WEDNESDAY, April 26, 2023 (HealthDay News) -- Women have heard for decades that cranberry products help prevent urinary tract infections. A new study appears to confirm that longstanding advice.

About 60% of women over age 18 will suffer one or more urinary tract infections in their lifetime. About 30% will have recurrent UTIs, averaging two to three episodes a year, according to background notes with the study.

A review of 50 randomized controlled trials found that taking cranberry supplements or drinking the juice reduced the risk of having repeat symptoms for a UTI by more than 25%.

In children, cranberry products reduced these infections by more than 50%.

People who were susceptible to a repeat infection after medical treatment such as antibiotics or probiotics saw a 53% 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,” said study author Jacqueline Stephens, senior lecturer in public health in the College of Medicine & Public Health at Flinders University in Australia.

This updated review of research from around the world included nearly 9,000 people. Randomized controlled trials are considered the "gold standard" of research studies.

“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.

Lead study author Gabrielle Williams, of the Centre for Kidney Research in Westmead, Australia, recalled that in 1973 her mother was told to drink cranberry juice to prevent “horrible and frequent UTIs.” And that still works for her, Williams said in a Flinders news release.

"She's continued to take it daily, first as the nasty sour juice and in recent years, the easy-to-swallow capsules. As soon as she stops, wham the symptoms are back," Williams said.

UTIs can affect anyone, but they're especially common in women because of their anatomy. The infection occurs most commonly in the bladder, the U.S. Centers for Disease Control and Prevention says. It happens when bacteria, typically from the skin or rectum, enter the urethra.

This can cause pain, frequent urination and other bothersome symptoms.

Infections can move to the kidneys, causing additional pain and complications. Very severe cases may lead to sepsis.

Dr. Johanna Figueroa, a urologist at Northwell Health in Syosset, N.Y., said UTIs often can self-resolve with enough hydration. That means drinking lots of water to flush the bacteria out of your system. Cranberry can be another tool, she said.

“If your symptoms are relieved, it could be that you may not even need to go and seek medical attention because your body itself is able to combat the bacteria that enter the bladder,” said Figueroa, who was not involved in the study.

In other cases, doctors often prescribe antibiotics to treat UTIs.

While the study review found cranberry to be effective in certain groups, it did not find cranberry products helpful in institutionalized men and women, in pregnant women or in adults with neuromuscular bladder dysfunction and incomplete bladder emptying.

Most of the studies reviewed compared use of cranberry products to taking a placebo or getting no treatment. The researchers also analyzed the results of trials comparing cranberry products with probiotics and antibiotics.

Why cranberries?

Cranberries contain substances known as proanthocyanidins, chemical compounds that can keep bacteria from sticking to the bladder walls, according to the study.

The most common side effect of taking cranberry seen in the study was an upset stomach.

The review did not identify the best dosage or best way to consume cranberries to have the most effect, Stephens said.

Figueroa said the takeaway is that cranberry supplements, “can be used if you feel like it's preventing and it's working.

“If it doesn't work, it's time for the providers to move on to another line of therapy,” Figueroa said.

It’s still important to drink water, she said. Good hygiene also helps to prevent UTIs.

The study findings were published April 17 in Cochrane Reviews.

More information

The U.S. Centers for Disease Control and Prevention has more on urinary tract infections.

SOURCES: Jacqueline Stephens, PhD, senior lecturer, public health, College of Medicine & Public Health, Flinders University, Australia; Johanna Figueroa, MD, urologist, Northwell Health, Syosset, N.Y.; Flinders University, news release, April 19, 2023; Cochrane Reviews, April 17, 2023