Beneficiary effect of dietary soy protein on lowering plasma levels of lipid and improving kidney function in type II diabetes with nephropathy

Objective: Heart and renal diseases are two major problems in diabetic patients. Hyperlipidemia is one of the main risk factors of cardiovascular complications in diabetes. The type of protein consumed also affects the changes in renal blood flow, glomerular resistance and renal function in these patients. Hence, this study was undertaken to show the effect of soy protein consumption on lipid profiles and kidney function of diabetic patients with nephropathy, who attended an educational university hospital as well as a private kidney disease clinic in Tehran. Subjects and methods: This crossover randomized clinical trial was conducted on 14 patients who were free of any uncontrolled condition or other renal diseases. The patients were asked to follow a usual nephropathy diet (0.8 g/kg protein, 70% animal and 30% vegetable protein) for 7 weeks. After a washout period of 4 weeks consuming the prestudy diet, subjects were readmitted to repeat the same cycle with a similar diet containing 35% soy protein and 30% vegetable protein. Paired t-test, carryover effect and period effect were used for statistical analysis. Result: There were 10 men and four women whose mean (s.d.) of weight was 70.6 (10.3) kg. Significant reductions were seen in total cholesterol (P<0.01), triglyceride (P<0.002) and LDL-c (P<0.04), urinary urea nitrogen and proteinuria (P<0.001) after soy vs animal protein consumption. There were no significant changes in HDL-c, LDL-c/HDL-c levels. We also saw a favorable effect on renal function. Conclusion: Soy inclusion in the diet can modify the risk factors of heart disease and improve kidney function in these patients.