Evidence of a lack of effect of a phytoestrogen regimen on the levels of C-reactive protein, E-selectin, and nitrate in postmenopausal women

Phytoestrogens are thought to be beneficial to vascular health. Possible mechanisms of action could involve C-reactive protein (CRP), endothelial E-selectin, and nitric oxide. We therefore designed a randomized, placebo-controlled, double-blind trial in which we studied the effects of isoflavonoids on CRP, E-selectin, and nitrate-nitrite (NOx; reflecting the release of nitric oxide) in postmenopausal women. Fifty-six postmenopausal women (FSH>30 U/liter) with a history of breast cancer used (in a randomized order) phytoestrogen (114 mg isoflavonoids) or placebo tablets daily for 3 months; the treatment regimens were crossed over after a 2-month washout period. The serum levels of CRP and E-selectin, and plasma levels of NOx were measured before and on the last day of each treatment. The phytoestrogen regimen did not affect the levels of either CRP (P=0.584) or NOx (P=0.270), but the levels of E-selectin were reduced by 4.0% (2.9 ng/ml; P=0.031) during phytoestrogen use and by 2.2% (1.3 ng/ml; P=0.023) during placebo use. No difference was found at any marker at 3 months between the groups. In conclusion, our data, suggesting neutral effects of phytoestrogens on CRP, E-selectin, and nitric oxide, fail to support a vasoprotective role of phytoestrogens.