Value of cranberries for UTI prevention called into question

By Helen Albert, Senior medwireNews Reporter

Results from an updated systematic review suggest that the value of cranberry juice or capsule consumption for prevention of urinary tract infections (UTIs) is likely to be limited.

The authors of the update, published in the Cochrane Database of Systematic Reviews, found some evidence to suggest that while there were small benefits for women with recurrent infections, they would have to consume large amounts of juice for long periods to prevent one infection.

The previous systematic review, published in 2008, suggested that consumption of cranberry juice or associated products moderately reduced the number of UTIs over a 12-month period, but the addition of 14 new studies in the current review indicates that the beneficial effects of cranberry juice are smaller than previously estimated.

"Now that we've updated our review with more studies, the results suggest that cranberry juice is even less effective at preventing UTIs than was shown in the last update," said lead researcher Ruth Jepson (University of Stirling, UK) in a press statement.

The new review included 24 studies with a total of 4473 participants. Of these, 13 evaluated cranberry juice or concentrate alone, nine assessed cranberry tablets or capsules alone, one compared capsules and tablets, and one compared cranberry juice and tablets. Comparison groups were assigned to placebo, no treatment, water, or antibiotics.

Overall, 13 studies were included in a meta-analysis. The team found that cranberry products did not significantly reduce the occurrence of symptomatic UTI overall or in any of the subgroups when compared with placebo, water, or no treatment.

In addition, compared with antibiotics there was no significant difference in the efficacy of infection prevention using cranberry products either for women or children.

Two small studies that were not included in the meta-analysis reported a significant positive effect of cranberries over placebo. Furthermore, four studies included in the meta-analysis (n=594) that included a placebo group showed a small, nonsignificant reduction in risk for recurrent UTI with cranberry products.

Low compliance and high dropout rates were common in many studies, which the authors suggest was due to poor palatability or acceptability of the products, with cranberry juice in particular being unpopular with participants. However, gastrointestinal adverse effects were comparable between those consuming a cranberry product compared with placebo or no treatment.

Although consumption of cranberry tablets or capsules could potentially overcome the problem of palatability, Jepson and team emphasize the need for the active ingredient in these preparations to be quantified using standardized methods to ensure potency.

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  1. Amy Howell Amy Howell United States says:

    I have been doing research at Rutgers University for the past 20 years and have found that cranberries prevent bacteria from sticking to bladder cells, which is the initial step in the urinary tract infection process.  I think we need to keep these latest findings in perspective with the totality of cranberry research that has been done over the last 100 years.  This latest review analyzed results from some of the clinical trials, using criteria that apply to studies on drug treatments. Cranberry is a food that comes in different forms (juices, powders, dried, etc.) making it difficult to compare results from different trials because the same form and dosage of cranberry were not used in each study.  

    Interestingly, three new UTI clinical studies, published after this report was prepared, have shown significant benefits in children, with as much as a 65% reduction in UTIs and reduced use of antibiotics.  Cranberries in many forms are enjoyed by millions of people globally on a daily basis.  If women are currently consuming cranberry products, the results of this one review do not provide a reason for them to change their current practices.  It is important that cranberry continue to be regarded and researched as a viable means to help address the public health challenge that UTIs and their treatment presents to antibiotic resistance.  The effects of the studies are clinically important to the 15 million women in the US with UTIs each year. - Amy Howell, PhD

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News-Medical.Net.
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