Cranberries are a healthy food choice—full of possible cancer-fighting antioxidants—but what other benefits does the bittersweet bog berry hold? Some studies have shown that cranberries are as effective as antibiotics in preventing and treating painful urinary tract infections (UTIs), while others found they have very little benefit. The latest analysis finds that cranberries are less effective than antibiotics in fighting infections, but doctors aren’t ready to abandon the fruit just yet.
In any given year, about 11% of women report having had an episode of UTI. Just over 50% will have one during their lifetime. And by one estimate, 30% of the women who have had at least one UTI will go on to have recurrent ones, defined as two or more infections a year. That’s a huge expense to our health care system: according to the New England Journal of Medicine, UTIs are responsible for approximately 3.6 million doctor’s visits per year at a cost of $1.6 billion.
Reporting in the Archives of Internal Medicine, Dutch researchers studied a cranberry supplement—which contains more of the fruit’s anti-infection agent than diluted juices do—to test cranberries head-to-head against antibiotic treatments. The fruit contains condensed tannins called proanthocyanidins that prevent E. Coli bacteria — the primary UTI culprit — from attaching to the walls of the urinary tract. The scientists split 221 women who suffered from recurrent UTIs (rUTIs) into two groups, and each received preventive therapy for 12 months. One group received Bactrim, a low-dose antibiotic that’s commonly given to women with rUTIs while the other group took a dose of cranberry extract.
Over the 12 months of study, the cranberry group had an average 4 recurrences, compared to 1.8 average recurrences among the antibiotic group. In addition, the drug group reported an average eight months before they had their first recurrence, compared to four months in the cranberry group.
Those results weren’t encouraging, but despite the cranberry supplement’s weaker showing, the researchers didn’t write it off entirely. They tested the women for drug resistance in fecal bacteria and E. Coli samples, and found that after just one month, the women who were taking the antibiotic were already far more likely than women taking the cranberry supplement to be resistant to the drug they were taking. Not only were 86% of fecal samples and 90.5% of E. Coli samples coming from Bactrim users resistant to the antibiotic, they were also more resistant to other antibiotics, like trimethoprim, amoxicillin and ciprofloxacin. By contrast, 24% of the fecal and 28% of the E. Coli samples from women on cranberry pills had the same resistances.
Avoiding drug resistance is one reason why cranberries, despite their weaker anti-bacterial effect, are worth considering, particularly among younger women. In older women, hormonal changes can cause atrophy in the lining of the vagina and urethra that make them more susceptible to bacterial infection; urologists estimate that 25% of all post-menopausal women will have recurrent rUTIs. For these women, a topical estrogen cream can help.
But in younger women, sexual activity is the primary cause of infection, since intercourse can introduce fecal bacteria to the urinary tract and urethra. For pre-menopausal women who suffer from rUTIs, prevention is just as important as treatment. “I always suggest preventative measures after the initial infection has cleared up to prevent further infections,” says Dr. Janice Santos, an urologist at Mount Sinai Medical Center in Miami. But because of the potential to develop resistance to antibiotics, some physicians are eager to suggest alternatives to the drugs, especially when it comes to preventing, and not treating infections.
Santos says antibiotic resistance is an important consideration for her when determining how to treat women with rUTIs. “I try to work with patients mostly in preventative measures instead of giving antibiotics all the time, because they can develop resistances or other problems,” says Santos, adding that she often recommends a cranberry supplement. Doctors are also advising their patients to take other precautionary measures such drinking at least six glasses of water per day, maintaining personal hygiene and avoiding spermicidal lubricants.
Still, physicians rely on scientific evidence to support their decisions, and when it comes to confirming the infection-fighting properties of cranberries, the results aren’t encouraging. In addition to the current report, others have shown that cranberries may not have as potent an effect against bacteria as researchers hopes. In one study released in late January of this year, investigators found that cranberry juice cocktail was ineffective in preventing urinary tract infections.
Experts note, however, that in that study, the researchers used OceanSpray Low Calorie Cranberry Juice Cocktail, which is high in sugar and low in actual cranberries. Sugar, it turns out, promotes bacterial growth, potentially confounding results — and the drink’s dilution may have provided doses too small to be effective.
“When you have a juice, there’s probably almost none of the proanthocyanidins that provide the benefit,” says Jillian Capodice, a holistic urologist who is the director of Director of Acupuncture and Integrative Service at the Columbia University College of Physicians and Surgeons. “It’s just not strong enough. So if you’re going to choose a cranberry supplement, it should be tested for bioavailability of the compound that fights infection.”
Giving women the power to protect themselves is another reason that some physicians are willing to give cranberries a try. Dr. Andrew Flisser, a gynecologist and urogynecologist in private practice in New York City who recommends both antibiotics and cranberry supplements, dismisses the gravity of antibiotic resistance for individual patients. But, he says, “Some women prefer something all natural, and another aspect of this is empowering women to care for themselves: a woman can buy cranberry capsules over the counter, which offers more flexibility. Even if the treatment is marginally less effective, there’s a trade-off.”
Self-treatment with cranberries may allow a woman with rUTIs to monitor herself and obtain a treatment without a prescription, it has a down side as well; some of the symptoms of a UTI are similar to those of other diseases, including pelvic floor dysfunction, for example, or a sexually-transmitted infection that require more intensive treatment.
That can be even more of a problem for women who take a prophylactic antibiotic treatment. “Patients self prescribe and take an antibiotic, but if it doesn’t clear up the infection, they come in and give a sample that’s been partially treated,” says Santos. “So you don’t really know what kind of bacteria you’re treating. It interferes with diagnosis.”
It’s clear that there are no simple answers to whether cranberries can prevent or treat UTIs, but they’re safe, somewhat effective, and widely available — and therefore certainly worth a conversation with your doctor.
Meredith Melnick is a reporter at TIME. Find her on Twitter at @MeredithCM. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.