Vaccinium macrocarpon · herb
Evidence tier: moderate
Prevents and treats urinary tract infections by blocking E. coli from adhering to the bladder wall, one of the most evidence backed natural UTI interventions
Cranberry carries A type proanthocyanidins, a form of tannin with an unusual double linkage that most other plants do not make. In the laboratory these interfere with the sticky hair like fimbriae that uropathogenic E. coli use to grip the bladder wall, so the bacteria are flushed out with urine instead of taking hold. This anti adhesion account is the standard explanation and is consistent with the fact that cranberry prevents but does not cure. It is a plausible mechanism, not a proven one in people, and Cochrane notes that the amount of proanthocyanidin actually delivered varies enormously between products.
Moderate, and this one genuinely earns it, but only for PREVENTION of recurrent UTI in specific groups. Cochrane's position on cranberry changed. The 2023 update (Williams G et al, Cochrane Database Syst Rev, PMID 37947276, 50 studies, 8,857 participants) concludes that the data support the use of cranberry products to reduce the risk of symptomatic, culture verified UTIs in women with recurrent UTIs, in children, and in people susceptible to UTIs following an intervention such as bladder radiotherapy. In women with recurrent UTIs specifically the pooled result is RR 0.74, 95 percent CI 0.55 to 0.99, from 8 studies in 1,555 participants, rated MODERATE certainty by GRADE. That is a real, replicated, independently graded effect and it should not be talked down. NCCIH puts it in consumer terms: cranberry products may cut the overall risk of symptomatic recurrent UTIs in women by about 25 percent. The limits are just as important. Cochrane found cranberry probably makes little or no difference in older people in institutions, in pregnant women, and in people with bladder emptying problems. And cranberry does NOT treat an existing infection: the companion 2023 Cochrane review on treatment (Jepson RG et al, PMID 38096261) found not a single randomised trial had ever been done, so there is no evidence at all that cranberry treats an active UTI. Prevention yes, in the right person. Treatment no.
No single sourced dose. Trials in the Cochrane review used juices, capsules and tablets of widely differing strength, and Cochrane specifically flags that the dose and the proanthocyanidin content of products vary and that this is a weakness of the literature. NCCIH adds that processing cranberries into tablets or capsules can reduce the proanthocyanidin content. Products are commonly standardised to 36 mg of A type proanthocyanidins daily, but that figure comes from the supplement industry, not from a regulator or from Cochrane.
For prevention: drink 240ml unsweetened cranberry juice daily or take 400 to 500mg cranberry extract. For acute UTI support: take twice daily with plenty of water. Works best as a preventive measure for recurrent UTIs.
Onset: ~7 days
Safe and well tolerated. High long term doses may increase kidney stone risk in oxalate stone formers. May increase INR in warfarin patients (multiple case reports), monitor closely. Does not treat active UTI.
Pregnancy: safe
Breastfeeding: safe
Used by Native American peoples for urinary tract complaints and as a food source for centuries. Adopted into European and North American folk medicine for urinary health in the 19th century. The proanthocyanidins in cranberry are among the best studied compounds for UTI prevention.
Active compounds: A type proanthocyanidins, quercetin, myricetin, ursolic acid, benzoic acid, vitamin C
Remedies using Cranberry · Browse by body system · Check it against what you take
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.