Taking people in BelgiumPhase 3

Predictive Value of Hydrogen/Methane Lactose Breath Testing on the Therapeutic Effect of Lactose-free Diet in Moderate to Severe ROME IV IBS.

Key facts

Who runs it: Universitair Ziekenhuis Brussel
Where: Jette, BelgiumSee the site
Trial code: NCT04974593
Status: Recruiting
Phase: Phase 3
People taking part: 90 people, planned
Started: 22 Oct 2021
Expected to end: 1 Jan 2028
Type of study: Interventional, 2 groups
Treatments tested: low fat diet
Record updated: 18 December 2025

Who can take part

Age: 18 years to 75 years
Sex: Women and men
Healthy volunteers: Cannot take part

The registry criteria, word for word

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Who can take part

Fulfilling the ROME IV criteria for IBS
Moderate symptom severity as defined by a IBS-SSS > 175
Consumption of lactose containing products

Who cannot take part

Prior abdominal surgery (with the exception of appendectomy)
Any prior diagnosis of cancer other than basocellular carcinoma
Current chemotherapy
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
Clinical suspicion of an organic disorder different from LI or IBS (patients can be included when this disorder had been excluded)
Known inflammatory bowel disorder
Known intestinal motility disorder
Active psychiatric disorder
Known systemic or auto-immune disorder with implication for the GI system
History of gastro-enteritis in the past 8 weeks
Known lactose intolerance or malabsorption
Alcohol (defined as more than 14 U per week) or other substance abuse
Intake of antibiotics, pre- or probiotics during the past 8 weeks
Dietary supplements unless taken at a stable dose for more than 8 weeks
LFD or low FODMAP diet in the past

Check if you might fit

Answer for yourself. This is not a decision: only the study team can say whether you can take part.

Are you between 18 and 75 years old?

Where in Belgium

UZ BrusselJette, BelgiumContact: Sébastien Kindt, MDTaking people

About the trial

What the trial wants to find out

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).

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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.