Association between alpha-tocopherol, gamma-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. Ho wever, little attention has been paid to the possible role of gamma -tocoph erol, a major component of vitamin E in the U.S. diet and the second most c ommon tocopherol in human serum. A nested case-control study was conducted to examine the associations of alpha -tocopherol, gamma -tocopherol, and se lenium with incident prostate cancer. Methods: In 1989, a total of 10 456 m ale 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 con trol subjects had toenail and plasma samples available for assays of seleni um, alpha -tocopherol, and gamma -tocopherol. The association between the m icronutrient concentrations and the development of prostate cancer was asse ssed by conditional logistic regression analysis. All statistical tests wer e two-sided. Results: The risk of prostate cancer declined, but not linearl y, 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 t he top four fifths of the distribution having a reduced risk of prostate ca ncer compared with individuals in the bottom fifth (P-trend = .27). Statist ically 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 su pplements should be considered in upcoming prostate cancer prevention trial s, given the observed interaction between alpha -tocopherol, gamma -tocophe rol, and selenium.