A clinical trial that included women with a history of urinary tract infections (UTIs) resulted in a 52% lower risk of UTI during a six-month period among women who received cranberry capsules in comparison with a placebo. Additionally, cranberry lowered the incidence of urinary tract infection caused by Escherichia coli (E. coli) bacteria by 51%, decreased the incidence of UTI with urinary urgency and frequency by 71%, delayed the time to the first urinary tract infection by 64% and lowered the average number of UTIs per participant by 59% compared with the placebo.

The authors explained that proanthocyanidins and flavonoids in cranberry have been shown to reduce the adhesiveness of harmful E. coli bacteria within the urinary tract, which helps protect against infection. They concluded that whole cranberry powder capsules “reduce the incidence of culture-confirmed UTI and several other UTI-related outcomes in healthy females with recurrent UTI history.”
 
The randomized, double-blind, placebo-controlled trial included 145 women between the ages of 18 and 65 years who had at least three UTIs within the year prior to enrollment, or at least two but no more than five UTIs during the previous six months. The participants, who were free of UTI at the beginning of the study, were given capsules that contained 500 milligrams of whole cranberry powder or a placebo for six months. To confirm the incidence of UTI, urine cultures were conducted at the beginning of the study and at three- and six-month clinic visits, as well as when participants reported experiencing UTI symptoms.
 
The findings were reported January 23, 2025, in The American Journal of Clinical Nutrition.
 
Apply What You've Learned: Urinary Tract Infection
Urinary tract infection will be experienced by about 60% of all women during their lifetimes. Men also get UTIs, but they are at lower risk. Although UTIs are treatable with antibiotic drugs, the need for effective preventive measures is significant.
 
Routine urinalysis may test for an enzyme called leukocyte esterase, which is produced by white blood cells. Leukocyte esterase is a screening test for white blood cells in the urine. When urine is positive for leukocyte esterase, it should then be examined for white blood cells. Although normal urine may have a small number of white blood cells, a high number suggests infection. A urine culture can then be ordered to determine the type of infectious agent present in the urine.
 
Like cranberries, blueberries contain compounds that help prevent E. coli bacteria from adhering to the lining of the urinary tract. Blueberries can be consumed whole, juiced or in the form of an extract.
 
Probiotics, particularly those in the Lactobacillus family, contribute to a healthy microflora that may help prevent an imbalance of undesirable bacteria that cause urinary tract infection.
 
Brenda R. Generali, CCII3, Naturopath
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