Soybean isoflavones are classified as phytoestrogens but they differ from the hormone estrogen. This difference has been demonstrated clinically as well as at the molecular level. In regard to the latter, isoflavones preferentially bind to and transactivate estrogen receptor-beta in comparison to estrogen receptor-alpha whereas estrogen binds with equal affinity to both receptors. Recently, high-dose soybean isoflavones were shown not to affect coagulation in postmenopausal women. This finding not only supports the safety of these soybean constituents but provides an excellent example of how isoflavones differ from the hormone estrogen, which increases coagulation. This newest study is especially notable because it was one year in duration and women in the active group received 300 mg/d isoflavones, an intake that is about 7-fold higher than typical Japanese intake.
Cheng WC, Lo SC, Tsai KS, et al. Effects of high-dose phytoestrogens on circulating cellular microparticles and coagulation function in postmenopausal women. J Formos Med Assoc. 2013 Dec 18. pii: S0929-6646(13)00397-5. doi: 10.1016/j.jfma.2013.11.001. [Epub ahead of print]