There’s Some Truth to the Folklore of Cranberry Juice and UTIs

“Drink lots of cranberry juice” is advice many mothers pass on to their daughters. Something in the juice, the thinking goes, helps to prevent painful and irksome urinary tract infections. Now, science has at least partially validated that mantra. While research has yet to confirm that drinking the juice has a significant impact on reducing UTIs, a new study did find that compounds from cranberries inhibit the external spread of UTI-causing bacteria, LiveScience reports.

One type of bacteria the cranberry compounds helped stop was P. mirabilis, which spreads through the environment or body with the help of long tentacle-like appendages called flagella. Most hospital-contracted UTIs come from this type of bacteria, which often colonize the surface of catheters.

Tufenkji’s group found that cranberry powder in a petri dish limited the growth of flagella and rendered the colony nearly motionless. Moreover, increased cranberry concentrations reduced the bacterium’s production of an enzyme called urease, which contributes to the virulence, or severity, of infection.

The cranberry trick also worked on E. coli, which causes most UTIs outside of the hospital environment, writes LiveScience.

Immobilizing bacteria — rather than killing it —is a good thing, Tufenkji explained. Bacteria are less likely to develop resistance to a substance that only is hindering their movement, as opposed to killing bacteria and preventing them from replicating.

Perhaps coating equipment with cranberry-derived compounds could help limit hospital infections, researchers suggest. Maybe even a cranberry-based anti-E. coli lotion will someday be available, since most E. coli infections result from bacteria already present on a woman’s body entering her urinary tract. As for cranberry juice itself, LiveScience points out that evidence is still lacking that drinking it actually makes a difference when it comes to preventing UTIs. 

More from Smithsonian.com:

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Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.