Phyto-oestrogens are polyphenolic compounds found in plants, including genistein and daidzein in soy beans, formononetin and biochanin in red clover and lignans in rye and flax seed.1 Depending on concentration, tissue type and the presence of oestrogen receptors, their steroidal structure allows them to exert oestrogenic or anti-oestrogenic effects. Whereas the anti-oestrogenic effects are a focus in cancer prevention research,2 the oestrogenic action is of interest as a treatment to alleviate menopausal symptoms without the risks of hormone replacement therapy.3 However, concerns have been expressed that the weak oestrogenic activity of isoflavones may promote breast cancer growth in survivors or high-risk women.4

Tempfer and colleagues address the safety of phyto-oestrogens in women. In a detailed search, the authors identified 174 potential reports and conducted a meta-analysis of 92 randomised trials with reported side effects. All studies administered phyto-oestrogens to participants, but they had many different end points, such as menopausal symptoms, mammographic density, endometrial …