Cranberry juice is a home remedy for urinary tract infections that has stood the test of time, but not necessarily scientific scrutiny. Finnish researchers add support to the benefits of cranberries with study results published in a recent issue of British Medical Journal.

The case for cranberry juice

One hundred and fifty women with an active urinary tract infection (UTI) were recruited for the study. After a course of antibiotics and a urine sample to confirm that the infection had cleared, they were placed on one of three interventions. One group received 50 mL of cranberry-lingonberry juice concentrate each day, the second group was assigned 100 mL of Lactobacillus GG drink five times a week, and the third group served as the control.

If a participant experienced new UTI symptoms (frequency, urgency, dysuria, haematuria, nocturia, fever, back, or flank pain) a urine sample was obtained and cultured in order to confirm if infection was present. The criterion for a UTI diagnosis was 100,000 cfu/mL or greater. A urine sample with no bacterial growth was required between two episodes for them to be regarded as separate events.

During the next 6 months, only 16% of the women in the cranberry group developed another UTI, compared with 39% in the lactobacillus group and 36% in the control group. This represented a 20% risk reduction in the cranberry group compared with the control group. Recurrence during the study period was significantly lower in the cranberry group than in the control group at 6 months (P = 0.014) and at 12 months (P = 0.052).

What's so special about cranberries?

The health benefits of cranberries may be due to their proanthocyanidin content, a type of compounds that may have antiviral, antibacterial, antiadhesive, or antioxidant properties. The juice seems to prevent UTIs by blocking the expression P fimbriae of E. coli, thereby limiting the bacteria's ability to colonize the uroepithelial cells.

Searching for alternative solutions

Sixty percent of women have a urinary tract infection at some point in their lives and at least a third of those will have another within one year. Recurrence is most common in women ages 25 to 29 and women over 55. Long-term use of antibiotics is indicated for recurrence, but emerging antimicrobial resistance emphasizes the need for alternative treatments.

This study makes cranberry juice look promising, but it differs from some other reports and the varying findings are difficult to explain. However, in this study the volunteers were not blinded to their treatment group which may introduce bias when they self-reported symptoms.

The study's findings are intriguing for both professionals and consumers. However, patients should understand that it is still not clear what role cranberry juice can play (if any) in the prevention of urinary tract infections. And, any indication of infection still warrants traditional treatment, such as antibiotics.