Cranberry extract
The classic UTI-prevention berry. Works through proanthocyanidins (PACs) that prevent E. coli adhesion — the same principle as D-mannose, by a different mechanism.
Moderate evidence for preventing recurrent UTIs in women — most consistent in those with high recurrence rate. Effect size smaller than D-mannose in head-to-head trials. Effects: prevention over weeks-months.
Cranberries contain proanthocyanidins (PACs), particularly A-type PACs, that prevent E. coli from adhering to the bladder wall. The mechanism is anti-adhesion, not antibacterial. Cranberry juice was the folk remedy for centuries; modern concentrated extracts deliver therapeutic PAC doses in capsule form without the sugar load. Effective for prevention of recurrent UTIs in some women (Cochrane reviews have been mixed — depends on PAC content and study design). Less useful for acute UTI treatment than D-mannose.
- Form
- Cranberry extract standardised to PAC content — look for ≥36 mg PACs per dose (the EFSA-recognised threshold). Cran-Max, Pacran are well-studied. Juice is much less concentrated and includes significant sugar.
- Dose
- 36–72 mg PACs daily (typically 500 mg cranberry extract or one capsule).
- Timing
- With or without food. PM is common (since UTI bacteria multiply overnight in urine).
- Schedule
- Daily for prevention.
- Side effects
- Generally well-tolerated. Mild GI upset. Tannins can cause minor stomach upset on empty stomach.
- Interactions
- Warfarin — multiple case reports of elevated INR with cranberry juice / high-dose extract. Monitor closely or avoid. Mild CYP enzyme effects in some studies.
- Contraindications
- On warfarin without monitoring. History of oxalate kidney stones (cranberry is high in oxalates).
- Lab markers
- Not standard. UTI symptom tracking.
- Food sources
- Fresh cranberries (very tart), dried cranberries (usually heavily sweetened), unsweetened cranberry juice. Food doses are far below therapeutic — supplementation is more practical.
Pairs with
D-Mannose (different anti-adhesion mechanism — synergistic). Probiotics with L. crispatus / L. rhamnosus GR-1 (vaginal flora). Vitamin C (urinary acidification, weak effect).
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