A limited number of studies have been devoted to the effects of phytoestrogens on human reproductive health. These investigations indicate that adult exposure to phytoestrogens has no effects on pituitary hormone concentrations and semen parameters, but possibly lowers testosterone concentrations in the male [13-15].

Does soy really lower testosterone?

Some research shows that regularly eating soy products like edamame, tofu, soy milk, and miso may cause a drop in testosterone levels. For example, one study in 35 men found that drinking soy protein isolate for 54 days resulted in decreased testosterone levels ( 3 ).

Can phytoestrogens reduce estrogen?

Phytoestrogens can also suppress the clinical symptoms of menopause caused by a decrease in the production of endogenous estrogen. Administration of 100 mg of isoflavones per day in postmenopausal women can reduce vasomotor symptoms.