Intake Of Phytoestrogens In Postmenopausal Women - Brief Article

Nutrition Research Newsletter, July, 2001

Postmenopausal estrogen use is associated with a lower cardiovascular disease risk, but also with an increased risk of endometrial cancer, breast cancer, and venous thrombosis. However, consumption of phytoestrogens--plant substances that are structurally and functionally comparable to estradiol and capable of producing estrogenic effects--has been associated with a lower risk of cardiovascular disease and several types of cancer.

Phytoestrogens can be classified into three main groups: isoflavones, coumestans, and lignans. Phytoestrogens, which are commonly consumed by Asian populations, seem to have many benefits. However, there have been few studies on regular dietary phytoestrogen intake in Western populations. To determine the importance of regular phytoestrogen intake on health and disease, more data must be obtained on the mean dietary phytoestrogen intake in these populations. A recent article in the Journal of Nutrition estimated the mean intake of dietary isoflavones, coumestans, and lignans in healthy Western postmenopausal women.

The subjects included 964 postmenopausal, Caucasian women who participated in the Framingham Offspring Study. All subjects completed the 130 item Willett food-frequency questionnaire (FFQ). All phytoestrogen food sources were then identified. The concentrations of 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 major isoflavones are genistein, daidzein, formononetin, and biochanin A. Coumestrol is the most important coumestan. The major lignans are enterolactone and enterodiol. The richest sources of daidzein are tofu, peas, alfalfa, nuts, tea, and coffee. Genistein is found in tofu, nuts, beans, dark bread, and coffee. Lignans are found in berries and some vegetables, while coumestrol is found mainly in alfalfa sprouts and broccoli. The estimated mean total intake of isoflavones was 154 [micro]g with the main sources being beans, peas, tea, coffee and nuts. The estimated daily intake of coumestans was 0.6 [micro]g, with the main source being broccoli. The median total intake of lignans was 578 [micro]g. The main source of lignans was plums, bananas, cantaloupe, watermelon, apples, pears, breads, cereal, rice, grains, and berries.

The results showed that phytoestrogen intake was low compared with that of Asian populations. The total dietary intake of phytoestrogens was less than 1 mg/day. Dietary lignan intake was the highest and coumestan intake was extremely low. The authors acknowledge the limitations of food frequency questionnaires but feel that the data from this study can be used with existing knowledge to create a database on phytoestrogens. Availability of such data will enable longitudinal studies of the health effects of dietary phytoestrogen intake in populations consuming a Western diet.

Miriam J. J. de Kleijn, Yvonne T. van der Schouw, Peter W. F. Wilson, et al. Intake of Dietary Phytoestrogens is Low in Postmenopausal Women in the United States: The Framingham Study, Journal of Nutrition 131 (June 2001) [Address correspondence to Yvonne T. van der Schouw. E-mail: y.t. vanderschouw@jc.azu.nl].