Evaluation of the health benefits of soy protein consumption in patients carrying the metabolic syndrome

Introduction: Circulating lipids are a modifiable risk factor for cardiovascular disease (CVD) and their improvement results in CVD risk prevention. Drug treatment is widely used in selected high-CVD risk patients, although dietary management of hyperlipidemias remains the main approach to reduce cholesterolemia and CVD risk. The use of vegetable proteins, namely soy proteins, offered positive results, providing a rationale for their use in the dietary management of individuals with borderline-high total and LDL-cholesterol and at risk of CVD. Aim: To evaluate the effect of a daily intake of 30 g soy protein on lipid parameters, visceral adipose accumulation, and adipokine levels. Study design: Randomized, parallel, single-centre study, intervention duration: 12 weeks. Patients: Sixty-six (32 M/34 F) patients with mild metabolic syndrome (3/5 NCEP-ATPIII criteria) were randomly allocated to either control diet (hypolipidic diet containing protein from animal sources; N=28; 15 M/13 F) or to soy diet (hypolipidic diet containing 30 g/day soy protein; N=36; 17 M/19 F). Results: Dietary soy intervention, compared to control diet, resulted in a significant reduction of total cholesterol (-6.7%, p=0.001), LDL-C (-6.7%, p=0.013) and apoB (-13.5%, p=0.002) levels. Total HDL-C and their subclasses did not change. Compared to control group, patients at soy showed significantly decreased body weight (-2.1%, p=0.015) and BMI (-2.2%, p=0.019). Waist circumference was reduced in both arms. Plasma leptin was reduced by -18.2% (p=0.03) in the soy group, vs. controls, but adiponectin was not affected in either arm, leading to a significant decrease of the leptin:adiponectin ratio only in patients at soy. A same trend was shown for insulin (-4.9%, p=0.05), HOMA-IR (-11,6%, p=0.03) and sICAM-1 (-5.3%, p=0.007). Conclusion: The results of the present study highlight the substantial safety and elevated compliance of this intervention, which resulted in a significant improvement of a series of biomarkers associated to primary CVD risk.