By Dimity McDowell, Yahoo! Health:
Myth: Drink 8 glasses of water per day
Truth: You do need a healthy dose of hydration daily,
but how much is an individual thing. "The eight glasses a day is totally
arbitrary," says Susan Yeargin, Ph.D., assistant professor of athletic
training at the University of South Carolina. "Everybody, especially
athletes, has different needs." The Institute of Medicine guidelines are
more specific, recommending 91 ounces per day for women and 120 for
men. But the institute notes that "the vast majority of healthy people
adequately meet their hydration needs by letting thirst be their guide."
Myth: Pee clear to be hydrated
Truth: Clear urine is a bit excessive. "As long as it
is a pale yellow, like lemonade, you're hydrated," says Yeargin. If it's
completely clear, it just means you're full to the brim; what's going
in is coming out. On the other hand, if your pee is the color of apple
juice or darker, or particularly smelly, you need to drink up.
Myth: Caffeine dehydrates you
Truth: While caffeine provides a performance-boosting
edge, it also acts as a diuretic, right? Not exactly. "Recent research
shows that caffeine doses between 250 and 300 milligrams -- about two
cups of coffee -- will minimally increase urine output for about three
hours after consuming it," says Yeargin, "But the research also shows
that exercise seems to negate those effects. If you run within one to
two hours of drinking coffee, you don't pee more." Most likely, during
exercise, blood flow shifts toward your muscles and away from your
kidneys, so urine output isn't affected, Yeargin explains. In addition,
if you always have a latte in the morning or a soda at lunch, your body
is acclimated to the caffeine, so its effect, on both your physiology
and performance, is minimal.
Myth: Thirst is a poor hydration tool
Truth: Thirst is definitely a very strong predictor of
hydration needs -- and some experts would argue it's the only one you
need. "Our thirst mechanism is pretty accurate," says Yeargin. "But it's
always a good idea to have some other methods to ensure you're
hydrated." Knowing your sweat rate is one way to track your needs,
particularly for long runs, says Doug Casa, Ph.D., professor of
kinesiology at the University of Connecticut and COO of the Korey
Stringer Institute. To calculate your sweat rate, weigh yourself naked
before and after an hour run. Keep track of how many ounces you consume
during the run and factor that into your calculation postrun. Every
pound you lose translates to about 16 ounces of fluid. "Your goal isn't
to match your sweat rate," says Casa, "but you should try to get as
close as is comfortably possible. For some runners, that may mean
replacing two-thirds of the fluid they sweat during the run." He adds
that you shouldn't try to consume more fluids than you've lost.
Myth: Pure water is the best hydration
Truth: Although water is a great way to hydrate, it may
not be the best choice in all situations. For an easy, hour-long run on
a coolish day, sipping water is fine. But if you're running 10 miles on
an August morning and are a salty sweater (you have white salt streaks
on your face or clothes postrun), you need to ingest some sodium as
well. "Salt helps you retain water," says Yeargin. "You're less likely
to pee it out." A sports drink, such as Gatorade, and water enhanced
with electrolytes, like Nuun, are good options; taking high-dose salt
tabs before a run is less so. "There's no way to 'preload' with sodium
to negate sodium loss," says Yeargin. "You just pee out anything you
don't use."
Myth: You can't drink too much
Truth: "You absolutely can drink too much," says Casa,
"and it can be deadly." Too much water can cause symptomatic
hyponatremia, a condition where the sodium levels in the blood become
dangerously low. Although Casa estimates that fewer than one percent of
marathoners develop symptomatic hyponatremia, certain groups are more
prone to it, including smaller runners; those who finish marathons in
more than four hours; and those who do a significant amount of walking
and running in cooler weather (when your sweat rate isn't as intense as
it is on warm days). "For recreational runners, the best way to prevent
hyponatremia is to listen to your thirst," says Casa.
Myth: Drinking lots of water is a good way to "detox"
Truth: "There is no evidence that excess water makes
your body more clean," says Dr. Stanley Goldfarb, M.D., a professor of
medicine in the Renal, Electrolyte, and Hypertension Division at the
University of Pennsylvania's Perelman School of Medicine. "If anything,
drinking too much water can slightly impair the ability of the kidneys
to filter blood." He adds that the only people who should drink more
water with a focus on their kidneys are those who have had kidney
stones.
