Soy's content of isoflavones are as much as 3 mg/g dry weight.
Isoflavones are polyphenol compounds, produced primarily by beans and other legumes, including peanuts and chickpeas.
Isoflavones are closely related to the antioxidant flavonoids found in other plants, vegetables and flowers.
Isoflavones such as genistein and daidzein are found in only some plant families, because most plants do not have an enzyme, chalcone isomerase which converts a flavone precursor into an isoflavone.
In contradiction to well known benefits of isoflavones, genistein acts as an oxidant (stimulating nitrate synthesis), and blocks formation of new blood vessels (antiangiogenic effect).
Some studies show that genistein acts as inhibitor of substances that regulate cell division and cell survival (growth factors).
A review of the available studies by the United States Health and Human Services Agency for Healthcare Research and Quality (AHRQ) found little evidence of substantial health improvements and no adverse effects, but also noted that there was no long-term safety data on estrogenic effects from soy consumption.
