Cranberry has long been used as both a food and a medicine to treat bladder and kidney conditions. Today, cranberry concentrate capsules are available in nutrition stores and promoted for use in preventing recurrent urinary tract infections. However, according to MedlinePlus, cranberry may increase your risk of developing kidney stones, or nephrolithiasis. Consult with your health care provider before taking cranberry to improve your health.
How Cranberry Works
Cranberry contains chemicals that produce various beneficial effects on your body. Some substances found in cranberry act to prevent bacteria from attaching to the walls of your bladder and causing an infection, which makes it useful for preventing urinary tract infections, or UTIs. Cranberry also contains antioxidants that may help to protect against heart disease by lowering your low-density lipoprotein, or bad, cholesterol; opening your blood vessels; and preventing plaque from accumulating in your arteries.
Dosing
According to MedlinePlus, cranberry capsules are usually taken in doses of 300 to 400 mg twice a day. One study used cranberry capsules in doses of 400 mg taken twice a day for three months to prevent UTIs. Some trials testing cranberry pills for preventing UTIs have used doses of six 400 mg capsules per day in divided doses for 13 months, according to PaloAltoMedicalFoundation.org.
Kidney Stone Risk
Cranberry juice and cranberry extracts contain a large amount of a substance called oxalate, which may contribute to the formation of some types of kidney stones. In fact, a study published in the journal "Urology" in 2001 demonstrated that cranberry extract pills can raise the amount of oxalate in the urine by about 43 percent after seven days of treatment. Since kidney stones are mainly composed of oxalate combined with calcium, cranberry may increase your risk of kidney stones.
Other Considerations
According to MedlinePlus, cranberry is generally safe for most people. However, you should avoid cranberry if you have an allergy to aspirin because cranberry contains salicylic acid, which is similar to aspirin. Also, avoid cranberry if you take warfarin, a blood thinner, because cranberry may increase how long warfarin stays in your body and increase your chances of bruising and bleeding.
References
- University of Maryland Medical Center: Cranberry
- MedlinePlus: Cranberry
- "Phytomedicine"; Can a concentrated Cranberry Extract Prevent Recurrent Urinary Tract Infections in Women? A Pilot Study; D.T. Bailey, et al.; April 2007
- PaloAltoMedicalFoundation.org: Cranberry
- DrugDigest.org: Cranberry
- "Urology"; Dietary Supplementation With Cranberry Concentrate Tablets May Increase the Risk of Nephrolithiasis; M.K. Terris, et al.; January 2001
