Anti-inflammatory and antioxidant effects of propolis: A systematic review and meta-analysis of the influences of the geographical origin and phenotype.

BACKGROUND: This systematic review and meta-analysis aimed to assess the effects of oral propolis on inflammatory and oxidative stress biomarkers in adults and to explore whether these effects differ by clinical phenotype and propolis origin. METHODS: PubMed, Scopus, and Web of Science were systematically searched up to August 2025 for randomized controlled trials comparing oral propolis with placebos. Evaluated outcomes included C-reactive protein (CRP), high-sensitivity CRP (hs-CRP), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), reduced glutathione (GSH), glutathione peroxidase (GPx), superoxide dismutase (SOD), total antioxidant capacity (TAC), malondialdehyde (MDA), and pro-oxidant-antioxidant balance (PAB). The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. RESULTS: Eighteen trials involving 498 participants were included. Most studies used Iranian poplar-type or Brazilian propolis at 250-1500 mg per day for 4-104 weeks. Pooled analyses indicated that propolis supplementation was associated with reductions in hs-CRP, IL-6, and TNF-α levels, while CRP and IL-10 showed no significant changes. GPx, GSH, SOD, and TAC exhibited increases; however, these findings were accompanied by substantial heterogeneity and low certainty of evidence. Furthermore, MDA and PAB levels showed no statistically significant changes. CONCLUSIONS: Oral propolis may improve selected inflammatory and antioxidant biomarkers in adults, particularly hs-CRP, IL-6, TNF-α, and GPx levels. However, the evidence for several outcomes remains limited by substantial heterogeneity and low certainty. The current findings support a possible context-dependent effect according to the clinical phenotype and product characteristics, but more standardized trials are needed.