September 06, 2006

The Cranberry UTI Connection

Last year, I shadowed an FP around her rural clinic. It was very educational and I'm willing to bet that I've forgotten more from her than I learned from medical school so far. ;-)

A lot of the most educational bits did not necessarily come from my interaction with her; rather, they came from my interactions with her patients. I can remember one in particular, when I was reading about "Woo" on Respectful Insolence. This lady came in for a routine checkup and she brought up the subject of frequent urinary tract infections.

"I've been doing a little research online..." she said.

Little red lights and alarms started going off in my head. Bweep bweep bweep! This is probably going to be something a little wacky... prepare yourself!

"And I started taking supplements of D-mannose. My urinary tract infections disappeared soon after that!"

Here's the simplified process of the urinary tract infection. Bacteria from the environment gets up into the ureter through the urethra. This is more common in women than men because guys have longer urethras (hehehehe... I'm still immature and I need to giggle a bit at that thought.) So male "hoses" are a protective mechanism preventing bacterial infection. One type of bacteria that normally infects the ureters is E. coli. No, not the nasty ones that people die from that cause bloody diarrhea and death... just your plain jane bacterial buddies that hang out in everyone's gut. The female anatomy is not well suited to prevent the bacterial transfer from anus to urethra... and that's a reason why female hygiene is so important!

E. coli can only fasten onto human cells if it has the right proteins and sugars to use as grippers. Special strains of E. coli with grippers aka type I pili that can bind mannose can climb more easily into the urethra from their old hangout spots. They get to relax and stretch out in their new home... but the body doesn't like it too much and that causes pain, redness and frequent urination.

Anyway, I wanted to talk about D-mannose. So, the lady hands the FP a small little packet that she printed out on these supplements. Without so much of a glance, the FP takes it and tosses it on her chaotic nest called a desk. I look at it and notice that the website is or something like that and I think nothing of it. Obviously, my FP didn't think it was anything worth mentioning to me... but I had wanted to learn more about it.

Does D-mannose turn the urinary tract into a sudden slip and slide for the E. coli bugs and wash them out? I tried to do a search on the efficacy of D-mannose pills on PubMed, but my uber-search skills were limited last year.

What does this have to do with cranberry juice? Well, cranberries are chockful of indigestible sugars like D-mannose!

Yesterday, I revisited the cranberry, D-mannose, UTI connection that I had previously dismissed and I was pleasantly surprised to find that there have been some studies done that have shown minor improvements in the prevention of UTI with cranberry juice and cranberry pills. However, I personally think that better awareness and hygiene would be a better alternative to drinking nasty stuff like cranberry juice. Yuck! It's a bit too bitter for my taste. Apparently, those E. coli think the same way.

Jepson, R.G. Cranberries for preventing urinary tract infections. Cochrane Database Syst Rev. 2004;(1):CD001321.

P.S. I put up a brief version of my findings on Wikipedia under mannose.

P.P.S. [edit 9/12/06]
According to Biotech Weblog, here's a few more things tha cranberry juice can do because of the tannins in the drink as well:

* They change the shape of the bacteria from rods to spheres.
* They alter their cell membranes.
* They make it difficult for bacteria to make contact with cells, or from latching on to them should they get close enough.

Wow! Sometimes its the simple stuff that I find most surprising in my learning of medicine.


  1. hi. my gf gets UTI very very often. she's done the whole cranberry juice and cranberry pill thing with no real long tern affects. if D-mannose is what makes cranberry pills kinda work, why not just take straight D-Mannose. i've read a lot about how the prevailing wisdom about cranberry being good for UTIs has changed. its not the definitive all natural cure all it was once thought to be.

  2. As with everything else, it depends on balance and moderation. Cranberry juice are good but should ensure that you are not too reliant on this, but at the same time always including them in your diet. This would increase the chances that you would become healthier!

    Urinary Incontinence