cranberriesDear Biosleuth,

Do cranberry products help in preventing bladder infections?


Thanks for asking!  Here is what I found in the medical research..

Our immune systems prevent infections that potentially occur from our daily encounter with invisible assailants (the microscopic world).  Pathobiology is the study of the various ways that pathogens evade all our defenses and the mechanisms in place to counter-attack in our defense (and subsequent health).  The microbial world and creative modes that pathogens use to invade our elaborate immune system fascinated me so much that I studied Pathobiology in graduate school and received a degree from the School of Public Health.  We live surrounded by bacteria and viruses; our immune systems successfully stave off infections that assault us every day of our lives.  (How cool is that?)  When the immune system or our bodies’ outer defenses (or inner) break down or are compromised, then we have problems.

Let’s look at ways we can help boost our immune system, especially when we have become more vulnerable to infection.  Anyone who has to self-catheterize is potentially providing an entry point for bacteria.  The body was not designed for foreign objects to be introduced upward through the ureters into the bladder.  The system is designed to provide an outlet for outward flow of urine from a sterile enclosure (the bladder) to the outside, which is covered in “normal flora”.  As long as the normal flora are kept on the outside, the skin is a barrier to their ability to cause infection.

Cranberry juice has for years been thought to boost the immune system’s ability to fight off Urinary Tract Infections (UTI) by bacteria.  Why?  Just as penicillin, produced by a mold, is able to kill some bacteria, cranberries contain a compound that interferes with adherence of some bacteria and yeast to attach to the cells lining the interior of the bladder (Rossi R, 2010).  Once bacteria have gained entry to a rich nutrient source like the inside of the urinary tract, their first goal is to attach, in order to start replicating and creating a thriving colony.  If they are unable to do so, although they may start multiplying, they will be continually dislodged and then washed out with the constant flow of urine through the bladder and urethra.  So, if proanthocyanidins, the compounds in cranberries that are thought to prevent adherence really are effective — that is good news for women who suffer from urinary tract infections.  However, it might depend on the type of bacteria that are living just outside the urethra, as to how susceptible they are to being prevented from sticking . . . and studies have indicated that women who chronically catheterize are not as likely to respond to the benefits of cranberry juice (Rossi R, 2010).

A recent review of the clinical literature as a whole (Jepson RG, 2012) concluded that cranberry juice is not effective against the prevention of UTI.  A follow-up article in the highly influential JAMA (Journal of the American Medical Association) suggested that the finding may actually be a flaw in the studies that were conducted or the way in which they were analyzed (Jepson R, 2013).  So, are we left with anecdotal stories of isolated cases where one woman has success in reducing the number of UTI’s with cranberry juice extract, where the next woman does not? . . . or is there something to it after all?  Dr. Oz is a big fan of the benefits of Cranberry Juice when it comes to treating chronic UTI’s (see  How about you?  Trudy is going to give Cranberry extract in a capsule form (Not Juice) a try — just twice a day to see if it helps her chronic UTI’s because she will be going off of her low-dose antibiotic next month.  If you want to take part in an informal “test” yourself — get some Cranberry Extract and try it along with her; log your progress by keeping track of each UTI your doctor diagnoses to determine if you have reduced the number of UTI’s you acquire with the nutrients found in cranberries.  Share your results with us by submitting your experiences under “Ask A Question” to ensure confidentiality (we will not share the names if we disclose any informal findings we make from feedback we receive).

We’d love to hear your general comments on this page as well!

Let’s talk more about ways to prevent UTI’s in the months ahead . . .

Take Care,

— Julia (The Biosleuth)


1: Jepson RG, Williams G, Craig JC. Cranberries for preventing urinary tract

infections. Cochrane Database Syst Rev. 2012 Oct 17;10:CD001321. doi:

10.1002/14651858.CD001321.pub5. Review. PubMed PMID: 23076891.


2: Jepson R, Craig J, Williams G. Cranberry products and prevention of urinary

tract infections. JAMA. 2013 Oct 2;310(13):1395-6. doi: 10.1001/jama.2013.277509.

PubMed PMID: 24084925.


3: Rossi R, Porta S, Canovi B. Overview on cranberry and urinary tract infections

in females. J Clin Gastroenterol. 2010 Sep;44 Suppl 1:S61-2. doi:

10.1097/MCG.0b013e3181d2dc8e. Review. PubMed PMID: 20495471.


4: Preventing UTIs

The Dr. Oz Television show

Posted on 12/17/2009