Bladder infections occur when bacteria gain access to your bladder, attach to its inner lining and begin to multiply. Women develop bladder infections more frequently than men do, and this condition is one of the most common reasons women seek medical care. A 2006 "American Family Physician" review reports that approximately 7 million women are diagnosed each year with bladder infections, and many of them experience recurrent episodes. If you suffer from frequent bladder infections, you may be wondering how much cranberry juice to drink to prevent the next one.
Cranberry Juice Interferes With Bacterial Adhesion
Cranberries have been a popular home remedy for decades for treating and preventing bladder infections. For many years it was assumed that cranberry juice acidified your urine and interfered with bacterial growth and division. However, in 2007, scientists at Yale University School of Medicine demonstrated that cranberry products -- specifically the proanthocyanidins in cranberries -- prevent bacteria from adhering to the epithelial cells that line the human bladder.
Cranberry Juice Does Not Cure Established Infections
Several studies, including a 2003 trial in "Journal of Food Protection," have demonstrated that cranberry concentrates can inactivate some bacteria, but only under conditions that are not reproducible in living tissues. There is no convincing evidence that cranberry juice will cure a bladder infection that is already causing signs and symptoms, such as urinary frequency or urgency, burning, bladder pain or bloody urine.
Optimal Cranberry Dosage Uncertain
Early studies examining the effects of cranberry juice on bladder infections have been criticized because they were inconsistent in the types of cranberry products used and the amounts administered. A commonly recommended dosage of 300 ml of cranberry juice containing at least 36 mg of proanthocyanidins was based on several trials that had demonstrated benefit. The authors of a 2010 study performed in multiple centers in the United States and Europe concluded that cranberry products offering at least 72 mg of proanthocyanidins daily conferred protection from bacterial adhesion, according to an April 2010 review published in the journal "BMC Infectious Diseases."
Considerations
Research demonstrates that cranberry juice offers potential benefits for preventing recurrent urinary tract infections in young to middle-aged women. Established bladder infections are less likely to respond to cranberry juice, and there is little scientific evidence to support its use for treating these infections. Dosage recommendations for prevention vary from one study to the next, but optimal results will probably accrue from using a cranberry product -- juice, extract, powder or tablets -- offering at least 72 mg of proanthocyanidins daily.
References
- "American Family Physician"; Treating Adult Women with Suspected UTI; M.H. Ebell; January 2006
- "The Journal of Urology"; Cranberry Products Inhibit Adherence of P-Fimbriated Escherichia Coli to Primary Cultured Bladder and Vaginal Epithelial Cells; K. Gupta, et al.; June 2007
- "Journal of Food Protection"; Inactivation of Escherichia coli 0157:H7, Listeria monocytogenes, and Salmonella in Cranberry, Lemon, and Lime Juice Concentrates; M.C. Nogueira, et al.; September 2003
- "BMC Infectious Diseases"; Dosage Effect on Uropathogenic Escherichia coli Anti-Adhesion Activity in Urine Following Consumption of Cranberry Powder Standardized for Proanthocyanidin Content: A Multicentric Randomized Double Blind Study; A.B. Howell, et al.; April 2010
- "Drugs"; Cranberry and Urinary Tract Infections; D.R. Guay; 2009
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