Mediterranean diet and risk of prostate cancer: a systematic review and meta-analysis of observational studies

Background Prostate cancer is the most common malignancy among men worldwide. In addition to non-modifiable risk factors, modifiable lifestyle factors are increasingly recognized in prevention. The Mediterranean diet (Med Diet), characterized by high intake of plant-based foods, unsaturated fatty acids, and antioxidant micronutrients, has been proposed as a protective dietary pattern. Methods A systematic search was conducted in PubMed, Web of Science, and Scopus examining associations between Mediterranean diet adherence and prostate cancer risk. Fourteen studies met eligibility criteria. Meta-analysis was performed in R applying a random-effects model (REML estimation; Hartung–Knapp adjustment). Heterogeneity was assessed with I² and τ²; publication bias was evaluated using a funnel plot, contour-enhanced funnel plot, and Egger’s test. Results Based on a random effects model, we did not find a statistically significant difference in risk of prostate cancer in men with high versus low Mediterranean diet adherence (RR = 0.98; 95% CI: 0.93–1.04). Heterogeneity was moderate (Q = 19.95, I² = 34.8%). Although Egger’s regression test did not indicate statistically significant publication bias ( p = 0.115), complementary analyses (Q-Q plot and limit meta-analysis) suggested a possible small-study effect, warranting cautious interpretation. Conclusion In this meta-analysis, no protective effect of the Mediterranean diet against prostate cancer was found. Nevertheless, biological plausibility and inconsistent epidemiological trends suggest that further research using standardized dietary assessments and incorporating genetic and microbiome-related factors is needed. Trial registration The review protocol was not prospectively registered.