Vital Need of the Body for Certain Unsaturated Fatty Acids I. Experiments with Fat-free Diets in Which Sucrose Furnishes the Sole Source of Energy* by Herbert M. Evans

Until recently, the chief physiological role assigned to dietary fats has been that which considered them merely as fuel for the expenditure of energy. In fact, the idea has prevailed that so long as the demands for the fat-soluble and other vitamins were satisfied, animals could dispense with fats entirely’ (l-3). When, in 1927, Evans and Burr (4) attempting further purity of synthetic diets, employed sucrose as the sole source of energy, the foundations were laid for the recognition of two phenomena, both of which deal with the role of fats in the physiological economy of the rat. One of these phenomena deals with a peculiar relationship of fats to vitamin B which they spare; that is, in the presence of fats, less vitamin B is required than in their absence. This was reported by Evans and Lepkovsky (5) in 1928. The other phenomenon deals with the impossibility of normal growth or physiological well being in rats on diets adequate in all known respects, but rendered rigidly fat-free. This was reported simultaneously in 1929 by Burr and Burr (6) and McAmis, Anderson, and Mendel (7). The deficiency of rats on fat-free diets is characterized by impairment of growth after an initial growth had been accomplished, dermatitis which results in scaliness of the skin and tail,