Factors affecting the rate of gastric emptying in man
The major factors influencing the rate of gastric emptying are volume, energy density and osmolality, and these were studied in a series of experiments. The time course of gastric emptying has been systematically evaluated using a double sampling gastric aspiration technique. Results showed dilute (2&'37) glucose solutions to empty from the stomach at the same rate as water; increasing the glucose concentration to 4&'37 or above delayed the rate of gastric emptying in proporition to the carbohydrate content. Dilute (4&'37 or less) isoenergetic solutions of glucose, glucose polymer and rice powder are emptied at the same rate. A protein hydrolysate solution isoenergetic with a 7&'37 glucose solution was emptied at the same rate as the glucose solution. When concentrated (18.8&'37) isoenergetic solutions of glucose and glucose polymer solutions were compared, the glucose polymer solution was emptied faster than the isoenergetic glucose solution. Isosmotic solutions of glucose and glucose polymer, and of glucose and protein hydrolysate were also compared; the solutions which had the highest energy density were emptied at the slowest rate. It appears that for water and dilute (2&'37) glucose solutions, a rapid rate of emptying can be maintained when the volume in the stomach is maintained high. Concentrated carbohydrate solutions (8.4&'37 or above) result in such strong negative feedback mechanisms that the rate of emptying remains slow although the volume in the stomach is high. In conclusion, although there is an interaction between volume, energy density and osmolality in the regulation of the rate of gastric emptying, energy density is the factor having the greatest effect in regulating the rate of gastric emptying or carbohydrate-containing solutions in man.