The Cranberry Cure.

From the WebMD Archives

June 29, 2001 -- You may have heard that women suffering from urinary tract infections should drink cranberry juice. Well, there hasn't been much evidence to support this advice -- until now.

A new study in the June 30 issue of British Medical Journal shows that the juice may just do the trick.

Women who have suffered from a urinary tract infection, or a UTI, are all too familiar with the frequent urge to urinate and the pain and burning that comes along with it.

Beyond being irritating, the condition has a serious side effect, too. Expert Gregor Reid, PhD, says that of the approximately 11 million women who suffered from a UTI in 1997, about 10% had the infection travel to their kidneys, which can have serious consequences and may require hospitalization.

But overdosing on the juice isn't such a good idea either. According to Reid, who was not involved in the study, too much cranberry juice can cause kidney stones. "But I think there is [compelling] evidence that if you take a glass of cranberry [juice a day,] it could prevent UTI." Reid, who reviewed the study for WebMD, is a professor of microbiology and immunology at the University of Western Ontario and associate scientific director of the Lawson Health Research Institute in London, Ontario.

Cranberry extract is also available in powder form, but no research has proved it works in the same way as juice, adds Reid.

The study researchers from the Finnish Student Health Services at Oulu University, recruited 150 women with persistent UTIs. Fifty drank just under 2 oz of cranberry juice a day for six months. Another 50 drank a preparation of Lactobacillus, a "friendly" bacteria that helps prevent yeast infections. The final 50 women were given no treatment.

After six months, only eight women taking cranberry juice had experienced a UTI, compared with 19 of those taking Lactobacillus, and 18 not taking anything.

"Since a relatively small amount of cranberry juice -- 50 milliliters of concentrate, which is well tolerated -- seems to be highly effective against UTI, it can be easily recommended to everyone who is suffering from UTI," study author Tero Kontiokari tells WebMD. "Scientifically, I find cranberry juice a fascinating example of how everyday food items can play a crucial role in infectious diseases control, and I am confident that there are plenty of other items yet to be discovered."

It is not clear how cranberry juice prevents UTIs. The most common theory among experts is that one or more of its ingredients prevent bacteria from attaching to the urinary bladder wall, so they get washed away more easily in the urine. Others speculate that cranberry juice, a drink high in acid, makes it difficult for bacteria to grow.

Women's health expert Marcella Roenneburg, MD, from the Gynecology Center of Mercy Medical Center in Baltimore, gives women these additional tips to help prevent UTIs:

  • Drink plenty of water.
  • Urinate often.
  • Urinate before and after sex.

For her patients who suffer from persistent UTIs, she recommends a glass of cranberry juice daily as well as vitamin C tablets to acidify the urine. She says patients can take cranberry in powdered extract form or by drinking the juice. But watch out, not all cranberry juices are created equal. Cranberry cocktail, for instance, is composed mainly of other ingredients.

Check labels to ensure a high proportion of actual cranberry juice in whatever preparation you choose.

With reporting by David Flegel