Cruciferous vegetables contain
isothiocyanates, which show potent chemopreventive activity against
bladder cancer in both in vitro and in vivo studies. However, previous epidemiologic studies investigating cruciferous vegetable intake and
bladder cancer risk have been inconsistent. Cooking can substantially reduce or destroy
isothiocyanates, and could account for study inconsistencies. In this hospital-based case-control study involving 275 individuals with incident, primary
bladder cancer and 825 individuals without
cancer, we examined the usual prediagnostic intake of raw and cooked cruciferous vegetables in relation to
bladder cancer risk. Odds ratios (OR) and 95% confidence intervals (CI) were estimated with unconditional logistic regression, adjusting for smoking and other
bladder cancer risk factors. We observed a strong and statistically significant inverse association between
bladder cancer risk and raw cruciferous vegetable intake (adjusted OR for highest versus lowest category = 0.64; 95% CI, 0.42-0.97), with a significant trend (P = 0.003); there were no significant associations for fruit, total vegetables, or total cruciferous vegetables. The associations observed for total raw crucifers were also observed for individual raw crucifers. The inverse association remained significant among current and heavy smokers with three or more servings per month of raw cruciferous vegetables (adjusted
ORs, 0.46 and 0.60; 95% CI, 0.23-0.93 and 0.38-0.93, respectively). These data suggest that cruciferous vegetables, when consumed raw, may reduce the risk of
bladder cancer, an effect consistent with the role of dietary
isothiocyanates as chemopreventive agents against
bladder cancer.