Association between α-tocopherol, γ-tocopherol, selenium, and subsequent prostate cancer

Background: Selenium and alpha -tocopherol, the major form of vitamin E in supplements, appear to have a protective effect against prostate cancer. However, little attention has been paid to the possible role of gamma -tocopherol, a major component of vitamin E in the U.S. diet and the second most common tocopherol in human serum. A nested case-control study was conducted to examine the associations of alpha -tocopherol, gamma -tocopherol, and selenium with incident prostate cancer. Methods: In 1989, a total of 10 456 male residents of Washington County, MD, donated blood for a specimen bank. A total of 117 of 145 men who developed prostate cancer and 233 matched control subjects had toenail and plasma samples available for assays of selenium, alpha -tocopherol, and gamma -tocopherol. The association between the micronutrient concentrations and the development of prostate cancer was assessed by conditional logistic regression analysis. All statistical tests were two-sided. Results: The risk of prostate cancer declined, but not linearly, with increasing concentrations of alpha -tocopherol (odds ratio(highest versus lowest fifth) = 0.65; 95% confidence interval = 0.32-1.32; P-trend = .28). For gamma -tocopherol, men in the highest fifth of the distribution had a fivefold reduction in the risk of developing prostate cancer than men in the lowest fifth (P-trend = .002). The association between selenium and prostate cancer risk was in the protective direction with individuals in the top four fifths of the distribution having a reduced risk of prostate cancer compared with individuals in the bottom fifth (P-trend = .27). Statistically significant protective associations for high levels of selenium and alpha -tocopherol were observed only when gamma -tocopherol concentrations were high. Conclusions: The use of combined alpha- and gamma- tocopherol supplements should be considered in upcoming prostate cancer prevention trials, given the observed interaction between alpha -tocopherol, gamma -tocopherol, and selenium.