Effect of genistein on endothelial function in postmenopausal women: a randomized, double-blind, controlled study

Genistein, a phytoestrogen found in soybeans, corrects endothelial dysfunction induced by oophorectomy in animals. Using a double-blind, controlled, randomized design, we evaluated its effects on endothelial function in women. We enrolled 79 healthy postmenopausal women (mean [± SD] age, 56 ± 4 years) and randomly assigned them to receive continuous estrogen/progestin therapy (n = 26; 17β-estradiol [1 mg/d] combined with norethisterone acetate [0.5 mg/d]), genistein (n = 27; 54 mg/d), or placebo (n = 26). Brachial artery flow–mediated, endothelium-dependent vasodilation and plasma levels of nitrites/nitrates (a marker of nitric oxide metabolism) and endothelin-1 were measured at baseline and after 1 year of therapy. Treatment with genistein increased levels of nitrites/nitrates (mean increase, 21 μmol/L; 95% confidence interval [CI]: 15 to 26 μmol/L; P