Sinaasappelsap tegen nierstenen.*
Uit een klein onderzoek blijkt dat sinaasappelsap een goede drank is om nierstenen tegen te gaan. Al langer is bekend dat citraten (zouten van citroenzuur) de vorming van nierstenen kunnen tegengaan. Bij een verhoogde waarde van citraten in de urine wordt de kristallisatie van urinezuur en cacliumoxalaat tegen gegaan. Deze laatste twee stoffen zijn de meest bekende bij de vorming van nierstenen. Zowel in limonade als sinaasappelsap zitten citraten doch deze worden in limonade, en ook bijv. in andere sappen vergezeld van een waterstof-ion in tegenstelling tot in sinaasappelsap en ook grapefruitsap waar ze begeleidt worden door een kalium-ion. Hierdoor ontstaan bij limonade en andere sappen geen verhoging van de citraten in de urine in tegenstelling tot bij sinaasappelsap en grapefruitsap.
Orange
Juice Best at Stopping Kidney Stones
It outperformed lemonade and other citrus juices, study found
-- 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.
More information
The American Medical Association has more about kidney stones (jama.ama-assn.org ).
(Sept. 2006)