Diet and lifestyle changes are the recommended first line treatments for symptom relief in irritable bowel syndrome (IBS). Currently the only diet that is widely recommended and for which there is good evidence of efficacy in IBS is one low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (low-FODMAP). While effective, the Low-FODMAP diet is burdensome and costly to patients and in clinical practice adherence to FODMAP restriction is less than optimal. Further, patients who respond to a FODMAP restriction often are reluctant to reintroduce more FODMAPs into their diet, which may deprive them of foods, particularly fruits and vegetables with important health benefits. Therefore, there is a need for other dietary interventions for IBS that are less burdensome to patients. This clinical trial assesses the efficacy of two dietary interventions.

Inclusion criteria

1. Patients with IBS-D diagnosed per Rome IV questionnaire and without any unexplained alarm features (rectal bleeding, weight loss, nocturnal symptoms, family history of inflammatory bowel disease or celiac disease)
2. Aged 18-65 years at the time of screening
3. Weekly average of worst daily (in the past 24 hours) abdominal pain score of ≥3.0 on a 0- to-10 point scale
4. At least 80% compliance in daily diary entries during the 7-day screening period

Exclusion criteria

1. Subjects adhering to a dietary IBS-treatments such as the low-fat diet, low FODMAP diet, or gluten-free diet within the past 6 months
2. Subjects with a known food allergy to eggs, peanuts, or milk (subjects with lactose intolerance who are experiencing IBS symptoms while on a lactose-free diet will not be excluded from the study).
3. Subjects with a history of insulin-dependent or non-insulin-dependent diabetes
4. Subjects with a known history of celiac disease, inflammatory bowel disease or microscopic colitis
5. Subjects with a history of an eating disorder requiring medical or behavioral treatment within the past 10 years.
6. BMI < 18.5