Preventing Urinary Tract Infections with Cranberry Extract
Bailey D, Dalton C, Daugherty FJ, Tempesta MS. Can a concentrated cranberry extract preventrecurrent urinary tract infections in women? A pilot study. Phytomed. 2007;14:237-241.
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Common in women, the elderly, and infants, urinary tract infections (UTIs) are defined as the"presence of a certain threshold number of bacteria in the urine (usually greater than 100,000 permL)." One in four women who have a UTI will have a recurrence. Cranberry (Vacciniummacrocarpon) products are often used to prevent UTIs. The authors report on a study to test theeffects of concentrated cranberry extract on women with recurrent UTIs.
Most urinary tract infections (UTIs) are caused by one type of bacterium -- Escherichia coli. TheE. coli strains that cause UTIs have proteinaceous macromolecules (fimbriae) that facilitate theadhesion of bacteria to uroepithelial cells in the urinary tract. In vitro and ex vivo studies indicatethat cranberry products prevent adhesion of bacteria to the cell walls of the urinary tract, thuspreventing UTIs.1,2 Further, biochemical studies have revealed that in addition to causing thefimbriae on the surface of the bacteria to become compressed, reducing their adhesion, theproanthocyanidins in cranberry may change the shape of the bacteria from rods to spheres andcause chemical changes in their surface membranes.3
The authors conducted an open-label pilot study for 4 months at Helios Integrated Medicine, PCin Boulder, Colorado. Twelve women aged between 25 and 70 years with a history of 6 UTIs inthe past year took 1 cranberry capsule twice daily for 12 weeks. Each capsule contained 200 mgcranberry extract standardized to 30% total phenols (much higher than dried cranberries anddried juices), produced by Phenolics, LLC (El Granada, CA), by selective extraction of theberries. The total cranberry proanthocyanidin intake during the study was approximately 100 mgper day.
All of the women completed a medical history questionnaire at the beginning of the study andwere asked to update it with any changes. The women had urinalysis within 24 hours beforestarting on the cranberry extract and monthly afterward for 4 months.
None of the women developed a UTI during the study, based on symptoms or laboratory results.
After 2 years, a follow-up was done, and the same medical history questionnaire was reviewedwith each woman. At that time, eight of the women reported no changes in their health since thestudy began. They all continued to take various cranberry supplements prepared by differentmanufacturers in doses ranging from 150 to 300 mg per day, and they continued to be free fromUTIs. Four women stopped taking cranberry supplements for various unrelated medical reasons.Of those, one remained free of UTIs and two developed symptoms, which resolved afterresuming the supplementation. The fourth developed a UTI confirmed by urinalysis and wastreated with antibiotics. She then resumed the cranberry supplements and did not have anyfurther symptoms.
This study adds evidence to three previous studies cited by the authors that indicate theeffectiveness of cranberry products in preventing UTIs in women. These study results are unique,however, in that none of the women had a recurrent infection during the study period. Also, thisstudy used a unique cranberry product standardized to 30% phenolics.
The authors suggest that more studies are needed to determine an optimal dose and to comparethis product with cranberry juice and other cranberry products containing lower concentrations ofproanthocyanidins. Patients who ingest cranberry concentrate products should be cautioned aboutthe risk for nephrolithiasis (kidney stones): urinary oxalate level in 5 volunteers were found toincrease by an average 43.4% while receiving cranberry concentrate tablets.4
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1Di Martino P, Agniel R, David K, Templer C, Gaillard JL, Denys P, Botto H. Reduction ofEscherichia coli adherence to uroepithelial bladder cells after consumption of cranberry juice: adouble-blind randomized placebo-controlled cross-over trial. World J Urol. 2006;24(1):21-27.
2Liu Y, Black MA, Caron L, Camesano TA. Role of cranberry juice on molecular-scale surfacecharacteristics and adhesion behavior of Escherichia coli. Biotechnol Bioeng.2006;93(2):297-305.
3Camesano TA. In: Proceedings of 232nd ASC Meeting, San Francisco, Calif.; September 11,2006.
4Terris MK, Issa MM, Tacker JR. Dietary supplementation with cranberry concentrate tabletsmay increase the risk of nephrolithiasis. Urology 2001; 57(1): 26-29.