Background and aims: Dietary fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) contribute to gastrointestinal (GI) symptoms in individuals with FODMAP sensitivity and irritable bowel syndrome. Oral enzyme supplementation is a strategy to reduce dietary FODMAP exposure and limit FODMAP-associated GI distress. This clinical trial investigated the safety of dietary supplementation with a food-grade, microbial inulinase known to hydrolyze fructan-type or inulin-type FODMAPs and related fructo-oligosaccharides in vitro.

Methods: A randomized, double-blind, placebo-controlled, parallel design trial was conducted in 60 healthy adult participants of both sexes. Following a 2-week run-in placebo phase, participants were randomized to consume inulinase or placebo capsules twice daily with meals for 4 weeks. The total daily dose of inulinase was 2000 inulinase activity units. Safety measures included blood clinical chemistry, hematology, lipid profile, high-sensitivity C-reactive protein, insulin, lactate, and uric acid. GI symptoms were recorded weekly using the 15-item Gastrointestinal Symptom Rating Scale.

Results: Fifty-eight participants completed the study. There were no clinically meaningful between-group differences in blood biomarkers. During the 4-week intervention period, 5 (16.7%) of 30 participants reported 5 adverse events in the inulinase group, and 8 (26.7%) of 30 participants reported 13 adverse events in the placebo group. No statistically significant between-group differences were observed in the change from baseline to 1, 2, 3, or 4 weeks of supplementation with respect to the 15-item Gastrointestinal Symptom Rating Scale overall or domain scores.

Conclusion: Microbial inulinase supplementation demonstrated a favorable safety profile in healthy adults. Further investigation in a dose-ranging study in individuals with dietary FODMAP, fructan, or inulin sensitivity or irritable bowel syndrome is warranted. ClinicalTrials.gov: NCT05744700.