Rationale: Irritable Bowel Syndrome (IBS) is functional gastrointestinal disorder that affects a large number of people. To date, no adequate treatment is available. This is partially due to the heterogeneity of the patients and the complicated pathology in which not all mechanisms are understood.

Based on results of in vitro screening within the IBSQUtrition project, we selected promising dietary supplements for validation of their potential beneficial effects on the microbiota of IBS patients.

Objective: The primary objective is to determine the bifidogenic effects of a 4-week intervention with one of four dietary supplements (Chondroitin sulfate, NOVELOSE® 3490, and Pea Fiber, and Lactium®) in IBS patients. The secondary objective is to determine the effects of the same intervention on fecal microbiota composition and SCFA concentration, IBS-related complaints, Quality of Life, and stool frequency and consistency in IBS patients.

Study design: a double-blind, randomized, placebo-controlled trial with five parallel arms. Study population: 70 adult (18-65 yrs) IBS patients Intervention: 4-week intervention period with five parallel arms: 1) Chondroitin sulfate, 2) NOVELOSE® 3490, 3) Pea Fiber, 4) Lactium®, and 5) Placebo supplement (Maltodextrin control), during which the study participants consume the respective supplement twice per day.

Main study parameters/endpoints: The main study parameter is the (relative) abundance of fecal Bifidobacterium. The secondary study parameters are fecal microbiota composition and Short-Chain Fatty Acids (SCFAs) concentration, stool frequency and consistency, IBS-related complaints, and Quality of Life (QoL).

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Study participants have to invest about 7.4 hours of their time in this study mainly to complete several questionnaires (short daily questionnaire, longer questionnaires at two occasions), which is conveniently all possible from home. On two occasions they have to collect stool (transported via courier to the research facility). They have to comply to consume a commercially available supplement twice daily for four weeks. There are limited risks for the study participants.

Inclusion Criteria:

• IBS patients that meet the Rome IV criteria. This will be evaluated by the medical supervisor;
• Male and female adults, aged 18-65 years;
• Having a Body Mass Index (BMI) between 18.5 and 30 kg/m2;
• Willing to keep a stable dietary pattern throughout the study;
• Having a smartphone to fill out the daily questionnaires.

Exclusion Criteria:

• Having a gastro-intestinal disease, such as celiac disease, Crohn's disease, or Ulcerative colitis;
• Having a history of intestinal surgery that might interfere with study outcomes. This does not include an appendectomy or cholecystectomy;
• Having a food allergy to milk protein or pulse protein;
• Presence of significant systemic diseases, such as diabetes mellitus, cancer, cardiovascular disease or respiratory disease;
• When applicable: currently pregnant or breastfeeding, or intending to become pregnant during the study, as this can affect stool patterns and wellbeing;
• Use of antibiotic treatment less than 3 months before start of the study and no use of antibiotics during the study;
• Use of prebiotics and/or probiotics (should be stopped 4 weeks before the start of the study) and infrequent use of other (fiber) supplements. Some supplements are allowed, but intake should be kept stable during the whole study period (Supplements will be judged by the medical supervisor MD Ben Witteman);
• Currently following a FODMAP-restricted diet;
• Use of medication that can interfere with the study outcomes, including anxiolytics, proton pump inhibitors, laxatives (Over-the-counter laxatives are allowed, but intake should be either stopped before the start of the study or kept stable during the complete study period), and codeine, as judged by the medical supervisor MD Ben Witteman;
• Participation in another clinical trial at the same time;
• Student or employee working at Food, Health and Consumer Research from Wageningen Food and Biobased Research;
• Alcohol intake ≥ 2 (women) or ≥ 4 (men) glasses of alcoholic beverages per day;
• Abuse of illicit drugs;
• Being incapacitated.