A new study shows that a daily glass of orange juice may help prevent recurrent kidney stones better than other citrus juices like lemonade.
Researchers say many people assume that all citrus juices prevent the formation of kidney stones. But these results suggest not all citrus juices have the same protective effect in people at risk for the painful condition.
Kidney stones develop when minerals and other chemicals in the urine become too concentrated. Over time, these crystals bind to form a stone.
People who have had a kidney stone are at high risk for recurrent stones and are advised to make diet and lifestyle changes to slow the rate of new stones forming.
Citrate Slows Kidney Stones
Studies have shown that potassium citrate supplements can slow the formation of kidney stones, but some people can't tolerate the supplements because of gastrointestinal side effects.
For those people, drinking citrus juices, which contain a natural form of citrate, may offer an alternative to the supplements.
Citrate helps prevent kidney stone formation by allowing for more citrate in the urine and decreasing the acidity of urine.
OJ Better Than Lemonade
In the study, researchers compared the effects of orange juice and lemonade in preventing recurrent kidney stones. Both juices contain comparable citrate levels.
Thirteen volunteers, some with a history of kidney stones and some without, participated in the three-phase study.
In random order, the participants drank approximately 13 ounces of either distilled water, orange juice, or lemonade three times a day with meals for one week, with a three-week interval before moving to the next phase. They also followed a special diet as recommended for preventing recurrent kidney stones.
The results showed that orange juice increased levels of citrate in the urine and decreased urine acidity, which reduced the risk of kidney stones. But lemonade did not have the same effect.
"Orange juice could potentially play an important role in the management of kidney stone disease and may be considered an option for patients who are intolerant of potassium citrate," says researcher Clarita Odvina, MD, assistant professor of internal medicine at the University of Texas Southwestern Medical Center at Dallas, in a news release.
Odvina says additional ingredients in citrus juices may affect their effectiveness in reducing the risk of developing new kidney stones. For example, the citrate in orange and grapefruit juice is accompanied by a potassium ion, while the citrate in lemonade and cranberry juice is accompanied by a proton. She says the proton may counteract the acid-lowering effects of these juices.
The results appear in the Clinical Journal of the American Society of Nephrology. Researchers say this was a small study and further research is needed to evaluate the role of orange and other citrus juices in preventing kidney stones.
The study was supported by research grants from NIH.
SOURCES: Odivina, C. Clinical Journal of the American Society of Nephrology, Aug. 30, 2006, online edition. News release, UTSW.
By Jennifer Warner
Reviewed by Louise Chang