But does this tart and tangy remedy really work? According to a comprehensive review of dozens of previous studies, the answer is yes—especially for people at high risk of recurrent infections.
The new review, published in The Journal of Urology, analyzed the results of 28 clinical trials involving nearly 5,000 patients. Overall, the authors found that the consumption of cranberry products (juices, capsules, tablets, or extracts) was associated with about a 32% reduced risk of repeat UTIs.
When the researchers looked closely at specific subgroups, they found that the benefits were particularly strong for people who had undergone gynecological surgery—a risk factor for recurrent infections.
Cranberries contain a unique type of antioxidant called proanthocyanidins (PACs for short) that keep E. coli and other infection-causing bugs from sticking to the bladder walls, the authors explain in their paper. “If the bacteria are not able to adhere to cells, they cannot grow and cause infection,” they wrote.
Some studies, and even a previous review of medical literature, have found little to no benefit from using cranberry products to prevent UTIs, and some experts say that commercial cranberry products don’t contain enough PACs to significantly affect urinary health.
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But the authors say their new paper, which includes more recent research and uses a newer analytical approach, paints a more complete picture of the overall body of evidence. (The review was part of a research fellowship supported by the Universidade da Beira Interior and the bank Santander/Totta, and the authors disclosed no industry funding or conflicts of interest.)
The studies included in the review used various doses and formulations of cranberries, so the authors were not able to develop specific recommendations for how much or what kind of products work best. But they say their findings support the idea that cranberries, in general, can be a powerful tool for fighting off frequent UTIs.
Still, some cranberry products may be more helpful than others. Sovrin Shah, MD, a urologist and specialist in female pelvic medicine and reconstructive surgery at Mount Sinai's Ichan School of Medicine in New York, says he recommends cranberry extract "for anyone who has recurrent urinary tract infections." Dr. Shah was not involved in the new review, and does not recommend drinking cranberry juice.
"Juice simply adds calories that are unnecessary, plus the cranberry juice is not concentrated," he says. "I think a person would have to drink an unhealthy amount of juice to get enough of the active ingredient to have a beneficial effect." When choosing an extract—in either liquid and capsule form—he suggests looking for one that contains ingredients certified by an independent lab.
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The new paper should give more doctors the confidence to recommend cranberry products as an inexpensive, drug-free option for the one in three women who experience a UTI by age 24, they authors say. (Want more protection? Peeing before and after sex, and getting frequent exercise, can help too.)
“The results of the current study could be used by physicians to recommend cranberry ingestion to decrease the incidence of urinary tract infections, particularly in individuals with recurrent urinary tract infections,” they wrote in their paper. “This would also reduce the administration of antibiotics, which could be beneficial since antibiotics can lead to the worldwide emergence of antibiotic resistant microorganisms.”