Many men are concerned when they see the relationship between soy products and estrogen, but it is important we make the distinction between them. First, soy isoflavones (or phytoestrogens) are very different to the body's own estrogen. Being over 1000 times less active, isoflavones have the ability to mildly stimulate or even block estrogen action in the body. It is due to these estrogen-blocking properties that men get benefits of protecting the prostate against Benign Prostatic Hyperplasia (BPH), and the associated urinary difficulty, and possibly prostate cancer.

It has been shown that soy isoflavones can inhibit the enzyme 5-alpha-reductase, reducing the conversion of potent testosterone to the less active dihydrotestosterone (DHT).