Effect of Propolis supplementation on serum CRP and TNF-α levels in adults: A systematic review and meta-analysis of clinical trials

Abstract Background Propolis is a natural Product and the antioxidant properties of Propolis appear to be principally responsible for its therapeutic effects. However, several studies have shown the positive effect of Propolis on the reduction the levels of inflammatory markers; some others have revealed non-significant impacts on them. Hence, the present systematic review and meta-analysis was conducted to investigate the effects of Propolis supplementation on inflammatory markers. Methods The systematic search was undertaken in scientific databases that included: PubMed, Embase, Scopus and Web of Science to find studies assessing the effects of Propolis on inflammatory markers up to December 2019. Standardized mean difference (SMD) and 95 % confidence intervals (CI) were pooled using fixed effect model. Potential publication bias was tested using Egger’s regression test. Results Seven studies comprising 471 participants were included in the meta-analysis. Pooled results of this meta-analysis showed that serum TNF-α levels (SMD = -0.52, 95 % CI = [-0.84, -0.20], P =  0.001, I2 = 59.5 %) and CRP (SMD = -0.55, 95 % CI = [-0.86, -0.25], P  Conclusion The present study concluded in the statistically and clinically improvement of serum CRP and TNF-α levels following Propolis administration.