Effects of various dietary fats on serum cholesterol, liver lipids and tissue pathology in rabbits.

Rabbits fed on semi-synthetic diets without added cholesterol develop hypercholesterolaemia and a form of atherosclerosis when butter (Wigand, 1959 ; Funch, Krogh & Dam, 1960) or hydrogenated fat (Wigand, 1959) is the sole dietary fat, whereas dietary vegetable oils or fat mixtures having high contents of polyenoic fatty acids increase the serum cholesterol levels only slightly and do not produce atheromatous lesions. The experiment reported here was designed to study factors in butter that might be responsible for the observed hypercholesterolaemic and atherogenic effects in rabbits. Jt was supposed that the hypercholesterolaemic effect of butter might be related to its cholesterol content, its low content of unsaturated fatty acids or its high content of short-chain fatty acids or a combination of the last two factors. The effect of a small amount of dietary cholesterol on serum cholesterol and atherosclerosis in rabbits was studied by comparing the effects of butterfat with those of cocoa butter or of cocoa butter to which'cholesterol had been added in an amount equal to that found in butterfat. Cocoa butter was chosen because it is a natural fat similar to butterfat in iodine value and contents of saturated, oleic and total polyenoic fatty acids, the primary differences being the high contents of short-chain fatty acids and cholesterol in butterfat. The other dietary fats used in the experiment were butterfat supplemented with maize oil and two fats, fractionated cocoa butter and hydrogenated arachis oil, that contained almost no polyenoic fatty acids.