Randomized controlled trial of the effects of soy protein containing isoflavones on vascular function in postmenopausal women.
BACKGROUND
The incidence of cardiovascular disease increases after menopause, possibly because of the decline in estrogen. Soy protein, a rich source of estrogen-like isoflavones, is hypothesized to improve vascular function.


OBJECTIVE
The objective of this study was to investigate whether supplementation with soy protein, a rich source of estrogen-like isoflavones, improves vascular function.


METHODS
We performed a 12-mo double-blind randomized trial to compare the effects of soy protein containing 99 mg isoflavones/d (aglycone weights) with those of milk protein (placebo) on blood pressure and endothelial function in 202 postmenopausal women aged 60-75 y.


RESULTS
Changes in endothelial function during the intervention were not significantly different between the soy and the placebo groups. After the intervention, systolic blood pressure increased in the soy group significantly more than it did in the placebo group; the difference in change was 4.3 mm Hg (95% CI: 0.3, 8.4 mm Hg; P = 0.04) for systolic blood pressure, but only 2.0 mm Hg (95% CI: -0.74, 4.71 mm Hg; P = 0.15) for diastolic blood pressure. In the soy group only, systolic and diastolic blood pressure decreased and endothelial function improved in the equol producers, whereas systolic and diastolic blood pressure increased and endothelial function deteriorated in the equol nonproducers.


CONCLUSIONS
The results of this trial do not support the hypothesis that soy protein containing isoflavones have beneficial effects on vascular function in older postmenopausal women. Whether certain subgroups of women (eg, equol producers) do benefit from the intervention remains to be elucidated.
Kreijkamp-Kaspers
Sanne
S
The Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Netherlands.
Kok
Linda
L
Bots
Michiel L
ML
Grobbee
Diederick E
DE
Lampe
Johanna W
JW
van der Schouw
Yvonne T
YT
D000368:Aged; D001794:Blood Pressure / Q000187:drug effects*; D004032:Diet; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects*; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D008875:Middle Aged; D008894:Milk Proteins / Q000494:pharmacology*; D017698:Postmenopause; D030262:Soybean Proteins / Q000494:pharmacology*
D007529:Isoflavones; D008894:Milk Proteins; D030262:Soybean Proteins