Flaxseed consumption influences endogenous hormone concentrations in postmenopausal women

Lignans, similar in structure to endogenous sex steroid hormones, may act i n vivo to alter hormone metabolism and subsequent cancer risk. The objectiv e of this study was to examine effects of dietary intake of a lignan-rich p lant food (flaxseed) on serum concentrations of endogenous hormones and bin ding proteins (estrone, estrone sulfate, 17 beta -estradiol, sex hormone-bi nding globulin, progesterone, prolactin, dehydroepiandrosterone sulfate, de hydroepiandrosterone, androstenedione, testosterone, and free testosterone) in postmenopausal women. This randomized, crossover trial consisted of thr ee seven-week feeding periods, during which 28 postmenopausal women, aged 5 2-82 yr, consumed their habitual diets plus 0, 5, or 10 g of ground flaxsee d Serum samples collected during the last week of each feeding period were analyzed for serum hormones using standard diagnostic kits. The flaxseed di ets significantly reduced serum concentrations of 17 beta -estradiol by 3.2 6 pg/ml (12.06 pmol/l) and estrone sulfate by 0.09 ng/ml (0.42 nmol/l) and increased prolactin by 1.92 mug/l (0.05 IU/ml), Serum concentrations of and rostenedione, estrone, sex hormone-binding globulin, progesterone, testoste rone, free testosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate were not altered with flaxseed feeding. In this group of postmenop ausal women, consuming flaxseed in addition to their habitual diets influen ced their endogenous hormone metabolism by decreasing serum 17 beta -estrad iol and estrone sulfate and increasing serum prolactin concentrations.