Effects of liquid formula diets on proximal gastrointestinal function.

Upper gastrointestinal function in response to liquid test meals of varying osmolality (337, 519, and 696 mosmol/kg) was studied in volunteers. The osmolality was varied by changing the carbohydrate component from a glucose polymer (Polycose) to sucrose. During the first hour, the least hypertonic meal was emptied most rapidly, leading to the highest rate of nutrient delivery to the duodenum. Most carbohydrate was hydrolyzed and absorbed (65-82%) in the duodenum. Higher flow rate and carbohydrate load at the ligament of Treitz soon after administering the Polycose meal had to be compensated by increased water and monosaccharide absorption in the first 30 cm of jejunum. Thus, at a point 30 cm into the jejunum, there were no significant differences in the flow and composition of chyme; all but about 10% of the carbohydrate load was absorbed; and the flow rate was no higher than after an ordinary meal.