Cranberry juice's preventive effects increase with intake.(Gynecology)

BOSTON -- The more cranberry juice one drinks, the better its effectiveness at preventing bladder infections, a study has shown.

Urine samples from volunteers who drank cranberry juice cocktail showed that 8 ounces of the drink resulted the adherence of fewer infection-causing bacteria to bladder epithelial cells compared with 4 ounces of the drink, Kalpana Gupta, M.D., reported at the annual meeting of the Infectious Disease Society of America.

Researchers have long postulated that a specific type of tannin found in cranberries helps keep P-fimbriated E. coli--the bacterium that causes most urinary tract infections--from sticking to the walls of the bladder, thus inhibiting infection. This study, by Dr. Gupta and her colleagues at Yale University, is the first to demonstrate a dose-response relationship.

The investigators collected urine samples from three volunteers before and 4-6 hours after the subjects consumed 4 ounces of 27% cranberry juice cocktail and again before and after the subjects consumed 8 ounces of the beverage. The researchers incubated E. coli in the urine samples, combined them with human bladder cells, and performed standard bacterial adherence assays to measure the number of bacteria that stuck to the bladder cells.

The consumption of both the 4-ounce and 8-ounce drinks was associated with a significant reduction in the number of bacteria sticking to the bladder cells, but the effect was two-fold greater with the 8 ounce drink, Dr. Gupta stated. The mean reduction in adherence associated with the 4-ounce drink was 33%, compared with pre-drink measures and the mean ...