Effect of barley β-glucan on postprandial glycaemic response in the healthy human population: A meta-analysis of randomized controlled trials

Background: Despite the many published studies examining the effects of barley and barley products on postprandial glycaemia (PPGR), to date, a meta-analysis to quantify the overall PPGR lowering effect of barley beta-glucan in the literature has not been published. Objective: The meta-analysis presented in this manuscript was designed to quantify the efficacy of barley and barley products on postprandial glycaemia. Methods: The review was registered on PROSPERO (registration number CRD42015027988). Analysis was performed on a total of 17 studies that included 68 different treatments (which covered a range of food types) and 212 subjects. Multiple comparisons or strata within studies were combined using a fixed effects model, and a random effects model was used to obtain an overall estimate on outcomes of interest. Results: Compared with controls, barley and/or β-glucan from barley significantly reduced glucose area under the curve (G iAUC) by −34.4 min × mmol/L. The glycaemic index (GI) was also significantly lower than that for control products (−24.3). Consumption of foods containing barley and/or β-glucan from barley significantly reduced insulin AUC by 2577 min × pmol/L, and a significant reduction in insulin index was observed (−33.8). The ratio of BG to AC did not meet the EFSA suggested amount of 4 g BG per 30 g AC in the majority of studies examined; meta-regression analysis indicated no significant dose–response relationship between BG dose and the mean difference in G iAUC. Conclusions: Results of the meta-analysis show that consumption of barley and barley β-glucan lowered postprandial glycaemic response, and that the magnitude of reduction in PPGR was large enough to be considered a physiologically relevant change. However, due to the relatively low number of studies eligible for inclusion in the meta-analysis, and the high inter-study heterogeneity observed among the studies included, this meta-analysis points to the need for more high quality dose–response studies to verify that barley can improve health outcomes of free-living humans who consume a varied diet.