Cranberry extract

What is cranberry?

The American cranberry (Vaccinium macrocarpon) is a tart red berry native to North America. It is eaten as juice, sauce and dried fruit, and sold as capsules and tablets made from concentrated juice or whole-berry powder. Cranberries are rich in polyphenols, especially a type called A-type proanthocyanidins (PACs).

PACs are thought to explain cranberry’s main traditional use: urinary tract health. Laboratory research suggests they can make it harder for certain E. coli bacteria to stick to the lining of the urinary tract, which is an early step in infection.

What the research says

Cranberry is one of the most studied supplements for urinary health. A 2023 Cochrane review included 50 randomized trials with 8,857 participants. Overall, cranberry products reduced the risk of symptomatic, culture-verified UTIs by about 30% compared with placebo or no treatment. The benefit was clearest in women with recurrent UTIs, in children, and in people susceptible to UTIs after bladder-related procedures. There was little or no benefit in institutionalized older adults, pregnant women, or adults with bladder-emptying problems caused by nerve or muscle conditions.

The NCCIH summarizes the evidence more cautiously, noting that findings are inconsistent and some research is low quality, and estimating that cranberry may reduce symptomatic recurrent UTIs in women by about 25%. It stresses that cranberry is not recommended as a treatment for an existing UTI, and that turning cranberry into tablets or capsules can lower PAC content and may reduce effectiveness.

Cranberry research focuses on infections. There is no good evidence that cranberry helps urinary incontinence, urgency or bladder control in the absence of infection.

How it’s used in supplements

Cranberry supplements vary enormously in quality and strength. The most useful labels state the amount of PACs per serving and the testing method used. Some trials of capsules have targeted about 36 mg of PACs or more per day, while juice studies typically used one or two glasses daily. A product that lists cranberry only inside a proprietary blend, even if standardized to a percentage of PACs, does not let you calculate the actual dose.

Cranberry is generally considered safe. Large amounts can cause stomach upset or diarrhea. Evidence on an interaction with the blood thinner warfarin is conflicting, so people on warfarin should check with their doctor. Anyone with symptoms of a UTI, such as burning, urgency, fever or blood in the urine, should see a clinician rather than rely on cranberry.