Background

High glycemic index (GI) and glycemic load (GL) diets are associated with increased risk for cardiometabolic diseases. Cardiometabolic diseases have decreased in certain populations, while other geographic regions have an increased prevalence. We prospectively investigated in a meta-analysis, diets high in GI and GL together with carbohydrates, high glycemic and refined carbohydrates, dietary fiber, and cereal fiber and their risks for developing type 2 diabetes (T2DM), coronary heart disease (CHD), stroke, and mortality within the US, Europe, and Asia. Secondary aims examined whether there were dose-response trends for dietary variables, and together through their interactions with GI and GL on disease risk

Methods

We included 32 prospective observational studies from Medline, Ovid Medline, PubMed, EBSCOhost biblio-databases restricted to incident data using Cox proportional hazard regression up to March 2018.Pooled hazard ratios (HR) and 95% confidence intervals (CI) utilizing random-effect method were reported.

Results

Higher GI (HR=1.16;CI:1.08-1.24) and GL (HR=1.09;1.07-1.11) increase risk for developing T2DM in three US studies but not in European or Asian studies. Higher GL increase risk of developing CHD in eight European studies (HR=1.08;1.01-1.16) but not in US or Asian studies. Higher GI and GL had the strongest magnitude of risks in overweight/obese participants for developing T2DM, CHD, and stroke, but not with mortality. Dietary fiber (HR=0.95;0.91-0.99) and more so cereal fiber (HR=0.88;0.83-0.94) had protective risks against developing T2DM in US studies. Moreover, we found a dose-response protective trend for daily cereal fiber intake and risk for developing of T2DM for every 5-g increase (HR=0.40;0.28-0.57). This relationship was evident in both men (HR=0.55;0.31-0.98) and women (HR=0.52;0.38-0.73).

Conclusions

These findings highlight the need to investigate whether overweight/obese persons could benefit from higher cereal fiber intake to decrease risk of developing T2DM.