Irritable Bowel SyndromePhase 3NCT04974593
Predictive Value of Hydrogen/Methane Lactose Breath Testing on the Therapeutic Effect of Lactose-free Diet in Moderate to Severe ROME IV IBS.
A Phase 3 study testing low fat diet in people with Irritable Bowel Syndrome and Lactose Intolerant, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
Trial summary
Lactose intolerance (LI) results from lactose malabsorption (LM) secondary to insufficient hydrolysis of the disaccharide lactose into galactose and glucose (Misselwitz 2019). The undigested lactose will eventually reach the colon, resulting in fermentation from colonic bacteria with production of different compounds… Read more about this study
- Who is it for?
- Ages 18 to 75 years
- Conditions the study is for
- Irritable Bowel Syndrome, Lactose Intolerant
- What is being tested?
- low fat diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 90 participants
- Where
- 1 siteBelgium
- Study dates
- 22 Oct 2021to 1 Jan 2028
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Fulfilling the ROME IV criteria for IBS;
- Moderate symptom severity as defined by a IBS-SSS > 175;
- Consumption of lactose containing products.
Who cannot join
- Clinical suspicion of an organic disorder different from LI or IBS (patients can be included when this disorder had been excluded);
- Known lactose intolerance or malabsorption;
- Known inflammatory bowel disorder;
- Known intestinal motility disorder;
- Alcohol (defined as more than 14 U per week) or other substance abuse;
- Active psychiatric disorder;
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- Known systemic or auto-immune disorder with implication for the GI system;
- Prior abdominal surgery (with the exception of appendectomy);
- Any prior diagnosis of cancer other than basocellular carcinoma;
- Current chemotherapy;
- History of gastro-enteritis in the past 8 weeks;
- Intake of antibiotics, pre- or probiotics during the past 8 weeks;
- Dietary supplements unless taken at a stable dose for more than 8 weeks;
- Treatment with neuromodulators (one neuromodulator taken at a stable dose for more than 12 weeks is allowed);
- Treatment with spasmolytic agents, opioids, loperamide, gelatin tannate or mucoprotect-ants during the past 8 weeks;
- LFD or low FODMAP diet in the past
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Belgium1 site, 1 recruiting
- Recruiting
UZ Brussel
Jette, Brussels Capital, 1090
Sébastien Kindt, MD
About this study
Lactose intolerance (LI) results from lactose malabsorption (LM) secondary to insufficient hydrolysis of the disaccharide lactose into galactose and glucose (Misselwitz 2019). The undigested lactose will eventually reach the colon, resulting in fermentation from colonic bacteria with production of different compounds such as short chain fatty acids, carbon dioxide, H2 and methane (Catanzaro 2021). These compounds have an osmotic effect and can stimulate colonic contractions. These pathophysiological mechanisms encountered in patients suffering from LI generate symptoms, such as abdominal pain and cramps, flatulence, diarrhea, borborygmi among others. As dairy products are highly present in our Western diet, LI will often be considered in patients presenting with these symptoms and they will be referred for further testing. When LM is diagnosed, a lactose-free diet (LFD) will be advocated to alleviate symptoms. However, studies indicate that individuals with LM should tolerate up to 12 g of lactose when administered in a single dose (Suchy 2010).
Irritable bowel syndrome (IBS) is another frequently encountered disorder. According to the Rome IV criteria, it is characterized by abdominal pain associated with a change in stool frequency or consistency, or with symptomatic improvement by defecation (Mearin 2016). Associated symptoms, such as bloating and flatulence, are frequently reported. As such, discerning between IBS and LI based on symptoms alone can be challenging. Moreover lactose is considered part of the so-called fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). A low FODMAP diet has been advocated for IBS with beneficial response in at least part of the patients (Halmos 2014).
Read more
Many studies investigated the role of lactose in IBS. These studies were performed in the pre-Rome IV era and before standardized interpretation rules for Hydrogen breath testing (H2BT) were published (meta-analysis by Varju 2019). This meta-analysis indicated that subjective LI was more frequently reported by IBS patients, but also objectively more prevalent in IBS patients, when assessed by any test modality. However, the role of a LFD in IBS remains uncertain.
This study aims to:
- Determine if the diagnosis of LM by H2BT predicts the short-term and long-term response to a LFD in moderate to severe IBS as defined by Rome IV criteria;
- Determine the changes in quality of life in response to a LFD in ROME IV IBS patients.
- Conditions
- Irritable Bowel Syndrome, Lactose Intolerant
- Being tested
- low fat diet
- Medical subject headings
- Irritable Bowel Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
low fat dietOther
A trained dietitian will provide instruction of the LFD according to standard practice.
| Study group | Role | What they receive |
|---|---|---|
| H2BT-positive | Experimental | Not described Receives: Other: low fat diet |
| H2BT-negative | Experimental | Not described Receives: Other: low fat diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
symptomatic improvement
To compare the symptomatic improvement by a LFD in Rome IV IBS patients with and without LM according to a H2BT.
Measured: from baseline till visit 4 (week 4)
Secondary outcomes (1)
reduction in Irritable bowel syndrome - symptom severity scale
reduction in IBS-SSS at the end of 4 weeks of a LFD in Rome IV IBS subjects identified as lactose mal-absorbers vs. lactose absorbers by lactose H2BT
Measured: baseline till visit 4 (week 4)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Jul 2021
- Study start22 Oct 2021
- Primary completion1 Jan 2028 (estimated)
- Study completion1 Jan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Irritable Bowel SyndromeStudies of the same condition, open and under way.
- More trials run by Universitair Ziekenhuis BrusselThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Diagnosis
- Allocation
- Non-randomised
- Intervention model
- Single group
- Masking
- Triple blind
- Who is masked
- Participant, Care provider, Investigator
- Enrolment
- 90 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Universitair Ziekenhuis Brussel
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04974593
- Sponsor's protocol ID
- PreVaIL
- Status last verified
- Dec 2025
- First submitted
- 13 Jul 2021
- Last updated
- 18 Dec 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 18 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Predictive Value of Hydrogen/Methane Lactose Breath Testing on the Therapeutic Effect of Lactose-free Diet in Moderate to Severe ROME IV IBS.
- ClinicalTrials.gov ID
- NCT04974593
- Acronym / sponsor ID
- PreVaIL
- Conditions
- Irritable Bowel Syndrome, Lactose Intolerant
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 90 participants (estimated)
- Lead sponsor
- Universitair Ziekenhuis BrusselUniversity, hospital or other
- Study start
- 22 Oct 2021 (actual)
- Primary completion
- 1 Jan 2028 (estimated)
- Study completion
- 1 Jan 2028 (estimated)
- First posted
- 23 Jul 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Lactose intolerance (LI) results from lactose malabsorption (LM) secondary to insufficient hydrolysis of the disaccharide lactose into galactose and glucose (Misselwitz 2019). The undigested lactose will eventually reach the colon, resulting in fermentation from colonic bacteria with production of different compounds such as short chain fatty acids, carbon dioxide, H2 and methane (Catanzaro 2021). These compounds have an osmotic effect and can stimulate colonic contractions. These pathophysiological mechanisms encountered in patients suffering from LI generate symptoms, such as abdominal pain and cramps, flatulence, diarrhea, borborygmi among others. As dairy products are highly present in our Western diet, LI will often be considered in patients presenting with these symptoms and they will be referred for further testing. When LM is diagnosed, a lactose-free diet (LFD) will be advocated to alleviate symptoms. However, studies indicate that individuals with LM should tolerate up to 12 g of lactose when administered in a single dose (Suchy 2010).
Irritable bowel syndrome (IBS) is another frequently encountered disorder. According to the Rome IV criteria, it is characterized by abdominal pain associated with a change in stool frequency or consistency, or with symptomatic improvement by defecation (Mearin 2016). Associated symptoms, such as bloating and flatulence, are frequently reported. As such, discerning between IBS and LI based on symptoms alone can be challenging. Moreover lactose is considered part of the so-called fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). A low FODMAP diet has been advocated for IBS with beneficial response in at least part of the patients (Halmos 2014).
Many studies investigated the role of lactose in IBS. These studies were performed in the pre-Rome IV era and before standardized interpretation rules for Hydrogen breath testing (H2BT) were published (meta-analysis by Varju 2019). This meta-analysis indicated that subjective LI was more frequently reported by IBS patients, but also objectively more prevalent in IBS patients, when assessed by any test modality. However, the role of a LFD in IBS remains uncertain.
This study aims to:
- Determine if the diagnosis of LM by H2BT predicts the short-term and long-term response to a LFD in moderate to severe IBS as defined by Rome IV criteria;
- Determine the changes in quality of life in response to a LFD in ROME IV IBS patients.
Study design
- Primary purpose
- Diagnosis
- Allocation
- Non-randomised
- Intervention model
- Single group
- Masking
- Triple blind (participant, care provider, investigator)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| H2BT-positive | Experimental | Other: low fat diet |
| H2BT-negative | Experimental | Other: low fat diet |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Fulfilling the ROME IV criteria for IBS;
- Moderate symptom severity as defined by a IBS-SSS > 175;
- Consumption of lactose containing products.
Key exclusion criteria (16 listed)
- Clinical suspicion of an organic disorder different from LI or IBS (patients can be included when this disorder had been excluded);
- Known lactose intolerance or malabsorption;
- Known inflammatory bowel disorder;
- Known intestinal motility disorder;
- Alcohol (defined as more than 14 U per week) or other substance abuse;
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| low fat dietA trained dietitian will provide instruction of the LFD according to standard practice. | Other | H2BT-negative, H2BT-positive |
Primary outcome
symptomatic improvement
Time frame: from baseline till visit 4 (week 4)
To compare the symptomatic improvement by a LFD in Rome IV IBS patients with and without LM according to a H2BT.
1 secondary outcome
reduction in Irritable bowel syndrome - symptom severity scale
Time frame: baseline till visit 4 (week 4)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 18 Dec 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing low fat diet in people with Irritable Bowel Syndrome and Lactose Intolerant, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 16 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 18 Dec 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Sébastien Kindt, MD (+32 2 476 ext. 37 15, Sebastien.kindt@uzbrussel.be), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
symptomatic improvement (time frame: from baseline till visit 4 (week 4)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 18 Dec 2025.