The Effects of Soy Protein and Isoflavones on Lipid Oxidation and Blood Lipid Profile on Humans Participating in Moderate Physical Activity

The purpose of our study was to compare the effects of dietary soy protein and animal protein (casein) on plasma lipoprotein concentrations, and exercise induced oxidation in human subjects. Sixteen normocholesterolemic young men participated in 30 min of cycling at 70% VO2pk to induce plasma oxidation. Each subject then followed a 4wk dietary treatment replacing 33g animal protein in a self-selected solid food diet with either soy protein or casein. The exercise was then repeated and plasma lipoproteins and oxidation were compared. Soy protein and casein dietary treatments did not affect plasma concentrations. Our study therefore, suggests that in healthy normocholesterolemic individuals, 33g of soy protein does not effectively reduce plasma lipoprotein concentrations or exercise induced oxidation.