Efficacy of Cranberry Capsules in Prevention of Urinary Tract Infections in Postmenopausal Women

Efficacy of Cranberry Capsules in Prevention of Urinary Tract Infections in Postmenopausal Women

Dear Editor:

Cranberries (particularly in the form of cranberry juice) have been used widely for several decades for the prevention and treatment of urinary tract infections (UTIs). ^1,2 Cranberries and blueberries are part of the Vaccinium species, which are rich sources of dietary flavonoids including anthocyanins and proanthocyanidins (condensed tannins). ¹ Although no definite mechanism of action has been established for cranberry in the prevention or treatment of UTIs, the main suggestion is that cranberries prevent bacteria (particularly Escherichia coli) from adhering (sticking) to uroepithelial cells that line the wall of the bladder. ¹ Without adhesion, E. coli cannot infect the mucosal surface of the urinary tract. The aim of our correspondence is to submit the results of a small study (the first in a Greek population to our knowledge) about administering cranberries in the form of capsules to healthy postmenopausal women with recurrent UTIs.

Our study included 10 Greek postmenopausal women (46–60 years old) who met the following criteria: (1) they developed ≥3 microbiologically documented episodes of symptomatic UTI in the last year or ≥2 episodes in the last 6 months; (2) they underwent a gynecologic and urologic evaluation including renal ultrasonography in order for us to rule out the presence of uterine, bladder, or rectal prolapse and urinary incontinence; and (3) they were ambulatory and did not have indwelling catheters. Moreover, their medical history was negative for diabetes mellitus or other serious medical conditions. Before the beginning of our study, they had a sterile urine culture. All women provided informed consent before participating in the study. Our patients were given four cranberry capsules per day (two in the morning, two in the evening; [Natural Cranberry Extract, 400 mg with vitamin C vegetable, capsules, Solgar Vitamin and Herb Company, Leonia, NJ]) for 6 months and urine culture was obtained every month. No change of their sexual habits was recommended during those 6 months. None of them experienced a symptomatic UTI, and almost all urine cultures were sterile. Three (3) of our patients complained of mild gastrointestinal problems, and the dosage was reduced to half (two capsules/day).

Results were rather impressive and confirm the efficacy of cranberry capsules in prevention of UTIs. We have to highlight, though, that our study referred to healthy postmenopausal women and also the number of participants was not representative. As Nowack and Schmitt emphasize, patients with recurrent UTI have a high level of suffering and tend to accept any promising remedy, especially if it is a “natural” one. ² That was exactly the case with our patients also, who were reluctant in taking prophylactic antibiotic therapy but on the other hand willingly accepted cranberries as a long-term prophylaxis. Further studies are needed in order to determine optimal duration of use, dosage, and preparation of cranberry products (juice, tablets, or capsules).