BackgroundPrevious data have suggested that genistein could exert beneficial effects on endothelial function and on predictors of cardiovascular risk in healthy postmenopausal women. In a randomized clinical trial, we studied the effects of genistein on endothelial function in postmenopausal women with metabolic syndrome (MS). MethodsTwenty postmenopausal women with MS, according to modified NCEP-ATP III criteria were randomly assigned to receive placebo or genistein (54mg/day) for 6months, along with a Mediterranean-style diet. Postmenopausal women without MS (n=15), served as controls. The primary goal was the assessment of endothelial function by flow-mediated vasodilation (FMD) of brachial artery; moreover, time-to-peak dilation in the FMD response has been evaluated. Secondary outcomes were fasting glucose, fasting insulin, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, visfatin, adiponectin and homocysteine blood levels. Data on adverse events were also recorded. ResultsAfter 6months of treatment, FMD at 50s and peak FMD significantly increased in genistein recipients compared with placebo. Moreover, genistein significantly decreased the blood levels of total cholesterol, triglycerides, homocysteine and visfatin compared with placebo, while blood adiponectin levels were increased. Genistein recipients neither experienced more side-adverse effects than placebo nor discontinued the study. ConclusionsSix months of treatment with genistein effectively improves brachial artery flow-mediated vasodilation in postmenopausal women with metabolic syndrome.