The aim of this study is to evaluate the effect of supplementation with Bifidobacterium longum 35624® Alflorex® on frequency and severity of symptoms of abdominal pain using an adapted Irritable Bowel Symptom Severity Scoring System (IBS-SSS) to accurately reflect the pediatric population using the aid of the validated Numeric Pain Rating Scale (NRS-II) in children with Functional Gastrointestinal Disorders (FGIDs).

This is an open label study to assess the safety and effectiveness of Bifidobacterium longum 35624® Alflorex® when consumed once daily by children with Functional Gastrointestinal Disorders (FGIDs). The 12-week intervention study will be conducted in 63 non-coeliac children aged 8 to 18 years old with an FGID who experience at least two episodes of abdominal pain per week. The study will consist of 5 visits over a 14 week period commencing with a screening visit. The second visit will be the baseline (start of intervention), followed by third (mid-intervention), fourth (end of treatment) and fifth (follow up) visit. Questionnaires will be administered from the second to the fifth visit. A blood sample will be taken before treatment to rule out coeliac disease.

Inclusion Criteria:

1. Age 8-18 years
2. Any sex
3. ROME IV diagnostic criteria Pediatric functional digestive disorders: in children and adolescents. H2. Functional abdominal pain disorders H2a. Functional dyspepsia H2b. Irritable bowel syndrome H2d. Functional abdominal pain not otherwise specified H3. Functional defecation disorders H3a. Functional constipation H3b. Non-retentive fecal incontinence Meet the criteria during the last three months with the onset symptoms for at least six months before diagnosis
4. IBS rated moderate to severe according to GSRS-IBS score (Spanish / LA)
5. At least two episodes of abdominal pain per week
6. No consumption of probiotics at least two weeks before baseline measurements (but preferably four weeks);
7. Dad, Mom, or Guardian able to understand the protocol;
8. Be willing to maintain stable dietary habits throughout the study period;
9. Be able to communicate well with the Investigator, to understand and comply with the requirements of the study and be judged suitable for the study in the opinion of the Investigator;
10. Signature of Informed Consent.

Exclusion Criteria:

1. Children with systemic, organic or metabolic diseases, immunosuppression, different from IBS
2. Previous major abdominal surgery;
3. Consumption of proton pump inhibitors, H2 antagonists;
4. Consumption of probiotics in the two weeks before baseline measurements;
5. Are less than 8 or older than 18 years of age at the time of consent;
6. Subject who has been on antibiotics during the past 3 months;
7. Subjects who have not had at least two episodes of abdominal pain per week;
8. Subject with a malignant disease or any concomitant end-state organ disease and/or laboratory abnormalities considered by Investigators to be risky or that could interfere with data collection;
9. Subject who are coeliac or lactose intolerant;
10. Known allergy to any of the components of the test product;
11. Participation in a clinical study with an investigational product within 60 days before screening, or plans to participate in another study during the study period;
12. Subject has a history of non-compliance;
13. Use of dietary supplements or other fermented foods that contain live bacteria.
14. Pregnant or lactating females.