DIGESTION OF NEUTRAL FATS BY HUMAN SUBJECTS 1

Several theories have been advanced to describe the digestion of fats in animals and in humans. Of these, two have been popular. The hydrolytic theory (1) suggests that triglycerides are broken down completely to fatty acids and glycerol which are then absorbed into the intestinal wall. The particulate theory (2) suggests that triglycerides are partially hydrolyzed in the intestinal lumen to monoglycerides, diglycerides, and fatty acids. The partial glycerides, fatty acids, and bile salts cause a fine emulsification of the remaining tri-glyceride. This emulsion, containing triglycer-ides, then enters the intestinal wall. Much indirect evidence exists for the formation of partial glycerides during fat digestion. Reiser, Bryson, Carr, and Kuiken (3) analyzed the lipids recovered from the thoracic ducts of rats fed tagged triglyceride and concluded that the major portion of ingested fat is hydrolyzed to mono-glyceride prior to absorption. Frazer and Sam-mons (4) noted that lipids isolated from the lu-men of the intestinal tract of rats had a high hydroxyl value and concluded that monoglyceride was present. Later Frazer (5) reported, without presenting experimental details, that he had found monoglycerides in the intestinal tracts of human subjects. The formation and presence of mono-glycerides in the intestinal tract during the di-gestion of fat has been reported in the dog (6), rat (3, 4, 7-9), cat (10), monkey (8), and man (5, 11). Theoretically the formation of two isomeric monoglycerides is possible when a triglyceride is digested to monoglyceride. It was not until th