Antibiotics Beat Cranberries at Fighting Urinary Tract Infections in Study

MONDAY July 25, 2011 -- Many women swear by cranberry juice or capsules for the treatment and prevention of urinary tract infections, but new Dutch research indicates that antibiotics may be more effective even if they contribute to a greater risk for antibiotic resistance.

"Cranberries are less effective in the prevention, but do not result in resistant microorganisms," said study author Dr. Suzanne Geerlings, an infectious diseases expert at the Academic Medical Center in Amsterdam. "Women with recurrent UTIs [urinary tract infections] do not like taking antibiotics for a long period because they know [about] the resistance problem. I think that doctors have to discuss the results of this study with the individual patients to make the best choice."

About half of all women will experience a UTI at some point in their lives, and 30 percent of women will develop recurrent UTIs. Escherichia coli is one of the most common causes of UTIs.

In the study, 221 women who had at least three recurrent UTIs in the previous year were randomly selected for a 12-month course of the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX) (Bactrim, Bethaprim, Cotrim, Septra), taken once daily with two placebo pills, or one cranberry capsule with 500 milligrams of cranberry extract taken twice a day with one placebo pill.

Women who took cranberry capsules were more likely to develop at least one symptomatic UTI compared with their counterparts who received the antibiotic, 4 versus 1.8, respectively. On average, women in the cranberry group developed a new UTI after four months, while recurrence occurred within eight months among those who received the antibiotic, the study showed.

Rates of antibiotic resistance tripled among women in the antibiotics group, but these did return to baseline three months after they stopped talking the medication.

After one month, antibiotic resistance to E. coli was higher than 85 percent in the antibiotic group and less than 30 percent among women who took the cranberry extract.

"Cranberry has long been touted as a natural preventative for UTIs, and numerous clinical studies using either juice or dry extracts have lent credence to this premise," Bill J. Gurley, of the University of Arkansas for Medical Sciences in Little Rock, wrote in an accompanying editorial.

Exactly how cranberries may prevent or treat UTIs is not fully understood, but cranberries contain fructose (fruit sugar) and type A proanthocyanidins, which can prevent E. coli from sticking to the bladder walls. The cranberry extract may not have been as bioavailable as the antibiotic, which could have skewed the findings in favor of the antibiotic in this study, Gurley wrote.

"We have been using cranberry juice extract and capsules for a long time," said Dr. Carolyn Dean, a naturopathic physician in Maui, Hawaii. "It stops adhesion of bacteria to the bladder wall."

Antibiotics kill bacteria, while the cranberry extract provides more of a mechanical solution, she explained.

Dean said there is still a role for cranberry juice and/or extract in preventing UTIs. "Sexually active women whose bladder feels irritated after sex should take cranberry capsules after intercourse as a preventative," she said. "If you do develop a UTI, you can increase the amount of cranberry extract you are taking or consider antibiotics."

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more on urinary tract infections.

Posted: July 2011


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