assessing carbohydrate quality in relation to T2D.