The Kidney Foundation of Canada says Canadian women make about 500,000 visits to doctors each year to treat urinary tract infections (UTIs). For years, scientists knew that cranberry could help prevent UTIs but could not explain why. Then in 1984, a researcher discovered that cranberry could inhibit “bacterial adherence,” or the ability of bacteria to stick to the urinary tract wall. (Later, this was found to be due to cranberry’s rich supply of proanthocyanins.) The 1984 study showed that cranberry juice inhibited E. coli bacteria from sticking by 75% in more than 60% of tests and in 80% of animal tests. In a human study, the researcher found that 15 of 22 people had significant anti-adherence activity only one to three hours after drinking 15 ounces of cranberry juice.

More recently, at the Division of Urology at UBC in Vancouver, researchers found that cranberry tablets were the most cost-effective prevention method for UTIs. In this study, 150 women aged 21 to 72, all prone to UTIs, supplemented with cranberry juice, cranberry tablets or a placebo for one year. The researchers assigned a “dollar cost per UTI prevented” and observed the women, noting number of UTIs experienced, time off work, total antibiotic consumption and other factors such as cost of protective undergarments.

After the trial period, the researchers calculated costs and determined that even though both tablets and juice significantly decreased the number of UTIs experienced, cranberry tablets were twice as cost effective as juice.

Sources: J Urol 1984 May;131(5):1013-6; Can J Urol 2002 Jun;9(3):1558-62