Intake of dietary phytoestrogens is low in postmenopausal women in the United States: The Framingham Study

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 mug (24-57 mug); of genistein, 70 mug (28-120 mug); of formononetin, 31 mug (13-44 mug); and of biochanin A, 6 mug (2-11 mug). Median total intake of isoflavones was 154 mug (99-235 mug). The main sources of isoflavones were beans and peas. The estimated daily intake of coumestans was 0.6 mug (0.2-1.7 mug), with broccoli as the main source. The estimated daily median intake of matairesinol was 19 mug (12-28 mug) and of secoisolariciresinol 560 mug (399-778 mug) The median total intake of lignans was 578 mug (416-796 mug). 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.