The association between glycemic index, glycemic load, and metabolic syndrome: a systematic review and dose-response meta-analysis of observational studies

Purpose The association of glycemic index (GI) and glycemic load (GL) with metabolic syndrome (MetS) is controversial. Therefore, we conducted this first systematic review and dose-response meta-analysis of observational studies to quantify these associations. Methods We searched PubMed, EMBASE, Web of Science, and the Cochrane Library for relevant studies up to 1 April 2019. Summary odds ratios (OR) and 95% confidence intervals (CI) were calculated by a random-effects model. This study was registered with PROSPERO (CRD42019131788). Results We included eight high-quality (n = 5) or medium-quality (n = 3) cross-sectional studies in the final meta-analysis, comprising 6058 MetS events and 28,998 participants. The summary ORs of MetS for the highest versus lowest categories were 1.23 (95% CI 1.10-1.38, I-2 = 0, tau(2) = 0, n = 5) for dietary GI, 1.06 (95% CI 0.89-1.25, I-2 = 36.2%, tau(2) = 0.0151, n = 6) for dietary GL. The summary OR was 1.12 (95% CI 1.00-1.26, I-2 = 0, tau(2) = 0, n = 3) per 5 GI units, 0.96 (95% CI 0.83-1.10, I-2 = 33.4%, tau(2) = 0.0059, n = 2) per 20 GL units. Conclusions Dietary GI was positively associated with the prevalence of MetS. However, no significant association was found between dietary GL and the prevalence of MetS. Further studies with prospective design are needed to establish potential causal relationship between dietary GI and the MetS.