Irritable Bowel Syndrome (IBS) is a disease that affects a large number of people. Adequate treatment is difficult, partially due to the heterogeneity of the patients and the complicated pathology in which not all mechanisms are understood. Based on literature and in vitro screening within the public private IBSQUtrition consortium project, a turmeric supplement was selected for in vivo validation of its potential beneficial effects on fat-induced intestinal barrier disruption as measured with LPS translocation in IBS patients with a diarrhea-predominant subtype (IBS-D).

The primary objective of this study is to determine the effect of turmeric supplementation on LPS translocation in IBS-D patients after a high-fat challenge. The secondary objective of this study is to determine the effect of turmeric supplementation on gastrointestinal complaints and LPS-related biomarkers in IBS-D patients after a high-fat challenge.

In this double-blind, randomized, placebo-controlled cross-over trial 20 adult (18-70 yrs) IBS-D patients will be included.

Study participants have to invest about 16 hours of their time in this study. They will visit the research facility three times. The risks for participation are very small if not negligible. Consumption of high amounts of saturated fat may cause some gastro-intestinal discomfort. Blood sampling will be performed via a cannula and the insertion can be a bit painful and may cause a bruise. The amount of blood that is drawn from participants is relatively small and within acceptable limits.

Inclusion Criteria:

• IBS patients that meet the Rome IV criteria + additional criteria specific for the diarrhea-predominant subtype, based on the most frequent self-reported stool types using the Bristol stool chart
• Male and female adults, aged 18-70 years;
• Having a Body Mass Index (BMI) between 18.5 and 30 kg/m2;
• Willing to keep a stable dietary pattern throughout the study.

Exclusion Criteria:

• Having a disease that may interfere with the outcomes of this study, such as a known autonomic disorder, inflammatory bowel disease, coeliac disease, cancer, dialysis patients, chronic kidney failure, depression or hypothyroidism.
• History of intestinal surgery (excluding appendectomy or cholecystectomy) or endometriosis.
• Use of medication that can interfere with the study outcomes, including codeine and antibiotics, as judged by the medical supervisor.
• Use of anticoagulants (as curcumin has inhibitory effects on platelet aggregation).
• Use of prebiotics and/or probiotics (should be stopped 4 weeks before the start of the study) and infrequent use of other supplements dedicated to bowel function improvements.
• Having swallowing problems with pills/capsules.
• Having a cow's milk allergy or other food allergies.
• If applicable: currently pregnant or breastfeeding, or intending to become pregnant during the study.
• Participation in another clinical trial at the same time.
• Student or employee working at Food, Health and Consumer Research from Food and Biobased Research, or Department of Human Nutrition & Health, Wageningen University.
• Alcohol intake ≥ 14 (women) or ≥ 28 (men) glasses of alcoholic beverages per week.
• Smoking and abuse of illicit drugs, soft drugs, and/or nitrous oxide.