Effect of a Low FODMAP Diet on SIBO Breath Test Positivity

Bloating is the most common symptom associated with disorders of brain-gut interaction (i.e., functional bowel disorders) such as irritable bowel syndrome, a disorder characterized by abdominal pain and altered bowel habits which affects up to 11% of world population. A common cause of bloating is small intestinal bacterial overgrowth (SIBO), a condition defined by excessive and/or abnormal type of bacteria in the small bowel. The potential role of SIBO for irritable bowel syndrome (IBS) was initially proposed by Pimentel et al. Using lactulose breath tests (LBTs), 78% of patients with IBS were also diagnosed with SIBO. After antibiotic therapy, 48% of patients no longer met the Rome criteria for IBS. A recent systematic review and meta-analysis concluded that the prevalence of SIBO is increased in IBS.

Study Overview

• Status: Terminated
• Conditions: SIBO
• Intervention / Treatment: Other: low FODMAP diet

Detailed Description

Despite the clinical efficacy of LFD in improving symptoms of IBS-D, its mechanism of action is not clear. Recently, Zhou et al have shown FODMAPs induce colonic tight junction dysfunction and visceral hypersensitivity in rat models, both of which are reversible when rats were fed an LFD. They further showed that this effect of FODMAPs is mediated by microbial dysbiosis and elevated fecal lipopolysaccharide level. However, studies evaluating the effect of LFD on colonic permeability of humans are lacking. Studies have shown significant differences in intra-individual luminal and mucosal microbiome of patients with functional gastrointestinal disorders as well as an increase in Prevotella abundance in IBS patients with SIBO as compared with IBS patients without SIBO. Thus, the exact effect of FODMAP on intestinal permeability and mucosal microbiome in humans is not clear and needs further evaluation.

• Study Type: Interventional
• Enrollment (Actual): 14
• Phase: Early Phase 1

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02215
      • Beth Israel Deaconess Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Aged 18-65 years at the time of screening
• Meet Rome IV criteria for functional bloating
• IBS-SSS score of at 176 (0-500)
• SIBO positive

Exclusion Criteria:

• individuals already on a LFD or other dietary restriction such as gluten free diet within the past 6 months
• individuals with peanut, soy, or seafood allergies or insulin-dependent diabetes
• known history of celiac disease, inflammatory bowel disease or microscopic colitis
• prior small bowel or colonic surgery or cholecystectomy
• pregnant patients
• antibiotics, excluding topical, in the past 3 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: low FODMAP diet; Consenting patients fulfilling the inclusion and exclusion criteria will undergo a 7-day screening period to assess baseline symptoms and then go on a 4-week low FODMAP diet	Other: low FODMAP diet; low FODMAP diet

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
SIBO Diagnosis	Number of Participants with Negative and Positive SIBO	four weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Rome IV Functional Bloating diagnostic criteria	Rome IV Functional Bloating	3 weeks
IBS-SSS	change in IBS-SSS from baseline to final	3 weeks

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
serum LPS level	change in serum LPS concentration from baseline to final	3 weeks
serum zonulin level	change in serum zonulin concentration from baseline to final	3 weeks

Collaborators and Investigators

• Sponsor: Beth Israel Deaconess Medical Center
• Investigators: Principal Investigator: Anthony Lembo, M.D, Beth Israel Deaconess Medical Center

Publications and helpful links

General Publications

• Lemos MPC, Zucoloto TG, Oliveira MC, de Oliveira GLV. Dysbiosis and Gut Microbiota Modulation in Systemic Sclerosis. J Clin Rheumatol. 2022 Mar 1;28(2):e568-e573. doi: 10.1097/RHU.0000000000001748.

Study record dates

Study Major Dates

• Study Start (Actual): November 15, 2020
• Primary Completion (Actual): December 15, 2024
• Study Completion (Actual): December 15, 2024

Study Registration Dates

• First Submitted: October 30, 2020
• First Submitted That Met QC Criteria: November 12, 2020
• First Posted (Actual): November 13, 2020

Study Record Updates

• Last Update Posted (Actual): July 4, 2025
• Last Update Submitted That Met QC Criteria: July 3, 2025
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: 2020P000622

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