Cranberry for Urinary Tract Infection
In specific groups (women with recurrent UTIs, children, and people at risk after procedures), cranberry products modestly lower the chance of getting another UTI, but the effect is small and inconsistent and cranberry does nothing for an active infection, which still needs antibiotics.
Why this grade7-layer evidence engine
The evidence is graded B (preliminary) because the studies point the same direction but the benefit is modest and population-restricted. The 2023 Cochrane review (PMID 37947276), pooling 50 trials and 8,857 people, found cranberry cut recurrent-UTI risk in women (RR 0.74), children (RR 0.46), and post-intervention patients (RR 0.47), but rated certainty only moderate and found no benefit at all in older institutionalized adults, pregnant women, or people with neurogenic bladders. Three further analyses agree on a roughly 25-50% reduction: a 2017 meta-analysis (PMID 29046404, RR 0.74), a 2024 network meta-analysis (PMID 39030132), and a 2025 trial (PMID 39863114).
It is flagged 'disputed' mainly because regulators split sharply. The US FDA allows only a qualified claim, calling the evidence 'limited and inconsistent,' while the EU's EFSA has rejected every cranberry-UTI claim (2009, 2011, 2025) for failing to prove cause and effect. The UK NHS says it 'may help' but warns warfarin users to avoid it. Clinics are likewise mixed: Mayo calls it unproven but 'likely not harmful,' Harvard is skeptical, while Cleveland Clinic and urology specialty guidance are more supportive.
Two cautions temper the grade. The women's-recurrence effect is borderline (Cochrane upper confidence limit 0.99, nearly no effect), and the strongest recent trial (PMID 39863114) was industry-funded, so bias cannot be ruled out. Bottom line: a reasonable preventive option for the right person, not a treatment and not a sure thing.
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 = 0.649
- 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 1 個 hard + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status