OBJECTIVETo determine the effects of dietary soy containing phytoestrogens on blood pressure and lipids in healthy volunteers.

METHODSTwo hundred thirteen healthy volunteers (108 men and 105 post-menopausal women, 50 - 76 years old) received either soy protein isolate (40 g soy protein, 118 mg isoflavones) or cassin placebo for 3 months in this randomized, double-blind trial.

RESULTSThere were 34 withdrawals (16%) and 179 people (96 men and 83 women) completed the study protocol. After 3 months treatment, urinary phytoestrogens was significantly increased and blood pressure was significant reduced in soy protein group than that in cassin placebo group [mean change in systolic (-7.5 +/- 1.2) mm Hg vs. (-3.6 +/- 1.1) mm Hg, P < 0.05; diastolic: -4.3 +/- 0.8) mm Hg vs (-1.9 +/- 0.7) mm Hg, P < 0.05; mean aortic blood pressure: (-5.5 +/- 1.0) mm Hg vs (-0.9 +/- 1.0) mm Hg, P < 0.008]. Low- to high-density lipoprotein ratio [(-0.33 +/- 0.10) mmol/L vs (0.04 +/- 0.10) mmol/L, P < 0.05] and triglycerides [(-0.20 +/- 0.05) mmol/L vs (-0.01 +/- 0.05) mmol/L, P < 0.05] were significantly reduced and Lp(a) lipoprotein significantly increased [42 (17 - 67) mg/L vs 4 (22 - 31) mg/L, P < 0.05] in soy protein group compared to cassin placebo group. Total, low-density lipoprotein, and high-density lipoprotein cholesterols all improved in both groups and were similar between the groups. No side-effect was observed in both groups and no effect on the hypothalamic-pituitary-gonadal axis was noted in study subjects.

CONCLUSIONIn normotensive men and post-menopausal women, phytoestrogens intake improved blood pressure and lipids status.