Author: J Kathy, et al
Source: JNCI J Natl Cancer Inst (2000) 92 (24): 2018-2023.
Publication Date: 12/1/2000
Background: Selenium and (alpha) a-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) y-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) a-tocopherol, and (gamma) y-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) a-tocopherol (odds ratio highest versus lowest fifth = 0.65; 95% confidence interval = 0.32–1.32; Ptrend = .28). For (gamma) y-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 (Ptrend = .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 (Ptrend = .27). Statistically significant protective associations for high levels of selenium and a-tocopherol were observed only when (gamma) y-tocopherol concentrations were high. Conclusions: The use of combined (alpha) a and (gamma) y- tocopherol supplements should be considered in upcoming prostate cancer prevention trials, given the observed interaction between (alpha) a-tocopherol, (gamma) y-tocopherol, and selenium.