Plasma and prostate phytoestrogen concentrations in prostate cancer patients after oral phytoestogen supplementation

BACKGROUND: Phytoestrogens have been suggested to reduce the risk of prostate cancer (CaP), but no data exists on how oral phytoestrogen supplementation influences phytoestrogen concentrations in prostate tissue. METHODS: Forty men with CaP, assigned for radical prostatectomy, received 240 mg of clover phytoestrogens or placebo daily for a 2-week period before their operation in a prospective and randomized study. Phytoestrogens were measured in plasma and prostate tissue by time-resolved fluoroimmunoassay (TR-FIA). RESULTS: All patients had low baseline phytoestrogen concentrations and only 35% had a detectable plasma concentration of equol. Oral supplementation with phytoestrogens induced a statistically significant (P<0.001) 23- and 7-fold increase in prostate tissue concentrations of the phytoestrogens genistein and daidzein, respectively. Supplemented patients demonstrated prostate tissue genistein and daidzein concentrations that were over twofold higher than their plasma. Interestingly, even though the placebo group did not receive phytoestrogen challenge, they also demonstrated twofold prostate tissue genistein and daidzein concentrations compared to their plasma values, suggesting that the prostate can concentrate available phytoestrogens. In addition, after the supplementation, 90% of the supplemented patients had a detectable plasma equol concentration. CONCLUSIONS: We conclude that prostate tissue can concentrate genistein and daidzein. Significant elevation of intraprostatic genistein and daidzein concentrations can be achieved with a short-term dietary phytoestrogen supplementation.