Effect of isoflavone supplement on endothelial function: does efficacy vary with atherosclerotic burden?

Endothelial dysfunction is widely considered as a prognostic marker of future cardiovascular events in clinical settings, even in patients who do not have untoward symptoms of cardiovascular disease.1 Thus, treatments aimed at restoring endothelial dysfunction have important implications Many studies have demonstrated that supplementary treatments can improve endothelial function.2 These favourable effects may be due to improved abnormal nitric oxide metabolism, mediated by mechanisms such as antioxidant or anti-inflammatory effects. Isoflavones are contained in soy and are mainly phyto-oestrogens, which are chemically similar in structure to physiological oestrogens. It has been demonstrated that isoflavones can lower blood pressure and serum lipid levels, as well as function as antioxidant and anti-inflammatory agents in both laboratory and clinical settings.3 It is therefore apparent that treatment with isoflavones could ameliorate endothelial dysfunction. However, the effect of isoflavone supplements on endothelial function remains controversial.4–15 The results of several studies regarding the effect of isoflavone supplementation on endothelial function, as determined by assessing brachial flow-mediated dilatation (FMD), are summarized in Table 1 . Because of the oestrogen-like nature of isoflavones, the subjects in many of these studies were menopausal women. It has been demonstrated that endothelial … *Corresponding author. Tel: +81 82 257 5540, Fax: +81 82 257 5554, Email: hteraga{at}hiroshima-u.ac.jp