Cranberries and cranberry juice have long been used to ward off UTIs, however, it is unclear how exactly they prevent infection. One theory, reported at a 2010 meeting of the American Chemical Society, suggests that certain sugars and flavanol compounds, present in cranberries, deter bacteria from sticking to cells that line the urinary tract.
For this new study Dr. Ruth Jepson and her team from the University of Stirling examined data from 24 studies that included a total of 4,473 people. The treatment groups were given cranberry juice, capsules or tablets, and those in control groups had placebo cranberry products, methenamine hippurate, antibiotics, lactobacillus, water, or nothing.
The authors pointed out that the results show that cranberry juice is significantly less beneficial than previous research has stated.
Cranberry juice was previously believed to offer protection against cystitis and other urinary tract infections.
In earlier studies, slight benefits were seen for women suffering from recurrent infections, but they would need to drink two glasses of cranberry juice per day for extensive periods of time to prevent one infection.
Other studies have also proven that antibiotics are more effective than cranberry. In collaboration with the new evidence, researchers have concluded that cranberry juice cannot effectively prevent UTIs.
Dr. Jepson does not recommend more studies, saying:
"We can't see a particular need for more studies of the effect of cranberry juice, as the majority of existing studies indicate that the benefit is small at best, and the studies have high drop-out rates."
Further studies could only be justified for women with recurrent UTIs, and only for cranberry products such as capsules or tablets that have the recommended amount of active ingredient.
Written by Kelly Fitzgerald