What are soy isoflavones?

Soy isoflavones are phytoestrogens that are commonly found in soy products (e.g., soybeans) but also in small amounts in other fruit and vegetables, especially legumes. The two most abundant types of soy isoflavones in soy products are called genistein and daidzein. The concentrations of each vary depending on the type of product and its processing; for example, fermented soy products might have higher concentrations than raw soy beans.^[1] They are structurally similar to the hormone estrogen and so can bind to estrogen receptors. Depending on the type of estrogen receptor and the type of tissue involved, they can have both estrogenic and antiestrogenic effects.^[2]