Clinical Trial: Randomised Placebo-Controlled Trial of Methylcellulose and Psyllium Gels on Inulin-Induced Colonic Gas

Background People with irritable bowel syndrome (IBS) often restrict their intake of FODMAPs because of associated gas and abdominal discomfort. Psyllium, a gel-forming fibre, reduces colonic gas after inulin ingestion.

Objective We aimed to determine whether methylcellulose, a low-cost, non-fermentable gelling agent, widely used in food manufacture, could be formulated to match psyllium's physical properties and similarly moderate colonic fermentation of inulin.

Methods 3-way randomised cross-over study giving 15 g inulin with 15 g methylcellulose, psyllium or maltodextrin (placebo) in 22 healthy volunteers. Participants underwent hourly MRI scans for 6 h and serial breath hydrogen measurements for 24 h when a final MRI scan was performed.

Results Methylcellulose and psyllium gels did not significantly alter AUC0–360 min, however, they were associated with less colonic gas after the gels reached the colon (AUC180–360 min, p = 0.02). The gels increased AUC0–240 min of small bowel free water (p < 0.0001 and 0.048, respectively), methylcellulose effect>psyllium (p = 0.0005). Both increased colon chyme wateriness (T1AC, AUC180–360 min, p < 0.0001) and volume of hydrated fibre in colon (AUC180–360 min, p < 0.0001 and 0.0009, respectively). Both parameters were greater after methylcellulose than psyllium (p = 0.01 and 0.02, respectively). 24 h measurements of breath hydrogen were not different between groups (AUC0–24 h, p = 1.0) but were reduced by psyllium in the 0–6-h period p = 0.008.

Conclusions Methylcellulose and psyllium reduce colonic gas produced by inulin after the gels reach the colon. Methylcellulose increases the water content of both the small and large bowel more than psyllium. This additional effect may allow improved tolerance of FODMAPs, particularly in IBS patients with constipation.

Trial Registration: ClinicalTrials.gov identifier: NCT06291272