Effect of propolis supplementation on oxidative stress markers: A systematic review of randomized controlled trials

Background: Propolis is a sticky, resinous substance produced by bees by mixing saliva and beeswax with substances obtained from plant parts, buds, and exudates. It has been reported that propolis has anti-oxidative properties that could help in the treatment of chronic diseases. This systematic review aims to summarize the results of randomized controlled trials (RCTs), which assessed the antioxidant effects of propolis.Method: PubMed, Scopus, and ISI Web of Science databases were searched up to July 2020. RCTs that evaluated the effects of oral propolis supplementation on oxidative stress parameters were included.Result: Six RCTs, totaling 364 participants were included in the systematic review. Propolis supplementation was shown to reduce biomarkers of oxidative stress, including carbonyls, malondialdehyde, oxidized low-density lipoprotein, and thiobarbituric acid reactive substances and markers of tissue damage, including lactate dehydrogenase and fructosamine. Propolis also increased serum levels of antioxidant factors, including superoxide dismutase, glutathione, glutathione peroxidase, and catalase, and increased serum total antioxidant capacity.Conclusion: Propolis can elicit antioxidant effects in patients with type 2 diabetes mellitus, infertile males, and healthy individuals. However, further studies are needed.Registration: The protocol of this systematic review was registered at PROSPERO (ID: CRD42020203354).