In brief, the present results demonstrate that equol: a) (R- and/or S-isomeric mixtures) has high binding affinity for 5α-DHT making it a potent selective androgen modulator (SAM), b) blocks the stimulatory androgen action of 5α-DHT in increasing prostate specific antigen (PSA) levels in human cancer (LNCap) cell cultures and, c) significantly decreases serum 5α-DHT and subsequently prostate weight without altering, testosterone, 17β-estradiol or LH levels. This evidence concerns the gene KLK3 and cancer.