Among the most tenacious folk remedies in alternative medicine is the claim that cranberries — particularly cranberry juice, but more recently cranberry capsules and other supplements — have antibacterial properties and thus are effective at treating and preventing urinary tract infections (UTIs), especially in women.
This belief has persisted despite scant evidence to support it — and despite the fact that studies that have found cranberries beneficial have tended to be funded by Ocean Spray or others with a financial interest in selling products made from the fruit.
Indeed, in 2012, a team of independent Cochrane reviewers examined 24 of the best studies to date on the effectiveness of cranberry products on UTIs and concluded that neither cranberry juice nor cranberry supplements did anything to prevent the infections.
But the lack of good evidence has not stopped many healthcare providers — conventional as well as alternative — from recommending cranberry juice or capsules to their patients as a way to prevent recurring UTIs.
A new study, published online Thursday in the Journal of the American Medical Association (JAMA), may finally change that. This study — a randomized, controlled, double-blinded clinical trial (considered the “gold standard” in research) — found that high-dose cranberry capsules had no effect on urinary infections among older women living in nursing homes.
Any healthcare providers who continue to recommend cranberry use “are doing their patients a disservice,” says an accompanying editorial.
Why nursing home residents
For the study, a team of researchers led by Dr. Manisha Juthani-Mehta of Yale University recruited 147 elderly women living in nursing homes.
They had a good reason for choosing this population.
UTIs are among the most commonly diagnosed infections in the United States, accounting for more than 8 million doctor visits each year, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD). For anatomical reasons (primarily, a shorter urethra), women are especially prone to these infections. Almost half of all women in the U.S. will experience a UTI at some point in their lives.
Common symptoms are a persistent need to urinate and a burning sensation when urinating. In older people, however, particularly those whose frail health requires nursing home care, the classic signs of a UTI are often hidden by behavioral symptoms, such as confusion and agitation.
UTIs are usually treated with antibiotics, but they can be stubborn to get rid of, and some people experience recurring infections. In recent years, many nursing homes have been giving their residents cranberry capsules as a preventive measure. (Cranberry juice, which has an acrid taste in its pure form and too much sugar in its “drink” form, is difficult to tolerate in large amounts, particularly among older adults.)
No statistical difference
At the start of the JAMA study, about a third (31 percent) of the women in the nursing homes tested positive for both bacteria and pus in their urine — evidence of an infection.
Half the women were randomly assigned to receive two cranberry capsules daily for a year. Together, the capsules contained 72 milligrams of the active ingredient proanthocyanidi (the equivalent to what is found in 20 ounces of cranberry juice). The other half of the women received identical-looking “placebo” capsules. None of the patients, their caregivers or the researchers knew which women received which type of capsule.
During the course of the study, 10 of the infections in the women receiving the cranberry capsules and 12 in the women receiving the placebo caused overt symptoms of a urinary tract infection, a difference that was not statistically significant.
The study also found no significant differences in deaths, hospitalizations or any other clinically meaningful outcomes between the two groups.
‘Time to move on’
On its website, the National Center for Complementary and Integrative Health warns people not to use cranberry products “in place of proven treatments for infections.
Although drinking cranberry juice is safe, large amounts can cause stomach upset, increase the risk of developing kidney stones, and interfere with the workings of the blood-thinning drug warfarin, the agency adds.
A better fluid to drink for UTIs is plain water, which can help dilute urine and flush out the bacteria.
In the editorial that accompanies the JAMA study, Dr. Lindsay Nicolle, an infectious disease specialist at the University of Manitoba, is quite blunt about the meaning of the study’s results. It should put an end to the debate about this particular folk remedy, she says.
The evidence — from this study and all the previous ones — “is convincing that cranberry products should not be recommended as a medical intervention for the prevention of UTI,” Nicolle writes. “A person may, of course, choose to use cranberry juice or capsules for whatever reasons she or he wishes. However, clinicians should not be promoting cranberry use by suggesting that there is proven, or even possible, benefits.”
“It is time to move on from cranberries,” she adds.