Effect of Propolis supplementation on C-reactive protein levels and other inflammatory factors: A systematic review and meta-analysis of randomized controlled trials

Abstract Propolis is a resin-like substance collected by honeybees from certain plants that have been shown to positive effect on inflammatory factors. Therefore, the aim of this study was to systematically review and meta-analyse the effects of Propolis supplementation on CRP, TNF-a, IL-1, and IL-6 in Randomized Controlled Trials (RCTs). A comprehensive systematic search of articles was conducted in PubMed/MEDLINE, Web of sciences, and Scopus to identify the potential titles up to August, 2019. PRISMA guidelines were performed for this study. Inclusion was 1-study design was parallel or cross over randomized controlled trial (RCT), 2- consumption of Propolis as intervention, 3- reported sufficient information about inflammatory factors, CRP, IL1, IL6, TNF-a. Six studies were identified by comprehensive search. This meta-analysis study found a significant reduction in IL-6, CRP, and TNF-α following Propolis consumption (Weighted mean differences (WMD): -17.96 pg/ml, 95% CI: -35.53, -0.38, I2 = 98% ), (WMD: -1.16 pg/ml, 95% CI: -2.28, -0.03, I2 = 97% ), and (WMD: -34.08 pg/ml, 95% CI: -60.25, -7.91, I2 = 97% ), respectively. Propolis did not showed any significant effect on IL-1 (WMD: -17.36 pg/ml, 95% CI: -37.60, 2.87, I2 = 97% ). In conclusion, the results demonstrated that CRP, TNF-a and IL-6 were significantly reduced following propolis supplementation.