The preventive effect is believed to be a result of compounds unique to cranberries called proanthocyanidins.
New findings published in The Cochrane Database of Systematic Reviews demonstrate that cranberry juice and supplements can prevent and reduce the risk of repeat urinary tract infections (UTIs) in women, children, and other at-risk individuals.
Researchers have long believed that cranberry products can prevent UTIs, and the new review further strengthens the preexisting evidence. In the review, investigators conducted a large-scale meta-analysis of 50 clinical trials with the goal of assessing the effectiveness of cranberry products in preventing UTIs in susceptible populations.1
The data bolstered existing evidence that consuming cranberries as juice, tablets, or capsules reduced the number of UTIs in women with recurrent UTIs, in children with UTIs, and in individuals susceptible to UTIs following an intervention involving the bladder.1
More than 400 million UTIs are reported each year globally, and cranberry products are often recommended as an easy, accessible, and cost-effective way to prevent the incidence and recurrence of the infections.1
Fifty studies were included in the review, including 8857 total randomized participants. Of those studies, 45 compared cranberry products with placebo or no specific treatment in 6 different groups of participants, and 26 of those could be meta-analyzed for the outcome of symptomatic, culture verified UTIs.2
In moderate certainty evidence, cranberry products reduced the risk of UTIs. When the studies were divided into groups according to the treatment indication, cranberry products probably reduced the risk of symptomatic, culture verified UTIs in women with recurrent UTIs, in children, and in those with a susceptibility of UTIs due to an intervention.2
However, in low certainty evidence, the review found that there may be little or no benefit in elderly institutionalized men and women, pregnant women, or adults with neuromuscular bladder dysfunction with incomplete bladder emptying.2 Amy Howell, PhD, has researched this for more than 30 years and has shown that daily consumption of cranberry juice and juice-based encapsulated powders work to reduce UTIs by preventing bacteria from sticking to the bladder wall.
This is believed to be a result of compounds unique to cranberries called proanthocyanidins (PACs).1
“The meta-analysis stresses the importance of utilizing cranberry products standardized for PAC content,” Howell explained in a press release. “We have determined that PACs in juice-based products are most effective for UTI prevention and should be consumed daily.”1
Because PACs prevent the bacteria from adhering to the bladder wall, UTIs are unable to progress. This also eliminates the need to use antibiotics by preventing the infection, which lessens the opportunity for antibiotic resistance and ensures efficacy when antibiotics are necessary. Additionally, reducing antibiotic use is ideal because antibiotics can negatively impact good bacteria necessary to maintain balance and health in the body.1
Other studies in the review compared cranberry products with probiotics or antibiotics, cranberry tablets with cranberry liquid, and different doses of PACs. Notably, compared to antibiotics, cranberry products may make little or no difference to the risk of symptomatic, culture verified UTIs or the risk of clinical symptoms without culture.
Compared to probiotics, cranberry products may reduce the risk of symptomatic, culture verified UTIs, according to the study. It was unclear whether efficacy differs between cranberry juice and tablets or between different doses of PACs.2
“After many years of research studying the health effects of cranberries, I am confident the results of the Cochrane Review will provide health care professionals and consumers with the clinical validation they need to recommend and utilize cranberry products for prevention of recurrent UTIs,” Howell said in the press release. “Daily cranberry intake could potentially lead to a reduction in UTIs, meaning better quality of life and reduced hospitalizations and complications that can result from these infections.”1