Soy protein with isoflavones has favorable effects on endothelial function that are independent of lipid and antioxidant effects in healthy postmenopausal women.
BACKGROUND
Controversy exists about the ability of soy protein and isoflavones to modulate vascular reactivity and biochemical cardiovascular disease risk markers in healthy, normolipidemic postmenopausal women.


OBJECTIVE
The objective was to investigate whether the consumption of soy protein with isoflavones would result in improved vascular reactivity and decreased biochemical markers of endothelial dysfunction and inflammation, independent of enhanced lipid and antioxidant effects.


METHODS
Healthy postmenopausal women (n = 28) were enrolled in a randomized, double-blind, crossover study, and they consumed 25 g of 3 protein products/d for 6 wk each, with intervening washout periods. The products were isolated soy protein with isoflavones, ethanol-washed isolated soy protein with trace isoflavones, and total milk protein, which supplied 107, 2, and 0 mg total isoflavone (aglycone) units/d, respectively. We studied vascular function by using brachial artery reactivity values, plasma concentrations of vasoactive factors, endothelial inflammatory markers, and plasma isoflavone concentrations. The resistance of whole plasma and isolated LDL to copper-mediated oxidation was measured by conjugated diene formation.


RESULTS
Postocclusion peak flow velocity of the brachial artery was significantly (P = 0.03) lower after treatment with isolated soy protein with isoflavones, which is consistent with a vasodilatory response, than after treatment with total milk protein. Plasma isoflavones and metabolites were significantly (P < 0.01) higher after treatment with isolated soy protein with isoflavones. There were no significant changes in biochemical cardiovascular disease risk markers or conjugated diene formation between the 3 dietary groups.


CONCLUSIONS
Daily consumption of soy protein with isoflavones can result in positive vascular effects that are independent of lipid and antioxidant effects in healthy postmenopausal women.
Steinberg
Francene M
FM
Department of Nutrition, University of California, Davis, 95616, USA. fmsteinberg@ucdavis.edu
Guthrie
Nicole L
NL
Villablanca
Amparo C
AC
Kumar
Kavita
K
Murray
Michael J
MJ
D000975:Antioxidants; D015415:Biomarkers / Q000097:blood; D001783:Blood Flow Velocity / Q000187:drug effects; D001916:Brachial Artery / Q000502:physiology; D018592:Cross-Over Studies; D004032:Diet; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D006801:Humans; D007529:Isoflavones / Q000097:blood / Q000494:pharmacology*; D050356:Lipid Metabolism; D008055:Lipids / Q000097:blood; D008894:Milk Proteins / Q000494:pharmacology; D010084:Oxidation-Reduction; D017698:Postmenopause; D030262:Soybean Proteins / Q000494:pharmacology*
D000975:Antioxidants; D015415:Biomarkers; D007529:Isoflavones; D008055:Lipids; D008894:Milk Proteins; D030262:Soybean Proteins