In a large-scale meta-analysis of 50 clinical trials, data suggested the consumption of cranberries as a juice, tablet, or capsule reduced the number of UTIs in women with recurrent UTIs, in children with UTIs and in people susceptible to UTIs.
However, the evidence used in the review could not support cranberry’s use in the elderly, patients with bladder emptying problems, or pregnant women.
The review was welcomed by trade association, the Cranberry Institute.
“The science has long shown that cranberry products can prevent UTIs, and now this review further bolsters evidence to prove their efficacy,” it said in a statement. “Reducing antibiotic use [to treat UTIs] is ideal as antibiotics can negatively impact good bacteria our bodies need to maintain balance and health, and antibiotic resistance can occur when used repeatedly, or long-term.”
Proanthocyanidins are the active compounds in cranberries
The study, published in the Cochrane Database of Systematic Reviews, centres on PACs’ mechanism of action that prevents further spread of the infection.
Dried fruit containing proanthocyanidins
“PACs found in cranberries help prevent bacteria from adhering to the bladder wall; this adhesion of bacteria is what causes UTIs,” said Amy Howell, associate research scientist (emeritis) at the Marucci Center for Blueberry Cranberry Research at Rutger’s University in the US, cited in the Cranberry Institute press release.
“Because bacteria are unable to ‘stick’ to the bladder, the UTI does not progress, eliminating the ultimate need to use antibiotics because the infection is prevented.”
The review is the latest piece of evidence that supports the use of cranberry-based products in addressing UTIs in select populations.
Notable research includes a study published in the FASEB journal that suggested the fruit could significantly reduce the risk of recurrent urinary tract infection (rUTI) in generally healthy women.
Likewise, a probiotic and cranberry blend showed promise in reducing recurrent UTIs in premenopausal women, shortening infection duration and reducing the need for antibiotic treatment.
Firms in the cranberry space such as such as Ocean Spray are even going as far as leveraging artificial intelligence (AI) to test and certify the biological efficacy of the cranberry.
‘It is time to move on from cranberries’
However, a 2012 review of 24 studies totalling 4,473 participants found little evidence of positive effects and concluded that cranberry juice, "cannot be recommended for the prevention of UTIs."
In a 2016 study that found no significant difference in the use of cranberry capsules vs placebo in treating UTIs, Lindsay E. Nicolle, an expert on UTIs from the University of Manitoba, said in the accompanying editorial, “clinicians should not be promoting cranberry use by suggesting that there is proven, or even possible, benefit. It is time to move on from cranberries”.
Whilst the Food and Drug Administration (FDA) approved a qualified health claim for cranberry juice beverages, the agency acknowledged that the evidence was at best “limited and inconsistent.”
One likely reason for the inconsistency is the variation in methodology amongst the evidence currently available as well as the quality of products tested in published research.
Inability to make firm conclusions
A recent article in The New York Times entitled, “Pills and Powders Aim to Replace Cranberry Juice as Go-To Prevention for U.T.I.s,” that highlights these limitations and their impact on making firm conclusions.
In response to the article, Rutger University’s Howell commented: “Cheaper supplements often have high amounts of the insoluble fibrous pulp and less soluble juice extract (which is a lot more effective for preventing bacterial adhesion than the fibre).
“The lower effectiveness of these products may be the reason some people have not had success with cranberry supplements,” she added.
Howell, who is also the chief marketing officer for food consultation firm Complete Phytochemical Solutions, stated that properly formulated products have been proven to work, and suggests on optimal dosage of 36 mg of PAC to be taken daily.
“Negative studies used products not standardised for the active PAC compounds,” she said.
“They didn’t have enough of the PACs (36 mg/day) or there were design flaws that made it impossible to determine if cranberry was effective or not.”
