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Previous observations from our laboratory have suggested that colonic filling from the ileum is characterised by a series of bolus movements. The present experiments were designed to test the hypothesis that bolus transit of ileal contents into the colon would not distinguish between solids and liquids. After a manometric infusion assembly was positioned by mouth into the ileum of 13 healthy volunteers, a mixture of nutrients (75 kcal), incorporating a solid phase radiolabel ("'In labelled resin pellets) and a liquid phase marker (99mTc-DTPA), was infused into the ileum. Transit of both labels from the ileum to colon was quantified scintigraphically and ileal motility was also recorded. When markers were infused into the proximal ileum, 100 cm proximal to the ileocolonic junction (six), there were clear cut examples of discriminant transit, when liquids moved more rapidly from the small to the large bowel than did solids. When isotopes were instilled into the distal ileum, less than 50 cm from the ileocolonic junction, no separate transit of the solid and liquid phases was observed. No specific motor pattern of the ileum was regularly associated with bolus filling of the colon. These results support the hypothesis that the distal ileum can discriminate between solids and liquids but that the ileocecal junction cannot.

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Olestra, the name proposed for the mixture of hexa-, hepta- and octaesters of sucrose and long-chain fatty acids, is a nondigestible, nonabsorbable lipid with physical properties and taste that are similar to those of natural triglycerides. Our aim was to determine whether substitution with up to 30 g of olestra in a 45-g fat meal would alter gastric, small bowel, and colonic transit. Five groups, each of six healthy volunteers, ingested 800-kcal, 22-g protein meals containing a total of 45 g of lipid (N = 24) or 15 g of lipid (N = 6). Among those receiving the 45-g fat meal, 0, 7.5, 15 and 30 g of lipid were substituted with olestra (N = 6 per group). The 15-g fat meal consisted entirely of natural triglyceride. A dual gamma camera scintigraphic method was used to estimate gastric and small bowel transit (99mTc pellets in the meal) and colonic transit (111In pellets). The latter was achieved by the delayed release of 111In pellets from a capsule coated with a pH-sensitive polymer, methacrylate, that disintegrated in the terminal ileum. There were no differences in the gastric, small bowel, or colonic transits of any of the five equicaloric meals. Some individuals had a significantly greater 48-hr stool weight after ingesting 15 g of olestra, but stool weights of subjects consuming 7.5 g or 30 g of olestra did not differ from controls. We conclude that substitution with olestra of up to 30 g in a 45-g fat meal does not significantly alter gastrointestinal transit in healthy subjects.