Soy protein diet significantly improves endothelial function and lipid parameters

Background: Replacement of animal protein with soy protein in the diet is a ssociated with decreased cholesterol levels. However, the effects of soy pr otein diet on endothelial function are not well known. Hypothesis: The aim of the study was to investigate the effects of soy prot ein diet on plasma lipids and endothelial function parameters assessed by t wo different methods. Methods: Twenty hypercholesterolemic, nonsmoker male patients (age 50.1 +/- 11.8 years), with a normal body mass index, were included. After calculati ng their daily requirements, a diet with 25-30% of energy from fats, 10-12% from proteins, and the rest from carbohydrates was instituted. Sixty perce nt of the animal source proteins of the diet were substituted by soy. The a nthropometric measures, lipid parameters, and endothelial functions of the subjects were assessed at baseline and 6 weeks after soy protein diet. Flow -mediated endothelium-dependent dilatation (EDD) and plasma thrombomodulin (TM) levels were evaluated as endothelial function parameters. Results: After diet, plasma total cholesterol, low-density lipoprotein chol esterol, apolipoprotein B, and triglyceride levels decreased significantly (p < 0.001, p < 0.001, p = 0.039, and p = 0.001, respectively). The mean pl asma TM levels were also significantly reduced with diet (p = 0.004). Studi es of the brachial artery indicated a borderline dilatation in baseline bra chial artery diameter (p = 0.05), however the diameter at reactive hyperemi a was significantly larger after diet (p < 0.001), resulting in a significa nt improvement of EDD (p = 0.002). Conclusion: Soy protein diet significantly improves plasma lipid profile in patients with hypercholesterolemia. Furthermore, the endothelial function, as judged by two different methods (EDD and plasma TM levels), also improv es with soy protein diet.