Effects of feeding 4 levels of soy protein for 3 and 6 wk on blood lipids and apolipoproteins in moderately hypercholesterolemic men

Background: Replacing animal protein with soy protein has been shown to red uce total and LDL-cholesterol concentrations in humans. However, the minimu m amount of soy protein required for significant reduction of blood lipids is not known. Objective: We evaluated the amount of soy protein needed to reduce blood li pids in moderately hypercholesterolemic men. Design: Eighty-one men with moderate hypercholesterolemia (total cholestero l concentration between 5.70 and 7.70 mmol/L) were studied. After a 3-wk le ad-in on a Step I diet, total cholesterol was measured and subjects were ra ndomly divided into 5 groups. For 6 wk, each group received 50 g protein/d, which included isolated soy protein (ISP) and casein, respectively, in the following amounts: 50:0, 40:10, 30:20, 20:30, and 0:50 (control group) g. Blood was collected at baseline and weeks 3 and 6 of the intervention. Results: At week 6, significant reductions (P < 0.05) from baseline compare d with the control group were found for non-HDL and total cholesterol and a polipoprotein (apo) B for all ISP groups (except total cholesterol with 40 g ISP). At week 3, significant reductions (P < 0.05) were found in apo B fo r the groups that consumed greater than or equal to 30 g ISP and in non-HDL cholesterol for the groups that consumed greater than or equal to 40 g ISP . HDL-cholesterol, apo A-I, lipoprotein(a), and triacylglycerol concentrati ons were not significantly affected by dietary treatment. Conclusion: Our findings show that consuming as little as 20 g soy protein/ d instead of animal protein for 6 wk reduces concentrations of non-HDL chol esterol and apo B by approximate to 2.6% and 2.2%, respectively.