Soy Protein Supplementation Reduces Clinical Indices in Type 2 Diabetes and Metabolic Syndrome

Purpose: Clinical trials have studied the use of soy protein for treating type 2 diabetes (T2D) and metabolic syndrome (MS). The purpose of this study was to outline evidence on the effects of soy protein supplementation on clinical indices in T2D and MS subjects by performing a meta-analysis of randomized controlled trials (RCTs). Materials and Methods: We searched PubMed, EMBASE, and Cochrane databases up to March 2015 for RCTs. Pooled estimates and 95% confidence intervals (CIs) were calculated by the fixed-and-random-effects model. A total of eleven studies with eleven clinical variables met the inclusion criteria. Results: The meta-analysis showed that fasting plasma glucose (FPG) [weighted mean difference (WMD), -0.207; 95% CI, -0.374 to -0.040; p=0.015], fasting serum insulin (FSI) (WMD, -0.292; 95% CI, -0.496 to -0.088; p=0.005), homeostasis model of assessment for insulin resistance index (HOMA-IR) (WMD, -0.346; 95% CI, -0.570 to -0.123; p=0.002), diastolic blood pressure (DBP) (WMD, -0.230; 95% CI, -0.441 to -0.019; p=0.033), low-density lipoprotein cholesterol (LDL-C) (WMD, -0.304; 95% CI, -0.461 to -0.148; p= 0.000), total cholesterol (TC) (WMD, -0.386; 95% CI, -0.548 to -0.225; p= 0.000), and C-reactive protein (CRP) (WMD, -0.510; 95% CI, -0.722 to -0.299; p= 0.000) are significant reduced with soy protein supplementation, compared with a placebo control group, in T2D and MS patients. Furthermore, soy protein supplementation for longer duration (>= 6 mo) significantly reduced FPG, LDL-C, and CRP, while that for a shorter duration (< 6 mo) significantly reduced FSI and HOMA-IR. Conclusion: Soy protein supplementation could be beneficial for FPG, FSI, HOMA-IR, DBP, LDL-C, TC, and CRP control in plasma.