Researchers confirm that cranberry juice is effective against urinary tract infections. Urinary tract infections (UTIs) affect more than 50% of women at least once, and a third of them develop recurrent UTIs. A new meta-analysis by Australian researchers on nearly 9,000 people confirms cranberry’s reputation as a useful supplement for people wishing to avoid recurrent UTIs.
In the scientists’ analysis, the protective effect of cranberries was evident in women, children, and those vulnerable to urinary tract infections as a result of medical interventions.
The authors say their work provides compelling evidence that cranberry juice may reduce the risk of UTIs in some people with recurrent UTIs.
Cranberry has long been considered a preventive or curative treatment for urinary tract infections. So far, however, research has produced conflicting evidence of its effectiveness.
Scientists from Flinders University and Westmead Children’s Hospital, Australia, recently published a global study showing that cranberry products may actually reduce the risk of UTIs in certain groups. This is the fifth update of a study first published in 1998 and last updated in 2012. It is published in the Cochrane Reviews.
E. coli bacteria and urinary tract infections
UTIs develop when bacteria enter and infect the urinary tract, which includes the urethra, bladder, ureter, and kidneys. Overgrowth of Escherichia coli (E. coli) in the urinary tract is the most common cause of UTIs. This bacterial strain is naturally present in the intestine, but it can enter the bladder following contamination by feces. It then adheres to the walls of the bladder and reproduces.
Symptoms are no picnic: People with recurring UTI symptoms are sometimes desperate for something to help. Untreated UTIs can progress to the kidneys and lead to complications such as sepsis. Prevention is the best way to reduce these risks.
Polyphenols: The Strike Force of Cranberries
Prescribing antibiotics is the most common prevention and treatment protocol, which has contributed to the increase in drug-resistant pathogens. Cranberries contain proanthocyanidins (PACs), a type of polyphenol. These “attack and defend” nutrients have remarkable antimicrobial and antioxidant potential. In a paper published in 2022, Canadian researchers found that PACs may help inhibit the formation of bacterial biofilms in the lining of the urinary tract. They also showed that PACs could prevent the activation of virulence genes from E. uropathogenic coli at an early stage in the intestinal reservoir.
An analysis of 50 studies
The researchers combed through the Cochrane Kidney and Transplant Specialized Register up to March 2023. They analyzed the results of randomized controlled trials of cranberry products compared to placebos, intervention with antibiotics or probiotics, or the absence of specific treatment for the prevention of urinary tract infections. The team added 26 new studies to this update, bringing the total number of studies to 50 with 8,857 participants.
The studies that were reviewed included a range of methods to determine the benefits of cranberry products. The vast majority compared cranberry products to placebo or no treatment for UTIs and found that drinking cranberry juice or capsules reduced the number of UTIs in women. with recurrent cases, in children, and in people who are at risk of getting UTIs from medical procedures such as radiation therapy to the bladder.
Cranberry juice brings significant benefits
The study authors found that consumption of cranberry products was strongly associated with a reduced risk of symptomatic, culture-verified UTIs in women with recurrent UTIs. Researchers observed a significant protective benefit in children and people at risk of UTIs due to interventions such as radiation therapy to the bladder. It is not known if cranberry juice, tablets or different doses of PAC are more effective against UTIs.
Few people have reported side effects from consuming cranberry products. The most common side effect was upset stomach. However, the study said the number of participants experiencing these side effects “probably does not differ between those taking cranberry products and those receiving a placebo or no specific treatment.”
Limited data
The research team noted that more studies are needed to determine which population with UTIs would benefit the most from consuming cranberries. Currently available data are limited or inconclusive regarding the use of cranberry products for the prevention of UTIs in pregnant women, the elderly, or people with bladder problems. More data is needed to be able to provide definitive guidance on the suitability of cranberry use for these groups of people.
