Soy protein intake, cardiorenal indices, and C-reactive protein in type 2 diabetes with nephropathy: a longitudinal randomized clinical trial.

OBJECTIVE Several short-term trials on the effect of soy consumption on cardiovascular risks are available, but little evidence exists regarding the impact of long-term soy protein consumption among type 2 diabetic patients with nephropathy. To determine the effects of long-term soy consumption on cardiovascular risks, we measured C-reactive protein (CRP) and kidney function indexes among type 2 diabetic patients with nephropathy. RESEARCH DESIGN AND METHODS This longitudinal randomized clinical trial was conducted among 41 type 2 diabetic patients with nephropathy (18 men and 23 women). Twenty patients in the soy protein group consumed a diet containing 0.8 g protein/kg body weight (35% animal proteins, 35% textured soy protein, and 30% vegetable proteins) and 21 patients in the control group consumed a similar diet containing 70% animal proteins and 30% vegetable proteins for 4 years. RESULTS Soy protein consumption significantly affected cardiovascular risks such as fasting plasma glucose (mean change in the soy protein versus control groups: -18 +/- 3 vs. 11 +/- 2 mg/dl; P = 0.03), total cholesterol (-23 +/- 5 vs. 10 +/- 3 mg/dl; P = 0.01), LDL cholesterol (-20 +/- 5 vs. 6 +/- 2 mg/dl; P = 0.01), and serum triglyceride (-24 +/- 6 vs. -5 +/- 2 mg/dl; P = 0.01) concentrations. Serum CRP levels were significantly decreased by soy protein intake compared with those in the control group (1.31 +/- 0.6 vs. 0.33 +/- 0.1 mg/l; P = 0.02). Significant improvements were also seen in proteinuria (-0.15 +/- 0.03 vs. 0.02 +/- 0.01 g/day; P = 0.001) and urinary creatinine (-1.5 +/- 0.9 vs. 0.6 +/- 0.3 mg/dl, P = 0.01) by consumption of soy protein. CONCLUSIONS Longitudinal soy protein consumption significantly affected cardiovascular risk factors and kidney-related biomarkers among type 2 diabetic patients with nephropathy.