Chitosan modifies glycemic levels in people with metabolic syndrome and related disorders: meta-analysis with trial sequential analysis

BACKGROUND: Chitosan supplementation has been shown to modulate glycemic levels; however, studies have reported conflicting results. The present meta-analysis with trial sequential analysis was conducted to verify the overall influence of chitosan on glycemic levels in patients with metabolic syndrome. METHODS: The PubMed, Cochrane library, and EMBASE databases were systematically searched for randomized controlled studies of chitosan intake and glycemic levels. RESULTS: A total of ten clinical trials including 1473 subjects were included in this meta-analysis. Pooled effect sizes were determined by random-effects meta-analysis. Subgroup analysis was performed to analyze the sources of heterogeneity and their influence on the overall results. The results revealed a significant reduction in fasting glucose levels (SMD: − 0.39 mmol/L, 95% CI: − 0.62 to − 0.16) and hemoglobin A1c (HbA1c) levels (SMD: -1.10; 95% CI: − 2.15 to − 0.06) following chitosan supplementation but no effect on insulin levels (SMD: − 0.20 pmol/L, 95% CI: − 0.64 to 0.24). Subgroup analyses further demonstrated significant reductions in fasting glucose levels in subjects administered 1.6–3 g of chitosan per day and in studies longer than 13 weeks. Trial sequential analysis of the pooled results of the hypoglycemic effect demonstrated that the cumulative Z-curve crossed both the conventional boundary and trial sequential monitoring boundary for glucose and HbA1c. CONCLUSIONS: The glucose level of patients who are diabetic and obese/overweight can be improved by supplementation with chitosan for at least 13 weeks at 1.6–3 g per day. Additional clinical research data are needed to confirm the role of chitosan, particularly in regulating glycosylated hemoglobin and insulin. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12937-020-00647-4.