FIBER-SUPPLEMENTED ENTERAL FORMULA SLOWS INTESTINAL TRANSIT BY INTENSIFYING INHIBITORY FEEDBACK FROM THE DISTAL GUT

Because an increase in flow rate accelerates intestinal transit, a red uction in the flow rate of formula delivery is recommended frequently for treatment of diarrhea that develops during enteral feeding. Becaus e intestinal transit is slowed by nutrient-triggered inhibitory feedba ck, the rate of intestinal transit during enteral feeding may depend o n a balance between the accelerating effect of flow and the inhibiting effect of the nutrient load. The addition of fiber to a formula may a lter this balance. By delaying absorption of nutrients, fiber may exte nd the length of small intestine exposed to nutrients and thereby trig ger more intense inhibitory feedback. To determine whether the additio n of fiber favors nutrient-triggered inhibition over flow-driven accel eration, we studied intestinal transit after perfusion of a low-residu e enteral formula compared with a fiber-supplemented formula at two pe rfusion rates (50 or 100 mL/h for 2 h) into the duodenum of dogs each with both a duodenal and midgut fistula. With the low-residue formula, intestinal transit accelerated when the flow rate increased from 50 t o 100 mL/h (P < 0.05). With the fiber-supplemented formula, however, i ntestinal transit was inhibited regardless of the flow rate. To determ ine whether the fiber-supplemented formula inhibited intestinal transi t by displacing nutrients distally, we compared intestinal transit whe n the two formulas, delivered at 100 mL/h, were diverted completely at the midgut fistula. Intestinal transit of the fiber-supplemented form ula increased by 400%, eliminating the difference in intestinal transi t speed between the two formulas. We concluded that the fiber-suppleme nted formula slowed intestinal transit by intensifying inhibitory feed back from the distal gut.