The effect of dietary soy intake on weight loss, glycaemic control, lipid profiles and biomarkers of inflammation and oxidative stress in women with polycystic ovary syndrome: a randomised clinical trial

Abstract Background The present study aimed to evaluate the effects of dietary soy intake on weight loss and metabolic status of patients with polycystic ovary syndrome (PCOS). Methods A randomised clinical trial was conducted among 60 women with PCOS. Participants were randomly assigned into two groups to receive either a test diet ( n = 30) or a control diet ( n = 30) for 8 weeks. Participants in the test group consumed a diet containing 0.8 g protein kg –1 body weight (35% animal proteins, 35% soy protein and 30% vegetable proteins) and participants in the control group consumed a similar diet containing 70% animal proteins and 30% vegetable proteins. Results Adherence to the test diet, compared with the control diet, resulted in significant decreases [mean (SD)] in body mass index (BMI) [−0.3 (0.6) versus +0.1 (0.5) kg m –2 , P = 0.02], fasting plasma glucose [−0.2 (0.5) versus +0.1 (0.3) mmol L −1 , P = 0.01], total testosterone [−0.3 (0.7) versus +0.3 (0.3) mmol L −1 , P < 0.001], insulin [−15.0 (18.0) versus +4.8 (18.6) pmol L −1 , P < 0.001] and insulin resistance [−0.6 (0.6) versus +0.2 (0.7), P < 0.001], as well as a significant increase in quantitative insulin sensitivity check index [+0.01 (0.01) versus −0.002 (0.02), P = 0.01]. In addition, significant decreases in triglycerides [−0.1 (0.4) versus +0.2 (0.3) mmol L −1 , P = 0.01] and malondialdehyde (MDA) [−1.2 (1.0) versus +0.2 (1.2) μmol L −1 , P < 0.001] and significant increases in nitric oxide (NO) [+13.6 (14.1) versus +0.9 (24.3) μmol L −1 , P = 0.01] and glutathione (GSH) [+170.1 (175.5) versus +24.2 (168.7) μmol L −1 , P = 0.002] were seen in the test group compared to the control. Conclusions Adherence to test diet among subjects with PCOS significantly decreased BMI, glycaemic control, total testosterone, triglycerides and MDA, and significantly increased NO and GSH compared to the control diet.