Dietary and serum α-tocopherol, β-carotene and retinol, and risk for colorectal cancer in male smokers

Objective: To study the association between dietary and serum antioxidant vitamins and carotenoids and risk for colorectal cancer in male smokers. Design: A prospective cohort study within a randomised, double-blind, placebo-controlled trial testing supplementation with alpha-tocopherol (50 mg/day), beta-carotene (20 mg/day) or both in preventing cancer. Subjects and methods: Participants of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study with complete dietary data and serum samples available from baseline. These included 26 951 middle-aged male smokers among whom 184 colorectal cancer cases were diagnosed during By of follow-up. Relative risks were calculated with Cox proportional hazards models adjusting for trial supplementation, age, body mass index, serum cholesterol, cigarettes smoked per day and physical activity. Results: There was no significant association between dietary vitamin C or E, alpha-or gamma-tocopherol, retinol, alpha- or beta-carotene, lycopene or lutein+zeaxanthin and risk for colorectal cancer. Serum alpha-tocopherol, beta-carotene or retinol was also not associated with the risk, neither did the season when baseline blood was drawn modify the relationship between serum beta-carotene and colorectal cancer risk. Conclusions: Our data support the results from previous studies in which no association between dietary antioxidant vitamins and carotenoids and risk for colorectal cancer has been observed. Likewise, no association between baseline serum antioxidant concentrations and colorectal cancer risk was evident. Sponsorship: The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study was supported by a contract with the US National Cancer Institute (N01-CN-45165).