Digestion of Neutral Fats by Human Subjects 1

Abstract

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 triglyceride. This emulsion, containing triglycerides, 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 monoglyceride prior to absorption. Frazer and Sammons (4) noted that lipids isolated from the lumen 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 monoglycerides in the intestinal tract during the digestion 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 the recent work of Mattson, Benedict, Martin, and Beck (7) that 2-monoglycerides were shown to 1

Studies of Intestinal Digestion and Absorption in the Human1

“…The percentage of free fatty acids in the non-phospholipid fat recovered from the intestinal content ( Figure 5) is at all levels around 65 to 70 per cent. These figures are higher than those earlier reported for lipids recovered from intestinal contents from animals and humans fed non-emulsified fat in large quantities (38,39,44). It seems very probable that the finely emulsified fat fed in this investigation favors a more rapid hydrolysis.…”

Differences in Absorption of the Various Fatty Acids Studied in Children With Steatorrhea

“…Other studies have relied upon analysis of the fats in the intestinal contents after administration of natural fats (9,10) or labeled fatty acids (11). This method is limited because it shows fat absorption only at a given moment rather than the net absorption after a fat feeding.…”