Vitamin E supplements and risk of prostate cancer in U.S. men.

Supplementation with alpha-tocopherol (a form of vitamin E) was associated with decreased risk of prostate cancer in a randomized trial among Finnish smokers. We examined the association between vitamin E supplement use and prostate cancer incidence in the Cancer Prevention Study II Nutrition Cohort. Participants in the study completed a detailed questionnaire at enrollment in 1992-1993. Historical information was also available from a questionnaire completed in 1982 at enrollment in a previous cohort. Through August 31, 1999, we documented 4,281 cases of incident prostate cancer among 72,704 men. Multivariate-adjusted rate ratios (RRs) were calculated using Cox Proportional Hazards models. Regular vitamin E supplement use (>/=4 times per week) was not associated with overall risk of prostate cancer or with risk of advanced prostate cancer at diagnosis. No trend was seen with increasing dose of vitamin E. Men who reported regular vitamin E use in both 1982 and in 1992-1993 were not at lower risk of prostate cancer. Among current smokers, there was a suggestion of slightly reduced risk with regular vitamin E supplement use [RR = 0.87, 95% confidence interval (CI) = 0.67-1.11]. Our results do not support an important role for vitamin E supplements in prostate cancer prevention.