The effect of Glucomannan on fasting and postprandial blood glucose in adults: a systematic review and meta-analysis of randomized controlled trials

Objective: Glucomannan is a dietary fiber that slows the absorption of carbohydrates and suppresses appetite, thereby reducing blood glucose. This meta-analysis sought to examine the effect of glucomannan supplementation on Fasting Blood Glucose (FBG) and Postprandial Glucose (PPG) in adults. Method: We searched PubMed, and SCOPUS databases, and Google Scholar from inception to May 2020, using relevant keywords. All randomized controlled clinical trials (RCTs) that examined the effect of glucomannan supplementation on FBG and PPG in adults were included. Weighted mean differences (WMD) and their 95% confidence interval (CI) were calculated using Stata. Subgroup analysis was used to discern possible sources of heterogeneity. Results: Overall, 6 trials were included, consisting of 124 participants. We found that glucomannan supplementation significantly reduced FBG (WMD): -0.60 mmol/L, 95% CI: -1.16, -0.05; P=0.03, but not PPG (WMD: -2.07mmol/L ; 95% CI: -5.09, 0.95; P=0.18), compared with controls group. We conducted subgroup analysis based on dosage and duration of intervention and health status of the population. Findings from subgroup analysis revealed a significant effect of glucomannan supplementation on FBG in diabetic patients (WMD: -1.28 mmol/L, 95% CI: -2.54, -0.02; P=0.04). Conclusion: Glucomannan supplementation can elicit significant reductions in FBG, but has no significant impact on PPG, in adults. More RCTs may find the exact effect of glucomannan on FBG and PPG.