Effects of soy protein on endothelium-dependent vasodilatation and lipid profile in postmenopausal women with mild hypercholesterolemia.
BACKGROUND
Estrogens appear to improve endothelium-dependent systemic and coronary vasodilator function, perhaps by increasing nitric oxide levels and the subsequent effect of nitric oxide on endothelial function and smooth-muscle relaxation. Because soybean foods contain phytoestrogens, we evaluated the effect of orally administered soy proteins on vascular responsiveness.


METHODS
This double-blind, placebo-controlled crossover study involved 24 postmenopausal women (mean age 55 yr) who were hypercholesterolemic, who were not taking hormone replacement therapy and had not taken antioxidants or lipid-lowering agents in the preceding 2 months. The patients were randomized to receive a 25-g soy protein supplement or a mild protein placebo for 6 weeks, separated by a washout period of 4 weeks. To evaluate nitric oxide bioactivity we used ultrasonography to measure endothelium-dependent dilator responses in the brachial artery to hyperemia. We induced hyperemia by inflating a blood pressure cuff on the forearm to 250 mm Hg for 5 minutes. We also determined the effect of the supplements on various lipids.


RESULTS
The mean (+/- standard deviation) brachial artery diameter was similar in both groups (3.94 [0.79] mm in the placebo group and 4.13 [0.74] mm in the soy protein group). In both placebo and protein groups, the serum triglyceride levels increased, and total cholesterol and low-density lipoprotein cholesterol levels fell significantly (p < 0.05). High-density lipoprotein cholesterol levels were little changed.


CONCLUSIONS
Consumption of a supplement of 25 g of soy protein daily for 6 weeks had no measurable effect on arterial diameter or vasodilatation in response to hyperemia.
Blum
Arnon
A
Department of Internal Medicine A, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel. navablum@hotmail.com
Lang
Nesia
N
Vigder
Fiona
F
Israeli
Pnina
P
Gumanovsky
Marina
M
Lupovitz
Sacha
S
Elgazi
Andrea
A
Peleg
Aviva
A
Ben-Ami
Moshe
M
D002784:Cholesterol / Q000378:metabolism; D008078:Cholesterol, LDL / Q000378:metabolism; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000188:drug therapy; D050356:Lipid Metabolism; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D010919:Placebos; D017698:Postmenopause; D030262:Soybean Proteins / Q000494:pharmacology*; D013997:Time Factors; D014463:Ultrasonography
D008078:Cholesterol, LDL; D010919:Placebos; D030262:Soybean Proteins; D009569:Nitric Oxide; D002784:Cholesterol