ABSTRACT
Abstract 302
Introduction 302
Dietary Sources of Phytoestrogens 302
Absorption and Metabolism 303
Estrogen Receptor Mediated Mechanisms of Action 305
Anti-Oxidant Activity 306
Cardiovascular Effects 308
Lipid Metabolism 308
Animal Studies 308
Clinical Studies 309
Blood Pressure 310
Inflammation and Cell Adhesion 313
Platelet Aggregation and Endothelium Reactivity 317
Conclusion 318
References 319
ABSTRACT
Experimental and epidemiological data are available to support the concept that
isoflavone-rich diets exert physiological effects in humans; however, to date most
research interest has focused on their potential hormonal activities. Dietary iso-
flavones are one of the major classes of phytoestrogens, and are currently receiv-
ing much attention because of their potential role in preventing coronary artery
and other chronic diseases. In the overall scheme of cardiovascular protection,
isoflavones appear to potentially have a more important role in conditioning
the vascular tree than on influencing cholesterol levels. The preferential
binding of isoflavones to the ERb and the increasing recognition of the role of this receptor in the endothelial wall provide justification for increasing the aware-
ness of the heart-health effects of diets rich in these phytoestrogens. Furthermore,
such effects are not restricted to soy isoflavones but also apply to lignans and
many other flavonoid sub-classes, which are abundant in cereals, pulses, fruits,
and vegetables. Potential anti-atherogenic effects of isoflavones include a
reduction in LDL cholesterol, modulation of pro-inflammatory cytokines, cell
adhesion proteins, and nitric oxide (NO) formation, protection of LDL against
oxidation, inhibition of platelet aggregation, and an improvement in vascular
reactivity. However, further molecular work is required to elucidate the exact
mechanisms by which isoflavones affect these processes and to define the phys-
iological relevance of these mechanisms relative to human exposure from these
compounds. Although epidemiological data and laboratory studies allude to the
possible protective effects of soy isoflavones at specific target tissues, random-
ized placebo controlled clinical trials are necessary to further address the relative
importance of these compounds for cardiovascular health.
