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Titolo: non bevete troppo!!!! [messaggio in inglese]

This article was in today's Boston Globe
HEALTH SENSE
When drinking too much water means disaster
By Judy Foreman, Globe Staff, 6/18/2002
Kelly Hall, 34, was in fantastic shape, routinely biking 100 to 200 miles a
week in preparation for last year's AIDS Ride from Boston to New York.
Usually she trained with other riders, who made it a point to take food and
hydration breaks. But one day last June, Hall, a strategic planner at
Partners Community Health Care in Needham, decided to ride alone, despite
the 95-degree heat.
The first 50 miles, around Concord, were a breeze. ''I thought I'd do
another 25,'' she recalled. She drank a little Gatorade, the sports drink
designed to restore normal blood levels of electrolytes, but relied mostly
on water, constantly sipping from the 70-ounce Camelbak water supply on her
back.
Halfway through the last loop, hyponatremia, a relatively rare but
potentially fatal condition in which blood levels of sodium sink dangerously
low, ''hit like a ton of bricks,'' Hall said.
She finished her ride ''really, really slowly,'' got back to her car, threw
up, drove home and threw up again. She made it to Brigham and Women's
Hospital, where she had a grand mal seizure.
Nearly the same thing happened to Sarah Snyder, 45, a Globe editor, who was
training with friends for another long benefit ride. She, too, was in good
condition, and she, too, dutifully sipped water for 56 miles. ''What a good
do-bee I'm being,'' she remembered thinking.
But after her ride, she threw up violently and was rushed to the hospital,
where she drifted in and out of consciousness for 18 hours. ''You drank too
much water. You screwed up your sodium,'' the doctors told her. When asked
to say her name, ''It came out like Swahili.''
Full-blown cases of hyponatremia (sometimes called water intoxication) are
relatively rare, roughly.1 to 4 percent of people who sweat steadily for
hours in grueling, long-distance events, said Scott Montain, a research
physiologist at the US Army Research Institute of Environmental Medicine in
Natick. The incidence of hyponatremia appears to be highest in events
lasting more than four hours, especially at high temperatures.
But the prevalence of warning symptoms is much higher - up to 27 percent of
athletes who seek attention in a medical tent during a long race - and
appears to be rising.
Typically, conscientious athletes get in trouble because they adhere too
diligently to one recommendation - drink lots of fluids - but ignore
another - keep electrolytes up. (Electrolytes are charged particles such as
sodium, potassium, calcium and bicarbonate that must be kept in near-perfect
balance.) Indeed, for most marathoners, Montain noted, the real problem is
drinking too much water, not failing to take in enough sodium.
Women in particular may be at risk, some researchers say, in part because
they may be too dutiful about drinking water.
Some studies suggest that certain drugs also may increase risk, among them
ibuprofen and other NSAIDS or nonsteroidal anti-inflammatory medications,
acetaminophen, some cancer drugs, nicotine, diuretics, narcotics and some
antidepressants and antipsychotic drugs. On the other hand, data presented
recently at the American College of Sports Medicine meeting suggest that
ibuprofen and other NSAIDS may not increase risk after all.
''When you sweat, you lose both water and salt,'' said Dr. Soheyla Gharib,
medical director of the women's health center at Brigham and Women's
Hospital. ''If you replace only water, the salt level in the blood gets
diluted.''
And that can be disastrous. Normally, the body tries to keep positively and
negatively charged electrolytes in balance to keep cells electrically
neutral, said Dr. Ronenn Roubenoff, associate professor of medicine and
nutrition and director of human studies at the Jean Mayer USDA Human
Nutrition Research Center at Tufts University. Though sodium is probably the
most important electrolyte for endurance athletes to worry about, he said,
''an imbalance of any one of the electrolytes can be harmful.''
Normally, sodium is plentiful in the blood and relatively low inside cells.
But when the concentration in the blood gets too low compared to the amount
inside cells - either because a person drank too much water, took in too
little sodium, or both - water rushes into cells. ''Water follows sodium as
day follows night,'' Roubenoff said.
The result is dangerous swelling, particularly in the brain, that can lead
to brain damage, coma and death.
Curiously, hyponatremia can occur whether a person is dehydrated, normally
hydrated or overhydrated because any of those conditions can happen while
blood levels of sodium are too low, Roubenoff said.
Further complicating things is that the symptoms of hyponatremia can be
easily confused with those of heat stroke and heat exhaustion. With heat
exhaustion (also called exertional heat injury), people feel ill, get
nauseous, have muscle cramps and may feel dizzy standing up quickly.
With heat stroke, people have all those symptoms plus another one -
mental-status changes; that is, confusion about who and where they are and
what day it is. People with genuine heat stroke also typically have
extremely high body temperatures. With hyponatremia, people also feel very
ill and may have mental-status changes, but don't have the high temperatures
of heat stroke. They also vomit forcefully and repeatedly and, unlike those
with heat exhaustion, do not feel better by resting and cooling off.
Treatment of hyponatremia may involve restricting fluid intake and promoting
urine production, but some people also need intravenous salt water with a
high concentration of salt, until blood electrolytes return to normal.
Resetting the water-salt balance ''must be done carefully and slowly,'' said
Dr. Gabriel Danovitch, professor of medicine at the School of Medicine at
the University of California at Los Angeles, because overly-rapid correction
of electrolyte imbalance can cause further problems.
To protect yourself against hyponatremia, start by paying attention to how
much you sweat. In general, women sweat less than men and their ability to
regulate core body temperature (and sweating) also may vary with different
phases of the menstrual cycle.
Individuals also vary considerably in how much sodium they lose in sweat.
You may be a heavy sodium loser if your sweat burns your eyes, tastes salty
or leaves a cakey-white residue on your skin.
You can also make sure you're getting enough sodium by drinking sports
drinks such as Accelerade, Cytomax, Gpush and Gatorade instead of plain
water during long events. (Check the labels for sodium content; some brands
have twice the sodium of others.) Sports drinks also typically contain
carbohydrates as well, which provides energy and helps with water and sodium
absorption.
If you don't like sports drinks, you could take salt tablets, but they may
make you nauseous. At the very least, you can eat salty foods prior to and
during a big event.
For ordinary mortals who work out for less than an hour, sports drinks are
unnecessary and plain old water (along with the salt you normally get in
food) will do just fine, said Roger Fielding, an exercise physiologist and
associate professor of health sciences at Boston University.
For endurance athletes doing events longer than an hour and sweating
profusely, it's probably wise to drink 6 to 8 ounces of fluid every 20
minutes to prevent both excessive dehydration and hyponatremia, said Montain
of the US Army lab. But don't drink more than 40 ounces per hour: That's
erring toward excess fluid intake.
Judy Foreman's column appears every other week in Health-Science. Her past
columns are available on Boston.com and 
www.myhealthsense.com
. Her e-mail
address is 
for...@globe.com
.

 This article was in today's Boston Globe
Capito una c@cchio!!!
--
61prla
(24, CO, 100,75, B-S)
ex alu artigianale
ex speed 10
ex gt lts
ex y33
ex gary fisher Pezzo replica
ex Trek 9800 shx
adesso Trek FUEL

 wrote in message
news:3D0F8658...@localdomain.com...


 drinks such as Accelerade, Cytomax, Gpush and Gatorade instead of
a quelli del Boston Globe piace il Gatorade... :-)
Cmq, interessante.
-- 
StefanoZ