The effect of dietary glycemic index and glycemic load on inflammatory biomarkers: a systematic review and meta-analysis of randomized clinical trials

To our knowledge, there is no study available that summarizes earlier findings on the effect of dietary glycemic index (GI) and glycemic load (GL) on inflammatory biomarkers. This systematic review and meta-analysis was conducted to systematically review the available clinical trials that examined the effects of low-GI (LGI) and low-GL (LGL) diets on several inflammatory biomarkers in adults. We searched for relevant articles published up to June 2017 through PubMed, Medline, SCOPUS, EMBASE, and Google Scholar with the use of relevant keywords. Clinical trials that examined the effect of dietary GI and GL on inflammation in adults were included. Overall, 28 randomized controlled trials (RCTs) including 2961 participants (59% women, 41% men) were included in this meta-analysis. By combining findings from 14 studies on high-sensitivity C-reactive protein (hs-CRP) concentrations, we found no significant effect of LGI or LGL diets on serum hs-CRP concentrations compared with the control diet [weighted mean difference (WMD) for dietary GI: -0.05 mg/L (95% CI: -0.21, 0.10 mg/L); and WMD for dietary GL: 0.08 mg/L (95% CI: -0.26, 0.42 mg/L), respectively]. After combining effect sizes from 5 studies, we did not find significant changes in serum tumor necrosis factor alpha (TNF-alpha) concentrations comparing control diets with LGI (WMD: -0.18 mg/L; 95% CI: -0.43, 0.06 mg/L) or LGL (WMD: -0.20 mg/L; 95% CI: -0.33, 0.07 mg/L) diets. Significant changes were also not seen in leptin and interleukin 6 (IL-6) concentrations after the consumption of LGI or LGL diets. We did not find any significant effect of dietary GI or GL on serum concentrations of inflammatory cytokines, including hs-CRP, leptin, IL-6, and TNF-alpha in adults. Additional RCTs-in particular, feeding trials-are required to shed light on this issue.