The effects of propolis supplementation on metabolic parameters: A systematic review and meta-analysis of randomized controlled clinical trials

Objective: Propolis is a sticky, resinous substance produced by honeybees from various plants. Various biological properties of propolis and its extracts have been recognized in previous studies including the antiseptic, anti-inflammatory, antioxidant, antiviral, hepatoprotective, antitumor, antibacterial and antimycotic properties. This study aimed to summarize the effect of propolis on metabolic parameters in human adults using systematic review and meta-analysis. Materials and Methods: A comprehensive systematic search was performed in ISI Web of Science, PubMed, Scopus, and Google Scholar up to July 2020 for controlled clinical trials evaluating the impact of propolis on lipid profile and liver enzyme biomarkers. A random effects model was used to calculate the weighted mean difference (WMD) and 95% confidence interval (CI) as the difference between the mean for the intervention and control groups. Results: The present meta-analysis included six randomized controlled trials. There was significant reduction in Aspartate Aminotransferase (AST) in comparison to the control groups (WMD=-2.01; 95% CI: -3.93--0.10; p=0.039). However, a non-significant effect was observed in Triglycerides (TG), Total cholesterol (TC), low-density lipoprotein (LDL), High-density lipoprotein (HDL) (WMD=-0.05 mg/dl; 95% CI: -0.27-0.18; p=0.688; WMD=7.08 mg/dl; 95% CI: -37.31-51.46; p=0.755; WMD=-0.94 mg/dl; 95% CI: -6.64-4.77; p=0.747; WMD=3.14 mg/dl; 95% CI: -1.84-8.13; p=0.216, respectively). Conclusion: Current meta-analysis revealed that propolis supplementation can reduce AST; nevertheless, there was no significant effect on lipid profile indices and ALT.