Why Cranberry Juice Works for UTI Prevention

By Carol J. Mulvihill, BSN, RN-C, Director of Health Services, University of Pittsburgh at Bradford,


I can't begin to count the number of times I have said to my patients with urinary tract infections (UTI's):
Drink plenty of liquids, up to 10 glasses of clear liquid per day. Avoid caffeine during a bladder infection because it can increase bladder spasms. Drink juices with Vitamin C. Include cranberry juice because it prevents infection of the urinary tract by keeping the urine an acid Ph.

Now, based on newer research findings, I have changed my script of health information/instructions for my UTI patients. It goes like this:

Drink lots of clear liquids - up to 10 glasses per day. Avoid caffeine which can increase bladder spasms. Drink plenty of cranberry juice. It can be very helpful in preventing and treating a urinary tract infection. It works by preventing bacteria from sticking to the walls of the bladder where it can multiply and cause infection. Cranberry juice acts like a natural antibiotic to the urinary system. Not all juices do this....but cranberry juice and blueberry juice are two that do.

Here's why I changed my script: A letter published in the New England Journal of Medicine (NEJM, October 8, 1998, Vol. 339, No. 13) told of a 1994 research study which validated the claim that cranberry juice prevents UTI's, and clarified that it is not because of the acidic nature of the cranberry juice, nor because of the Vitamin C content. It is if fact due to specific compounds called condensed tannins (specifically proanthocyanidins) in cranberries, blueberries and other vaccinium fruit species which prevent the attachment of P-Fimbriated E.Coli to the walls of the urinary tract. P-Fimbriated E. Coli bacteria is a major culprit in UTI's.

I suggest reading the NEJM article in its entirety. The article, Inhibition of the Adherence of P-Fimbriated Escherichia coli to Uroepithelial-Cell Surfaces by Proanthocyanidin Extracts from Cranberries can be read on the internet at
It is always helpful to know the scientific basis of the health information which we share with our students.

Patient teaching has been a part of the nursing process since the days of Florence Nightingale. Now that we are in the information age, patient teaching continues to be an integral element of our care and treatment plan. I make every effort to explain the why of the prevention and treatment options I recommend to my patients, and I also try to frame my explanations in language which the average college student consumer can understand.

The use of the internet to access up-to-date health information, as well as information shared on the SHS (Student Health Service) listserv has greatly enhanced my ability to do state-of -the art health teaching with my patients. By providing access and pointing to credible, research-based information resources, the SHS listserv and a variety of Internet health information resource sites have enhanced the practice of college health nursing in ways I never would have imagined ten or twenty years ago. As a result, I do my job better and my patients are more informed than ever!

My sincere thanks goes to Peter Nobes, P.A. pnobes@ZOO.UVM.EDU who shared the news about the article in NEJM about Cranberries and UTI's with the SHS listserv.

Note: The research on cranberries and UTI's was supported in part by a grant from Ocean Spray Cranberries, Inc. Also, my thanks go to Ocean Spray for providing the very nice cranberry juice image for this article. bar

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