Diet and risk of bladder cancer: a systematic review of epidemiological evidence.
PURPOSE Although tobacco use and occupational exposures are established risk factors for urothelial cancer (UC), the influence of dietary factors remains uncertain. We conducted a systematic review to synthesize evidence from prospective cohort studies examining associations between dietary exposures and UC incidence. METHODS A comprehensive literature search of MEDLINE, Embase, and Web of Science (May 2025) was performed to identify prospective studies evaluating dietary factors with UC incidence. The risk of bias was assessed using standard tools (CRD420251043101). RESULTS From 6253 records screened, 32 prospective cohort studies were included, encompassing 2 277 677 participants. Investigated exposures included fluid intake (four studies, n = 562 038), coffee (four, n = 1 013 624), milk (three, n = 613 141), tea (three, n = 532 949), alcohol (three, n = 694 585), fruits (three, n = 597 753), vegetables (three, n = 555 685), protein (two, n = 469 339), fibre (two, n = 466 577), and cruciferous vegetables (two, n = 1 071 313). Only one study specifically assessed upper tract urothelial carcinoma (n = 80 388). Two studies suggested a borderline inverse association between high fluid intake and bladder cancer (BC) risk (upper 95% confidence interval >0.95), whereas two others found no such association. Three of four coffee studies reported no significant association after adjustment for smoking; one reported a modest increased risk. Fruit and vegetable intake showed modest inverse associations with BC risk in three studies. Most included studies were at moderate risk of bias, and residual confounding-particularly by smoking-remains a concern. CONCLUSION Available evidence does not support a strong or consistent association between dietary factors and BC incidence. Although a healthy diet is beneficial for overall well-being, patients should be informed that dietary modifications alone are unlikely to meaningfully alter their BC risk.