Digestive Enzymes for Irritable Bowel Syndrome
Over-the-counter digestive enzyme supplements have only weak, inconsistent evidence for irritable bowel syndrome (IBS), and no major guideline recommends them. The strongest signal comes from a small subgroup of patients who turn out to have a separate pancreatic disorder rather than true IBS.
Why this grade7-layer evidence engine
This earns a weak grade because the IBS-specific trials are few, small, and conflicting. A double-blind RCT of pancrealipase (PMID 22095308, n=49) missed its primary endpoint (61% patient preference, p=0.078), with benefit confined to a post-hoc subgroup. A crossover RCT of alpha-galactosidase (PMID 33619835, n=20) was outright negative, matching placebo on both symptoms and breath gas. An open-label trial (PMID 28724171, n=43) showed improvement, but it tested a beta-glucan plus inositol plus enzyme blend, so no enzyme-specific effect can be isolated.
The one consistent positive signal is misleading. In a cross-sectional study (PMID 19835990, n=514), about 6% of diarrhea-predominant IBS patients had low fecal elastase, meaning misdiagnosed exocrine pancreatic insufficiency (EPI); enzymes helped only that subgroup, not patients with normal pancreatic function. That is a different diagnosis, not evidence of efficacy in genuine IBS.
Regulators (FDA, NHS, WHO) endorse pancreatic enzymes only as prescription replacement therapy for diagnosed pancreatic insufficiency, not as OTC supplements for IBS. Cleveland Clinic and Harvard Health call the evidence limited, and neither the ACG nor AGA IBS guidelines recommend digestive enzymes, which keeps this at a weak rating with a warning rather than a clear endorsement.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.46
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 無高階證據可裁決
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status