DIETARY INTERVENTION STUDY TO ASSESS ESTROGENICITY OF DIETARY SOY AMONG POSTMENOPAUSAL WOMEN

We tested the hypothesis that postmenopausal women on a soy-supplement ed diet show estrogenic responses. Ninety-seven postmenopausal women w ere randomized to either a group that was provided with soy foods for 4 weeks or a control group that was instructed to eat as usual. Change s in urinary isoflavone concentrations served as a measure of complian ce and phytoestrogen dose. Changes in serum FSH, LH, sex hormone bindi ng globulin, and vaginal cytology were measured to assess estrogenic r esponse. The percentage of vaginal superficial cells (indicative of es trogenicity) increased for 19% of those eating the diet compared with 8% of controls (P = 0.06 when tested by ordinal logistic regression). FSH and LH did not decrease significantly with dietary supplementation as hypothesized, nor did sex hormone binding globulin increase. Littl e change occurred in endogenous estradiol concentration or body weight during the diet. Women with large increases in urinary isoflavone con centrations were not more likely to show estrogenic responses than wer e women with more modest increases. On the basis of published estimate s of phytoestrogen potency, a 4-week, soy-supplemented diet was expect ed to have estrogenic effects on the liver and pituitary in postmenopa usal women, but estrogenic effects were not seen. At most, there was a small estrogenic effect on vaginal cytology.