Phytosterol feeding induces alteration in testosterone metabolism in rat tissues

The objective of the present study was to examine the metabolism of testosterone in rat tissues as influenced by dietary phytosterols. Testosterone metabolism includes reductions to more active metabolites or aromatization to estrogen. Both higher levels of androgens and estrogens are implicated as risk factors in the development of prostate cancer. Tissues studied included liver, testis, and prostate. Feeding 2% phytosterols with 0.2% cholic acid to rats for 22 days resulted in a 33% reduction in serum testosterone compared with controls, which received only 0.2% cholic acid in the diet. 5-α-Reductase was reduced by 41 to 44% and 33% in the liver and prostate, respectively. No effect of phytosterols was observed in the testis. Only aromatase activity of the prostate was reduced by 55% upon feeding phytosterols. It was concluded that dietary phytosterols may reduce the risk of prostate cancer by lowering the activities of the enzymes of testosterone metabolism.