Cranberries have long been touted as a remedy for urinary tract infections, but a new study suggests that the health benefits may be overblown – or worse, nonexistent.
A research team studying the incidence of urinary tract infections among nursing home residents found that taking cranberry capsules – containing active ingredients found in the tart berries – had no effect on the frequency and course of urinary tract infections when compared to a placebo.
“The findings from this trial demonstrated no significant difference in presence of bacteriuria plus pyuria among women who received cranberry capsules vs. placebo over one year,” explains the research team in the Journal of the American Medical Association (JAMA).
The presence of bacteriuria plus pyuria, which is prevalent among older adults in general and nursing facility residents in particular, often leads to a diagnosis of a urinary tract infection, which researchers note is “the most commonly diagnosed infection among nursing home residents.”
Bogged down by data
The JAMA study, conducted by researchers at the Yale School of Medicine and Public Health, appears to contradict accepted wisdom about the preventive powers of cranberries. Some previous studies show that drinking a cranberry cocktail can cut down on urinary tract infections.
Overall, the cranberry craze is something of a mixed bag.
“Many studies of cranberry products have been conducted over several decades with conflicting evidence of its utility for UTI prevention,” stated the researchers.
Currently, the Yale Medicine website states, “There is some support that cranberries can help prevent [urinary tract infections].” Companies like Ocean Spray also tout the benefits of cranberries for urinary tract infections.
The new study appears to cast those claims aside. In studying the efficacy of cranberry capsules, the research team tracked 185 nursing home residents with an average age of about 86 over the course of one year. One group of patients took two cranberry capsules daily, while the other group took a placebo – that is, two pills with inactive ingredients meant to mimic the cranberry pills.
Ultimately, 80 percent of the patients in the study group adhered to the twice-daily regimen. Among those who finished the study, the researchers found “no significant difference” between the two groups in the frequency of urinary tract infections.
They also noted no difference in other quality markers related to urinary tract infections, such as rates of hospitalization, antibiotic use or death rates.
“Cranberry capsules have not shown meaningful clinical benefit and have not been cost-effective,” the study’s authors wrote.
While the 365-day picture was a wash, researchers did notice a wrinkle about midway through the study. “There appeared to be an initial effect on bacteriuria plus pyuria in the first six months,” they wrote. However, “these rates returned to baseline in the second six months of study.”
The six-month findings have researchers theorizing that “slightly lower adherence in the second six months could have contributed to this finding.”
The new study also investigates why past studies assessing cranberry capsules have shown different results. In one study, which appeared to show slight improvements, “all participants were instructed to drink eight ounces of water twice a day with each capsule administration, so it is possible that the fluid load was necessary along with cranberry product.”
But as the headline on an accompanying editorial notes, when it comes to cranberries and urinary tract infections, researchers believe it’s “time to move on.”
Richard Scott is a health care reporter focusing on health policy and public health. Richard keeps tabs on national health trends from his Philadelphia location and is an active member of the Association of Health Care Journalists.