Vaccinium macrocarpon, commonly known as cranberry, is a fruit native to North America that has traditionally been used to treat and prevent urinary tract infections and other ailments of the bladder and kidneys. Modern scientific research indicates cranberry products may provide some benefit for urinary tract health. However, if you're concerned about your urinary tract health, see a doctor before attempting self-treatment with cranberry supplements.
Efficacy
According to a paper published by "American Family Physician" in 2004, in clinical research, cranberry has demonstrated a modest effect in preventing urinary tract infections; however, evidence regarding its efficacy in treating existing UTIs is lacking. Moreover, MayoClinic.com notes that while there is evidence supporting use of cranberry juice and extracts for UTI prevention, most available research is of poor quality. Also, while cranberry supplements may provide some benefit for UTI prevention, its preventative effects are not as great as those of antibiotics, according to a study published in "Archives of Internal Medicine" in July 2011.
Mechanisms
While it was once hypothesized that cranberry's urinary tract health benefits were related to its effects on urine acidity, it was later discovered that substances called proanthocyanidins in cranberries are likely responsible for the fruit's therapeutic benefits. In laboratory studies, proathocyanidins from cranberries have exhibited an anti-microbial effect on the E. coli bacteria that causes UTIs, according to The Cranberry Institute. Although some other plants also contain proanthocyanidins, the proanthocyanidins in cranberries have a different chemical structure, which may explain cranberry's unique anti-microbial activity against E. coli, according to Rutgers University researcher Dr. Amy Howell.
Safety
Though cranberry's benefit in UTI prevention may not be as strong as that of antibiotics, cranberry juice and supplements are safe, well-tolerated and have no known drug interactions, according to "American Family Physician." Also, cranberry does not cause the antibiotic resistance associated with antibiotic treatment for UTIs. "American Family Physician" also notes, however, that a small study linked cranberry to elevated urinary oxalate levels, which can cause kidney stones; doctors should therefore be cautious in recommending cranberry supplements to patients with a history of kidney stones.
Considerations
The best dosage of cranberry for UTI prevention has not been determined; however, the dosages that have demonstrated benefits in clinical research, according to "American Family Physician," include twice-daily 300 mg or 400 mg tablets, or 8 oz. unsweetened cranberry juice three times daily. Many cranberry juice cocktails are sweetened with added sugar, which can cause weight gain and health problems, particularly for patients with diabetes or glucose intolerance. MayoClinic.com notes that while cranberry should not be considered a first-line treatment for UTIs, in some cases, it may be used as an adjunct therapy to conventional antibiotic treatment.
References
- "American Family Physician"; Cranberry for Prevention of Urinary Tract Infections; Darren M. Lynch, M.D.; December 2004
- "Archives of Internal Medicine"; Cranberries vs. Antibiotics to Prevent Urinary Tract Infections; Mariëlle A. J. Beerepoot, M.D.; July 2011
- MayoClinic.com; Cranberry (Vaccinium macrocarpon); July 2011
- The Cranberry Institute: Urinary Tract
