Background and aims: There is a growing interest for the use of probiotics for chronic constipation. A recent randomized controlled trial (RCT) showed a positive effect of Lactobacillus reuteri (L. reuteri) on bowel movement frequency in infants with chronic constipation. The aim of the present study was to evaluate the effects of L. reuteri in adult patients with functional constipation.

Methods: A double-blind, placebo RCT was conducted in 40 adults (18M/22F, 35+/-15 years) affected by functional constipation according to the Rome III criteria. Patients were randomly assigned to receive a supplementation of L. reuteri (DSM 17938), or matching placebo for 4 weeks. The increase of bowel movements/week was the primary outcome, while the improvement of stool consistency was the secondary outcome.

Results: At week 4, the mean increase in bowel movements/week was 2.6 (SD +/-1.14, 95% CI:1.6-3.6) in the L. reuteri group and 1.0 (SD+/-1. 95% CI:0.12-1.88) in the placebo group (p=0.046). At the end of the treatment, the mean bowel movements/week was 5.28+/-1.93 in the L. reuteri group and 3.89+/-1.79 in the placebo group. There was a not significant difference in the stool consistency between the two groups.

Conclusions: L. reuteri is more effective than the placebo in improving bowel movement frequency in adult patients with functional constipation as previously demonstrated in children, even if it seems to have no effect on stool consistency.