Protection against Urinary Tract Infection

Cranberries have been valued for their ability to reduce the risk of urinary tract infections for hundreds of years. In 1994, a placebo-controlled study of 153 elderly women was published in the Journal of the American Medical Association that gave scientific credibility to claims of cranberries effectiveness in preventing urinary tract infection. In this study, the women given cranberry juice had less than half the number of urinary infections as the control group (only 42% as many, to be precise), who received a placebo imitation “cranberry” drink. The daily dose of cranberry juice in this initial study was just 300 milliliters (about one and one-quarter cups). Since then, a number of other studies have also confirmed anecdotal tales of cranberry’s ability to both treat and prevent urinary tract infections. In most of these later studies, subjects drank about 16 ounces (2 cups) of cranberry juice daily.

How does cranberry juice help prevent urinary tract infections? It acidifies the urine, contains an antibacterial agent called hippuric acid, and also contains other compounds that reduce the ability of E. coli bacteria to adhere to the walls of the urinary tract. Before an infection can start, a pathogen must first latch on to and then penetrate the mucosal surface of the urinary tract walls, but cranberries prevent such adherence, so the E. coli is washed away in the urine and voided. Since E. coli is pathogen responsible for 80-90% of urinary tract infections, the protection afforded by cranberries is quite significant.

Studies attempting to explain cranberries’ protective effects on urinary tract health were presented at the Experimental Biology Conference held in 2002. Amy Howell, research scientist at the Marucci Center for Blueberry Cranberry Research at Rutgers University and Jess Reed, professor of nutrition at the University of Wisconsin-Madison, compared the proanthycyanins (active compounds) in cranberries to those found in grapes, apples, green tea and chocolate. They discovered that “the cranberry’s proanthocyanidins are structurally different than the proanthocyanidins found in the other plant foods tested, which may explain why cranberry has unique bacterial anti-adhesion activity and helps to maintain urinary tract health.”