Studies of gastrointestinal interactions. VII. Characteristics of the absorption pattern of sugar, fat and protein from composite meals in man. A quantitative study.

The absorption of sugar, fat, and protein after feeding two meals, differing in their content of glucose, was investigated in 7 healthy subjects, in double experiments with the multiple indicator dilution method. An average of 75% of the emptied amounts of sugar and 80% of the emptied fat and protein was absorbed during transit of the proximal 70 cm of the intestine. Differences in the absorption pattern between the meals were recorded, resulting from their different intragastric behaviour and gastric emptying pattern. Within the first hour significantly higher amounts of fat and protein were absorbed after the glucose-free than after the glucose-containing meal, whereas from the latter most of the glucose was absorbed early after ingestion. The absorptive capacity of the investigated segment was not exceeded for any component of the meals, owing to compensatory mechanisms by which the gastric emptying rate was inhibited and the transit time through the segment prolonged. The efficiency of sugar absorption was related to the transit time through the segment, in that a constant fraction was eliminated from the intestinal lumen per minute increase of the mean transit time. The net endogenous contribution of protein and fat at the exit of the segment amounted to an average of 3.0 g protein and 1.2 g fat during 3 hours.