Dietary glycaemic index and glycaemic load in relation to the risk of type 2 diabetes: a meta-analysis of prospective cohort studies

Epidemiological studies of dietary glycaemic index (GI) and glycaemic load (GL) in relation to diabetes risk have yielded inconsistent results. We aimed to examine the associations between dietary GI and GL and the risk of type 2 diabetes by conducting a meta-analysis of prospective cohort studies. Relevant studies were identified by a PubMed database search up to February 2011. Reference lists from retrieved articles were also reviewed. We included prospective cohort studies that reported risk estimates with 95 % CI for the associations between dietary GI and GL and the risk of type 2 diabetes. Either a fixed- or random-effects model was used to compute the summary relative risk (RR). We identified thirteen prospective cohort studies of dietary GI or GL related to diabetes risk. The summary RR of type 2 diabetes for the highest category of the GI compared with the lowest was 1·16 (95 % CI 1·06, 1·26; n 12), with moderate evidence of heterogeneity (P = 0·02, I(2) = 50·8 %). For the GL, the summary RR was 1·20 (95 % CI 1·11, 1·30; n 12), with little evidence of heterogeneity (P = 0·10, I(2) = 34·8 %). No evidence of publication bias was observed. In addition, the associations persisted and remained statistically significant in the sensitivity analyses. In conclusion, the present meta-analysis provides further evidence in support of significantly positive associations between dietary GI and GL and the risk of type 2 diabetes. Reducing the intake of high-GI foods may bring benefits in diabetes prevention.