Kidney stones are made of certain substances that precipitate out of the urine, forming large crystals. Larger kidney stones may get stuck in the kidney or the ureter, which is the tube that carries urine from the kidney to the bladder. The most common type of kidney stone is made of calcium combined with either oxalate or phosphate; but other stones may occur, including those made of uric acid or struvite. Cranberry juice, which is known to help prevent urinary tract infections, may be useful in preventing kidney stones, but more research is needed.
Causes
Kidney stones form when the concentration of substances that form kidney stones becomes too high or those that prevent kidney stones become too low. When the conditions allow, certain substances precipitate out of the urine, forming hard, pebble-like crystals. Alternatively, natural inhibitors of kidney stone formation are present in the urine, which include magnesium and citrate. Drinking cranberry juice alters the levels of these chemicals in the urine.
Calcium Oxalate Stones
An effective natural beverage for the prevention of kidney stones raises the level of inhibitors of kidney stones, while reducing the level of substances that make up the stones. Relevant to the formation of calcium oxalate stones, cranberry juice increases the amount of citrate, magnesium, calcium and oxalate in the urine. In other words, cranberry juice increases two of the inhibitors but also two of the components of calcium oxalate kidney stones.
Struvite Stones
Struvite stones are made of magnesium, phosphate and ammonium, and they only occur in conjunction with urinary tract infections. Drinking cranberry juice aids in the prevention of urinary tract infections by preventing bacteria from sticking to the bladder wall. Therefore, drinking cranberry juice may help prevent struvite stones by preventing a urinary tract infection. Even though cranberry juice does increase the amount of one urinary component of struvite stones, magnesium, the prevention of urinary tract infections in the first place should preclude these stones from developing.
Recommendations
Different medical centers have different recommendations with respect to cranberry juice and kidney stones. The University of Maryland Medical Center recommends not drinking cranberry juice if you are susceptible to calcium oxalate stones; NYU Langone Medical Center notes that your doctor may recommend drinking more cranberry juice; and the Mayo Clinic notes that data are insufficient as of 2011 to make an accurate conclusion about the effects of cranberry juice on kidney stones. These conflicting recommendations indicate that no final conclusion has been made about whether or not cranberry juice prevents kidney stones. Before beginning a regimen of drinking cranberry juice to prevent kidney stones, check with a medical professional to see what course of action is right for you.
References
- MayoClinic.com; Cranberry (Vaccinium Macrocarpon); April 2011
- University of Maryland Medical Center; Kidney Stones -- Prevention; Harvey Simon; July 2009
- NYU Langone Medical Center; Kidney Stones; Diane Savitsky; September 2010
- Merck Manuals; Stones in the Urinary Tract; Glenn M. Preminger, MD; August 2007
