Soya protein and athersclerosis

Abstract

Cholesterol-free, semipurified diets produce hypercholesterolemia and atherosclerosis in rabbits when casein is used as dietary protein, but not when the casein is replaced by soya protein. In general, animal proteins produce higher levels of plasma cholesterol in rabbits than plant proteins. At least part of this difference appears to be related to differences in the amino acid composition of the proteins. Rabbits fed soya protein had a faster turnover of plasma cholesterol, absorbed cholesterol from the intestine less readily, and excreted more fecal neutral sterols and bile acids than rabbits fed casein. Differences in composition and turnover of plasma lipoproteins were also observed. Some, but not all, studies on humans with either normal or elevated levels of plasma cholesterol have shown that these levels can be lowered by replacing animal protein in the diet by soya protein. Epidemiological data have also provided evidence of an association between coronary heart disease and amount of animal protein in the diet. Relatively small changes in the diet can substantially decrease the ratio of animal to plant protein, and this may offer a means of lowering serum cholesterol levels and decreasing the high incidence of coronary heart disease in industrialized countries. The use of soya protein for this purpose minimizes the risk of essential amino acid deficiency, because its amino acid composition tends to complement that of cereal proteins, which are the major source of plant protein in most human diets.