Objective: To review the current literature on the effects of soy isoflavones, one class of phyto-oestrogens, on cardiovascular diseases, osteoporosis, cancer and climacteric symptoms. Design: Many study designs were employed in the reports reviewed here, including prospective human trials, observational human studies, animal experiments and in vitro cell studies that explored the protective or preventive effects of soy isoflavones (genistein, daidzein and glycitein alone or mixed). Setting: Diverse settings were employed, depending on study design. Subjects: Human subjects, mostly menopausal or postmenopausal, were included, as were animal models and specific cell types. Results: The findings were: (i) isoflavones plus soy protein together were needed to obtain the highly significant beneficial results on blood lipids and arterial dimensions; (ii) isoflavone treatments alone at high doses (relative to above) consistently improved bone parameters in rodent ovariectomized models, but not in humans or primates; (iii) isoflavones were not consistent in exerting positive effects regarding the prevention or treatment of cancers of the mammary glands, uterus and colon; and (iv) the effects of isoflavones on climacteric symptoms were not clear-cut.
Conclusions:The promise of soy isoflavones reducing chronic disease risk seems to be non-uniform, with the most conclusive benefits occurring in the prevention of cardiovascular diseases, but other organ systems, such as skeletal and reproductive tissues, may also benefit from the consumption of soy and soy-derived products. Phyto-oestrogenic molecules have received a great deal of attention over the last few years because of their potentially preventive roles against a few of today's most prevalent chronic diseases, namely, cardiovascular disease, osteoporosis and hormone-related cancers 1,2 . The particular plant molecules of interest are isoflavones, which are found in abundance in soybeans and their derivative foods, such as tofu, miso and others. Of the several isoflavones that are made by soybeans, genistein, in particular, has been experimentally shown to be the most efficacious in human subjects and animal models. For the last several years, a concerted effort has been mounted to identify alternatives to traditional hormone replacement therapy (HRT). Pharmaceutical companies have been developing selective oestrogen receptor modulators (SERMs), which ideally will provide the beneficial effects of oestrogen replacement for bones, cardiovascular system and cognitive function, without adverse effects on breast and endometrial cancer. As a result, SERMs should not require co-administration with a progestin, which can eliminate the side effects that some women experience with that hormone. The first molecules of this new class of drugs to become available are tamoxifen and raloxifene, which exhibit many, but not all, of the qualities of an ideal HRT. Many consumers would also prefer to avoid synthetic molecules in favour of natural products. Soy phytooestrogens, na...