Can a glass of cranberry juice a day keep the urologist away? You might have heard that cranberries help prevent urinary tract infections (UTIs), but are these berries really as medicinal as they are tart and tasty?
There is some science behind the claims that cranberries can protect against urinary tract infections, especially in women who are prone to getting UTIs. Yet the benefit for other groups of people isn't as clear. Plus, there are no real recommendations on how much cranberry juice you'd need to drink to get any protection against UTIs.
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Here's a look at the research on cranberries for urinary tract health and what the health experts have to say about their benefits.
Cranberries: The Science Behind Urinary Tract Protection
Scientists used to believe that cranberries protected against UTIs by making the urine more acidic and, therefore. inhospitable to bacteria like Escherichia coli (E. coli) that cause urinary tract infections. Now the thinking has shifted.
Researchers now believe that cranberries contain substances that prevent infection-causing bacteria from sticking to the urinary tract walls. There are a couple of different theories about how exactly cranberries do this. Some studies show that certain antioxidants in cranberries change the bacteria so that they can't stick to the urinary tract. Another idea is that cranberries create a Teflon-like slippery coating on the urinary tract walls that prevents E. coli from getting a good grip.
Do Cranberries Really Prevent UTIs? The Evidence
Studies that have analyzed the effects of cranberry products on urinary tract infections have gotten mixed results. Here's an overview of the evidence:
A few studies have found that drinking cranberry juice or taking cranberry pills can prevent UTIs, especially in women who are at risk for these infections:
One study looked at women who had a history of urinary tract infections caused by E. coli bacteria. Women who drank 1.7 ounces of cranberry-lingonberry juice concentrate every day for six months lowered their risk of getting a UTI by 20% compared to women who didn't use any intervention.
In another study, cranberry juice and cranberry tablets were linked to fewer patients who experienced at least one symptomatic UTI. In the study, sexually active women took one tablet of concentrated cranberry twice a day, drank about 8 ounces of pure unsweetened cranberry juice three times a day for 12 months, or were given a placebo.
In a third study, older adults who ate cranberry products were about half as likely to have bacteria and white blood cells in their urine in the setting of no UTI symptoms -- a sign of urinary tract infections. But other studies in older people showed no difference in symptomatic UTI in people using cranberry and those who didn’t.