Food consumption, meat cooking methods and diet diversity and the risk of bladder cancer.

Background: Since food metabolites are eliminated by the urinary tract, several studies have investigated the association between diet and bladder cancer risk. Recently, the World Cancer Research Fund International/American Institute for Cancer Research (WCRF/AICR) suggested a potential beneficial effect of some foods (mainly vegetables, fruit, and milk) in the development of bladder cancer. We investigated the association between food groups and bladder cancer risk, seeking insights into food diversity as well as meat cooking methods.

Methods: Data were derived from an Italian multicentre case-control study, conducted between 2003 and 2014, including 690 bladder cancer cases and 665 frequency-matched controls. Odds ratios (ORs) and the corresponding 95% confidence intervals (95%CIs) for various dietary aspects were estimated by unconditional logistic regression models adjusted for energy intake and the major known risk factors for bladder cancer.

Results: Comparing the highest versus the lowest quartiles, consumption of vegetables (OR = 0.62; 95%CI: 0.44-0.88) and milk/yogurt (OR = 0.62; 95%CI: 0.44-0.87) reduced the risk of bladder cancer. Conversely, consumption of meat increased bladder cancer risk with an OR of 1.57 (95%CI: 1.07-2.31), particularly when the meat was stewed (OR = 1.47; 95%CI: 1.03-2.09) or roasted (OR = 1.41; 95%CI: 1.00-1.99). There was a suggestion that a diversified diet reduced the risk of bladder cancer, but this was not significant.

Conclusions: Our study consolidates the role of diet in bladder cancer aetiology, showing a reduced risk for vegetable and milk/yogurt consumption and an increased risk for meat consumption, especially when the meat is stewed or roasted.