Thirty percent of women report having had at least one
urinary tract infection (UTI)
, a very uncommon occurrence in men. Although these infections can be effectively treated with medications, for an unfortunate few they have a tendency to recur despite adequate treatment. Can drinking cranberry juice help these women avoid repeated infections?
Evidence for the Health Claim
Most urinary tract infections are caused by
bacteria, which live in human feces. Under certain circumstances, these bacteria are able to reach the bladder lining, which normally contains no bacteria, through the urethra (exterior passageway from bladder). Women are far more susceptible to urinary tract infections than men because of their relatively short urethra.
Researchers have found that the chemical properties of cranberry juice interfere with the ability of bacteria to adhere to urinary tract cells, making it more difficult for them to establish an infection. Three acids in cranberry juice are believed to hinder bacterial growth in the urinary tract: citric, quinic, and malic acid.
In one study, researchers measured the number of bacteria adhering to the lining of the urinary tracts of 15 people with spinal cord injuries (a group particularly susceptible to UTIs) for two weeks. During the first week, subjects drank three glasses of water three times a day. During the second week, the same subjects drank eight ounces of cranberry juice three times a day instead. The number of bacteria was significantly reduced during the week the subjects drank cranberry juice compared with the previous week.
In another study of 150 women, researchers compared those who drank cranberry juice with those who didn’t during a six-month period, and found that 16% of the cranberry juice drinkers got urinary tract infections, while 36% of those who did not drink cranberry juice got urinary tract infections.
Evidence Against the Health Claim
Not all studies support the claim that drinking cranberry juice reduces the risk of UTIs. Furthermore, there is little evidence to suggest that drinking lots of cranberry juice once UTI symptoms appear will resolve an acute infection any quicker.
There is probably sufficient evidence at this point to recommend cranberry juice as a safe preventive treatment for women who are prone to repeated UTIs. Those who suffer from repeated infections might want to add the juice to their regular diets, having at least one serving daily.
People who drink cranberry juice daily should tell their doctors when they are prescribed antibiotics. Some studies have suggested that cranberry juice may inhibit the effectiveness of some commonly prescribed antibiotics, including
Howell AB, Vorsa N, Der Marderosian A, Foo LY.Inhibition of the adherence of P-fimbriated Escherichia coli to uroepithelial-cell surfaces by proanthocyanidin extracts from cranberries.
N Engl J Med
. 1998 Oct 8;339(15):1085-6.
Kontiokari T, Laitinen J, Järvi L, et al. Dietary factors protecting women from urinary tract infection.
Am J Clin Nutr
. 2003 Mar;77(3): 600-604. Available at:
. Accessed November 5, 2008.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a