Cranberries have traditionally been used for a variety of ailments, including scurvy, liver problems, bladder and kidney disorders, stomach ailments and even cancer. Although there is insufficient evidence to recommend using cranberries for most of these conditions, research supports their use in preventing recurrent urinary tract infections, or UTIs. Cranberry juice and cranberry pills are equally useful for this purpose. Ask your doctor about the benefits of cranberry products.
Mechanism
Until the 1980s, it was believed that cranberries exerted their antibacterial effects by acidifying your urine and preventing the growth of microorganisms in your urinary tract. However, in the May 1984 issue of "The Journal of Urology," investigators revealed that cranberry juice simply prevents bacteria from adhering to the inner membranes of your urinary tract. It is believed that compounds called proanthocyanidins in cranberries interfere with the function of finger-like projections used by bacteria to invade your bladder wall. Both cranberry pills and cranberry juice contain proanthocyanidins.
Prevention Only
Current scientific evidence only supports the use of cranberry juice or pills for the prevention of recurrent urinary tract infections. Since cranberry products inhibit bacterial adhesion but not bacterial growth or replication in your urinary tract, they have not been proven effective for treating established infections. Thus, once you have developed symptoms of a urinary tract infection -- urinary frequency, urgency or burning -- cranberry products are less likely to be useful, because these symptoms indicate the bacteria have already invaded the lining of your urinary tract.
Dosage
There is no discernible difference in benefit among cranberry juice and cranberry extract preparations -- pills or capsules -- when these formulations are standardized for their proanthocyanidin content. A study published in the April 2010 issue of "BMC Infectious Diseases" demonstrated that capsules containing at least 72 mg of cranberry proanthocyanidins are effective for preventing UTIs, while lower doses are not.
Considerations
Cranberry preparations -- juice, pills or capsules -- are equally effective for preventing recurrent UTIs when they are standardized for their proanthocyanidin content. A daily proanthocyanidin consumption of 72 mg appears to be the minimum effective dose. If you choose to take juice, the volume needed to acquire adequate doses of proanthocyanidins could lead to stomach upset, and all cranberry products may slightly increase your risk for developing kidney stones. Scientists are investigating cranberries' other properties, including their antioxidant and anticancer activities, but there is insufficient evidence to support their use for other medical conditions. Your physician can help you decide if cranberries are appropriate for you.
References
- "American Family Physician"; Cranberry for Prevention of Urinary Tract Infections; D.M. Lynch; December 2004
- "The Journal of Urology"; Inhibition of Bacterial Adherence by Cranberry Juice: Potential Use for the Treatment of Urinary Tract Infections; A.E. Sobota; May 1984
- "BMC Infectious Diseases"; Dosage Effect on Uropathogenic Escherichia coli Anti-adhesion Activity in Urine following Consumption of Cranberry Powder Standardized for Proanthocyanidin Content: A Multi-centric Randomized Double Blind Study; A.B. Howell, et al.; April 2010
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