Lactose Intolerance and Intestinal Permability (LI)

February 23, 2026 updated by: Bezmialem Vakif University

Observational Cross-Sectional Study of Intestinal Permeability in Adults With Lactose Intolerance

"This study evaluates the interplay between lactose intolerance, intestinal barrier function (zonulin), and intestinal inflammation (fecal calprotectin) in adults, aiming to clarify their independent contributions to symptom severity and quality of life."

Study Overview

Status

Enrolling by invitation

Conditions

Detailed Description

The gastrointestinal system's barrier functions play a critical role in maintaining intestinal and overall health. Tight junction structures, regulated by zonulin, are key components of this barrier, and elevated zonulin levels can increase intestinal permeability, facilitating translocation of luminal particles into the systemic circulation and promoting inflammation. Fecal zonulin-related proteins (ZRP) provide a non-invasive marker of intestinal barrier integrity.

Calprotectin, a pro-inflammatory protein complex released from neutrophils, serves as a reliable biomarker of mucosal inflammation. While typically normal in functional disorders such as irritable bowel syndrome (IBS), fecal calprotectin (FC) is significantly elevated in inflammatory bowel diseases (IBD), helping to distinguish organic inflammatory conditions from functional disorders.

Lactose intolerance (LI) results from lactase deficiency and is characterized by abdominal pain, bloating, and diarrhea. Traditionally attributed to mechanical and fermentative processes, recent evidence suggests that immunological and inflammatory mechanisms may also contribute. LI can be primary (genetic lactase deficiency) or secondary (due to epithelial damage or barrier dysfunction), with barrier disruption potentially exacerbating symptom severity.

Recent studies have reported elevated fecal calprotectin in individuals with self-reported milk intolerance (Seidita et al., 2023), even among those confirmed as lactose intolerant by hydrogen breath testing, suggesting that additional inflammatory or allergic mechanisms may be involved. Moreover, dietary interventions in IBS patients with food intolerances, including lactose, have been shown to significantly reduce calprotectin levels (Schnedl et al., 2023), indicating that inflammation may be modifiable.

Therefore, evaluating zonulin and calprotectin levels in lactose-intolerant adults can provide insights not only into mechanical or chemical causes of symptoms but also into intestinal barrier dysfunction and underlying inflammation. Current literature on combined assessment of these biomarkers in adults is limited. This study aims to:

Investigate the relationship between lactose intolerance and zonulin/fecal calprotectin levels.

Assess the independent contribution of zonulin (intestinal permeability) separate from calprotectin (inflammation).

Explore associations between these biomarkers, symptom severity, and quality of life.

Study Type

Observational

Enrollment (Estimated)

200

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), 34093
        • Bezmialem Vakıf University Medical Faculty Hospital

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

Sampling Method

Probability Sample

Study Population

Patients with IBS, aged 18-70 years, both male and female, who meet the Rome-4 criteria, were included in this study. They were recruited from the Gastroenterology outpatient clinic of Bezmialem Vakıf University Hospital, with a minimum total of 200 patients.

Description

Inclusion Criteria:

  • Adults aged 18-70 years; experiencing chronic symptoms (diarrhea, bloating, abdominal pain, constipation, flatulence) for the past 3 months, potentially fitting IBS criteria.

Exclusion Criteria:

- Acute gastroenteritis (< 4 weeks), Active gastrointestinal bleeding (stomach, small intestine, and colon), Known celiac disease, Bariatric surgery or short bowel syndrome, Pregnancy or lactation, Type I and II Diabetes mellitus, Antibiotic use within the last 2 weeks, High-dose NSAIDs within the last 2 weeks, Initiation of probiotics or prebiotics within the last 4 weeks, High-dose PPI use (optional), Inflammatory bowel disease (IBD; ulceretive colitis and Crohn's colitis) with active severe flare (excluded from primary analyses, evaluated separately in subgroup analyses)

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

Cohorts and Interventions

Group / Cohort
Patients with Irritable bowel sydrome.
IBS-C, IBS-D and IBS-M.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
To determine the relationship between lactose intolerance (LI) and fecal biomarkers, zonulin (Z) and fecal calprotectin (FC), in adults with IBS.
Time Frame: Baseline assessment (single time point measurement of biomarkers and symptoms)
The primary outcome of this study is to evaluate the relationship between lactose intolerance (LI) and fecal biomarkers-Z (as mg/kg), a marker of intestinal permeability (IP), and fecal calprotectin (FC) (as mg/kg), a marker of intestinal inflammation-in adults with irritable bowel syndrome (IBS). This includes assessing whether levels of these biomarkers are associated with the presence of LI and the severity of gastrointestinal symptoms related to lactose ingestion. The analysis aims to clarify how intestinal barrier function (Z) and inflammation (FC) contribute individually and jointly to symptom manifestation in LI patients within the IBS population.
Baseline assessment (single time point measurement of biomarkers and symptoms)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
FC predictive value with Z. Z correlation with symptom severity. Z in IBS subtypes / FC and organic pathology. Z mediation between LI and symptoms. IgE anti-casein and symptom severity. LTT correlation with IP biomarkers. Celiac serology prevalence.
Time Frame: Baseline assessment (single measurement at the time of evaluation)

Predictive value of FC (mg/kg) and Z (mg/kg) for LI. Correlation of Z with gastrointestinal symptom severity (GSRS) and irritabl bowel disese-symptom severity score (IBS-SSS).

Z levels across IBS subtypes and association of FC with organic pathology. Mediating role of Z between LI and symptoms. Relationship between IgE anti-casein (kIU/Lt) positivity and symptom severity according to IBS-SSS.

Correlation of lactose tolerance test (LTT) results with intestinal permeability biomarkers. Prevalence of positive celiac serology (anti IgA endomycium antibody (titre) and Anti IgA transglutaminase antibody (RU/ml).
Baseline assessment (single measurement at the time of evaluation)

Collaborators and Investigators

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

Sponsor

Bezmialem Vakif University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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 10, 2026

Primary Completion (Estimated)

December 15, 2026

Study Completion (Estimated)

June 15, 2027

Study Registration Dates

First Submitted

February 16, 2026

First Submitted That Met QC Criteria

February 16, 2026

First Posted (Actual)

February 20, 2026

Study Record Updates

Last Update Posted (Actual)

February 25, 2026

Last Update Submitted That Met QC Criteria

February 23, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • E-54022451-050.04-212534

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

"Due to privacy and confidentiality concerns, individual participant data will not be shared."

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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