By Richard R. Watkins, MD, MS, FACP, FIDSA
Associate Professor of Internal Medicine, Northeast Ohio Medical University; Division of Infectious Diseases, Cleveland Clinic Akron General Medical Center, Akron, OH
Dr. Watkins reports that he has received research support from Actavis.
SYNOPSIS: A randomized, double-blind, placebo-controlled trial found that giving cranberry capsules to elderly women residing in nursing homes did not result in any significant benefits, including no reduction in symptomatic urinary tract infections.
SOURCE: Juthani-Mehta M, Van Ness PH, Bianco L, et al. Effect of cranberry capsules on bacteriuria plus pyuria among older women in nursing homes: A randomized clinical trial. JAMA 2016 Oct 27. doi: 10.1001/jama.2016.16141. [Epub ahead of print].
Preventing urinary tract infections (UTIs) in elderly women is a frequent clinical problem. Unfortunately, options are limited and sometimes costly, leading to frustration for patients and physicians alike. Juthani-Mehta et al aimed to determine whether daily cranberry capsules would be beneficial in this patient population for preventing UTIs.
The study was a double-blind, randomized, placebo-controlled trial of the efficacy of two cranberry capsules daily compared to two placebo capsules daily. Inclusion criteria included female sex, long-term care residents, English speaking, and age 65 years or older. Exclusion criteria included patients not expected to be in the nursing home for at least a month, those taking chronic antibiotics for UTI prevention, hemodialysis, inability to produce a clean-catch urine sample, taking warfarin, history of nephrolithiasis, having an indwelling Foley catheter, allergy to or treatment with cranberry products, and nursing home residence for less than four weeks. The primary outcome was the presence of bacteriuria plus pyuria, which was measured every two months after randomization for a total of six assessments over 12 months. The secondary outcomes were symptomatic UTI, all-cause mortality, all-cause hospitalization, all multidrug-resistant organisms, antibiotics for suspected UTI, and total antibiotic prescriptions.
Of 5,045 nursing home residents who were screened, 185 were randomized, including 92 to the treatment group and 93 to the control group. The mean age of the participants was 86.4 years. There were 10 symptomatic UTIs in the treatment group and 12 in the control group. For the primary outcome of bacteriuria plus pyuria, the adjusted analysis showed no significant differences between the two groups (29.1% vs. 29.0%; odds ratio [OR], 1.01; 95% confidence interval [CI], 0.61-1.66; P = 0.98). Regarding the secondary outcomes, there were no significant differences in mortality, hospitalization, bacteriuria from multidrug-resistant gram-negative bacilli, or antibiotic use between the treatment and control groups (P > 0.05 for all). Finally, the frequency of adverse events was similar in both groups.
The use of cranberry juice, more precisely the quinic acid in cranberries that is metabolized to hippuric acid in the bladder, is an attractive strategy for preventing UTIs. It is inexpensive, widely available, and avoids the potential risks associated with antibiotics, such as disruption of the microbiome and the promotion of antibiotic resistance. Previous clinical trials that investigated the efficacy of cranberries for preventing UTIs produced mixed results. The report by Juthani-Mehta et al appears to have settled the debate. Their well-designed and conducted study found no differences in any of the outcomes between the use of cranberry capsules and placebo. While disappointing, these results signal it is time to move past using cranberries in elderly women and explore novel approaches for UTI prevention.
So why were the cranberry capsules ineffective? There are a couple of possible explanations. As the authors noted, during the first six months of treatment there was a decrease in bacteriuria with pyuria in the group that received cranberry capsules, but it was not sustained for the next six months. This may have been due to a decrease in adherence. Another issue relates to the fact that some previous studies that found a benefit used cranberry juice instead of capsules. Hydration may be an important benefit with cranberry juice that is lacking with the capsules. For example, a study in which subjects took cranberry capsules with 8 ounces of water twice a day over six weeks found a 50% reduction in UTIs.1 Moreover, drinking water with the cranberry capsules avoids the high glycemic load from cranberry juice, which can be deleterious in diabetic elderly patients. Finally, incontinence and changes in the vaginal microbiome with age may have made the capsules less effective. Additional studies using cranberry capsules in younger women with recurrent UTIs should be conducted to determine if there are any benefits in this population.
- Foxman B, Cronenwett AE, Spino C, et al. Cranberry juice capsules and urinary tract infection after surgery: Results of a randomized trial. Am J Obstet Gynecol 2015; 213:194.e1-8.