Effects of long-term α-tocopherol supplementation on serum hormones in older men

BACKGROUND. α-tocopherol supplementation significantly reduced risk of prostate cancer in the Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) Study. Sex hormones are thought to be involved in the etiology of prostate cancer. We examined whether long-term supplementation with α-tocopherol modified serum hormone levels. METHODS. Men who were cancer-free consumed ≥ 90% of the study capsules, and who had both baseline and follow-up blood available, were eligible for the study. One hundred men who received α-tocopherol were matched on age, study center, and length of time between blood draws to 100 men who received a placebo. Multivariate linear regression models which allowed for a separate intercept for each matched pair were used to evaluate the effect of α-tocopherol supplementation on follow-up hormone concentrations. RESULTS. Compared to men who received a placebo, we found significantly lower serum androstenedione (P=0.04) and testosterone (P=0.04) concentrations among men who received α-tocopherol, after controlling for baseline hormone level, follow-up serum cholesterol concentration, body mass index, smoking, and fasting time. Geometric mean (95% confidence interval; CI) androstenedione concentration among men who received α-tocopherol was 145 ng/dl (CI, 137-153) after adjusting for covariates, compared to 158 ng/dl (CI, 148-167) among men who received a placebo. Mean testosterone concentrations for men who received α-tocopherol and placebo were 539 (CI, 517-562) and 573 (CI, 549-598) ng/dl, respectively. CONCLUSIONS. These results suggest that long-term α-tocopherol supplementation decreases serum androgen concentrations, and could have been one of the factors contributing to the observed reduction in incidence and mortality of prostate cancer in the α-tocopherol treatment group of the ATBC Study.