An inverse association between the Mediterranean diet and bladder cancer risk: a pooled analysis of 13 cohort studies

Purpose: The role of diet in bladder carcinogenesis has yet to be established. To date most studies have investigated dietary components individually, rather than as dietary patterns, which may provide stronger evidence for any influence of diet on bladder carcinogenesis. The Mediterranean diet has been associated with many health benefits, but few studies have investigated its association with bladder cancer risk. Methods: We investigated the potential association between the Mediterranean diet score (MDS) and risk of developing bladder cancer by pooling 13 prospective cohort studies included in the BLadder cancer Epidemiology and Nutritional Determinants (BLEND) study and applying a Cox regression analysis. Results: Dietary data from 646,222 study participants, including 3639 incident bladder cancer cases, were analysed. We observed an inverse association between Mediterranean diet and bladder cancer risk (HR high 0.85 [95% CI 0.77, 0.93]). When stratifying the results on non-muscle-invasive or muscle-invasive disease or sex the association remained similar and the HR estimate was consistently below 1.00 both for medium and high adherence to the Mediterranean diet. A consistent association was observed when disregarding fat or alcohol intake. Conclusion: We found evidence that adherence to the Mediterranean diet was associated with reduced risk of developing bladder cancer, suggesting a positive effect of the diet as a whole and not just one component.