Researchers found that cranberry juice made with high concentrations of proanthocyanidins (PACs) cut kids' risk of repeat urinary tract infections by two-thirds, versus a comparison juice.

Since the juice on your supermarket's shelves may not have that PAC level, the researchers say their findings are not an endorsement of any product.

But the results, published in the Journal of Urology, do give support to cranberry as a UTI fighter, according to a pediatric urologist not connected to the study.

PACs are the compounds thought to give cranberries their bacteria-fighting potential. Women have long turned to cranberry juice and supplements to help prevent recurrent urinary tract infections (UTIs) - though studies have been mixed on whether they work.

There has been little research on kids, even though UTIs are relatively common in children. Girls have about an 8 percent chance of contracting the infection at some point in childhood; boys have a 2 percent chance.

Besides being uncomfortable, recurrent UTIs can eventually damage the kidneys in some children. So doctors may prescribe antibiotics to help prevent them.

But antibiotics can have side effects, and using them long-term can breed drug-resistant bacteria. So researchers are looking at whether cranberry products can be a good alternative.

For the new study, doctors at the University of British Columbia in Vancouver, Canada, recruited 40 children who'd had at least two UTIs in the past year. They randomly assigned the kids to drink one of two juices made for the study: a cranberry juice rich in PACs or a juice free of all "cranberry products."

Over the next year, kids who drank cranberry juice had UTIs at a rate of 0.4 per child, compared with 1.15 in the comparison group.