According to MedlinePlus, the cranberry plant is a small evergreen shrub that is native to North America. American Indians used cranberries for a number or urinary conditions, and both the juice and fruit are used as medicine. Cranberry is also available in a supplement form called cranberry extract. Consult a health care professional before using cranberry extract.
About Cranberries
The Encyclopedia of Alternative Medicine says that cranberries contain many substances that promote healing, such as bioflavonoids that can help prevent urinary tract infections; quinic acid, which provides the sour taste and helps to prevent kidney stones by acidifying the urine; and vitamins and minerals, especially vitamin C. According to MedlinePlus, cranberries also contain salicylic acid, which is similar to aspirin, and a chemical called oxalate.
Kidney Stones
Kidney stones occur in about 10 percent of Americans, according to the University of Maryland Medical Center. Men are more likely to develop kidney stones than women, UMMC continues. The stones, growing slowly over a period of months or years, are composed of various minerals such as calcium, uric acid and oxalate. A kidney stone attack may exhibit no symptoms, or may be accompanied by excruciating pain in the abdomen, back, buttocks or genital area. Nausea and vomiting, fever and chills potentially accompany a bout as well. If you fail to drink enough water, eat a diet high in calcium or other minerals or have a problem with calcium metabolism or high blood pressure, you are more likely to develop kidney stones.
The Research
Research results and recommendations for the use of cranberry extract for kidney stones are mixed. A study reported in the January 2001 issue of "Urology" noted that cranberry extract increased urine oxalate and could be a factor in causing kidney stones. MedlinePlus notes that some cranberry extract tablets can increase urinary oxalate as much as 43 percent. The Encyclopedia of Alternative Medicine cautions that drinking large amounts of cranberry juice can cause kidney stones and defines a large amount as one liter per day, although it does not specifically mention cranberry extract in this regard.
Reccomendations for Cranberry Extract
However, UMMC recommends using cranberry extract for the prevention of kidney stones. The suggested dose is 300 to 400 mg of standardized extract daily, or eight to 16 ounces of unsweetened cranberry juice daily. The Encyclopedia of Alternative Medicine says that you would need to drink 16 ounces of unsweetened cranberry juice each day to prevent kidney stones, and that one capsule of cranberry extract equals half an ounce of juice, which would require 32 cranberry extract capsules for an equivalent dose.
Final Considerations
In the absence of definitive research, recommendations for use of cranberry extract for kidney stones are conflicting. If you have questions or concerns, consult a health care professional.
References
- University of Maryland Medical Center; Cranberry; Steven D. Ehrlich, NMD; November 2008
- "Urology"; Dietary Supplementation With Cranberry Concentrate Tablets May Increase the Risk of Nephrolithiasis; M.K. Terris, et.al.; January 2001
- MedlinePlus; Cranberry; June 2011
- Encyclopedia of Alternative Medicine; Cranberry
- University of Maryland Medical Center; Kidney Stones; Steven D. Ehrlich, NMD; June 2010
