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