Soy consumption, markers of inflammation, and endothelial function: a cross-over study in postmenopausal women with the metabolic syndrome

OBJECTIVE

To determine the effects of soy consumption on markers of inflammation and endothelial function in postmenopausal women with the metabolic syndrome.

RESEARCH DESIGN AND METHODS

This randomized cross-over clinical trial included 42 postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control diet (Dietary Approaches to Stop Hypertension [DASH]), soy protein diet, or soy nut diet, each for 8 weeks. Red meat in the DASH diet (one serving/day) was replaced by soy protein in the soy protein diet and by soy nut in the soy nut diet.

RESULTS

For nitric oxide levels, the difference from the control diet was 9.8% (P < 0.01) on the soy nut and -1.7% (P = 0.10) on the soy protein diets. The difference from the control diet for serum E-selectin was -11.4% (P < 0.01) on the soy nut consumption and -4.7% (P = 0.19) on the soy protein diet. Soy nut consumption reduced interleukin-18 compared with the control diet (difference from the control diet: -9.2%, P < 0.01), but soy protein did not (difference from the control diet: -4.6%, P = 0.14). For C-reactive protein, the difference from the control diet was -8.9% (P < 0.01) on the soy nut diet and -1.6% (P < 0.01) on the soy protein diet.

CONCLUSIONS

Short-term soy nut consumption reduced some markers of inflammation and increased plasma nitric oxide levels in postmenopausal women with the metabolic syndrome.