Dietary Phytoestrogens, Including Isoflavones, Lignans, and Coumestrol, in Nonvitamin, Nonmineral Supplements Commonly Consumed by Women in Canada

Twenty-one nonvitamin, nonmineral dietary supplements commonly consumed by women in Canada were analyzed for isoflavones (formononetin, daidzein, genistein, glycitein), lignans (pinoresinol, lariciresinol, secoisolariciresinol, matairesinol), and coumestrol to complement our previously published food phytoestrogen database. Supplements containing soy or red clover had the highest concentrations of total isoflavones (728.2-35,417.0 ug/g) and total phytoestrogens (1030.1-35,517.7 ug/g) followed by licorice and licorice-containing supplements (41.3-363.3 ug/g isoflavones; 56.5-370.0 ug/g total phytoestrogens). Other supplements had considerably less isoflavones (</= 19.0 ug/g) and total phytoestrogens (</= 44.2 ug/g). Lignans were present in all (</= 298.9 ug/g), whereas coumestrol was either not present or present in only small amounts (</= 3.0 ug/g). Supplements differed in phytoestrogen profiles. The daily intake of isoflavones and lignans from some supplements may greatly exceed those from several servings of soy or vegetables. Hence, the intake of supplements should be taken into consideration in clinical or epidemiological studies for more accurate estimation of phytoestrogen intakes.