Effect of soy protein and isoflavones on fasting lipoprotein particle sizes
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The traditional lipid profile may underestimate the risk for cardiovascular disease. This underestimation may explain some of the discrepancies in results between studies analyzing the beneficial effects of soy. Therefore, our purpose was to quantify the number of lipoprotein particles, subclasses, and diameters/sizes using nuclear magnetic resonance (NMR) in 30 sedentary males, between 18 and 30 years of age, consuming one of the following three supplements for 28 days: milk protein (Milk), isoflavone-poor soy protein (Soy-) or isoflavone-rich soy protein (Soy+). Fasting EDTA blood samples were collected at baseline and after supplementation and analyzed for the number and size of VLDL, LDL, and HDL particles, respectively. In addition the concentrations of triglycerides (TG), VLDL triglycerides (VLDL-TG), and HDL cholesterol (HDL-C) were calculated from the data on the particles. Fasting heparin blood samples were collected at baseline and after supplementation and analyzed for apolipoproteins A-I, A-II, B, C-II, C-III and E. There were less small HDL particles (-21.4%), and more larger LDL (+1.9%) and HDL (+2.3%) particles after Soy+ supplementation compared with Soy- (+14.6%, -1.4%, and -1.1%, respectively) (P < 0.05). HDL-C, Apolipoproteins A-I and A-II increased after supplementation irrespective of the protein source. Results indicate that Soy+ reduces cardiovascular disease risk in normocholesterolemic, sedentary males by remodeling lipoproteins such that there are fewer small, dense particles that potentially may penetrate the endothelial lining of blood vessels. Protein supplements were donated by The Solae Company (St. Louis, MO).