Writing in the JAMA's Archives of Internal Medicine, researchers from the funded by the Netherlands Organisation for Health Research and Development, report that in premenopausal women who have repeated urinary tract infections (UTIs), the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX) appeared more effective than cranberry capsules for preventing recurrent infections.
The 12-month study concluded that compared to the cranberry tablets, antibiotics were more effective at preventing a recurrent UTI. However the authors, led by Mariëlle Beerepoot from the Academic Medical Center, Amsterdam, noted that the use of TMP-SMX also contributed to antibiotic resistance
The Cranberry Institute said that antibiotics should not be the first choice in UTI prevention given the “substantial increase in multiple antibiotic resistance development”
“Unlike antibiotics, cranberry does not kill bacteria. The fruit contains compounds that prevent the pathogenic bacteria from sticking to the bladder wall, which is the initial step in the infection process. Interrupting the adhesion prevents the bacteria from growing and causing a UTI,” said Dr Amy Howell, from the Marucci Center for Blueberry Cranberry Research at Rutgers University.
Urinary tract infections are common in women, affecting nearly half at some point in their lives, said Beerepoot and his colleagues.
They reported that for premenopausal women who have three or more UTIs a year, low-dose preventative antibiotics are usually recommended. However, the long term use of antibiotics has the risk of developing drug resistance to other antibiotics.
Cranberries have been used for the prevention of UTIs for many years but it has not been established how they work. The authors noted that although studies of cranberries and cranberry products have shown some effectiveness in preventing recurrent UTIs, such trials have not compared those interventions directly with TMP-SMX, the standard antibiotic used in these cases.
Beerepoot and his team therefore wanted to see whether a cranberry tablet would prevent UTIs to a similar extent to antibiotics.
The study compared the effectiveness of antibiotics to cranberry extract (Cran-Max; Proprietary Nutritionals, USA) at preventing UTIs in a group of premenopausal women who were prone to getting them. The participants, who all had at least three infections over one year, were given either the extract or the antibiotic for 12 months.
Beerepoot and his colleagues reported that after 12 months, the cranberry group experienced more symptomatic UTIs than the TMP-SMX group. On average there were four infections in the cranberry group compared to 1.8 in the antibiotics group.
The cranberry group also had a higher proportion of women who had experienced at least one symptomatic UTI (78.2 percent versus 71.1 percent in the antibiotic group). Whilst women in the cranberry group had their first recurrence on average four months after starting treatment compared to eight months with the antibiotic group.
However, after one month of using TMP-SMX, resistance to this antibiotic had increased approximately three fold to 72.5% and 90.5% in faeces and the urine samples respectively.
The authors concluded that TMP-SMX is more effective than cranberry capsules for the prevention of recurrent UTIs, but noted that this “should be weighed against the greater development of antibiotic resistance.”
Dean Mosca, president of Proprietary Nutritionals, said that the study “confirmed the concern that many women have about contracting drug-resistant bacteria using a long-term antibiotic therapy.”
Peter van Hogerhuis director and owner of Springfield Nutraceuticals, the Netherlands, who supplied the Cran-Max capsules for the study, said that the results “clearly show that cranberries have a positive effect on recurrent urinary tract infections.”
“The authors also rightfully pointed out that any advantages of the drug should be weighed against the greater development of antibiotic resistance,” said Mosca.
In an accompanying commentary to the study Dr Bill Gurley, of the University of Arkansas for Medical Sciences, said: “Such a marked reduction in antibiotic resistance certainly favors the therapeutic potential of cranberry as a natural UTI preventative.”
The Cranberry Institute added that the study also showed that cranberry should still be considered as an alternative for prevention of recurrent UTI, even though its efficacy was slightly lower than that of the drug.
“Cranberry has not only been shown clinically to prevent UTI, but it also has a wide range of other health benefits, including reducing certain risk factors for heart disease,” added Dr Howell.
Source: Archives of Internal Medicine
Volume 171, Issue 14, Pages 1270-1278, doi: 10.1001/archinternmed.2011.306
“Cranberries vs Antibiotics to Prevent Urinary Tract Infections: A Randomized Double-blind Noninferiority Trial in Premenopausal Women”
Authors: M.A.J. Beerepoot, G. ter Riet, S. Nys, W.M. van der Wal, et al