Dietary soy containing phytoestrogens does not activate the hemostatic system in postmenopausal women.

The soybean is rich in isoflavone phytoestrogens, which are ligands for estrogen receptors, but it is unknown whether soy/phytoestrogens have similar procoagulant effects to estrogen. In this randomized double-blind trial, 40 healthy postmenopausal women of age 50-75 yr received soy protein isolate (40 g soy protein, 118 mg isoflavones) (n = 19) or casein placebo (n = 21). Plasma markers of coagulation, fibrinolysis, and endothelial dysfunction were measured at baseline and 3 months. The baseline characteristics of the two groups were similar. Compared with casein placebo, soy decreased triglycerides (P < 0.005) and low-density lipoprotein/high-density lipoprotein ratio (P < 0.001) and increased lipoprotein (a) (P < 0.05). Activity of coagulation factor VII (VIIc) decreased similarly in both groups (P < 0.005). Prothrombin fragments 1 + 2 (a marker of thrombin generation) decreased in the soy group (P < 0.005), but the change was not different from the casein group. There was no effect of soy on soluble fibrin (a marker of fibrin production), plasminogen activator inhibitor-1 (a marker of fibrinolytic inhibitory potential), D-dimer (a marker of fibrin turnover), or von Willebrand factor (a marker of endothelial damage). In conclusion, the results of the current study do not support biologically significant estrogenic effects of soy/phytoestrogens on coagulation, fibrinolysis, or endothelial function.

Dietary soy containing phytoestrogens does not have detectable estrogenic effects on hepatic protein synthesis in postmenopausal women.

BACKGROUND: Dietary phytoestrogens are ligands for the estrogen receptor and may mimic estrogenic effects in vivo. OBJECTIVE: To assess the biological activity of isoflavone phytoestrogens, we analyzed the effect of dietary soy isoflavone supplementation on in vivo bioassays of estrogenicity. DESIGN: Fifty healthy postmenopausal women aged 50-75 y participated in a double-blind, placebo-controlled trial in which they received either soy protein isolate (40 g soy protein, 118 mg isoflavones) or casein placebo. Measurements were made at baseline and at 3 mo. Urinary isoflavone excretion was measured to reflect compliance. The bioassays of estrogenicity included measurement of hepatic proteins and gonadotropin concentrations. RESULTS: Baseline characteristics were not significantly different between the soy and placebo groups. Urinary isoflavone excretion increased in the soy group and at the end of 3 mo was higher in the soy group than in the placebo group. In plasma samples from both groups, C-reactive protein increased significantly over the 3-mo treatment period, whereas sex hormone-binding globulin and thyroid-binding globulin decreased significantly. However, there were no significant differences between the groups in hepatic protein synthesis (change over 3 mo +/- SEM in the soy and placebo groups, respectively): C-reactive protein, 0.42 +/- 0.2 and 0.48 +/- 0.2 U/mL; sex hormone-binding globulin, -6.9 +/- 1.5 and -10.0 +/- 2.1 micro g/mL; thyroid-binding globulin, -16 +/- 8 and -26 +/- 7 nmol/L. Furthermore, gonadotropin and dehydroepiandrosterone sulfate concentrations did not change significantly in either group. CONCLUSIONS: In healthy postmenopausal women, dietary soy isoflavones do not affect in vivo biological indicators of estrogenicity, including hepatic protein synthesis and gonadotropin concentrations. This suggests that soy isoflavones have little biologically relevant estrogenic effect in vivo in postmenopausal women.

The lack of effect of isoflavones on high-density lipoprotein cholesterol concentrations in adolescent boys: a 6-week randomised trial.

BACKGROUND: A substantial fall in high-density lipoprotein cholesterol (HDL-C) during puberty in boys, but not girls, has been reported in Western populations. The fall in boys is believed to be due to hormonal changes--androgens have been shown to be associated with lower HDL-C, whereas oestrogens are associated with higher HDL-C. The fall in HDL-C during puberty was not observed, however, in a study of Moslem boys in Israel, nor in a group of Japanese boys. A diet high in phyto-oestrogens may account for the lack of a fall in HDL-C in these populations. OBJECTIVE: To examine the effect of dietary supplementation with phyto-oestrogens on the HDL-C concentration of adolescent boys from a Western population. We hypothesised that dietary supplementation of 50 mg of the isoflavones daidzein and genistein would produce a 12% higher HDL-C concentration than in controls at the end of a 6-week intervention period. DESIGN: A randomised controlled trial. SETTING: Hellyer College in Burnie (Tasmania, Australia). SUBJECTS: Adolescent boys (aged 16-18 years) were recruited through a letter sent to parents. A total of 132 eligible participants enrolled and five subjects withdrew from the trial. RESULTS: No significant increase in HDL-C was observed in the treatment group (-0.02 mmol l(-1), standard error (SE)=0.03, P = 0.53) or the placebo group (0.05 mmol l(-1), SE = 0.03, P = 0.11). CONCLUSIONS: Factors other than isolated dietary isoflavones may be responsible for the lack of fall in HDL-C during puberty in Japanese and Moslem boys.

Randomised, controlled, cross-over trial of soy protein with isoflavones on blood pressure and arterial function in hypertensive subjects.

OBJECTIVE: To examine the effects of dietary soy/isoflavones on 24 hr blood pressure profiles and arterial function [systemic arterial compliance (SAC), pulse wave velocity (PWV) and brachial arterial flow mediated vasodilation (FMD)] compared to non legume-based plant protein without isoflavones, in hypertensive subjects. DESIGN: In a 6 month double-blind, placebo controlled, cross-over trial, 41 hypertensive subjects (26 men, 15 postmenopausal women), 30-75 years, received soy cereal (40 g soy protein, 118 mg isoflavones) and gluten placebo cereal, each for 3 months. RESULTS: Thirty-eight subjects completed protocol with results expressed as mean or mean change (+/-SEM) with each intervention. Soy increased urinary isoflavones (daidzein: 8-fold; genistein: 8-fold; equol: 9-fold; ODMA: 18-fold) with no change during gluten placebo. There was no difference in the change in individual 24 hr ambulatory BP parameters (SBP: 2 +/- 2 vs -1 +/- 1 mmHg, p = 0.21; DBP: 1 +/- 1 vs -1 +/- 1 mmHg, p = 0.06) central BP (cSBP: -4 +/- 2 vs 0 +/- 2 mmHg, p = 0.2) or the change in arterial function (FMD: 0.3 +/- 0.5 vs -0.2 +/- 0.5%, p = NS; SAC: 0.02 +/- 0.02 vs -0.02 +/- 0.02 U/mmHg, p = NS; PWV central: -0.2 +/- 0.2 vs 0.0 +/- 0.2 m/sec, p = NS; PWV peripheral: 0.01 +/- 0.3 vs -0.4 +/- 0.4 m/sec, p = NS) noted between interventions. Analysis of the area under curve of 24 hr BP outputs demonstrated that soy protein compared to gluten protein resulted in higher 24 hr systolic BP by 2.3 mmHg (p = 0.003), a higher daytime systolic BP by 3.4 mmHg (p = 0.0002) and a higher daytime diastolic BP by 1.4 mmHg (p = 0.008). Overall 24 hr diastolic BP, night systolic BP and night diastolic BP were not significantly different between groups. Furthermore, soy protein compared to gluten protein resulted in higher 24 hr heart rates by 3.5 bpm (p < 0.0001). CONCLUSIONS: In hypertensive subjects, compared to gluten placebo, soy dietary supplementation containing isoflavones had no effect on arterial function, on average 24 hr ambulatory blood pressure parameters or central blood pressure in men and women with hypertension. Area under the curve of 24 hr profiles demonstrated that daytime BP was higher after soy compared to gluten.

Characteristics of soy bread users and their beliefs about soy products.

A two-stage random telephone/mail survey was conducted during the last quarter of 1998 among Adelaide residents to determine consumers' use of soy bread and other soy products and their health expectations of soy products. One in five (21%) of 1477 telephone subscribers usually consumed soy bread and related soy products. Comparisons of soy bread consumers and non-consumers, based on the mail survey sample, showed that more soy bread consumers used dietary supplements and ate low fat and vegetarian diets, though their experiences of ill health were similar. Soy bread consumers held stronger universalism (pro-nature) values than non-consumers. They also held more positive expectations about the benefits of soy consumption, including reductions in menstrual and menopausal symptoms, increased bowel regularity and reductions in the risk of heart disease and cancer. The findings are discussed in relation to the psychology of dietary supplementation, values orientations and physiological plausibility. Further investigations are suggested.

The effects of soy protein containing isoflavones on lipids and indices of bone resorption in postmenopausal women.

OBJECTIVE: To assess the effect of a dietary soy protein supplement containing isoflavones on lipids and indices of bone resorption in postmenopausal women. DESIGN: Placebo-controlled, double-blind, randomized study. PATIENTS: One hundred and six postmenopausal women were randomized to dietary soy supplementation (n = 51) or placebo (n = 55) for 3 months, of which 78 were included in the final analysis. MEASUREMENTS: Lipid profiles including total, low-density lipoprotein (LDL) and HDL cholesterol as well as triacylglycerol were measured. Pyridinoline and deoxypyridinoline were used as markers of bone resorption. Urinary isoflavone excretion was measured to assess compliance. RESULTS: There was a significantly greater increase in urinary isoflavone excretion detected in the soy group compared to placebo. Lipid profiles improved with significant decreases in LDL cholesterol (-0.60 +/- 0.10 vs.-0.29 +/- 0.09 mmol/l, P < 0.05), triacylglycerol (-0.22 +/- 0.07 vs. +0.01 +/- 0.05 mmol/l, P < 0.005) and the LDL : HDL ratio (-0.32 +/- 0.10 vs. +0.20 +/- 0.10, P < 0.005) in the soy group compared to placebo. There were no significant differences between the soy and placebo groups for urinary excretion of pyridinoline (-3.8 +/- 3.1 vs.-0.8 +/- 3.1 nmol/mmolCr, P = 0.4) or deoxypyridinoline (-0.8 +/- 0.9 vs.-0.3 +/- 0.7 nmol/mmolCr, P = 0.4). CONCLUSIONS: In postmenopausal women, dietary supplementation with soy protein containing isoflavones does not appear to have oestrogenic effects on markers of bone resorption. Soy protein favourably affected lipids; however, these effects (fall in triacylglycerol and no change in HDL) differ from those observed with oral oestrogen. These findings suggest that soy may not have biologically significant oestrogenic effects on bone resorption and we hypothesize that the lipid effects may be mediated, at least in part, through nonoestrogenic mechanisms.

Effects of a diet rich in phytoestrogens on prostate-specific antigen and sex hormones in men diagnosed with prostate cancer.

OBJECTIVES: To determine the effects of diets rich in soy and linseed compared with a control diet on biochemical markers of prostate cancer in men diagnosed with prostate cancer. METHODS: Twenty-nine men diagnosed with prostate cancer and scheduled to undergo a radical prostatectomy were randomized to one of three groups: soy (high phytoestrogen), soy and linseed (high phytoestrogen), or wheat (low phytoestrogen). A bread was specially manufactured to incorporate 50 g of heat-treated (HT) soy grits or 50 g of HT soy grits and 20 g of linseed as part of the study participant's daily diet. Baseline and preoperative levels of prostate-specific antigen (PSA), free PSA, testosterone, sex hormone-binding globulin, free androgen index, and dihydrotestosterone were measured. RESULTS: Statistically significant differences were detected between the HT soy grits group and the control wheat group for the percentage of change in total PSA (-12.7% versus 40%, P = 0.02) and the percentage of change in free/total PSA ratio (27.4% versus -15.6%, P = 0.01); and between the HT soy grits group and the HT soy grits and linseed group for the percentage of change in free androgen index (16.4% versus -15.5%, P = 0.04) and the percentage of change in free/total PSA ratio (27.4% versus -10%, P = 0.007). CONCLUSIONS: The data from this study indicate that a daily diet containing four slices of a bread rich in HT soy grits favorably influences the PSA level and the free/total PSA ratio in patients with prostate cancer. This work provides some evidence to support epidemiologic studies claiming that male populations who consume high phytoestrogen diets have a reduced risk of prostate cancer development and progression.