Inhibition of postmenopausal atherosclerosis progression: A comparison of the effects of conjugated equine estrogens and soy phytoestrogens

Experimental evidence was sought concerning whether soy phytoestrogens (SPE s) inhibit postmenopausal atherosclerosis progression/extent and, if so, th eir effectiveness relative to traditional estrogen replacement therapy. Pre menopausal cynomolgus monkeys were fed a moderately atherogenic diet (26 mo nths) to induce atherosclerosis. After ovariectomy, the moderately atheroge nic diet was continued, and they were treated (36 months) with a control di et (soy protein depleted of SPEs), a diet containing SPEs in soy protein is olate, or a diet containing SPE-depleted soy protein with conjugated equine estrogens (CEE; Premarin) added. SPE effects on plasma lipids were better than those of CEE (higher high density lipoprotein cholesterol and no incre ase in triglyceride). Relative to the control group, CEE treatment inhibite d (P = 0.0001), and SPE treatment partially inhibited (P = 0.10) the progre ssion of atherosclerosis (common iliac artery atherosclerosis before and af ter treatment). CEE-treated monkeys had much less coronary artery atheroscl erosis than the controls (P = 0.0002), whereas SPE-treated monkeys were int ermediate in lesion extent between the controls and the CEE-treated animals (P = 0.02). Both CEE and SPE significantly reduced the extent of common ca rotid and internal carotid artery atherosclerosis, and the two treatment gr oups were not significantly different.