"Phytoestrogen content of foods--a compendium of literature values."
Plant compounds with estrogenic activity may play a role in cancer prevention, moderation of menopausal symptoms, and other health effects. To facilitate research on these possible actions, the literature was reviewed for quantitative data on the levels of known phytoestrogens (daidzein, genistein, coumestrol, formononetin, and biochanin A) in food plants. For comparative purposes, all phytoestrogen levels were recalculated on a wet weight basis. Details on analytic procedures are given as well. High-performance liquid chromatography was the method most often used to analyze these compounds in foods. Most significant sources of isoflavone and coumestan phytoestrogens include soybeans, soy flour, soy flakes, isolated soy protein, traditional soy foods such as tofu and soy drinks, second-generation say foods, sprouts, and other legumes.
Finally, medians among reported values of phytoestrogen content are provided for some of the most commonly eaten foods with quantitative data available. These may be used to calculate dietary intake of daidzein, genistein, coumestrol, formononetin, and biochanin A.
"Broadly defined, phytoestrogens include isoflavones, coumestans, and lignans. A number of these compounds have been identified in fruits, vegetables, and whole grains commonly consumed by humans. Soybeans, clover and alfalfa sprouts, and oilseeds (such as flaxseed) are the most significant dietary sources of isoflavones, coumestans, and lignans, respectively.
Studies in humans, animals, and cell culture systems suggest that dietary phytoestrogens play an important role in prevention of menopausal symptoms, osteoporosis, cancer, and heart disease. Proposed mechanisms include estrogenic and antiestrogenic effects, induction of cancer cell differentiation, inhibition of tyrosine kinase and DNA topoisomerase activities, suppression of angiogenesis, and antioxidant effects. Although there currently are no dietary recommendations for individual phytoestrogens, there may be great benefit in increased consumption of plant foods."
Honestly before I looked into it my assumption was just based on suspicion since soy is always the first mentioned when phytoestrogen is discussed. These studies back up my suspicions