Propolis

Strongest evidence The strongest evidence for propolis, rated as moderate, centers on three outcomes. For C-reactive protein, all three meta-analyses reported beneficial reductions (moderate effect size), with the largest 2025 review of 12 RCTs in type 2 diabetes showing a mean difference of -2.68 mg/L. For plaque index, three of four studies found benefits, though effect sizes varied; a 2024 RCT using 0.2% propolis mouthwash over 21 days showed a large reduction in chronic gingivitis patients. For triglycerides, two of three meta-analyses found small reductions in people with type 2 diabetes or metabolic syndrome. Doses across these studies were not consistently reported, preventing dose recommendations.

Mixed or weaker evidence Evidence is weaker and more mixed for five other outcomes. For gingival index and clinical attachment (both low strength), the largest meta-analysis in type 2 diabetes patients found no significant benefit, while smaller studies showed positive effects. Interleukin-6 reduction shows conflicting results: two studies beneficial (including a large effect in one meta-analysis) but two high-quality reviews found no effect. Tumor necrosis factor alpha had three beneficial studies (small to large effects) but publication bias is a concern. Probing depth showed small benefits in two of three studies, but the highest-scoring meta-analysis was neutral. In all these cases, the small number of studies (3–4) and inconsistent dosing limit confidence.

Effective dose patterns No consistent effective dose range emerged across the evidence base. Studies used propolis in various forms—mouthwash (e.g., 0.2%), gels, and oral supplements—with doses and durations rarely standardized. The lack of dose reporting in many abstracts prevented identification of optimal regimens.

Population insights Most research focused on two populations: adults with type 2 diabetes and those with periodontal disease (gingivitis or periodontitis). In type 2 diabetes, propolis showed moderate evidence for reducing CRP and triglycerides, but mixed results for inflammatory cytokines and oral health measures. In periodontitis, short-term studies (around 21 days) using propolis mouthwash showed benefits for plaque and gingival indices, but longer-term data are lacking.

Notable caveats Several caveats apply across the research. All outcomes are based on small numbers of studies (3–4), making conclusions preliminary. The evidence is subject to potential publication bias, as positive results are more likely to be published. Many syntheses noted that doses, forms, and study durations were inconsistently reported, limiting dose-response analysis. The highest-quality meta-analyses sometimes contradicted smaller studies, particularly for interleukin-6 and gingival index, indicating unresolved inconsistency.