Psyllium in Pediatric IBS

This clinical trial, led by Dr. Bruno Chumpitazi and currently recruiting, is testing whether psyllium — a soluble dietary fiber — can reduce gut symptoms in children with irritable bowel syndrome (IBS) who are sensitive to fructans, a type of fermentable carbohydrate found in common foods like wheat and onions. The core idea is that psyllium might change how gut bacteria ferment fructans, potentially shifting the process in ways that produce less gas and fewer symptoms. The study first screens children by having them eat a fructan-rich diet across two three-day periods to confirm that fructans actually worsen their IBS; only those confirmed to be fructan-sensitive then advance to the main trial. Confirmed participants then undergo two weeks of dietary baseline followed by two weeks eating a fructan-containing diet alongside either psyllium (at one of two doses) or a glucose placebo. The study measures several detailed microbial outputs including intracolonic pH, hydrogen gas production, gut microbiome composition, fecal short-chain fatty acids (SCFAs), lactate, and glycomics — making it one of the more mechanistically thorough fiber trials in pediatric IBS. The dual-aim design means it can connect microbial fermentation changes directly to symptom outcomes, which is relatively rare in pediatric functional GI research. Results could help explain why some fiber interventions improve IBS while others worsen it, and could offer a practical dietary strategy for fructan-sensitive children.

• Trial is actively recruiting as of 2026; no results have been published yet — all findings listed here reflect the study's pre-specified aims and outcome measures, not observed data.
• Primary mechanistic aim (Aim 1): the study will quantify whether psyllium at two doses modifies microbial fructan fermentation as measured by intracolonic pH, H2 gas production, gut microbiome composition, fecal SCFAs, lactate, and glycomics.
• Primary clinical aim (Aim 2): the study will determine whether psyllium co-ingested with a fructan meal reduces fructan-induced gastrointestinal symptoms in children with IBS who have been prospectively confirmed as fructan-sensitive.

This is a randomized, placebo-controlled clinical trial enrolling children with IBS who demonstrate symptom worsening during a standardized fructan dietary challenge across two three-day run-in periods. Fructan-sensitive participants then complete two weeks of unmodified baseline diet followed by two weeks on a controlled fructan-containing diet supplemented with either psyllium (one of two doses) or glucose as placebo. Outcome measures span both functional fermentation biomarkers (intracolonic pH, breath hydrogen, microbiome 16S or metagenomic profiling, fecal SCFA/lactate/glycomics) and patient-reported GI symptom severity. The trial is registered under NCT06639984 with an estimated completion date of May 2026.

Because the trial is still recruiting, no efficacy or safety data are yet available, and all mechanistic interpretations remain speculative pending results. The two-week dietary intervention window may be insufficient to capture stable microbiome remodeling, and it is unclear whether effects will persist once psyllium supplementation stops. The fructan-sensitivity screening design, while rigorous, means findings will apply only to a select subgroup of pediatric IBS patients, limiting generalizability to the broader IBS population. A longer-term follow-up arm comparing microbiome trajectories post-intervention would clarify whether any observed fermentation shifts are durable.

This trial extends [§76], which examined how a gel-forming dietary fiber (OptiFibre/partially hydrolyzed guar gum) altered carbohydrate metabolism and intestinal microbiota fermentation in adults with type 2 diabetes, by applying a similar fiber-fermentation mechanistic framework to pediatric IBS with fructan-specific dietary provocation. It parallels [§73], which probed how Mediterranean diet shifts bile acid profiles and gut microbiome composition to reduce colorectal cancer risk, in that both studies treat the microbiome as a functional intermediary between a dietary input and a downstream clinical outcome rather than a static compositional snapshot. The glycomics and SCFA readouts connect it conceptually to [§75], which tracked early microbial colonization and metabolite production in healthy infants receiving probiotics, demonstrating that microbial metabolic output — not just taxonomy — is the proximal driver of gut physiology. Taken together, the trial occupies an important niche in the corpus: it is the only registered RCT using dual-dose fiber co-administration with a fermentable substrate challenge and multi-omic fermentation readouts in a pediatric functional GI population, making its eventual results a likely reference point for interpreting fiber-microbiome interactions across the other studies indexed here.

• The Effect of OptiFibre Dietary Fiber on Carbohydrate Metabolism and Intestinal Microbiota Metabolism in Patients With Type 2 Diabetes Mellitus
  Most directly analogous mechanistic design: tests how a dietary fiber supplement reshapes gut microbiota fermentation and carbohydrate metabolism using SCFA and metabolite readouts, though in adults with type 2 diabetes rather than children with IBS.
• Mediterranean Diet and Weight Loss: Targeting the Bile Acid/Gut Microbiome Axis to Reduce Colorectal Cancer
  Uses the microbiome as a functional bridge between a structured dietary intervention and a clinical endpoint (cancer risk reduction), mirroring this trial's logic of linking psyllium-altered fermentation to IBS symptom relief.
• Influence of Probiotics on Early Gut Microbial Colonization
  Offers a pediatric microbiome baseline for comparison: examines how early microbial colonization and metabolite profiles respond to a biological intervention, useful context for interpreting microbiome plasticity in child cohorts.
• A single-strain dropout screen reveals mechanistic links between microbial ecology and metabolism
  Single-strain dropout experiments provide mechanistic resolution on how individual microbial species drive ecological and metabolic outcomes — directly relevant to interpreting which taxa mediate psyllium's effect on fructan fermentation in this trial.