RESUMEN
Postmenopausal women with the metabolic syndrome are at a high risk of oxidative stress. Several studies have suggested possible antioxidant properties of soy, but little evidence is available regarding the effect of soy on oxidative stress in postmenopausal women with the metabolic syndrome. The aim of this study was to determine the effects of consumption of soy and soy protein on the plasma total antioxidant capacity [TAC] and malondialdehyde [MDA] levels in postmenopausal women with the metabolic syndrome. This randomized cross-over trial was conducted on 42 postmenopausal women with the metabolic syndrome as defined by ATP III. Participants were randomly assigned to consume a control diet, a soy-protein diet, or a roasted soy diet. Dietary Approaches to Stop Hypertension [DASH] was used in all three intervention periods. Red meat [1 serving/day] was substituted by soy protein or roasted soy in the respective diets. Each intervention period was 8 weeks and each wash-out period 4 weeks. Means of the variables were calculated by the repeated measures analysis of variance. There were significant differences among the control, soy-protein and roasted soy diets as regards the final MDA values [0.70, 0.64, and 0.63, micro mol/L, respectively; global P<0.01]. The final TAC values were also different among the 3 groups in the same order [1.95, 2.03, and 2.11 micro mol/ml, respectively; P<0.01]. As compared to the control values, the final TAC values for TAC increased by +4.5% on the roasted soy diet [p<0.01] and by +5.8% on the soy-protein regimen [p<0.01], while MDA levels decreased [7.9% in the roasted soy group; p<0.01, and 9.4% in the soy protein group; p<0.01]. Soy consumption reduced plasma MDA and increased plasma TAC levels in postmenopausal women with the metabolic syndrome