Cranberries contain two compounds that keep infection-causing bacteria from adhering to the lining of the urinary tract. Whether provided in juice or tablet form, the contents of the berries have been the subject of clinical study since 1966 in association with urinary tract infections and bacteriuria (the existence of bacteria in the urine). The review noted, however, that limitations in many of the studies conducted, such as small size, short duration, or use of a wide variety of cranberry products and dosing levels, make the results difficult to assess and compare.
The group most likely to reap benefits from regular doses of cranberry juice or tablets is sexually active adult women with recurring UTIs, who may experience a 50 percent drop in infection rates, according to some findings. Cranberry juice's value in treating already-established cases of UTI is unknown, as most studies have focused on its ability to prevent infection.
The appeal of cranberry juice as a potential preventative of UTI lies not just in its taste and familiarity, though, according to lead author Dr. Raul Raz of Haemek Medical Center in Afula, Israel. "It is a natural tendency to take 'natural products' instead of antibiotics, not only for UTI. I believe that if good clinical studies are conducted showing a beneficial effect of cranberries in UTI, physicians will also recommend using it," Dr. Raz said.
If more controlled studies of cranberries' effect on UTI do take place, Dr. Raz believes they should be varied. "In general, we need more clinical studies with different population groups, different dosages, and comparison between juice and capsules," he said.
Contact: Jeff Minerd
Infectious Diseases Society of America