Tests of seven popular cranberry-pill brands in the U.S. showed that
most contained too little of the key bacteria-fighting ingredient to
have any effect.
“There is a lot of variability in quality and efficacy of cranberry
supplements, making it difficult for consumers to know which ones
will work for them,” said lead author Dr. Bilal Chughtai, assistant
professor of urology at Weil Cornell Medical College in New York.
UTIs affect some 8 million people each year in the U.S.
Approximately half of all women will experience one at some point,
Chughtai and his colleagues write in the American Journal of
Obstetrics and Gynecology.
UTIs are caused by bacteria and usually treated with antibiotics,
but antibiotic overuse and resistance are problematic, so finding
effective ways to prevent UTIs is important, the authors write.
Cranberry juice and supplements have long been used to stave off
UTIs. They were once thought to prevent the infections by affecting
the acidity of urine, the researchers note.
More recent investigations show that cranberries or cranberry juice
may actually work because they contain proanthocyanidins –
antioxidant “flavonoids” like those found in blueberries, grape
seeds and chocolate that also prevent bacteria from sticking to the
bladder wall and beginning the growth process.
Past studies have shown that to prevent recurrent UTIs, cranberry
products need to contain at least 36 milligrams of proanthocyanidins
per gram, the researchers note.
Herbal medications like cranberry supplements are not regulated by
the Food and Drug Administration and so many brands may not contain
the needed amount of proanthocyanidins or even any at all, Chughtai
told Reuters Health by email.
He and his colleagues analyzed seven over-the-counter cranberry
supplements, testing each product in cultures of bacteria and red
blood cells to see how effectively it prevented bacterial growth.
Only one supplement studied contained more than the needed amount of
proanthocyanidins, with 175 mg of the compounds per gram of product.
That supplement also prevented bacterial growth in culture.
Another supplement contained 25 mg/g of proanthocyanidins and also
showed activity against the bacteria, while the other four
supplements contained less than 5 mg/g of proanthocyanidins and had
no effects against the bacteria.
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The report does not identify the brands.
Chughtai noted that cranberry powders may be made from dried juice
or from dried skins left over from the juicing process. Supplements
made from juice act much faster and are more effective than those
made from skins, he said.
“But since supplement manufacturers are not required to list which
parts of the cranberry are in the supplement, all forms of powdered
supplements (whether from juice or skins) are able to call
themselves ‘cranberry’,” Chughtai said.
"Urinary tract infections (UTIs) are very common, particularly in
women, and result in major costs related to antibiotic use,
hospitalizations as well as time lost from work," said Dr. Deborah
Wing, a gynecology professor at University of California, Irvine,
who was not involved in the study. "Approaches to either prevent or
treat UTIs which are based on use of food products could reduce some
health care costs and minimize human pain and suffering," Wing told
Reuters Health by email.
Overall, Wing said, cranberry may be better for prevention than for
treatment. To treat a UTI, she said, people should consume cranberry
products daily and in frequent doses throughout the day, which may
be very hard to do.
She also noted that other compounds in cranberries might work with
proanthocyanidins to treat UTIs. For this reason, it may be more
effective to take supplements made from cranberry juice rather than
other extracts.
SOURCE: bit.ly/1Nb4a3H American Journal of Obstetrics and
Gynecology, online April 5, 2016.
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