Protein and Carbohydrate Effects in Atherosclerosis

Abstract

The longstanding emphasis on lipid effects in atherosclerosis and the recent interest in dietary fiber together account for the bulk of published work on diet and atherosclerosis. However, all components of the diet may affect lipid metabolism and atherosclerosis. The first studies relating diet to atherosclerosis were carried out by Ignatowski on the hypothesis that a toxic metabolite of animal protein was atherogenic. Subsequent studies have shown that casein (the most common example of animal protein) is more atherogenic than soy protein (the usual example of vegetable protein). Carroll has shown that different animal and plant proteins can have very different cholesterolemic effects. In general, cholesterol turnover is slower in rabbits fed casein. A 1 : 1 mixture of animal and vegetable protein is not more cholesterolemic or atherogenic than vegetable protein. Protein effects on cholesterolemia are also moderated by the type of fiber or carbohydrate in the diet. We have suggested that the ratio of lysine/arginine, which is high in animal protein and low in vegetable protein, may be a factor in determining the effects of protein. Other investigators have found other amino acids that may influence protein effects. It has also been suggested that casein may not be the proper model for animal protein.

Using semipurified, cholesterol-free diets, it has been shown that fructose and sucrose are more atherogenic for rabbits and sudanophilic for baboons than is glucose. Lactose is atherogenic for baboons only when the diet contains cholesterol. The small differences in serum cholesterol levels of baboons fed carbohydrates of different sudanophilic propensities suggest a role beyond effects on lipid metabolism, possibly an effect on aortic glycosaminoglycans.