Effect of dietary-free glutamate on gastric emptying rate and postprandial sensation for protein-rich liquid diet.

Abstract

Free glutamate activates the taste receptors in the oral cavity and excites taste nerves to elicit a unique taste eumami. Recently the receptors sensitive to free glutamate were also found in the upper gastrointestinal (GI) tract. These reports suggest that glutamate acts as a modulator of gastric function. Therefore, we examined its effect on gastric emptying and the postprandial sensation for protein-rich meal in healthy volunteers. The base liquid meal (400 kcal/400 ml) consisted of 12.5% dextrin and 12.5% casein-calcium. To enrich free glutamate, monosodium L -glutamate (0.5% w/v) was supplemented. The following two studies comparing glutamate-enriched meal with control one were performed separately. Gastric emptying was measured by 13C breath test. The intensities of postprandial sensations were assessed at 15 min intervals for 4 h using a questionnaire with visual analogue scales (VAS). Glutamate significantly reduced gastric half-emptying time (153+34.6 /212.7+102.6 min, glutamate +/−, mean+S.D., n =10, p p =0.202) of the subjects older than 45 years old ( n =14). These data suggest that glutamate may affect the subject with declined GI function by aging.