April 27, 2023
Most women experience a urinary tract infection at least once in their lives, and some struggle with recurrent infections. Drinking cranberry juice often has been touted as an easy way to prevent bacteria from building in the urinary tract, but studies on its effectiveness have been mixed.
The latest research, however, may change that. Researchers from Flinders University in Australia found that drinking cranberry juice or taking cranberry supplements may reduce the risk of repeat urinary tract infection symptoms by more than 25%.
The study found that cranberry supplements reduced the risk UTIs by 50% in children. People who were vulnerable to recurrent UTIs after medical treatment had a 53% risk reduction.
"For the first time, we have consensus that cranberry products (concentrated liquid, capsules or tablets) work for some groups of people; specifically, people who experience recurrent UTI, children and people susceptible to UTI because of medical intervention," study author Jacqueline Stephens told U.S. News & World Report.
A urinary tract infection can affect any part of the urinary system, including the kidneys, ureters, bladder and urethra. Most infections, however, occur in the bladder and urethra. E. coli cause more than 90% of bladder infections, according to the Cleveland Clinic. Serious complications can arise if the infection spreads to the kidneys.
The most common UTI symptoms are a strong, constant urge to urinate, a burning sensation when urinating, feeling pressure to urinate but only passing small amounts of urine, urine that smells, and urine looks cloudy or red-tinged. Some women may also experience pelvic pain. But not everyone who develops a UTI experiences symptoms.
Cranberries have long been thought to have medicinal qualities. The fruit contain proanthocyanidins, which help keep bacteria from adhering to the bladder walls. Before the first antibiotics were available, cranberries often wear recommended to treat urinary tract infections.
Cranberries also were used by Native Americans to treat bladder and kidney symptoms. And in the 17th century, the fruit was used to relieve blood disorders, stomach and liver problems, scurvy and cancer.
According to the American Family Physician, cranberries are a well-tolerated herbal supplement that do not have significant drug interactions. The Flinders University study identified an upset stomach as the most common side effect.
The study reviewed data from 50 randomized controlled trials. Nearly 9,000 people were included in the analysis. Researchers said the best dosage and best ways to consume cranberries still need to be studied.
The researchers also found that cranberries did not help prevent UTIs in institutionalized men and women, in pregnant women or in adults with bladder dysfunction.
"The inclusion of the totality of the global evidence and the rigorous review process means we are confident of the results, even when the results have changed compared to previous versions of this review," Stephens said.
Previous research didn't present as robust evidence as this latest review, offering a mixed bag of results. Most of the past studies suggested that cranberry juice and supplements don't have enough proanthocyanidins – a class of polyphenols – to prevent bacteria from sticking to the urinary tract. But there also have been studies that have shown more positive results.
More recent randomized controlled trials have found that cranberries offer some protection. One 2013 analysis found that when compared to a placebo, cranberry juice and tablets reduced the occurrence of UTIs in women with recurrent infections. Another systemic review, published in 2021, also found that cranberry supplements significantly reduce the risk of recurrent UTI.
Other important measures to prevent the spread of bacteria in the urinary tract include drinking plenty of water to flush out any bacteria, wiping front to back after going to the bathroom, emptying the bladder soon after sex and avoiding potentially irritating feminine products. Changing birth control methods also also help. Spermicide can foster bacterial growth.
Post-menopausal women who suffer recurrent UTIs may find relief from a combination of topical estrogen and probiotics.
Urinary tract infections are typically treated with antibiotics. If left untreated, they can lead to permanent kidney damage and sepsis. Pregnant women with untreated UTIs are at risk of delivering low-birth and premature babies.