After otitis media, urinary tract infections (UTIs) are the most common bacterial infection globally.

González de Llano D, Moreno-Arribas MV, Bartolomé B. Cranberry polyphenols and prevention against urinary tract infections: relevant considerations. Molecules. 2020;25(15):3523.

A review in Molecules states that half of all people assigned female at birth experience a symptomatic UTI in their lifetime. And a quarter have recurrent UTIs caused by the same or different microorganisms. These infections can have a significant impact on quality of life and lead to more serious complications, particularly if antibiotic resistance develops over time.

 

Effective prevention strategies are essential to reduce hospital visits and reliance on antibiotics. 

 

Here are the latest findings.

 

Who benefits from cranberry?

 

The 2023 Cochrane report is the 5th update to an initial review published in 1998, to which researchers have added data from 26 new high-quality studies. The current review includes 50 studies in total, representing 8,857 randomized participants. Cranberry products were provided as juice, tablets, or capsules. Of the 50 studies, 45 were randomized controlled trials comparing cranberry products to placebo or no treatment.

For females with recurrent UTIs, cranberry products were shown to reduce the number of infections. Children with UTIs and adults at risk for UTIs following medical interventions also benefit from the preventive effects of cranberry products. However, this review also identified a few subgroups for whom cranberry was ineffective, including individuals who have trouble emptying their bladder due to neuromuscular dysfunction, pregnant women, and elderly patients in institutions.

 

How does cranberry help?

 

Cranberries are a natural source of proanthocyanidins, compounds that help block UTI-causing E. coli bacteria from sticking to the bladder wall. Although other bacterial strains can cause urinary infections, uropathogenic E. coli is believed to be responsible for 85% of cystitis, according to the researchers writing in Molecules.

There are three basic steps for the progression to a UTI. First, pathogens colonize the area, then they adhere to the uroepithelium receptors, and finally, they invade the cells of the urinary tract. Sometimes, a secondary kidney infection occurs if untreated uropathogens ascend to the kidneys. The bacterial wall of uropathogenic E. coli contains hair-like organelles (fimbriae or adhesins) that enable attachment to the urogenital epithelial receptors. 

 

Additional potential effects of cranberry haven’t been quantified but may still benefit these patients. These potential benefits include the reduction of infection-related inflammatory cascades and positive impacts on the immune system through gut microbiota.

 

What’s the harm in cranberry?

 

In the Cochrane review, cranberry products were well-tolerated with minimal side effects. A low number of participants reported abdominal pain. Perhaps the only downside of recommending cranberry products, according to the Molecules authors, is the cost of supplements for patient groups for whom there are no established clinical benefits. 

 

In addition, some cranberry juices have lots of added sugar to combat their natural tartness, which patients should be mindful of. Patients must also understand that despite cranberry’s preventative properties for UTIs, cranberry alone cannot substitute medical treatment for an existing UTI.

Nonetheless, cranberries are rich in antioxidants, including vitamin C and health-promoting flavonoids and phenolic compounds. When consumed in the absence of added sugars, says the Cleveland Clinic, cranberries help lower inflammation, support heart health, and protect against certain cancers. They also promote a healthy gut microbiome, according to the Molecules authors, suggesting that a combination of probiotics and cranberry could optimize future UTI prevention strategies.