Physical properties of starch meals in vivo and in vitro and their influence on gastric emptying and oral glucose tolerance test.

In study A, consisting of four groups of six subjects each, we measured the differences in pH, viscosity, and osmolality of in vivo and in vitro samples of steamed rice, congee, and 16.6 and 5% glucose solutions in 300-ml volumes. The physical properties of starch meals in vivo are different from in vitro samples, which may account for discrepancies among previous studies of glucose tolerance and gastric emptying. In study B, test meals of 300 ml of steamed rice, congee, 16.6% glucose, 5% glucose or a combined congee-metoclopramide meal (in which 10 mg metoclopramide i.v. was given 15 min before the congee was eaten) were given to seven subjects. Blood samples were taken, and the serum glucose and insulin responses were determined. The meals were labeled with 99mTc pentetic acid microcapsules, and the gastric emptying rates were calculated. Metoclopramide increased the gastric emptying of congee to that approaching steamed rice. The incremental glucose response to steamed rice was greater than that to congee, but the incremental insulin response was greatest with congee plus metoclopramide. The physical form of the food influences the blood glucose and insulin response and the rate of gastric emptying. The gastric emptying rate may be the major mechanism for the increased insulin response.