Cranberry supplements, or better yet drinking unsweetened cranberry juice, will cut down on recurrences of a urinary tract infection. We have long known that this folk remedy has scientific backing. What’s new is a better understanding of the preventive effect and better studies to demonstrate it. Antibiotics are the standard treatment for UTI, which is the most common bacterial infection. But too often the UTI returns again and again, escalating the treatment to yet-another more powerful antibiotic. Given the worldwide concerns about antibiotic resistance, any alternative treatment that can safely reduce antibiotic use for UTI deserves research attention.
The latest confirmation of the cranberry effect comes from Taiwanese researchers who did an analysis of the 10 best clinical trials that compared users of cranberry products (juice or capsules) with nonusers (cranberry-free placebo capsules). Altogether these trials had 1,494 study participants, mostly women and some children. The trials were conducted in North America and Europe; most lasted less than six months. The researchers, led by Chih-Hung Wang, MD, of the National Taiwan University Hospital, published their conclusions in the July 9 issue of Archives of Internal Medicine.
All 10 trials asked the same research question: Will regular consumption of cranberry products reduce UTI recurrences in people with symptoms of recurrent UTI? While the answer is yes, there were too many variations in these trials to provide additional crucial information.
No study, for example, had compared one type of cranberry product against another, yet Dr. Wang and colleagues say that drinking cranberry juice “might be more favorable” than taking cranberry supplements. They suspect that scientists have yet to provide a complete picture of all the active components of cranberries. (How do cranberries work? They prevent infection by interfering with the attachment of bacteria to the cells lining the urinary tract.)
No trial compared sweetened against unsweetened cranberry juice, such as the cranberrry concentrate sold in health food stores. Ocean Spray provided its sweetened product in most of the trials with the single purpose of proving it better than a placebo juice. The researchers say that drinking large amounts of cranberry juice with high sugar content “might raise concerns” about sugar control in diabetics, as well as severe gastrointestinal upset or other adverse effects in some people. Therefore, the researchers concluded that unsweetened cranberry juice might be a better choice.
Dosages used in the trials were all over the lot, ranging from 0.4 to 194.9 grams. More is better, say the researchers, who observed that highest effectiveness was shown in “people using cranberry-containing products more than twice daily.” To their credit, these trials had a wide range of study participants. Most were otherwise healthy women, and some had recruited only elderly nursing home residents, pregnant women, or people with a chronic condition called neuropathic bladder.
In summary: Cranberry products can reduce UTI recurrences in a wide range of people whose symptoms return despite antibiotics therapy. There is, however, no definitive information about the most effective dose, or whether unsweetened cranberry juice is better than supplements. (Dietary supplements, by the way, are unregulated, which means that manufacturers do not have to do testing that shows effectiveness or safety. Read: “The consequences of ineffective regulation of dietary supplements.”)
Endnote: A word about symptomless UTIs. Though not addressed by any of the 10 trials, UTIs without symptoms are common, especially in elderly people. It is usually detected in the standard dipstick screening urine test and follow-up culture. It is important to know that the U.S. Preventive Services Task Force does not advise urine testing for people without symptoms. Why? The antibiotic regimen that is prescribed by many physicians is riskier than no treatment.
Here is the USPSTF recommendation: “The USPSTF recommends against screening for asymptomatic bacteriuria in men and nonpregnant women. In men and nonpregnant women, adequate evidence suggests that screening men and nonpregnant women for asymptomatic bacteriuria is ineffective in improving clinical outcomes. Harms of Detection and Early Treatment: Potential harms associated with treatment for asymptomatic bacteriuria include adverse effects from antibiotics and development of bacterial resistance. Without evidence of benefits from screening men and nonpregnant women, the potential harms associated with overuse of antibiotics are especially significant. There is moderate certainty that the harms of screening for asymptomatic bacteriuria outweigh the benefits.”
Maryann Napoli, Center for Medical Consumers©