Effects of oral soy protein on markers of inflammation in postmenopausal women with mild hypercholesterolemia

Abstract Background Nitric oxide (NO) may protect arteries against atherosclerosis, as suggested by experimental studies. Estrogen therapy enhances the bioactivity of NO in the vasculature of healthy postmenopausal women, but is not acceptable for long-term use by many women. Observational studies have demonstrated beneficial cardiovascular effects of soy protein in premenopausal and postmenopausal women. We examined whether the consumption of isolated soy protein may improve markers of vascular inflammation in postmenopausal women with hypercholesterolemia. Methods and Results In a randomized, double-blind, placebo-controlled, crossover study, 24 postmenopausal women with hypercholesterolemia received 25 g of soy protein or a placebo daily for 6 weeks, with treatment periods separated by 1 month. Markers of vascular inflammation were measured by enzyme-linked immunosorbent assay methods, including: soluble interleukin-2 receptor (sIL-2r), E-selectin, P-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1). There was no effect of soy protein in comparison with placebo on the inflammatory markers: the sIL-2r level was 942.2 ± 335.3 pg/mL with soy protein and 868.5 ± 226.9 pg/mL with placebo ( P =.311); E-selectin was 39.6 ± 16.5 ng/mL with soy protein and 42.1 ± 17.6 ng/mL with placebo ( P =.323); P-selectin was 157.9 ± 67.9 ng/mL with soy protein and 157.5 ± 47.6 ng/mL with placebo, ( P =.977); ICAM-1 was 266.0 ± 81.3 ng/mL with soy protein and 252.5 ± 82.7 ng/mL with placebo ( P =.435); VCAM-1 was 402.7 ± 102.1 ng/mL with soy protein and 416.4 ± 114.8 ng/mL with placebo ( P =.53). Conclusions Consumption of 25 g of isolated soy protein daily for 6 weeks does not substantially affect markers of vascular inflammation in postmenopausal women with hypercholesterolemia. (Am Heart J 2003;145:e7.)