The diffusion of gastrointestinal (GI) chronic diseases is significantly increased during the last century in western countries. In the USA and Northern Europe, constipation is twofold the prevalence found in the East and Southern Europe. In Italy, constipation affects up to 15-17% of the whole adult population. Of them, more than half (about 10%) treats this disorder by assuming laxatives, while the remaining does not even assume drugs. A close relationship between intestinal environment and bacterial flora has been found. As a matter of fact changes in the intestinal physiology can modify the composition of bacterial flora as well as modifications in the intestinal microbiota can modify the physiology of the gut. The probiotic effects on the GI motility can be due to substances released by bacteria and/or products of their fermentation. Also, probiotic may indirectly act by the release of neuroendocrine factors and/or substances released by the immune system. Clinically, it has already been demonstrated that probiotics exert a positive effect on symptoms and intestinal habit in constipated IBS patients. In this framework, the idea to perform a long lasting intervention study in patients with functional constipation treated with probiotics sounds convincing. The present study is a randomized, double blind, placebo controlled, monocentric study, concerning the evaluation of efficacy of 3 months administration of Lactobacillus reuteri DSM 17938 in patients with functional constipation, as defined by the Rome criteria. Clinical, physiological, hematological and immunologic variables will be evaluated.

Inclusion Criteria:

• Fulfilment of the Rome Criteria III for functional constipation
• Availability of at least one GI imaging study during the last five years (colonoscopy, sigmoidoscopy, abdominal ultrasound, barium enema)
• Commitment to availability for the whole study period

Exclusion Criteria:

• Major abdominal surgery
• Presence of any concomitant diseases such as organic GI diseases and/or lactose and gluten intolerance; medical or psychiatric illness
• Alarming symptoms (rectal bleeding, weight loss, etc)
• Family history of peptic ulcer, colorectal cancer, or IBD
• Abnormal laboratory data or thyroid function.