Cranberry is often recommended as an alternative therapy for cystitis and urinary tract infections (UTIs). Originally, complementary doctors thought that cranberry acidified the urine to create an antibacterial effect. Further research showed that patients would need to drink 1,500 mL (about 6-1/3 cups) to bring the urine’s pH to 5.5, the level that would kill bacteria. That’s a whole lot of cranberry juice.
More recent research shows that cranberry keeps bacteria from binding to the bladder and the gut, so it is passed out of the body without causing a urinary tract infection. Even small doses of cranberry do make the urine more acidic, but it’s the blocking action that prevents cystitis from taking hold. Since blueberries and bilberries are related to cranberry, they also offer some protection from bladder infections, though to a lesser extent.
Cranberry should be used as a preventative for bladder infections rather than being counted on to cure UTIs. However, it offers a good alternative to traditional antibiotic therapy, which kills both the good and bad bacteria throughout the body. Because infection-causing bacteria can’t remain inside the bladder, the risk of urinary tract infections is greatly reduced.
Cranberry extract in doses up to 400 milligrams per day completely prevents UTIs, according to one study. Another study found that even smaller daily doses of cranberry juice (six ounces) prevented cystitis in some patients. The extract may be taken in capsule form for those who don’t like the taste of unsweetened cranberry. By taking cranberry extract capsules, you can also avoid drinking more than 6 cups of juice to get the same effect.
Abascal, K., and Yarnell, E. (2008). Botanical medicine for cystitis. Alternative and Complementary Therapies, 14(2), 69-77.