PHYTO-ESTROGENS - WHERE ARE WE NOW

Phyto-oestrogens have emerged from their esoteric role in animal husba ndry following the hypothesis that the human Western diet is relativel y deficient in these substances compared with societies where large am ounts of plant foods and legumes are eaten. Evidence is beginning to a ccrue that they may begin to offer protection against a wide range of human conditions, including breast, bowel, prostate and other cancers, cardiovascular disease, brain function, alcohol abuse, osteoporosis a nd menopausal symptoms. Of the two main classes of these weak oestroge ns, the isoflavones are under intensive investigation due to their hig h levels in soyabean. Like the 'anti-oestrogen' Tamoxifen, these seem to have oestrogenic effects in human subjects in the cardiovascular sy stem and bone. Although previously only available from food, isoflavon es are now being marketed in health-food supplements or drinks, and ta blets may soon be available over the counter as 'natural' hormone-repl acement therapy. In cancer, antioestrogenic effects are thought to be important, although genistein especially has been shown to induce wide -ranging anti-cancer effects in cell lines independent of any hormone- related influence. There are few indications of harmful effects at pre sent, although possible proliferative effects have been reported. In i nfants, the effects of high levels in soya milk formulas are uncertain . The second group, lignans, have been less investigated despite their known antioestrogenic effects and more widespread occurrence in foods . Investigation of the possible benefits of phyto-oestrogens is hamper ed by lack of analytical standards and, hence, inadequate methods for the measurement of low levels in most foods. This problem may prove to be a major dilemma for regulatory authorities, clinicians and others wishing to advise the general public on whether these compounds really do have the health benefits attributed to them.