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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
(Oral Abstracts)Soy and Heart Disease :
Hypocholesterolemic Effects of SoyRole of the Main Components of Whole Soybean Products, Soy Protein and Soy Oil, in Reducing Hypercholesterolemia
E.M. Kurowska1, J. Jordan1, J.D. Spence1, S. Wetmore1, L. Piche2, M. Radzikowski2 and K.K. Carroll1. 1University of Western Ontario, London, Ontario, N6A 5C1, Canada, 2Brescia College, London, Ontario N6G 1H2, Canada.Dietary substitution of soy protein for animal protein is known to be associated with a reduction of plasma total and LDL cholesterol levels, especially in individuals with hypercholesterolemia. It was hypothesized that this reduction would be greater if whole soybean products (containing both soy protein and soy oil) were substituted for animal products (containing animal protein and fat). To investigate this, the effect of whole soybean products vs. an animal product, milk, was studied in 34 hypercholesterolemic individuals (17 men, 17 women). Using a three-treatment three-period, cross-over design, the subjects received sequentially three types of beverages, each for a period of 4 weeks, with two 2-week washout periods: i) 2% cow's milk products, ii) a combination of skim milk products and soy oil, iii) whole soybean products containing soy protein and 2% soy oil. Daily intake of calories, protein, carbohydrates and total fat was unaffected by treatment as assessed by three-day food records. Also, treatment had no significant effect on fasting plasma total and LDL cholesterol, total apo B, apo A1 or triglycerides. However, the whole soybean treatment significantly increased HDL cholesterol (by 7%, P < 0.04) and reduced LDL/HDL cholesterol ratio (by 14%, p < 0.007). Similar, but less pronounced changes were observed after intake of skim milk/soy oil products but not after intake of 2% milk products. In 24 participants, called "responders," treatment with whole soybean products significantly reduced LDL cholesterol (by 11%, p < 0.05) and LDL/HDL cholesterol ratio (by 19%, p < 0.008). In this group, intake of skim milk/soy oil products induced a 12% reduction of LDL/HDL cholesterol ratio. The magnitude of observed beneficial changes in plasma lipoprotein profile depended on baseline characteristics of the subjects. Changes in LDL/HDL cholesterol ratio induced by the intake of soybean products were inversely related to the initial LDL/HDL cholesterol ratio (r = -0.56, p < 0.0007) and positively correlated with the initial HDL cholesterol concentrations (r = 0.52, p < 0.002). Similar correlation was observed in "responders" (which had also initial LDL cholesterol 15% higher and initial LDL/HDL cholesterol ratio 15% higher than the remaining subjects). In summary, our results demonstrated that 1) in individuals with moderate hypercholesterolemia, intake of whole soybean products can improve plasma lipid profile and the effect appears to be mostly but not entirely due to soy protein, 2) susceptibility to treatment with soybean products is greater in subjects with higher initial LDL and lower initial HDL cholesterol levels.
Supported by Alpro Natural Soyfoods, Wevelgem, Belgium.
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