Radiolabeled fiber: a physiologic marker for gastric emptying and intestinal transit of solids.

We report here a study of radiolabeled cellulose as a marker for gastric emptying and intestinal transit of fiber in a dog model. A chemically stable radioisotopic label (131I) was employed to facilitate external monitoring of the tracer. 131I-labeled fiber was found to be biologically stable, since no iodine was absorbed during passage through the canine digestive system. In comparison with water-soluble tracers, gastric emptying of [131I]fiber is very slow. This is consistent with the expected behavior of fiber as a nondigestible solid. We anticipate this new radiolabeled marker will prove to be a useful tool for studies on gastric emptying, intestinal transit, fate and actions of dietary fiber in nonruminant experimental animals and, eventually, in man.