SUMMARYAim: To investigate the effects of a probiotic formulation, VSL#3, on gastrointestinal transit and symptoms of patients with Rome II irritable bowel syndrome with predominant diarrhoea. Methods: Twenty-five patients with diarrhoea-predominant irritable bowel syndrome were randomly assigned to receive VSL#3 powder (450 billion lyophilized bacteria/day) or matching placebo twice daily for 8 weeks after a 2-week run-in period. Pre-and posttreatment gastrointestinal transit measurements were performed in all patients. Patients recorded their bowel function and symptoms daily in a diary during the 10-week study, which was powered to detect a 50% change in the primary colonic transit end-point. Results: There were no significant differences in mean gastrointestinal transit measurements, bowel function scores or satisfactory global symptom relief between the two treatment groups, pre-or post-therapy. Differences in abdominal bloating scores between treatments were borderline significant (P ¼ 0.09, analysis of covariance). Further analysis revealed that abdominal bloating was reduced (P ¼ 0.046) with VSL#3 [mean post-minus pre-treatment score, ) 13.7; 95% confidence interval (CI), ) 2.5 to ) 24.9], but not with placebo (P ¼ 0.54) (mean post-minus pre-treatment score, ) 1.7; 95% CI, 7

VSL# 3 reduces flatulence scores and retards colonic transit without altering bowel function in patients with IBS and bloating.