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

July 21, 2026 updated by: Antalya Bilim University

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

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

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.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
72

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
      • Istanbul, Turkey (Türkiye)
        • Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine, Department of Gastroenterology

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Low-FODMAP → Lactose- and Gluten-Free Diet
Participants received the low-FODMAP diet for 4 weeks, followed by a 1-week washout period and then the lactose- and gluten-free diet for 4 weeks.
Behavioral: Low-FODMAP Diet
Participants followed a low-FODMAP diet for 4 weeks under the supervision of a dietitian.
Behavioral: Lactose- and Gluten-Free Diet
Participants followed a lactose- and gluten-free diet for 4 weeks under the supervision of a dietitian.
Experimental: Lactose- and Gluten-Free Diet → Low-FODMAP
Participants received the lactose- and gluten-free diet for 4 weeks, followed by a 1-week washout period and then the low-FODMAP diet for 4 weeks.
Behavioral: Low-FODMAP Diet
Participants followed a low-FODMAP diet for 4 weeks under the supervision of a dietitian.
Behavioral: Lactose- and Gluten-Free Diet
Participants followed a lactose- and gluten-free diet for 4 weeks under the supervision of a dietitian.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
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.
Baseline, Week 4, and Week 9

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
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.
Baseline, Week 4, and Week 9
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.
Baseline, Week 4, and Week 9
Change in body weight
Time Frame: Baseline, Week 4, and Week 9
Change in body weight measured in kilograms.
Baseline, Week 4, and Week 9
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.
Baseline, Week 4, and Week 9

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Antalya Bilim University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Hatice Kübra Aras, Antalya Bilim University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
September 1, 2020

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
November 25, 2021

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
January 20, 2022

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
July 16, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 21, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
July 23, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
July 23, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
July 21, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 2020/034

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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