Urinary tract infections are associated each year with 7 million U.S. office visits, over 100,000 hospitalizations, $1.6 billion in medical costs, and innumerable telephone calls and faxed prescriptions for patients in absentia.
Seems like every other week a clinical trial or meta-analysis is published on the benefits (or lack thereof) of cranberry juice for the prevention of urinary tract infections (UTIs). Many of us recommend it – or not – based on what we believe to be the true efficacy of this intervention and on how much we want to empower our patients to help us reduce antibiotic prescriptions in a world of increasing bacterial resistance. Data that support our views may be reviewed; those data that do not may be ignored.
Cranberries and cranberry juice have been recommended to patients for years. Originally, it was thought that it acidified the urine, but this theory has been refuted. More recent data suggest that the active ingredient in cranberry is the antiadhesion constituent proanthocyanidins (PACs). PACs appear to be able to wrap around E. coli and prevent adherence.
Dr. Chih-Hung Wang of the National Taiwan University Hospital in Taipei and colleagues rose to the challenge and conducted a systematic review and meta-analysis of randomized trials of cranberry-containing products (juice, capsules, or tablets) for the prevention of UTIs. Thirteen trials were identified with 1,616 subjects. Most trials administered cranberry for 6 months. Cranberry users had a pooled lower risk for UTIs (odds ratio, 0.62; 95% confidence interval, 0.49-0.80). Cranberry products appeared to be more efficacious in women, women with recurrent UTIs, children, and cranberry juice users as opposed to users of cranberry tablets or capsules and when cranberry juice was consumed more than twice a day (Arch. Intern. Med. 2012;172:988-96).
What is the right dose? First, a couple of facts: approximately 1,500 g of fresh fruit produces 1 L of juice, and cranberry juice cocktail is roughly 26%-33% pure cranberry juice sweetened with fructose or artificial sweetener. Information on MedlinePlus suggests that cranberry juice doses of 1-10 ounces per day should be used for UTI prevention. Consuming 1 L/day may increase the risk for oxalate kidney stones. At 3-4 L/day, it may cause gastrointestinal distress. At reasonable doses, however, cranberry juice and tablets are very well tolerated and worth trying for our patients with recurrent UTIs.
Jon O. Ebbert, M.D., is professor of medicine and a primary care clinician at the Mayo Clinic in Rochester, Minn. He is an investigator on a clinical trial investigating the safety of varenicline. The opinions expressed are solely those of the author. Contact him at ebbert.jon@mayo.edu.