Association of vitamin C, vitamin D, vitamin E and risk of bladder cancer: a dose-response meta-analysis

A dose-response meta-analysis was conducted to assess the association of vitamin C, D, E with risk of bladder cancer. Pertinent studies were identified in PubMed and Embase. The random-effect model was used. The relative risk (95% confidence interval) of bladder cancer was 0.99 (0.95-1.03) for every 100 IU/day increment in vitamin D from diet plus supplement and 0.95 (0.90-1.00) for every 10 nmol/L increment in circulating vitamin D. The effect for every 10 mg/day increment was 0.96 (0.90-1.02) for vitamin E from diet plus supplement, 0.83 (0.72-0.95) from diet and 0.88 (0.67-1.15) from supplement, and the effect was 0.84 (0.76-0.94) for every 1 mg/dL increment in circulating α-Tocopherol and 1.22 (1.00-1.49) for every 0.1 mg/dL increment in circulating γ-Tocopherol. The observed association for vitamin D and vitamin E was significant among smokers but not among non-smokers. No significant association was found between vitamin C and risk of bladder cancer in the dose-response analysis. Based on the dose-response analysis, the risk of bladder cancer might be inversely associated with vitamin D and E (especially α-Tocopherol), but positively associated with γ-Tocopherol.