Effect of soy protein and isoflavones on blood pressure and endothelial cytokines: a 6-month randomized controlled trial among postmenopausal women.J Hypertens. 2013 Feb; 31(2):384-92.JH
Despite data from animal models and observational studies that are generally supportive for the soy/isoflavones lowering blood pressure (BP) and improving vascular function, the current findings from clinical trials are still inconclusive.
To examine whether soy protein with isoflavones or isoflavones alone reduce BP and endothelial cytokines, and whether the effects differed by baseline BP level.
A double-blind randomized, placebo-controlled trial was conducted among 180 postmenopausal Chinese women with mild hyperglycemia. Participants were randomly assigned to one of the three arms to receive either 15 g soy protein and 100 mg isoflavones (Soy group), or 15 g milk protein and 100 mg isoflavones (Iso group), or 15 g milk protein (placebo group) on a daily basis for 6 months.
No significant difference was observed in the change and %change of BP and endothelial cytokine levels among the three study groups. However, a subgroup analysis among 130 pre and hypertensive women suggested that soy protein and isoflavones significantly reduced SBP [-4.25%, 95% confidence interval (CI) -7.9 to -0.6%, P = 0.02] and the level of soluble intercellular adhesion molecule (sICAM)-1 (-22.6%, 95% CI -42.8 to -2.3%, P = 0.02) relative to milk protein after 6-month intervention.
: Our 6-month randomized controlled trial in prediabetic postmenopausal women indicated that soy protein and isoflavones had no significant effect on BP and endothelial molecules; however, a favorable reduction on SBP, sICAM-1 and E-selectin was observed among women with initial elevated BP.