For thousands of years, Native Americans have used cranberries as a remedy for bacterial infections, like those of the bladder.

Today, unsweetened cranberry juice is often recommended by doctors as a treatment for urinary tract infections (UTIs), and yet given a lack of solid scientific evidence, some researchers have argued that "any continued promotion" of this remedy goes beyond the data.

Researchers at Bond University in Australia are now inclined to disagree.

Their recent meta-analysis, which includes 20 studies, suggests cranberry juice may not be so useless after all. Consumed regularly for weeks to months in randomized controlled trials (RCTs), the risk of developing a UTI has been found to drop.

Comparing the results of five such trials, researchers found that drinking cranberry juice led to a 27 percent lower rate of UTIs than a placebo liquid.

This result was reported with moderate certainty, which means the true effect size is probably close to the estimation.

Researchers also found that those drinking cranberry juice had a 49 percent lower rate of antibiotic use than the placebo group.

This doesn't mean that cranberry juice is a replacement for modern medicine, but it does suggest that the fruit drink can help keep recurrent infections at bay and reduce the future need for antibiotics.

"With moderate to low certainty, the evidence supports the use of cranberry juice for the prevention of UTIs," write researchers.

"While increased liquids reduce the rate of UTIs compared with no treatment, cranberry in liquid form provides even better clinical outcomes in terms of reduction in UTIs and antibiotic use and should be considered for the management of UTIs."

To improve on the certainty of those results, more randomized controlled trials are needed. These studies will have to tease apart how much cranberry juice needs to be consumed to have an impact on UTIs and for how long. They will also need to consider how cranberry juice impacts people of different ages and sexes.

More than 60 percent of women in the US will get a UTI at some point in their life, and roughly a quarter of all those infections will recur again within a year.

Despite the common nature of the infection, doctors in the US all too often prescribe the wrong antibiotics or wrong doses for UTIs. As a result, the bacteria behind these infections are growing resistant to many of our front line medicines.

Some studies have found more than 90 percent of UTIs currently exhibit bacterial resistance to antibiotics, and without alternative treatments, some women are forced to live with lifelong recurrences.

Cranberries could be a useful tool to prevent those recurrences. They may not even need to come in juice form. A trial that was included in the Bond review found that compared to no treatment, cranberry tablets produced a 35 percent lower rate of UTIs.

The findings echo another meta analysis, published in April of 2023, that reviewed 50 trials and found the risk of UTIs and recurrent UTIs was significantly lowered by the intake of cranberries, delivered in juice, tablet, or powder form.

Unfortunately, those benefits were seen only in children and women with recurrent UTIs. None were observed for older adults, pregnant women, or people with bladder problems.

The current review from Bond University included trials that mostly looked at adult women, which means it's unclear how well the results extend to other groups.

As new evidence emerges, however, it's getting harder to dismiss the potential health benefits of the little red fruit from North America.

Without the time-honored knowledge of some Native American tribes, scientists studying UTIs might never have thought to consider the cranberry.

The meta analysis was published in the European Urology Focus.