Evidence for this natural remedy is still confounded by the benefits of drinking more liquids of any kind.
Drinking cranberry juice can halve the occurrence of urinary tract infections compared with no treatment, according to a new Australian systematic review.
And compared with drinking other liquids, cranberries reduced the incidence of these infections by a third.
Evidence for the popular home remedy has been inconclusive to date, said the authors, from Bond University. Still, this new finding – made with low to moderate certainty – has the potential to not only reduce morbidity but also spare the use of antibiotics at a time of growing drug resistance in the bacteria that cause UTIs.
In the study, published in European Urology Focus, researchers analysed 20 randomised and non-randomised controlled trials (with a total of 3091 participants, mostly female) that compared cranberry (in liquid or tablet form) with either no treatment or another placebo liquid – water, other juice or even beer.
Those who drank cranberry liquid had less than half (46%) as many UTIs as those on no treatment and three-quarters (73%) as many as those who drank other liquids. Other cross comparisons didn’t reach significance.
Six of the studies also compared rates of antibiotic use between treatment groups. A meta-analysis found cranberry liquid drinkers used antibiotics half as much as those on placebo and 40% as much as those on no treatment.
“The evidence supports the use of cranberry juice for the prevention and treatment of UTIs,” the authors wrote. “However, the evidence sits at moderate to low certainty, highlighting the need for additional RCTs to be conducted.”
The active component of cranberry is unknown, but could be its concentration of proanthocyanidins, “which have been identified to inhibit some bacterial and fungal growths”.
They noted the confounding effect of increased liquid consumption on the apparent benefits of cranberry.
Recommending patients increase their liquid consumption was likely to provide longer-term benefits, they said.
“It is likely that the fewer voids per day, the concentrated and acidic urine, and the inhibited immune function correlated with dehydration all contribute to the increased susceptibility to UTIs.”
