Probiotics and Biomarkers in Irritable Bowel Syndrome

Inclusion Criteria: * Diagnosed with IBS according to ROME V criteria * IBS-SSS greater than or equal to 75 * Adult over 18 years old * BMI 18.5-35 kg/m2 * Able to understand the participant information sheet and willing to comply with the study protocol * Able to give informed consent * Able to complete the Swedish questionnaires Exclusion Criteria: * History of any gastroenterology disease including coeliac disease, heart, liver, neurological, or current psychiatric disease, diabetes, any surgery to the abdomen that affects intestinal function (not including cholecystectomy, appendectomy, ceasarean section). * The use of opioids 1 month prior to screening and throughout the study * The use of probiotic supplements from 14days before randomization and during the study (not including foods with probiotic components) * Consumption of antibiotics 3 months prior to screening and throughout the study * The start of any new drugs that affect the gastrointestinal tract or symptoms within the last month before the start of the study. As well as the start of new diets of psychological therapy as treatment for IBS symptoms. * Participation in any medical research during the last month * Clinically relevant lab abnormalities at the time of screening (fecal calprotectin greater than or equal to 150 ug/g as absolute cutoff. If calprotectin is between 50 - 150ug/g the decision is made on clinical judgement) * Pregnancy, plan to become pregnant during the study, breastfeeding * alcohol consumption \>14 units per week * Use of recreational active drugs during 1 month before screening or during the study * Use of medication that primarily affects bowel function, transit time, stool consistency 2 weeks before the intervention or during the 12 week intervention period