PROTEIN-ABSORPTION DEPENDS ON LOAD-DEPENDENT INHIBITION OF INTESTINALTRANSIT IN DOGS

Ileal perfusion of protein slows intestinal transit. Because optimal a bsorption of nutrients requires adequate time in contact with the muco sa, slowed intestinal transit may increase protein absorption by incre asing the residence time of nutrients in the small intestine. Although protein supplements are routinely added to enteral feeding to correct protein malnutrition, little information is available on the effect o f increasing the load of protein on intestinal transit and the efficie ncy of protein absorption. In six dogs equipped with duodenal and midi ntestinal fistulas, intestinal transit and the efficiency of protein a bsorption (percentage protein absorbed as estimated from the output of midintestinal fistula) were compared during intestinal perfusion with 0-, 50-, 100-, and 200-g/L solutions of a whey-based protein suppleme nt. We found that intestinal transit slowed in a load-dependent fashio n (P < 0.05); the amount of protein absorbed within the proximal one-h alf of the small intestine increased in a load-dependent fashion (P < 0.05) as intestinal transit slowed, and the percentage protein absorbe d (reflecting the efficiency of protein absorption) was maintained at a high and nearly constant value of 66.5-72.5% across protein loads of 9-36 g. We conclude that enhanced protein absorption is associated wi th a load-dependent inhibition of intestinal transit.