OBSERVATIONS ON PROTEIN DIGESTION IN VIVO: II. DIETARY FACTORS AFFECTING THE RATE OF DISAPPEARANCE OF CASEIN FROM THE GASTROINTESTINAL TRACT

The effects of various dietary changes on the emptying of solids and nitrogen from the stomach and on the disappearance of nitrogen from the gastrointestinal tract of rats trained to consume a single meal daily are described. When the animals were fed 5 g of food the presence of casein in the diet caused a general deceleration of stomach-emptying and altered the shape of the stomach-emptying curve. The presence of 50% of casein in the diet did not result in an accumulation of nitrogen in the intestine much above the amount found when a protein-free diet was fed. When dextrin was the dietary carbohydrate the diet emptied from the stomach as a homogeneous mixture, whereas when sucrose was the dietary carbohydrate the casein emptied from the stomach more slowly than did the other components of the diet. Raising the dietary level of fat to 50% caused a general deceleration of emptying and abolished the above-mentioned carbohydrate effect. No delay in stomach-emptying due to the presence of casein in the diet was noted when only 1.5 g of diet was fed. As the level of food intake was raised the total quantity of nitrogen emptying from the stomach per unit time increased although a greater percentage of the amount ingested emptied from the stomach when the level of food intake was low.