You’ve probably heard that cranberry juice can help prevent or cure a common, nasty infection called a urinary tract infection, or UTI. The belief is that it somehow flushes out bacteria or changes the conditions in your body so that bacteria cannot thrive there.
These ideas are slowly being debunked by science, and it now looks like chugging down cranberry juice might not be any better at curing an infection than a glass of water.
A new study, lead by Dr Manisha Juthani-Mehta from the Yale School of Medicine, investigated the effects of high-dose cranberry capsules on 185 women in a nursing home. The pills contained the equivalent of 20 ounces of juice, and the women were given the pills once a day.
The participants were divided into two groups; half were given cranberry capsules and the other a placebo. A year later, there was no difference in the presence of the common UTI bacterium known as bacteriuria plus pyuria between the two groups.
In an editorial accompanying the paper, Lindsay E. Nicolle, a professor of internal medicine and medical microbiology at the University of Manitoba, wrote that clinicians should no longer promote cranberry use or claim that there is any benefit to drinking it for infections.
“It is time to move on from cranberries,” she wrote.
Nicolle’s conclusion is backed up by several other studies, including a small one done in 2003 and another larger study from 2012. In 2003, researchers from Wayne State University Medical School compared concentrated cranberry juice with a placebo and found no conclusive evidence that it effectively treated UTIs.
In 2012, a Cochrane review of 24 studies with a total of 4,473 participants concluded that there was little evidence of positive effects of cranberry juice on UTI incidence, and it “cannot be recommended for the prevention of UTIs.”
Where did the idea that cranberry juice is good for infections come from?
People didn’t start believing that cranberry juice had special qualities for no reason. Initially, it was given a good name because of the fact that cranberries contain A-type proanthocyanidins (PACs), which were shown to help block the adhesion of bacteria to the wall of the bladder. In reality though, this active ingredient is long gone before it gets that far.
Plus, a few studies have suggested that drinking cranberry juice or taking cranberry pills may prevent — but not treat — UTIs, especially for women who are at risk of getting these infections. For example, a 2016 study from the University of Delhi showed that cranberry extract was superior to a placebo for reducing the amount of UTI bacteria in two groups of people. However, the authors admitted further controlled trials are needed.
Another 2016 study funded by cranberry juice manufacturer Ocean Spray suggested that drinking the juice lowered the number of clinical UTI episodes in women with a recent history of having one after 24 weeks.
So although the theories might be based in fact, the evidence that cranberry juice is an effective treatment for UTIs is shaky at best. Instead, it’s advised to get the proper medical treatment, which is a short course of antibiotics. Plus, drinking too much juice in general can have some unpleasant effects on your body, like acid reflux and an upset stomach.
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