Legacy AI grade · Sources dated 2026-06-01. Not expert reviewed. Coverage is limited to the listed sources. About the new summary workflow
Prebiotics for Constipation
Prebiotics such as chicory inulin may modestly improve bowel regularity in people with chronic constipation, but only at roughly 12 g/day for several weeks, and the evidence is inconsistent. They are not a reliable first-line fix and commonly cause gas and bloating.
Why this grade7-layer evidence engine
The grade is held to weak because the trials disagree. A 2014 inulin-specific meta-analysis of 5 RCTs (PMID 25208775, n=252) found significant gains in stool frequency, consistency and transit time, and a small 2025 cross-over RCT at 12 g/day (PMID 41233756) was positive in people with functional constipation. But the larger and more recent 2022 fibre meta-analysis (PMID 35816465, n=1251) found that, in its fibre-type subgroup, inulin-type fructans did NOT significantly raise stool frequency, with the benefit driven by psyllium, pectin and wheat bran instead.
Benefit is also conditional. A 2017 RCT (PMID 27680592) using 8 g/day in people with normal bowel habits showed no change, confirming that any effect depends on a constipated population and an adequate dose. A 2022 review (PMID 36570175) calls inulin the most promising prebiotic for constipation yet stresses that solid human evidence is still limited. Several positive trials are industry-funded, and flatulence is a consistent, statistically significant side effect.
Regulators and clinics are split, which fits a mid-tier verdict. The US FDA recognises inulin-type fructans as dietary fibre, and EFSA authorises a chicory-inulin claim for normal defecation at 12 g/day. However, the NHS and WHO simply advise getting fibre (25-30 g/day) from whole foods rather than supplements, and Mayo Clinic is cautious, noting fermentable fibres may add gas with no constipation relief and preferring psyllium.
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 = 0.504
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 0 negative)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status