Inclusion Criteria:  Age 18-70 y/o (70 years included) Male or female subjects IBS-D and IBS-M (i.e. IBS-non-C) according to Rome IV criteria Moderate to severe symptom severity as defined by the Irritable bowel syndrome severity scoring system (IBS-SSS) (i.e. IBS-SSS >175 points) Provide written informed consent to participate in the study Women of child-bearing potential agree to apply a highly effective method of birth control during the entire duration of the trial. Highly effective birth control is defined as those which result in a low failure rate (i.e., less than 1% per year) when used constantly and correctly such as implants, injectables, combined oral contraceptive method, or some intrauterine devices (IUDs), sexual abstinence, or vasectomized partner. Women of non-childbearing potential may be included if surgically sterile (tubal ligation or hysterectomy) or postmenopausal with at least 2 year without spontaneous menses. Subjects who are capable to understand the study and the questionnaires, and to comply with the study requirements.  Exclusion Criteria:  - Pregnant or breastfeeding women History of major surgery of the gastrointestinal tract (cholecystectomy and uncomplicated appendectomy are allowed) Symptoms predominantly associated with functional dyspepsia or gastro-esophageal reflux disease Immunoglobuline E (IgE)-mediated food allergies identified by immunocap blood tests or skin prick testing Known underlying organic gastrointestinal disease Current or recent use of NSAIDs, proton-pump inhibitors, systemic histamine-receptor antagonists, mast cell stabilizers, corticosteroids, opioids (need to be stopped at least 2 weeks). Use of antibiotics in the past 6 weeks. Allergy to Fluorescein, Xylocaine or Propofol Known celiac disease Following a diet interfering with the study diet in opinion of the investigator