Can cranberry juice cure urinary tract infections?

Contrary to popular belief, cranberry juice does not cure a urinary tract infection, a doctor says.

Capsules are better

Many people drink cranberry juice in an attempt to ease their symptoms, but it will do nothing to help them, said Dr Timothy Boone, vice dean of the Texas A&M Health Science Centre College of Medicine, Houston campus.

"Cranberry juice, especially the juice concentrates you find at the grocery store, will not treat a UTI [urinary tract infection] or bladder infection," he said in a centre news release.

Read: Urine samples unnecessary for UTIs

"It can offer more hydration and possibly wash bacteria from your body more effectively, but the active ingredient in cranberry is long gone by the time it reaches your bladder," Boone said.

Each year, more than 3 million Americans have a urinary tract infection – an infection in any part of the urinary system, kidney, bladder or urethra, according to the news release.

Large concentration of cranberry needed

The active ingredient in cranberries – A-type proanthocyanidins (PACs) – is effective against UTI-causing bacteria, but is found only in cranberry capsules, not in cranberry juice, Boone said.

Read: Study supports UTI protection from cranberries

"It takes an extremely large concentration of cranberry to prevent bacterial adhesion," Boone said. "This amount of concentration is not found in the juices we drink. There's a possibility it was stronger back in our grandparents' day, but definitely not in modern times."

However, one study found that taking cranberry capsules reduced the risk of urinary tract infections by 50 percent in women who had a catheter in place while having gynaecological surgery, he noted.

"In this study, they took the cranberry itself and put it in a capsule – the equivalence of drinking 16 ounces of cranberry juice. As you can see, it takes a large amount of pure cranberry to prevent an infection," Boone said. 

Read more: 

Antibiotics prevent UTIs better than probiotics 

Cranberry juice help ward off UTIs 

Oestrogen may prevent urinary tract infections