Phyto-oestrogens and cardiovascular disease risk.

Aim: To present the currently available evidence on the cardiovascular benefits and risks associated with phyto-oestrogens. DATA-SYNTHESIS: Medline search from 1966-1999 updated with cross-check of references of papers with keywords such as phyto-oestrogens, isoflavones, lignans, genistein, daidzein, enterolactone, enterodiol, cardiovascular disease, cardiovascular disease risk factors.
Conclusions: Phyto-oestrogens are plant chemicals divided into three main classes: isoflavones, coumestans, and lignans that display oestrogen-like activity due to their ability to bind to the oestrogen receptor. They are found in grains, beans, green vegetables, fruits, nuts, and grasses. Isoflavones are primarily found in soybeans and soy foods. For epidemiological studies of the relation between phyto-oestrogen intake and disease parameters, intake is estimated with several measures, such as biomarkers (concentrations in urine or blood) or dietary questionnaires, though the optimal method is not yet clear. Phyto-oestrogens are considered to act as selective oestrogen receptor modulators (SERM), exerting both oestrogen agonist and antagonist action. Supplementation with isolated soy protein containing the isoflavones genistein and daidzein reduces serum total and LDL-cholesterol and triglycerides in animals and in humans. Vascular reactivity might be improved by supplementation with isolated soy protein or isoflavones isolated from red clover. Studies on atherosclerosis in animals indicate a potential for risk reduction. Evidence in humans is still scanty. The little we know of the effects of regular dietary phyto-oestrogen intake comes from studies in which phyto-oestrogens were added to the usual diet. Most supplementation studies have been conducted with soy isoflavones, whereas the importance of lignans has not been determined, though they could be more important sources than isoflavones in Western populations. Research has been focused on risk factors. Studies of clinically manifest endpoints are urgently needed.