Inulin is an ideal substrate for a hydrogen breath test to measure the orocaecal transit time

Background: A better substrate is needed for a hydrogen breath test to measure the orocaecal transit time. The currently used substrate, lactulose, accelerates the orocaecal transit time by increasing the osmolality of the gut contents. The recently developed lactose C-13-ureide breath test is reliable, but a hydrogen breath test is preferred, as it allows the simultaneous investigation of the digestion and absorption of nutrients by means of C-13-labelled compounds. Methods: The usefulness of different types of inulin as a substrate for a hydrogen breath test was studied. Raftilin HP(> 99% inulin with a degree of polymerization of between 5 and 60 and < 0.5% glucose, fructose and sucrose) was further evaluated and compared with lactulose with regard to its effects on gastric emptying and the digestion of protein and lipids. Results: A good correlation was found between the orocaecal transit times using Raftilin HP ( 338 min; interquartile range, 300-383 min) and lactose C-13-ureide ( 353 min; interquartile range, 285-375 min) (r = 0.85; P < 0.001). The administration of 5 or 10 g Raftilin HP had no influence on the orocaecal transit time, whereas lactulose significantly shortened the orocaecal transit time. Neither inulin nor lactulose had a significant influence on gastric emptying or protein or lipid assimilation. Conclusion: Raftilin HP is an ideal substrate for a hydrogen breath test to measure the orocaecal transit time.