An independent study finds that orange juice
beats lemonade and other citrus fruit juices
in helping to keep kidney stones at bay.
Experts have long known that potassium citrate
-- found in citrus juice -- can slow stone
formation in people with a history of the
condition.
But this study, by a team from the University
of Texas Southwestern Medical Center at Dallas,
found that other components can affect a juice's
ability to prevent stones.
Thirteen volunteers (some with a history
of kidney stones and some without) took part
in the multi-phase trial, which was funded
by the U.S. National
Institutes of Health. For one week,
participants drank distilled water, for another
week orange juice, and then lemonade for another
week. There was a three-week interval between
each of these weeks.
During each phase, the participants drank
13 ounces of orange juice, lemonade or distilled
water three times a day with meals. They were
also put on a low-calcium, low-oxalate diet,
which also helps cut stone formation.
The study found that orange juice increased
levels of citrate in the urine and reduced
the crystallization of uric acid and calcium
oxalate, the most common components of kidney
stones. Lemonade did not increase citrate
levels.
"One reason might be the different constituents
of various beverages," study lead author
Dr. Clarita Odvina, assistant professor of
internal medicine at the Charles and Jane
Pak Center for Mineral Metabolism and Clinical
Research, said in a prepared statement.
Odvina noted that the citrate in orange and
grapefruit is accompanied by a potassium ion
while the citrate in lemonade and cranberry
juice is accompanied by a hydrogen ion. While
hydrogen ions counteract the beneficial effects
of high citrate content, potassium ions do
not.
The study is available online and was expected
to be published in the Oct. 26 print issue
of the Clinical Journal of the American
Society of Nephrology.
