Meat Intake and the Risk of Bladder Cancer: A Systematic Review and Meta-Analysis of Observational Studies

The evidence for the association between meat intake and the risk of bladder cancer (BC) is still inconclusive. A total of 29 studies involving 1,475,125 participants and 18,836 cases of BC were included in the meta-analysis. Among these studies, 11 reported total meat intake, 20 reported red meat intake, 19 reported processed meat intake, 15 reported white meat intake, and 15 reported fish intake. The results suggested that there was an overall increase in BC risk associated with total meat intake (RR = 1.10; 95% confidence interval: 0.92-1.31; I2 = 55.20%; P = 0.014), and a higher red meat (RR = 1.23; 95% CI: 1.08-1.39; I2 = 51.30%; P = 0.004) or processed meat (RR = 1.16; 95% CI: 1.08-1.25; I2 = 28.00%; P = 0.125) intake may increase the risk of BC. In contrast, a higher intake of fish (RR = 0.80; 95% CI: 0.67-0.95; I2 = 62.90%; P = 0.001) was inversely associated with the risk of BC. Moreover, we did not observe an association between white meat (RR = 0.96; 95% CI: 0.83-1.10; I2 = 53.70%; P = 0.007) and the risk of BC. Our findings suggested that dietary intervention may be an effective approach to preventing BC, which still needs to be confirmed by further well-designed observational studies.