Urinary tract infections are the second most common type of infection in U.S. adults, accounting for about 8.1 million visits to health care providers each year. It’s a long-standing adage that drinking cranberry juice can help, but what does the evidence say?

A systematic review published in the Cochrane Library last year found that cranberry-containing products don’t prevent urinary tract infections.

The review included 24 trials with a total of more than 4,400 participants comparing cranberry products with no treatment or alternative treatments. There was a small trend towards fewer UTIs in women with recurrent infections who drank cranberry juice over the course of a year, but the finding was not statistically significant.

A second review published in the Journal of the American Medical Association this year found similar results. It included 13 studies with a total of more than 1,600 participants. Like the Cochrane review, it found that cranberry products may protect against UTIs for some people, but “the conclusion should be interpreted with great caution” because the data are not clear.

In the end, more evidence is needed on this topic. Since there are few, if any, side effects to drinking cranberry juice, it can’t hurt for people who suffer from urinary tract infections. But the data certainly don’t demonstrate that this practice is consistently helpful.