The Vall d'Hebron Barcelona Hospital Campus has led a study that compares the effect of a low fermented residue diet (FODMAP) with the effect of a prebiotic to improve the symptoms associated with intestinal gas production, such as flatulence, abdominal distension or sensation of fullness. Although they have an opposite effect on the intestinal microbiota, both the diet and the prebiotic can improve the symptoms, and in the case of prebiotics, their effect is maintained up until to two weeks after having stopped taking them. This randomized and double blind study has been conducted by Dr. Fernando Azpiroz, Chief of the Department of Digestive Diseases at the Vall d'Hebron University Hospital and Head of the Physiology and Pathophysiology of the Digestive Tract research group at the Vall d'Hebron Research Institute (VHIR). It has been published in the journal Gastroenterology and has been carried out with the collaboration of the General Hospital of Catalunya. The study involved 44 patients with gastrointestinal disorders (irritable bowel syndrome and abdominal distension) that referred flatulence. Of these, 40 completed the 7-week study that was divided into 3 phases: 1 week of pre-treatment, 4 weeks of treatment and 2 weeks of follow-up. Patients were randomly split into two groups. One of them followed a diet low in FODMAP and the other was given a normal and prebiotic diet. This phase of treatment lasted 4 weeks and a similar improvement was noted in both groups of patients. "However, when studying the metabolism and the composition of the microbiota, we observed that the FODMAP diet and the prebiotic had an opposite effect: while the diet low in fermentable residues impoverished the microbiota, the prebiotic produced a proliferation of beneficial bacteria", explains Dr. Fernando Azpiroz. Upon finishing the phase of treatment of the patients who had followed the FODMAP diet, they had a rebound effect, that is, their symptoms increased again. On the other hand, the improvement in the symptoms was maintained for two weeks in patients in the prebiotic group. The enrichment of the microbiota that is obtained with the prebiotic would explain why the improvement in the symptoms persists after stopping the treatment. "Both the FODMAP and the prebiotic diet have a similar effect while they are administered, but since the diet low in fermentable residues requires a continued administration with the risk of producing long-term damage to the microbiota, the prebiotic supplement could be given intermittently so that the effect persists for a while after treatment", concludes Dr. Azpiroz.