Objective: Urinary bladder cancer (UBC) incidence and mortality in Uruguay show the highest rates in Latin America. Epidemiological research shows that iron and fluid intake have been inconsistently related to UBC risk regarding nutritional items. The present study was conducted to explore dietary iron and total water consumption on the incidence of UBC in the Uruguayan population since its intake of meat and “mate” infusion is the highest worldwide.
Patients and methods: A case-control study was performed using a specific multi-topic questionnaire, including a food frequency questionnaire. The sample included 255 UBC incident cases and 510 controls (675 men and 90 women). Controls were matched by sex and age (± 5 years) to cases. Food-derived water was calculated from available databases. Dietary iron was calculated according to its heme or non-heme source, adjusted by energy. Odds Ratios (ORs) were calculated through unconditional logistic regression, adjusting for potential confounders. Animal/plant and heme/non-heme (H/NH) ratios were created for analysis purposes.
Results: Total iron, plant-based, and non-heme-iron intake were inversely associated with UBC risk (OR=0.69, 0.43, and 0.54, respectively, for 3rd vs. 1st tertile). Animal-based iron lacked risk association (OR=1.06). Heme-iron risk showed a significant linear trend (p=0.04). The Animal/Plant and H/NH iron ratios were directly associated (OR=2.10 and 2.33, respectively). High water intake displayed a risk increase (OR=2.33), even higher for rural residents than urban ones (OR=5.98 vs. OR=1.97, respectively).
Conclusions: The present study gives evidence of a role for dietary iron and the intake of water in the UBC risk. Regarding iron intake, it showed different associations with UBC risk according to its source.