Cranberry offers alternative to antiobiotics for the prevention of urinary tract infections

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Less than a month ago I wrote about one specific hazard associated with the taking of antibiotics, specifically their capacity to disturb the ‘ecosystem’ within the gut. In the short term this may lead to symptoms such as diarrhoea, but theoretically there may be longer-term consequences too, in the form of chronic digestive symptoms such as bloating, wind and altered bowel habit. One way to insure against such problems is to take probiotics (health gut organisms) during and/or after a course of antibiotics. My blog of last month focused on the research which has found this to be a generally worthwhile strategy for the prevention of gut upset in the short term.

Urinary tract infections (UTIs) are typically treated with antibiotics, and are much more common in women. Over the years I have seen many women who seem to be especially prone to UTIs. Quite often the picture is one of repeated UTIs interspersed with bouts of vaginal thrush (yeast infection) as a result of taking antibiotics. What is likely to be happening here is that the antibiotics are leading to the yeast overgrowth in the body (including the vagina) which then manifests as thrush. The ability for antibiotics to alter the ‘ecosystem’ in the vagina may be especially relevant, because this may make it more likely that unhealthy organisms (including the bacterium E. coli) will be able to colonise the area in numbers sufficient to make their way up the urethra (the pipe from the bladder to the outside) and into the bladder to set up an infection here.

How to break this cycle? Well, I believe probiotics have a role to play here in helping to establish the better ecosystem in the gut and elsewhere, including the vagina.

The other major strategy is to try and do without antibiotics, of course. In a previous post here I wrote about the potential use of cranberry in this regard, as well as including some other strategies in the form of a previous piece. Cranberry has the ability to inhibit the attachment of E. coli organisms to the bladder wall, and so makes it less like that this organism will set up camp here can cause a full-blown infection.

I was interested to read of a recent study where the effectiveness of cranberry was tested in terms of its ability to prevent UTIs in women [1]. In this study, 137 women prone to UTIs were treated either with cranberry (500 mg of extract each day) or the antibiotic trimethoprim (commonly used in the treatment or prevention of UTIs) at a dose of 100 mg per day. There was no statistically significant different in the average time it took to the next UTI between the two groups. Also, trimethoprim led to more side-effects, and the drop-out rate from the study was about twice that in the group taking cranberry.

This study, I think, is hampered by not having a control group taking placebo (inactive medication). However, what it does show is that cranberry offers a viable alternative to long-term antibiotics for women suffering from recurrent UTIs. The authors of the study were suitably impressed, and concluded Our findings will allow older women with recurrent UTIs to weigh up with their clinicians the inherent attractions of a cheap, natural product like cranberry extract whose use does not carry the risk of antimicrobial resistance or super-infection with Clostridium difficile or fungi.


1. McMurdo ME, et al. Cranberry or trimethoprim for the prevention of recurrent urinary tract infections? A randomized controlled trial in older women. J Antimicrob Chemother 2008 Nov 28 [Epub ahead of print]

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