A systematic review on the benefits of cranberry products published in Cochrane Reviews found that cranberry juice and cranberry supplements reduced the risk of repeated symptomatic urinary infections in women by more than a quarter, the risk in children by more than half, and the risk in people susceptible to urinary infections following surgery/medical procedures by about 53%.
Cranberry juice and its supplements, in capsule and tablet form, have long been promoted as a readily available remedy to avoid infection. Without knowing whether it was a truly effective method and why, many doctors recommended cranberry juice to their patients.
Already centuries ago, Native Americans had the custom of eating cranberries to solve bladder problems. Therefore, researchers have tried several times to understand whether cranberries were effective and by what mechanism they could work to prevent urinary tract infections. However, the most recent review from 2012, which included results from 24 studies, had shown no benefit from these products.
Doctors from Flinders University and the Children's Hospital at Westmead wanted to update these results. To try to determine the effectiveness of cranberry products, they reviewed 50 more recent studies that included almost 9000 participants.
UTIs are painful and very common. About one third of women suffer from them, as do many elderly people and people with bladder problems due to spinal cord injuries or other diseases. If the UTI persists untreated, it can also involve the kidneys and cause more pain and further complications, including sepsis in severe cases. Prevention is therefore the most effective way to reduce risks and complications.
Most UTI are treated effectively and fairly quickly with antibiotics. Sometimes a single dose is enough to solve the problem. Unfortunately, in some people, UTIs keep recurring.
The studies examined in this systematic review included a variety of methods to determine the benefits of cranberry products. Most compared cranberry products with a placebo or no treatment for UTIs and determined that drinking cranberries as juice or taking capsules reduced the number of UTIs in women with recurrent cases, in children, and in people susceptible to UTIs following medical interventions such as bladder radiotherapy.
The authors demonstrated the efficacy of cranberry products for the treatment of UTI using all the evidence published on this topic since the mid-1990s. Earlier versions of this review lacked sufficient evidence to determine the efficacy of this remedy.
Subsequent clinical studies have shown different results, and in this updated review, the amount of data has highlighted this new finding.
According to the researchers, it is also important to consider that, based on the results, few people reported side effects, the most common of which was abdominal pain. Not enough information was found on whether cranberry products were more or less effective than antibiotics or probiotics in preventing further UTIs.
The study authors conclude that although cranberry products help to prevent UTI in women with frequent recurrences, further studies are needed to further clarify who, among UTI patients, would benefit most from cranberry products.