| Roman Bystrianyk 2004-10-03, 10:22 pm |
| http://www.healthsentinel.com/news....ist_item&id=198
Alison McCook, "Too Much Caffeine Ups Risk of Kidney Stones", Reuters,
September 3, 2004,
Link: http://www.reuters.com/newsArticle....storyID=6146350
People who are prone to kidney stones should limit their caffeine
intake, new research suggests.
When investigators gave people with a history of kidney stones a dose
of caffeine equivalent to that found in two cups of coffee, they began
to excrete more calcium in their urine, putting them at increased risk
of forming kidney stones.
Study author Dr. Linda K. Massey told Reuters Health that stone
suffers should limit themselves to less than two cups of coffee per
day or a comparable amount of caffeine from other sources. And that
limit of two cups means, literally, 16 ounces-not two enormous mugs of
coffee, which can contain much more caffeine, she said.
Massey, who is based at Washington State university in Spokane,
explained that a spike in urinary calcium increases the risk of stones
because calcium is an important ingredient in kidney stones -- so the
more there is, the more likely there will be stones.
Previous research has shown that people who do not tend to form kidney
stones also excrete more calcium in their urine after consuming
caffeine.
To investigate whether the same thing happens in people prone to
stones, Massey and Dr. Roger A. L. Sutton at the university of British
Columbia in Vancouver, asked 39 people with kidney stones and nine who
never had stones to drink caffeine added to water after 14 hours of
fasting. The researchers tested their urine 2 hours before and after
they consumed caffeine.
As the investigators report in the Journal of Urology, after caffeine,
the stone-formers showed an increase in calcium, sodium, magnesium and
citrate in their urine. The same pattern also occurred in the people
with no history of kidney stones.
In an interview, Massey explained that more calcium and sodium in
urine likely increases the risk of kidney stones, while increases in
magnesium and citrate appear to protect people from kidney stones.
However, after plugging these changes into a formula that predicts
kidney stone risk, Massey said, "The increase in magnesium and citrate
did not offset the increase in calcium."
SOURCE: The Journal of Urology, August 2004.
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