Intake of dietary phytoestrogens is low in postmenopausal women in the United States: the Framingham study(1-4).

Many plants that are consumed contain phytoestrogens. Only a few published studies have examined the dietary intake of phytoestrogens in the general Western population. The potentially positive health effects of phytoestrogens might be of relevance to postmenopausal women. The aim of the present study was to estimate the intake of dietary isoflavones, coumestans and lignans by healthy Western postmenopausal women. For this purpose, we studied 964 postmenopausal, Caucasian women who participated in the Framingham Offspring Study and completed the Willett food-frequency questionnaire (FFQ). By searching the medical and agricultural literature and contacting experts, we identified food sources of phytoestrogens. The concentrations of the different isoflavones, coumestrol and lignans in each food in the FFQ were scored in seven categories and multiplied by the serving size of the food and the frequency of its consumption. The estimated daily median intake of the isoflavone daidzein was 39 microg (24-57 microg); of genistein, 70 microg (28-120 microg); of formononetin, 31 microg (13-44 microg); and of biochanin A, 6 microg (2-11 microg). Median total intake of isoflavones was 154 microg (99-235 microg). The main sources of isoflavones were beans and peas. The estimated daily intake of coumestans was 0.6 microg (0.2-1.7 microg), with broccoli as the main source. The estimated daily median intake of matairesinol was 19 microg (12-28 microg) and of secoisolariciresinol 560 microg (399-778 microg). The median total intake of lignans was 578 microg (416-796 microg). The main source of the lignans was fruits. The daily dietary intake of phytoestrogens in healthy postmenopausal Caucasian women in the United States is <1 mg.

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.