Fruit and vegetable consumption and risk of bladder cancer: an updated meta-analysis of observational studies

This meta-analysis was conducted to assess the association between fruit and vegetable intake and bladder cancer risk. Eligible studies published up to August 2014 were retrieved both through a computer search of PubMed, Embase and the Cochrane library and through a manual review of references. The summary relative risks with 95% confidence intervals (CIs) for the highest versus the lowest intakes of fruits and vegetables were calculated with random-effects models. Heterogeneity and publication bias were also evaluated. Potential sources of heterogeneity were detected with metaregression. Subgroup analyses and sensitivity analyses were also performed. A total of 27 studies (12 cohort and 15 case-control studies) were included in this meta-analysis. The summary relative risks for the highest versus lowest were 0.84 (95% CI: 0.72-0.96) for vegetable intake and 0.81 (95% CI: 0.73-0.89) for fruit intake. The dose-response analysis showed that the risk of bladder cancer decreased by 8% (relative risk=0.92; 95% CI: 0.87-0.97) and 9% (relative risk=0.91; 95% CI: 0.83-0.99) for every 200 g/day increment in vegetable and fruit consumption, respectively. Sensitivity analysis confirmed the stability of the results. Our findings suggest that intake of vegetables and fruits may significantly reduce the risk of bladder cancer. Further well-designed prospective studies are warranted to confirm these findings.