There is some evidence that cranberry juice may decrease the number of occasions when people notice they have a urinary tract infection (UTI), a Cochrane Systematic Review has found. This is particularly the case for those who have recurrent UTIs.
UTIs are one of the most common reasons why people seek outpatient medical treatment, and lead to over one million hospital admissions a year in the USA alone. Cranberries, and particularly cranberry juice, have been used for decades as a means of preventing or treating UTIs. The mechanism of action is unsure. One theory is that molecules in the juice may make it harder for bacteria such as E. coli to stick to surfaces, and therefore make it difficult for an infection to build up.
A team of Cochrane Researchers set out to establish whether there was good evidence that cranberries were effective. They identified 10 studies that included a total of 1,049 participants. The trials compared various combinations of cranberry products, placebos and water.
They found some evidence that cranberry juice and capsules could prevent recurrent infections in women, although there was no evidence of benefit in elderly men or elderly women. In addition, cranberry juice had no benefit for people using catheters.
“It’s worth noting that many people in the trials stopped drinking the juice, suggesting that it may not suit everyone’s taste, or it may be too burdensome and costly to drink the two recommended glasses a day,” says lead researcher Ruth Jepson who works at the Department of Nursing and Midwifery, University of Stirling, UK.
“We now need to discover how much a person needs to drink, and how long it needs to be used before the juice starts to have an effect,” says Jepson.