More Cranberry Juice Better Against Urinary Tract Infections -
Researchers Find Evidence That 8 Ounces are More Effective Than 4

(September 2004) New evidence shows that patients with urinary tract infections (UTIs) need to be drinking more cranberry juice in order to prevent future bladder problems. According to a pilot study presented in October at the annual meeting of the Infectious Diseases Society of America in Boston, drinking more cranberry juice is better than drinking less.

Tannins contained in cranberries interact with the tiny, hair-like protrusions on E. coli bacteria, the most common cause of UTIs. The infection-causing bacteria loose their stickiness and, instead of adhering to the walls of the bladder and causing infection, get washed away in urine.

In the study led by investigator Dr. Kalpana Gupta, an assistant professor at Yale University School of Medicine, researchers found that drinking eight ounces of cranberry juice resulted in a 71 percent reduction in the amount of E. coli bacteria sticking to the bladder walls; a four-ounce serving of juice produced a 33 percent reduction in the unwanted bacteria. Eight ounces of juice had a twofold greater effect than four ounces. The study also concluded that at least four ounces of cranberry juice are needed to make a considerable difference.

Although there is not yet a standard amount of cranberry juice recommended, the new information provides doctors with a better guideline to treat their patients who suffer from UTIs. The information from this study shows that more juice is better.

Researchers tested cranberry dosing by collecting urine from three symptom-free volunteers before they consumed pre-determined amounts of cranberry juice and four to six hours afterward. The juice they used was a 27 percent cranberry juice cocktail, the kind commonly found in grocery stores.
Then the investigators incubated E. coli in the urine samples and combined it with human bladder cells to test how well cranberry juice would prevent the bacteria from sticking to those cells.

The preventive effect of cranberry juice appears to be dose-dependent. Researchers have already launched a larger study that will involve many more subjects and compare several different doses of juice.

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