In general, it's a good idea to stay away from non-bioidentical hormones, and especially non-bioidentical estrogens. Although they come from a natural source, phytoestrogens are not bioidentical. They have a different chemical structure from the estrogens that occur naturally in the human body, and they behave differently. There's not much in the way of published research looking at the effects of taking phytoestrogens long term, but other non bioidentical estrogens (e.g. DES, ethinylestradiol and premarin) can be very dangerous, and are associated with things like blood clots, strokes and heart attacks. By contrast, bioidentical estradiol appears to be much safer (particularly the transdermal and injected forms), with little or no increased risk of blood clots or other adverse effects.
