This study aimed to evaluate the effects of a Low-FODMAP diet on intestinal permeability, symptom severity, and quality of life in patients with Irritable Bowel Syndrome (IBS). Twenty-four patients diagnosed with IBS according to the Rome IV criteria were randomized to either a Low-FODMAP diet or a traditional diet for four weeks. Stool zonulin family peptides (ZFP), IBS Symptom Severity Score (IBS-SSS), and IBS Quality of Life (IBS-QOL) questionnaires were recorded at baseline and after the dietary intervention. In the Low-FODMAP group, FODMAP-containing foods were gradually reintroduced under dietitian supervision, and assessments were repeated at week 16 to evaluate long-term effects.

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by recurrent abdominal pain and altered bowel habits without an identifiable organic cause. Dietary factors and increased intestinal permeability have been proposed as potential mechanisms contributing to symptom development.

The Low-FODMAP diet has been shown to improve IBS symptoms by reducing fermentable carbohydrate intake. However, its effects on intestinal barrier integrity remain unclear.

This prospective randomized single-blind study was conducted at Istanbul Medipol Mega University Hospital between December 2023 and December 2024. Patients aged 18-65 years diagnosed with IBS according to the Rome IV criteria were included. Participants were randomized to follow either a Low-FODMAP diet or a traditional diet for four weeks. Stool zonulin family peptides (ZFP) were measured as a biomarker of intestinal permeability. Symptom severity and quality of life were evaluated using validated IBS-SSS and IBS-QOL questionnaires.

After four weeks, patients in the Low-FODMAP group began a structured reintroduction phase where restricted foods were gradually reintroduced over twelve weeks. Follow-up assessments were performed at week 16 to evaluate long-term outcomes.

The study investigated whether dietary FODMAP restriction could improve intestinal barrier function in addition to reducing symptom severity and improving quality of life in patients with IBS.

Inclusion Criteria:Age between 18 and 65 years

Diagnosis of Irritable Bowel Syndrome (IBS) according to Rome IV criteria

Patients presenting to Internal Medicine or Gastroenterology outpatient clinics

Ability to provide written informed consent

Willingness to comply with the assigned dietary intervention and follow-up schedule

Patients who were mostly compliant or fully compliant with the dietary protocol (≥51%)

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Exclusion Criteria:

• IBS-specific treatment within the last 1 month

Antibiotic or probiotic use within the previous 2 weeks

History of major abdominal surgery

Active malignancy

Heart failure

Renal failure

Autoimmune disease

Inflammatory bowel disease

Celiac disease

Lactose intolerance

Individuals currently following another dietary regimen

Pregnancy

Poor adherence to diet protocol (<51%)

Failure to submit dietary diaries regularly

Need for antibiotic therapy during the intervention period

Individual participant data collected during the trial will not be publicly available but may be provided by the corresponding author upon reasonable request.