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.


METHODS
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.
Teede
Helena J
HJ
Jean Hailes Research Group, Monash Institute of Health Services Research, Monash Medical Centre, Melbourne, Australia. helena.teede@med.monash.edu.au
Giannopoulos
Dimitra
D
Dalais
Fabien S
FS
Hodgson
Jonathan
J
McGrath
Barry P
BP
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001794:Blood Pressure / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005983:Glutens / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D007529:Isoflavones / Q000009:adverse effects* / Q000494:pharmacology* / Q000652:urine; D008297:Male; D008875:Middle Aged; D030262:Soybean Proteins / Q000737:chemistry*; D017211:Treatment Failure
D007529:Isoflavones; D030262:Soybean Proteins; D005983:Glutens