Isoflavones improve vascular reactivity in post-menopausal women with hypercholesterolemia

Abstract

This randomized clinical trial was designed to assess the effects of dietary isoflavones on vascular reactivity, lipid levels, and markers of inflammation in post-menopausal women. Epidemiological studies have revealed that populations consuming large amounts of soy protein have lower cardiovascular morbidity and mortality. The benefits of soy protein may be due to its hypolipidemic effects; its anti-oxidant properties; its high content of L-arginine; and/or or its phytoestrogen content. Two putative mediators of the effects of soy protein are the isoflavones genistein and daidzein. Forty post-menopausal, hypercholesterolemic women who did not take estrogen replacement therapy were recruited for this study of isoflavone supplementation. Baseline flow-mediated vasodilation and response to nitroglycerin were measured, along with urinary isoflavone and nitrite/nitrate levels and serum lipids. After 6 weeks of 90 mg of isoflavones daily versus placebo, women receiving isoflavones demonstrated improved responsiveness to nitroglycerin, an assessment of endothelium-independent vasodilation, with an effect size (percentage points change from baseline) of 7.2 +/- 1.9 versus 1.2 +/- 1.3; p = 0.01. There was a trend towards improvement of flow-mediated vasodilation, which is an endothelium-dependent response (effect size: 3.4 +/- 2.0% versus -0.6 +/- 1.7%; p = 0.12). Lipid levels were unchanged after isoflavone treatment. In conclusion, dietary isoflavones may have cardiovascular benefit in the form of improved vascular reactivity, but not by lowering cholesterol, for women who do not take estrogen replacement therapy.

Identification of urinary isoflavone excretion phenotypes related to the cholesterol lowering ability of soy protein in Golden Syrian hamsters

“…Also, a previous study found a tendency toward a decline in endothelium-dependent vasodilatory function of coronary arteries in male monkeys fed isoflavone-replete soy protein for 6 mo compared with monkeys fed isoflavone-deficient soy protein (Honoré et al 1997). In contrast with the above studies, Lissin et al (2004) reported these findings conflict with those from studies of women and female monkeys, in which isoflavone-containing soy supplements seemed to improve vascular reactivity.…”

Soybean Products Consumption in the Prevention of Cardiovascular Diseases

“…Regarding endothelial function, it has been reported that the consumption of soy isolated protein improved the flow-induced dilatation in postmenopausal women (Cuevas et al 2003;Hall et al 2008), independently of changes in the lipid profile. This effect has been also observed using soybean isoflavones (Colacurci et al 2005;Lissin et al 2004). The mechanisms of action by which soybean products may improve endothelial function include effects on the production of nitric oxide, a key regulator of the cardiovascular function.…”

El Consumo De Frutas Y Hortalizas Ayuda a Prevenir El Daño Endotelial

“…Se ha descrito que el consumo de isoflavonas de la soya mejora la vasodilatación inducida por flujo en mujeres menopáusicas (140,141). Los mecanismos por los cuales los flavonoides de la soya mejoran la función endotelial también incluyen la producción de NO.…”