Isoflavones, equol and cardiovascular disease: pharmacological and therapeutic insights

Isoflavones are an important class of phytoestrogens that are found at extrememly high levels in soy. Up until recently, daidzein and genistein were considered to be the most important and hence most studied isoflavones, however more recently attention has shifted to isoflavone metabolies. Equol represents the main active product of daidzein metabolism, produced via specific microflora in the gut. It has a longer half life and greater biological activity, including superior antioxidant activity. Yet, whilst the majority of animals produce equol following soy consumption, as much as 30-50 % of the adult human population cannot. This inability to produce equol in as much as half the population is thought to provide some explanation for the failure of soy to reveal any substantial health benefits in clinical studies. This article will comprehensively review literature investigating the potential cardiovascular benefits of daidzein and its metabolites, paying particular attention to equol. It will focus on the relative vasorelaxant activity, effects on nitric oxide synthase (NOS), antioxidant activity and potential for the treatment and prevention of hypertension and stroke. Findings obtained in both animal and human studies will be reviewed with the hope of gaining an insight into the experimental and clinical importance of equol to the cardiovascular benefits of soy.