Objective: Low urine pH may be an important risk factor for bladder cancer, although few studies have evaluated this association. We examined the relationship between estimated renal net acid excretion (NAE), an indirect measure of urine pH based on nutrient intake and anthropometry, and bladder cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study.
Methods: At baseline, 27,096 male smokers 50-69 years old completed a dietary questionnaire that assessed usual frequency of consumption and portion sizes for the previous 12 months, had height and weight measured, and provided a history of smoking. A total of 446 incident bladder cancer cases were identified during up to 17.4 years of follow-up.
Results: In multivariate proportional hazards models, the relative risk (RR) for bladder cancer was 1.15 (95% confidence interval (CI)=0.86-1.55) for individuals in the highest (i.e., most acidic) versus the lowest (i.e., least acidic) NAE quintile (p=0.38). Among men who smoked for more than 45 years, there was a suggestion of increased risk with higher NAE levels (RR=1.72, 95% CI=0.96-3.10, p=0.08).
Conclusions: These findings do not indicate that urine pH is a major risk factor for bladder cancer, although certain subsets of individuals may be at increased risk.