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NCT Number: NCT07722572

Low-FODMAP vs Lactose-Gluten-Free Diet in Patients With Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder that substantially affects quality of life. Dietary therapy is considered one of the primary treatment approaches; however, the optimal sequence of dietary interventions remains unclear. This randomized crossover trial was designed to compare the effects of a low-FODMAP diet and a lactose-free, gluten-free diet on gastrointestinal symptoms, psychological status, anthropometric measurements, and biochemical parameters in adults with IBS. Participants were randomly assigned to one of two dietary sequences, with each intervention lasting four weeks and separated by a one-week washout period. Outcomes were assessed using validated symptom and psychological questionnaires together with anthropometric and biochemical measurements before and after each intervention period.

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Key information

Conditions

Irritable Bowel Syndrome Anxiety Disorders Colonic Diseases Colonic Diseases, Functional Digestive System Diseases Gastrointestinal Diseases Intestinal Diseases Mental Disorders

Age range

18 year–64 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Department of Gastroenterology

Istanbul, Turkey (Türkiye)

About this study

This randomized crossover trial was designed to evaluate the comparative effects of a low-FODMAP diet and a lactose- and gluten-free diet in adults with irritable bowel syndrome (IBS). Participants were randomly assigned to one of two dietary sequences, with each intervention lasting 4 weeks and separated by a 1-week washout period. Gastrointestinal symptoms, psychological outcomes, anthropometric measurements, and biochemical parameters were assessed before and after each intervention period.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18-64 years.
  • Diagnosis of Irritable Bowel Syndrome according to the Rome III criteria.
  • Ability and willingness to comply with the dietary intervention.
  • Written informed consent provided.

Exclusion criteria

  • Pregnancy or lactation.
  • Diabetes mellitus.
  • Organic gastrointestinal disease.
  • Current follow-up for cardiologic, neurologic, oncologic, or psychiatric disorders.
  • Following a therapeutic diet within 1 month before enrollment.

Treatment and study plan

Low-FODMAP Diet

Behavioral

Participants followed a low-FODMAP diet for 4 weeks under the supervision of a dietitian.

Lactose- and Gluten-Free Diet

Behavioral

Participants followed a lactose- and gluten-free diet for 4 weeks under the supervision of a dietitian.

Primary outcomes

  1. Change in Irritable Bowel Syndrome Symptom Severity Score (IBS-SSS)

    Time frame: Baseline, Week 4, and Week 9

    Change in Irritable Bowel Syndrome Symptom Severity Score (IBS-SSS). The IBS Symptom Severity Score assessed the severity of IBS symptoms based on four questions, scoring between 0 and 100 points for each symptom. A total score of 75-174 points indicated mild IBS, 175-299 points indicated moderate IBS, and >300 points indicated severe IBS.

Secondary outcomes

  1. Change in Gastrointestinal Symptom Rating Scale (GSRS) score

    Time frame: Baseline, Week 4, and Week 9

    Change in gastrointestinal symptom severity assessed using the Gastrointestinal Symptom Rating Scale (GSRS). The GSRS assessed gastrointestinal symptoms based on 15 items categorized into five subdimensions: abdominal pain, reflux, diarrhea, indigestion, and constipation. The scale measures symptom severity over the past week, with higher scores indicating more severe symptoms.

  2. Change in Hospital Anxiety and Depression Scale (HADS) score

    Time frame: Baseline, Week 4, and Week 9

    Change in anxiety and depression symptoms assessed using the Hospital Anxiety and Depression Scale (HADS). The HADS is a 14-question scale that identifies anxiety and depression risks. The scale is divided into two subscales, one for anxiety and one for depression, with scores ranging from 0 to 21. Scores between 0-7 are considered normal, 8-10 borderline, and ≥11 indicates anxiety and/or depression.

  3. Change in body weight

    Time frame: Baseline, Week 4, and Week 9

    Change in body weight measured in kilograms.

  4. Change in body mass index

    Time frame: Baseline, Week 4, and Week 9

    Change in body mass index (BMI), calculated as weight in kilograms divided by height in meters squared.

Sponsors and collaborators

Lead sponsor

Antalya Bilim University

Other

Registry information

Official study title

Comparative Effects of Low-FODMAP and Lactose-Gluten-Free Diets on Gastrointestinal Symptoms and Mental Health in Irritable Bowel Syndrome: A Randomized Crossover Trial

Important dates

Study start
2020
Primary completion
2021
Study completion
2022
First posted
Jul 23, 2026
Registry last updated
Jul 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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