Probiotics for Diarrhea
"Probiotics for diarrhea" is too broad to verify as a single claim: the evidence is genuinely strong for preventing antibiotic-associated and C. difficile diarrhea but weak, conditional, or even discouraged for other types, so no clean overall grade is warranted. Which strain, dose, and exact diarrhea scenario you mean matters enormously.
Why this grade7-layer evidence engine
The grade is Unverified not because probiotics fail, but because "diarrhea" lumps together very different situations that the underlying trials treat separately. Five 2021-2025 systematic reviews and meta-analyses all point positive: a 2025 Cochrane review found probiotics roughly halved C. difficile-associated diarrhea (RR 0.50, NNT 65; PMID 40931979), and two adult meta-analyses cut antibiotic-associated diarrhea by 37-40% (RR 0.63, PMID 34385227; RR 0.60, PMID 40191517), with multi-strain formulas outperforming single strains.
But the signal weakens at the edges. In children with acute gastroenteritis the benefit was statistically positive yet imprecise, with an implausibly wide confidence interval (PMID 40739406), and for travelers' diarrhea the effect was small and strain-dependent (RR 0.85; PMID 36221413). Clinical bodies split accordingly: Cleveland Clinic and Harvard call antibiotic-associated diarrhea the strongest use case, while the AGA conditionally supports probiotics for C. difficile prevention but advises against them for pediatric acute gastroenteritis.
Regulators add caution that keeps an umbrella endorsement off the table. EFSA has rejected gut-health claims, finding no established cause-and-effect relationship, the UK NHS says little evidence backs most marketed claims, and the FDA has not approved any probiotic as a drug and has flagged serious safety concerns in infants. The honest read: helpful for specific, well-defined scenarios and strains, not a blanket "probiotics treat diarrhea."
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 = 0.646
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (5 篇 > 0 negative)
- tier_strict_requirement_check — | B→U 因 scope.conflation_risk=true 且 L11 獨評較低 (B7-2 tier cap)
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status