Small bowel transit time of food in man: measurement, regulation and possible importance.

Studies on the relevance of scintigraphy and breath hydrogen analysis to the measurement of small bowel transit time are outlined. The main dietary factor influencing small bowel transit time appears to be the level of unabsorbable carbohydrate. The rates of gastric emptying and small bowel transit seem to be largely independent of one another. A weak correlation exists between the time for 50% of a meal to enter the caecum and the contraction frequency of the upper jejunum. Unabsorbed food in the ileum may increase the period over which material remains in the small intestine. Absorption cannot be predicted from a knowledge of transit kinetics alone. Diarrhoea may arise if rapid small bowel transit causes unduly rapid entry of fluid into the colon. In the irritable bowel syndrome, accelerated small bowel transit occurs in patients with diarrhoea.