8-Ounces Better than 4 to Prevent Bladder Infections

Cranberry’s protective effects against bladder infections may be dose responsive, with 8-ounces of cranberry juice being twice as effective as 4-ounces, suggests preliminary research presented at the 42nd Annual Meeting of the Infectious Diseases Society of America by Kalpana Gupta from the University of Washington.

Gupta reported the details of a very small trial in which three volunteers were given 27% cranberry juice cocktail. Urine samples, collected before and 4-6 hours after drinking the cranberry juice, were combined with human bladder cells and incubated with Escherichia coli (the most common cause of bladder infections). The number of bacteria able to adhere to the bladder cells (the first step a pathogen must achieve to be able to cause infection) was significantly reduced in the urine of all women who drank the cranberry juice cocktail, and the effect was doubled when the women drank eight ounces of cranberry rather than four ounces.

Cranberry’s protective effect is thought to be due to a specific type of tannin, found only in cranberries and blueberries, which interferes with projections on the bacterium, preventing it from sticking to the walls of the bladder and causing infection. However, once the bacteria have established a hold, it’s best to seek medical advice. No evidence shows cranberry juice is able to cure an established bladder infection, which can lead to a more serious kidney infection. The researchers plan further studies in a larger group of women to investigate the optimal amount and frequency of cranberry juice consumption.