Interactions among dietary fat, protein, and cholesterol in atherosclerosis-susceptible pigeons. Effects on serum cholesterol and aortic atherosclerosis

In a 3x 2x 2 factorially designed experiment, White Carneau pigeons were kept nine months on diets containing three levels of protein (5 per cent, 15 per cent, and 30 per cent casein) and two types of dietary fat (10 per cent oil or 10 per cent hydrogenated coconut oil). Identical groups received, in addition, 0.25 per cent cholesterol. Analysis for serum cholesterol, and for cholesterol, total lipids, and phospholipids in the aorta, and measurements of atherosclerotic index were carried out. The data were subjected to statistical evaluation by analysis of variance. The addition of cholesterol to the diets elevated the level of cholesterol in the serum and the aorta and increased the severity of atherosclerosis. A significant interaction was found to exist between the type of fat in the diet and the presence or absence of cholesterol. Among cholesterol-fed birds only, corn oil exerted a significant cholesterol-lowering action. Suggestive evidence was obtained for the concept that the severity of atherosclerosis is influenced by the type of dietary fat, the level of protein, and the presence or absence of cholesterol in the diet, and that bio-logical interactions exist among these dietary variables.