Dietary isoflavones are considered to be cardioprotective due to their structural similarity to estrogen. Estrogen is believed to have beneficial effects on endothelial (blood vessel lining) function and may be one of the mechanisms by which premenopausal women are protected against cardiovascular disease.
Decreased nitric oxide production and endothelial nitric oxide synthase activity, and increased endothelin-1 concentrations, impaired lipoprotein metabolism and increased circulating inflammatory factors often result from estrogen deficiency. Endothelin-1 constricts/tightens blood vessels. Nitric oxide is a molecule produced by endothelial cells. Nitric oxide regulates blood pressure and blood flow and has anti-atherogenic factors.
Estrogen acts by binding to estrogen receptors alpha and beta. Isoflavones have been shown to bind with greater affinity to estrogen receptor beta. Estrogen receptor beta is expressed more in the vasculture (blood vessels) than estrogen receptor alpha.
Phytoestrogens are plant derived nonsteroidal compounds with structural similarity to estrogen. Phytoestrogens have ligands for the estrogen receptors ERa and ERb. A ligand is an ion, a molecule, or a molecular group that binds to another chemical entity to form a larger complex. Phytoestrogen possess weak estrogen like biological activity. As such, phytoestrogens help reduce some symptoms of diminished estrogen during late menopause.
Genistein and red clover are isoflavone phytoestrogens. However, soy and red clover contain different mixtures of isoflavones. For example, studies indicate the isolated isoflavones from red clover are cardioprotective because they reduce arterial stiffness and total vascular resistance.
Studies indicate that in addition to antioxidant activities, genistein also has anti-carcinogenic, anti-atherogenic and anti-osteoporotic activities. Legumes such as soy beans and chickpeas are the major dietary source of genistein.
Soybean and red clover are members of an isoflavone subgroup that includes daidzein, formononetin (daidzein precursor), genistein, and biochanin (genistein precursor).
Epidemiological studies indicate reduced cardiovascular risk in populations consuming high-isoflavone diets.
Source:
Arteriosclerosis, Thrombosis, and Vascular Biology. 2003;23:1066.
Isoflavones Reduce Arterial Stiffness
A Placebo-Controlled Study in Men and Postmenopausal Women
Helena J. Teede; Barry P. McGrath
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