Dietary intervention study to assess estrogenicity of dietary soy among postmenopausal women.

Abstract

We tested the hypothesis that postmenopausal women on a soy-supplemented diet show estrogenic responses. Ninety-seven postmenopausal women were 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. Changes in urinary isoflavone concentrations served as a measure of compliance and phytoestrogen dose. Changes in serum FSH, LH, sex hormone binding globulin, and vaginal cytology were measured to assess estrogenic response. The percentage of vaginal superficial cells (indicative of estrogenicity) 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. Little change occurred in endogenous estradiol concentration or body weight during the diet. Women with large increases in urinary isoflavone concentrations were not more likely to show estrogenic responses than were women with more modest increases. On the basis of published estimates of phytoestrogen potency, a 4-week, soy-supplemented diet was expected to have estrogenic effects on the liver and pituitary in postmenopausal women, but estrogenic effects were not seen. At most, there was a small estrogenic effect on vaginal cytology.

Effect of a phytoestrogen food supplement on reproductive health in normal males

“…A soy supplement suppressed mid-cyle peaks of LH and FSH, increased plasma oestradiol levels and had a stimulatory effect on breast tissue, as assessed by an elevated number of proliferating epithelial cells and appearance of hyperplastic epithelial cells and an increased number of progesterone receptors [16,17,30]. This endocrine disruption was not observed in postmenopausal women [16,31], suggesting that phytoestrogen actions are determined, in part, by the concentrations of endogenous oestrogens.…”

Biosynthesis and genetic engineering of proanthocyanidins and (iso)flavonoids

“…Inverse correlations have been reported between the intake of isoflavones and the incidence of breast and prostate cancers (Lee et al 1991;Denis et al 1999). Isoflavones can also relieve the symptoms of other hormone-related illnesses, such as osteoporosis and post-menopausal ailments (Baird and Umbach 1995;Potter et al 1998). Although flavonoid phytoestrogens have been less studied than the isoflavonoid phytoestrogens, 8-prenylnaringenin isolated from hop extract bound to ER more tightly and was shown to have higher estrogenic activity than the isoflavonoids genistein or coumestrol (Kitaoka et al 1998;Milligan et al 1999Milligan et al , 2000Milligan et al , 2002.…”

Soy proteins and cardiovascular disease

“…This hypothesis was supported by a clinical study in healthy women [39], but not in a similar study on postmenopausal women [40], and data on the possible use of soy isoflavones for relieving menstrual symptoms have been mostly negative. Isoflavones, present in varying amounts in soy preparations, have highly variable absorption (in some individuals close to nothing) that are highly dependent on the gut microflora [41].…”