Antibiotics were better than cranberry capsules at preventing urinary tract infections in a new study of women in the Netherlands who suffered from recurring infections.

Women taking the drugs had fewer UTIs over the next year than those taking cranberry capsules, but they also built up resistance to the antibiotics, meaning that their bodies might not respond to the drugs if they needed them to treat another infection.

When it comes to antibiotics for UTIs, "there's a really important need here to look for alternatives and to reconsider both what we've done in terms of treatment and prophylaxis," said Betsy Foxman, an epidemiologist at the University of Michigan School of Public Health in Ann Arbor who didn't participate in the new research.

Cranberries have long been thought to help prevent UTIs through "anecdotal evidence," she told Reuters Health, but doctors aren't sure how they might work, and more rigorous studies have shown mixed results on their effectiveness.

Up to three in ten women suffer from recurring UTIs at some point in their lives, the authors of the new study write in Archives of Internal Medicine. The infections often come with a strong urge to urinate frequently as well as a burning sensation during urination.

While they usually go away on their own, UTIs are treated with antibiotics to ease the symptoms and to prevent rare complications. Sometimes, doctors also prescribe an antibiotic to women who have already had a few UTIs to prevent another one, because "the longer you can go without having one, the more likely it is that you'll never have another one," Foxman explained.

In the new study, researchers led by Dr. Marielle Beerepoot of Amsterdam's Academic Medical Center randomly assigned 221 premenopausal women with at least three UTIs in the past year to take the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX) or cranberry capsules each day.

After one year, women taking the antibiotic had reported an average of close to two UTIs, compared to four in the cranberry group. On average, women got their first new infection eight months after starting the drug treatment versus four months into taking cranberry capsules.

One woman taking the antibiotics had a serious reaction to the drugs.

Resistance to TMP-SMX, and some similar antibiotics, also shot up in the antibiotic group within one month.

That's important because resistant bacteria won't be killed off by many common antibiotics and the same bacteria that become resistant to UTI drugs can also cause more serious infections.

"My concern is this: UTI is one of the most common bacterial infections," Foxman said. "When you give antibiotics even for a short duration on a large scale, you definitely push toward antibiotic resistance."

When the drugs are given for prevention and not just for treatment, that risk of resistance increases, she said.

In women in the study taking antibiotics, resistance levels did return to normal a few months after they stopped taking the drugs.

Foxman said that women with recurrent UTIs should have a conversation with their doctor about preventing the infections, taking issues such as antibiotic resistance into consideration.

The question, she said, is "whether you feel like you're so miserable that you really need them or you want to go to alternatives first."

Taking vitamin C or making sure to urinate often enough might also help ward off UTIs, she added.

And, "certainly taking cranberry juice is not going to hurt you and it may help."

Bill Gurley, from the University of Arkansas for Medical Sciences in Little Rock, told Reuters Health that one issue with these studies is that the cranberry doses used may be too low to be effective for UTI prevention. However, the best dose of the active ingredients in cranberries has yet to be figured out, he added in a commentary published with the study.

Both TMP-SMX and cranberry capsules start at about 25 cents per day.

The authors note that the cranberry capsules used in the study were provided by Springfield Nutraceuticals and that the rest of the study funding came from a national health research organization.

The take-home message of the study, Beerepoot told Reuters Health, "is that cranberries are less effective than the antibiotics, but antibiotic resistance is a big problem." Other studies have pointed to a possible benefit of cranberry juice or extract, she said, without serious side effects.

"Maybe therefore cranberries can be an alternative for those women who don't want to take antibiotics" because of resistance worries, she said.