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, doubleblind 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. (J Clin Endocrinol Metab 88: 5180 –5185, 2003)