The association between digestion-resistant and bioactive peptide content of dairy products and bladder cancer: a case-control study.

Background: Bladder cancer is the sixth most common cancer worldwide. Bioactive peptides (BP) are digestion-resistant (enzymatically stable) and absorbable fragments that exert physiological functions in the body. We conducted this case-control study to examine the association between dairy-derived BPs and bladder cancer.

Methods: The present case-control study (103 cases and 200 controls) was a hospital-based investigation conducted in three referral hospitals in Tehran, Iran. Dietary intake was assessed using a validated 168-item Food Frequency Questionnaire (FFQ). Intake of BPs was estimated based on dairy product consumption recorded in the FFQ. Logistic regression analysis was used to examine the association between the content of digestion-resistant BPs in dairy products and the odds of bladder cancer.

Results: After adjusting confounding factors, it was observed that the odds of bladder cancer were significantly lower in the second and last tertiles (T) of total peptide intake from dairy products compared to the first tertile (T₂: odds ratio (OR) = 0.285; 95% confidence interval (CI): 0.116-0.699, T₃: OR = 0.130; 95% CI: 0.032-0.527). Additionally, in the adjusted model, a significant inverse association was found between other dairy-derived peptides and the odds of bladder cancer.

Conclusions: The findings suggest a potential inverse relationship between milk-derived BPs and bladder cancer risk, which warrants further investigation in longitudinal or interventional studies. However, further studies are needed to elucidate the biological properties and mechanism of action of milk-derived BPs.