Effect of Various Oils and Fats on Serum Cholesterol in Experimental Hypercholesterolemic Rats

Abstract

A two-week curative assay in rats made hypercholesterolemic by a diet (Hauge and Nicolaysen, '59) containing 10% of hydrogenated coconut fat and 1% of cholesterol was used in a number of comparisons of the anticholesterolemic effect of various sources of polyunsaturated fatty acids. A synthetic arachidonic acid and the fatty acids from cod liver oil gave a distinct depressive effect on serum cholesterol. The unsaponifiable fraction of cod liver oil, in amounts corresponding to what gives nearly maximal serum cholesterol depression following administration of the whole cod liver oil, gave no depression. It is therefore concluded that the polyenoic fatty acids are largely responsible for the anticholesterolemic effect observed. The fatty acids did not give the full effect of the cod liver oil, however, it is possible, therefore that the medium in which the fatty acids are administered will also prove to be of influence. The cholesterol-depressive effect of marine oils such as cod liver oil and various fish body oils corresponded fairly well to their content of polyunsaturated fatty acids, chiefly of the penta- and hexaenoic type. Following a number of comparisons of marine oils and vegetable oils such as soybean oil and corn oil, it was calculated on the basis of the content of polyenoic fatty acids that the marine fatty acids had about 4 times the cholesterol-depressive effect of linoleic acid when given in their natural media. The fat of egg yolk, and the whole egg yolk were used in two experiments in which the type of fat was the one variable. The cholesterol-depressive effect corresponded fairly well to the content of polyenoic fatty acids, chiefly linoleic acid. This result does not support the view that egg yolk contains an unknown factor which will increase serum cholesterol. In a long-term prophylactic test with butter, three types of margarine of varied fat-base and with soybean oil in hydrogenated coconut fat, it was found that the serum cholesterol correlated well with the content of polyenoic fatty acids in the fats, irrespective of the variation in the type of fatty acids in the fat.