CranberryInfectionSpinal Cord

Cranberry extract prevents urinary tract infection

It’s almost as good as low-dose trimethoprim (Bactrim, Septra) with fewer side effects, according to researchers at the University of Dundee in Scotland.

Although, based on these results, it is as good.

First, the details.

  • 137 women older than 45 years participated.
  • They had a history of at least 2 antibiotic-treated urinary tract infections (UTIs) in the past year.
  • They were randomly assigned to take 500 mg of cranberry extract or 100 mg of trimethoprim for 6 months.

And, the results.

  • 28% of the women had an antibiotic-treated UTI.
    • 25 in the cranberry group and 14 with trimethoprim — not a significant difference.
  • The time to first recurrence of UTI was not significantly different between the groups.
  • There was no difference in the number of women who discontinued treatment.
  • Itchiness or rash was more common with trimethoprim.
  • Gastrointestinal upsets did not differ between groups.

The bottom line?
The authors concluded, “Trimethoprim had a very limited advantage over cranberry extract in the prevention of recurrent UTIs in older women and had more adverse effects.”

I don’t see the “limited advantage.” The authors are apparently hedging their bet. Yes, the number of UTIs was higher with cranberry extract, but there was no statistical difference between groups.

It’s cheap and natural, not to mention effective and apparently safe.

Cranberry extract also doesn’t carry the risk of antimicrobial resistance or super-infection with Clostridium difficile or fungi.

The results of other studies with cranberry extract or concentrate support these findings.

  • Researchers from VA Boston Health Care System reported, “Cranberry extract tablets should be considered for the prevention of UTI in spinal cord injured patients with neurogenic bladder.”
  • Researchers from Colorado reported no UTIs after 2 years of taking cranberry concentrate.

The value of drinking cranberry juice to prevent recurrent UTI is less clear here, and here.

1/7/09 10:50 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.