GASTRIC PHYSIOLOGY AND FUNCTION - EFFECTS OF FRUIT JUICES

The stomach stores food and starts digesting protein and fat. Lipids, sugars, certain amino acids, and nutrients of high osmolality trigger sensory mechanisms from the intestine which inhibit gastric emptying. Food rich in carbohydrates leaves the stomach slower than protein-rich food, and emptying is slowest after a meal containing lipid. For carb ohydrate beverages, the gastric emptying rate is primarily determined by the volume, caloric content, and osmolality of fluid ingested. Gast ric emptying rates vary among isocaloric beverages of different type ( e.g., sucrose, fructose, galactose) or forms (e.g., maltodextrins, sta rches) of carbohydrate. For instance, gastric emptying is faster for a fructose solution compared with isocaloric glucose and galactose solu tions. A maltodextrin or a sucrose solution empties faster than a gluc ose solution. This is possibly due to the greater inhibitory feedback associated with the introduction of glucose in the duodenum. In additi on, fruit juices contain soluble fibers which further modulate the gas tric emptying. Noninvasive methods to study gastric emptying have rece ntly been developed. The pattern of the myoelectric activity of the ga stric contraction and the effect of meals on this pattern can now be r ecorded by cutaneous electrodes. In healthy children ingesting differe nt juices, the myoelectric pattern of the stomach (indicator of the ga stric emptying) correlates with the carbohydrate absorption (measured by breath hydrogen excretion). Fast gastric emptying was associated wi th greater production of breath hydrogen. The malabsorption of juice c arbohydrates may in part be related to their effect on gastric motilit y.