Recent studies of fat digestion and absorption.

HE MECHANISM WHEREBY water-insoluble fat can pass through the intestinal epithelium and into the blood has been a very intriguing as well as a most refractory problem. Obviously, the fat must either pass as particles or it must be solubilized, and various theories have been devised based on both possibilities. Most studies on the degree of hydrolysis of fat during digestion have been undertaken to obtain clues of the mechanism of the absorption of fat. If it could be demonstrated, for example, that fat is always completely hydrolyzed in the lumen of the intestine, it would be necessary to explain the absorption of fatty acid but not of glycerides. On the other hand, if it could be demonstrated that hydrolysis is not complete, then, ipso facto, glycerides must be absorbed and the mechanism of their absorption must be explained. Up to the advent of the use of isotopes as tracers, no experiment was designed which could demonstrate unequivocally whether or not hydrolysis is complete or whether glycerides are absorbed.