Diet and the Blood Lipids.

Abstract

The lipids, cholesterol and its fatty acid esters, phospholipids and fat are always found in the blood of animals. In the corpuscles, the content of cholesterol and phospholipid is about the same for all animals, in the plasma the content of these substances is variable, being in general much higher in the plasma of carnivora than in that of herbivora. It was at first thought that the plasma content of lipids was fairly constant and characteristic for each species and that it was possible to speak of normal levels and normal variations from these levels. Evidence is, however, accumulating which goes to show that these conceptions will have to be modified since there are often wide variations in individuals of the same species under similar conditions and still greater variations when the conditions are different. The greatest single factor influencing the level of the blood lipids appears to be diet and in particular the amount of fat which the food contains. Attention was called to this factor by results obtained by Glusker in this laboratory with dogs on a diet containing very little fat. Values for phospholipid were obtained far below any previously found in this laboratory or reported in the literature. Cholesterol values were also low but as markedly so as those of the phospholipids. The present report has to do with further feeding experiments on 4 of these dogs and on 4 rabbits. The dogs were alternated between the dog biscuit diet which contained 2.56% fat, 17.91% protein and 61.8% carbohydrates and a diet containing the same biscuit but with about 1/3 the caloric value replaced by lard. Variations of from about 140 mgm. % on the low fat to 190 mgm. % for phospholipid on the high fat diet and from about 65 mgm. % to 90 mgm. % for cholesterol were obtained.