Urinary tract infections (UTIs) are one of the most common bacterial infections in women and children.
Painful and avoidable, they also require antibiotics, which doesn't necessarily prevent further infections.
The unnecessary use of antibiotics has led to the rise of drug-resistant bacteria, a major problem globally.
Could cranberry juice, a commonly believed aid in UTIs, actually help reduce the use of antibiotics?
Ocean Spray, the largest cranberry producer in the world, would like you to think so.
The health benefits of cranberry juice are, after all, a large focus of their marketing strategy.
Last week, Ocean Spray released the results of a study, published in the American Journal of Clinical Nutrition, which suggests drinking an 8-ounce glass of cranberry juice every day could help reduce the likelihood of a UTI by 40 percent, at least in women over 40 who frequently have the infection.
Calling the "landmark" study the largest clinical trial of its kind, the press release states cranberry juice "may be a useful strategy to decrease worldwide use of antibiotics" by preventing the need for the drugs.
So how do their claims match up to the evidence?
"That's a bit of a stretch," Dr. Aaron Glatt, chair of the Department of Medicine and Hospital Epidemiologist at South Nassau Communities Hospital in New York, told Healthline. "The landmark isn't a landmark."
The Official Results
For the study, women with a median age of 40 were assigned to two groups. One group drank 8 ounces of an Ocean Spray cranberry cocktail per day, which contained 27 percent actual cranberry juice. The group other received a placebo.
Ocean Spray financially supported the study, including providing the cranberry cocktail. Two of its employees, Kerrie L. Kaspar and Christina Khoo, head of research sciences, were involved in all aspects of the research.
Ocean Spray representatives said the study was conducted by an independent research company, registered with clinicaltrials.gov, and published in a peer-reviewed journal. The research also followed necessary protocols, including board and ethics committee approval.
Kalpana Gupta, an associate professor of infectious diseases at Boston University, was the only researcher on the study who reported no conflicts of interest. She's also been researching infectious disease for 20 years, including studying cranberries for the National Institutes of Health (NIH).
She called the study "beautifully done" because of its size, compliance to treatment, and follow-up.
There were 373 women in the final study. All had experienced a recent UTI.
During the study period, researchers diagnosed 39 UTIs in people who drank cranberry juice. In the placebo group, there were 67 UTIs.
Overall, researchers concluded, there was a 40 percent reduction in UTI symptoms in women who drank the cranberry cocktail.
Taking a Closer Look
There are, however, points of concern.
The study examined a woman's symptoms, not laboratory-confirmed bacterial infections.
Secondly, they counted all of the UTIs among the subjects and piled them together, not addressing the individual infection rates.
Gupta said symptoms were measured because that's what's used in the clinical setting.
"Symptoms of a UTI are why people go see their doctors," she told Healthline. "These women with recurring UTIs will do anything to prevent them."
Despite this and Ocean Spray's involvement, Gupta says she's confident in the findings and that they're in line with other research.
While Gupta says she wasn't paid for her role in the study, she now speaks on the issue and Ocean Spray compensates her for her travel expenses.
In 2012, Gupta co-authored research in the journal Mayo Clinic Proceedings that found cranberry juice didn't significantly reduce UTIs risk in women. Ocean Spray didn't fund that research.
When it comes to studying UTI risk, Glatt says other factors could have been at play and should have been controlled for, such as a woman's sexual activity and contraception use, which can increase her likelihood of a UTI.
"These are well-known factors that need to be controlled for," Glatt said.
Some research has shown that cranberries possess molecules that can interfere with how bacteria affix themselves inside the urinary tract. Those results, however, are at the type of concentrations for cranberries typically found in concentrated pills. Even then research on cranberry's protective effects is limited.
"The amount you would have to drink is much, much larger" than what subjects drank in the current study, Glatt said.
Drinking more cranberry cocktail could come with some unintended consequences.
Ocean Spray's Cranberry Juice Cocktail contains 28 grams of sugar per 8-ounce serving, which is higher than some sodas. That's 7 teaspoons of sugar, one more than the daily recommended maximum for women.
While she didn't say what Ocean Spray product was tested, Gupta did say it was a low-calorie version.
"We use something people can go out and get," she said. "It empowers many people to go out and get it."
But, at least according to a urologist at Texas A&M University, it may not do any real good.
"Cranberry juice, especially the juice concentrates you find at the grocery store, will not treat a UTI or bladder infection," Dr. Timothy Boone, Ph.D., told the school's Vital Record in February. "It can offer more hydration and possibly wash bacteria from your body more effectively, but the active ingredient in cranberry is long gone by the time it reaches your bladder."
A study published in Clinical Infectious Diseases in 2011 tested ingesting 16 ounces of 27 percent cranberry juice per day. The study was based on results collected from 319 college women with UTI symptoms. Researchers concluded that overall the juice didn't help protect a second infection within six months.
Where Research Is Published Matters
Another of Glatt's concerns is where the recent Ocean Spray study was published.
He points out it was in a nutrition journal, not one focusing on infectious diseases.
"They had plenty of time to submit it to other journals," he said.
The American Journal of Clinical Nutrition (AJCN) has a history of publishing industry-funded research. Its board's conflict-of-interest disclosures are numerous. While none disclose ties to Ocean Spray, they do extend to other major sugary drink manufacturers, including Ocean Spray's distributor, Pepsi Co.
Michele Simon, who writes at EatDrinkPolitics.com, has been critical of the American Society of Nutrition, the publisher of the AJCN, because of its close affiliation with major food manufacturers.
"I would just say it's part of an industry pattern of funding research that -- surprise! -- benefits their bottom line," Simon commented to Healthline about the Ocean Spray study.
Khoo, however, says Ocean Spray has always upheld the highest standards in its research.
"As the cranberry experts, we provided information on the cranberry components in the products and information regarding the most recent research on the mechanism of action of these cranberry components," she told Healthline. "We were not involved in the execution of this trial and had no contact with the clinics running the trial. We were not involved in the collection, or statistical analysis of the data and the preparation of the results of this study."
Dr. Dennis M Bier, editor-in-chief of the AJCN, did not respond to a request for comment.
One study published in the journal Clinical Infectious Diseases, compared drinking up to 10 ounces of Ocean Spray's Cranberry Classic per day with drinking the same amout of a placebo.
Of the 255 children who completed the trial -- all who'd recently experienced a UTI -- 16 percent had another UTI within a year, compared with 22 percent who received the placebo.
While a small improvement, the hardest part, researchers noted, was getting the kids to drink the juice, a common complaint of people in cranberry juice studies.
Research conducted by Ocean Spray researchers, however, often deliver more conclusive results, such as the case with a study published in April 2015, which concluded cranberry concentrate or juices helps prevent bacteria from adhering to the urinary tract.
But a review of studies regarding cranberries and UTIs performed in 2012 found "Cranberry juice does not appear to have a significant benefit in preventing UTIs and may be unacceptable to consume in the long term."
So how can the same evidence lead to conflicting advice?
That was the question an Ocean Spray-funded review asked in May in the journal Advances in Nutrition, another publication of the American Society for Nutrition. Overall, they found good reason for more research into cranberries as a preventative measure against recurring UTIs in women.
Industry-Funded Favorable Outcomes
Industry funded research is common in our food chain. Sometimes the results of this research are overstated to the consumer, especially when it comes to sugary drinks.
Last month, the U.S. Supreme Court declined to review the case of Pom Wonderful. The Federal Trade Commission had chastised the company for overstating health claims in advertisements.
In 2009, Pom unsuccessfully sued Ocean Spray for making a cranberry-pomegranate drink that only contained 2 percent pomegranate juice and that piggybacked off Pom's success.
These cases, however, call into question the validity of research as well as the health claims associated with them. Still, many believe there could be good reason to suggest cranberries could have legitimate health benefits related to UTIs.
Amesh A. Adalja, an infectious disease physician at the University of Pittsburgh Medical Center, says he doesn't automatically discount industry-funded research, but it is something to keep in mind when evaluating studies.
As to the effectiveness of cranberry juice for UTI treatments, he says no studies have "really provided consistent or impressive results."
"Because cranberry juice is a cheap and easy intervention, it isn't something I discourage people from drinking if they are prone to UTIs," Adalja told Healthline. "This study provides more evidence that there may be an effect present. However, future studies looking at, for example, biomarkers in the urine of cranberry juice drinking women would be useful in fully determining if a causal effect from cranberry juice is actually present."
A survey of Healthline readers revealed that a majority of people seem to believe cranberry juice can help with a urinary tract infection.
About 60 percent who answered the unscientific online poll the past few days said they have had a UTI in the past. Half said their doctor had recommended drinking cranberry juice to treat or prevent the infection.
About 72 percent said they have used cranberry juice to help with a UTI. Of the women who answered, 75 percent said they had used cranberry juice. Of the men, nearly 60 percent said they had.
About 68 percent said they believed cranberry juice can treat or prevent UTIs. Of the women who answered, 72 said they believed the juice can help. About 54 percent of men said they did.
In all, 600 Healthline readers responded to the survey.
By Brian Krans