>>2756318One difficulty in interpreting the soy intervention data in general is that the intervention product often is described inadequately. It is essential to have an accurate understanding of isoflavone content for hormone-related health outcomes. Isoflavone content varies not only among different types of soy products but among the same types of products and from batch to batch among the same soy product. For the purpose of this meta-analysis, we contacted the authors to obtain accurate product information. Unfortunately, many investigators relied on the product manufacturer for this information rather than having the product directly analyzed. Moreover, the isoflavone information included in the published article often lacks specifics about the form in which the isoflavones occur. Furthermore, information on other biologically active components of soy, such as saponins, is often lacking. Relatively little is known about the possible physiologic effects of these other components and, importantly, whether they interact with or affect the biologic actions of isoflavones.
https://www.ncbi.nlm.nih.gov/pubmed/9751507?dopt=AbstractIn summary, while the estrogenic potency of industrial-derived estrogenic chemicals is very limited, the estrogenic potency of phytoestrogens is significant, especially for ER beta, and they may trigger many of the biological responses that are evoked by the physiological estrogens.
