The Low FODMAP Diet in Individuals With Small Intestinal Bacterial Overgrowth (SIBO)

February 20, 2026 updated by: dr hab. Ewa Lange, prof. SGGW, Warsaw University of Life Sciences

Assessment of the Impact of the Low FODMAP Diet on Gastrointestinal Symptoms and Nutritional Status in People With Small Intestinal Bacterial Overgrowth (SIBO)

This study aims to assess the impact of a low FODMAP diet (LFD) on gastrointestinal symptoms and nutritional status in individuals diagnosed with small intestinal bacterial overgrowth (SIBO). Participants were randomly assigned to either an intervention group or a control group following completion of antibiotic therapy. The intervention group followed a LFD, while the control group followed a normal diet, in accordance with the principles of rational nutrition. Gastrointestinal symptoms, nutritional status, and quality of life were assessed using questionnaires, dietary records, anthropometric measurements, and blood biochemical parameters.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

51

Phase

  • 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

  • Poland
      • Warsaw, Poland, 02-776
        • Warsaw University of Life Sciences (WULS-SGGW)

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

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • age > 18 years,
  • SIBO diagnosed by a doctor based on a hydrogen and methane breath test,
  • the use of one type of antibiotic at the same dose and for the same period of time.

Exclusion Criteria:

  • BMI < 18.5 kg/m2,
  • pregnancy and breastfeeding,
  • the occurrence of allergies and food intolerances,
  • previous operations on the digestive tract (except appendectomy and hemorrhoidectomy),
  • eating disorders,
  • inflammatory bowel diseases,
  • celiac disease,
  • cancer, heart, liver and lung diseases with severe course, as well as neurological or psychiatric diseases,
  • use of dietary modifications in the last 3 months,
  • use of antibiotics other than those prescribed by a doctor to treat SIBO in the last 3 months,
  • implanted stimulators (limitation of body composition measurement)

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: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Low FODMAP Diet Intervention Group
Participants diagnosed with SIBO who followed a low FODMAP diet after completion of antibiotic therapy.
Other: Low FODMAP Diet
Following a low FODMAP diet (elimination and reintroduction phases for 4 and 8 weeks, respectively, for a total of 12 weeks)
Sham Comparator: Control Group
Participants diagnosed with SIBO who followed a diet consistent with the principles of healthy eating after completion of antibiotic therapy.
Other: Healthy Eating Diet
Applying recommendations consistent with proper nutrition principles, with particular focus on breaks between meals and the principle of mindful eating

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Gastrointestinal Adverse Symptoms Assessment Questionnaire (GASAQ) total score
Time Frame: 12 weeks
Change in gastrointestinal symptom severity assessed using the Gastrointestinal Adverse Symptoms Assessment Questionnaire (GASAQ). The total score ranges from 0 to 100 points, with higher scores indicating more severe gastrointestinal symptoms. Assessments were performed at baseline and after the dietary intervention.
12 weeks
Nutritional status - Mini Nutritional Assessment (MNA)
Time Frame: 12 weeks
Change in nutritional status assessed using the Mini Nutritional Assessment (MNA) questionnaire. The total score ranges from 0 to 30 points, with higher scores indicating better nutritional status. Assessments were performed at baseline and after the dietary intervention.
12 weeks
Nutritional status - Blood biochemical parameters (Serum vitamin D concentration)
Time Frame: 12 weeks
Change in serum vitamin D levels measured in ng/mL at baseline and after the dietary intervention.
12 weeks
Nutritional status - Blood biochemical parameters (Serum folate concentration)
Time Frame: 12 weeks
Change in serum folate levels measured in ng/mL at baseline and after the dietary intervention.
12 weeks
Nutritional status - Blood biochemical parameters (Iron status parameters)
Time Frame: 12 weeks
Change in serum iron concentration (µg/dL) measured at baseline and after the dietary intervention.
12 weeks
Nutritional status - Blood biochemical parameters (Serum albumin concentration)
Time Frame: 12 weeks
Change in serum albumin levels measured in g/L at baseline and after the dietary intervention.
12 weeks
Nutritional status - Anthropometric parameters (body weight)
Time Frame: 12 weeks
Change in body weight (kg) measurements at baseline and after the dietary intervention.
12 weeks
Nutritional status - Anthropometric parameters (body mass index (BMI)
Time Frame: 12 weeks
Change in BMI (kg/m²) at baseline and after the dietary intervention. BMI calculated from measured body weight and height (kg/m²).
12 weeks
Nutritional status - anthropometric parameters (body fat percentage)
Time Frame: 12 weeks
Change in body fat percentage (%) at baseline and after the dietary intervention. Body fat percentage measured using bioelectrical impedance analysis (ACCUNIQ BC720).
12 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Quality of life - IBS-specific (Irritable Bowel Syndrome-Quality of Life (IBS-QOL) total score)
Time Frame: 12 weeks
Change in quality of life assessed using the Irritable Bowel Syndrome-Quality of Life (IBS-QOL) questionnaire. Scores range from 0 to 100 points, with higher scores indicating better quality of life. Assessments were performed at baseline and after the dietary intervention.
12 weeks
Quality of Life - General (Short Form-36 Health Survey (SF-36) total score)
Time Frame: 12 weeks
Change in general quality of life assessed using the Short Form-36 Health Survey (SF-36), Polish version. Scores range from 0 to 100 points, with higher scores indicating better perceived health status. Assessments were performed at baseline and after the dietary intervention.
12 weeks

Collaborators and Investigators

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

Sponsor

Warsaw University of Life Sciences

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)

February 8, 2024

Primary Completion (Actual)

September 18, 2025

Study Completion (Actual)

January 15, 2026

Study Registration Dates

First Submitted

February 8, 2026

First Submitted That Met QC Criteria

February 13, 2026

First Posted (Actual)

February 20, 2026

Study Record Updates

Last Update Posted (Actual)

February 24, 2026

Last Update Submitted That Met QC Criteria

February 20, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 11/RKE/2023/U

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

The study will not share individual participant data to protect participant confidentiality and privacy.

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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