Apparent nutrient absorption and upper gastrointestinal transit with fiber-containing enteral feedings

Upper gastrointestinal tract function in humans was investigated by studying the acute effects of supplementing enteral feedings with dietary fiber. Serum concentrations of folate, zinc, and glucose were determined at timed intervals for 4 h after ingestion of nutritionally complete liquid meals containing test doses of folate and Zn of two and six times the RDA, respectively, with or without addition of 10 or 15 g of soy polysaccharide fiber. Mouth-to-cecum transit time was determined by measuring breath hydrogen produced from lactulose added to the meals. Both levels of fiber significantly lengthened transit time. Serum folate concentrations were significantly lower from 45 to 150 min after one or both fiber-containing meals relative to the fiber-free meal. Only the higher-fiber meal significantly lowered serum Zn concentrations. This study demonstrated that dietary fiber can decrease apparent nutrient absorption and increase transit time in the upper gastrointestinal tract without affecting apparent glucose absorption.