Isoflavonoids have a molecular structure similar to steroidal estrogen (female sex hormone) and are therefore also called phytoestrogens. However, their hormonal activity is lower by a factor of 100 to 1,000 compared to the estrogen formed in the mammalian organism. Due to their chemical-structural similarity to the female sex hormones, isoflavones ingested with food can bind to the so-called type 2 estrogen receptor and block it for endogenous estrogen. Accordingly, isoflavones in postmenopausal women with low endogenous estrogen levels exhibit a more estrogenic effect, whereas isoflavones in premenopausal women have an antiestrogenic effect by blocking estrogen receptors.
