Much Water Should You Drink?
(HealthScoutNews)-- The mantra on daily water consumption may
be a washout.
When you ask for advice on how much of the clear, cool liquid
you should swig each day, there's a good chance you'll hear the
following: At least eight 8-ounce glasses, or 64 ounces, of water
But a New Hampshire doctor says that advice is hogwash, a national
myth with no basis in physiologic fact.
Dr. Heinz Valtin, of Dartmouth Medical School, has researched
the matter of adequate water intake and found a desert of evidence
in support of the "8 x 8" theory.
Instead, Valtin says, those 64 ounces a day will get you little
farther than the bathroom. In rare cases, people who drink too
much may suffer "water intoxication" by overloading
their kidneys. This phenomenon has been seen in athletes, Ecstasy
users and even healthy people.
True, some of us may indeed need that half-gallon of water on
some days -- when we're working out in the heat or flying for
long distances in a dry airplane cabin. However, those situations
appear to be the exceptions, not the norm.
"I have found no scientific proof that absolutely every
person must drink at least eight glasses of water a day,"
says Valtin, a kidney specialist, in a statement. His review of
the subject appears in the latest Internet edition of the American
Journal of Physiology.
Valtin says the 64 ounces-a-day figure might have been a bastardization
of recommendations from the National Research Council's Food and
Nutrition Board, which in 1989 called for roughly a milliliter
of water coming in for every calorie of energy expended.
However, the guidelines go on to state that most of that amount
-- 64 ounces to 80 ounces, on average -- can be obtained in prepared
foods that are rich in fluids.
Items like juice, milk, soda and coffee are almost entirely
water and may be reasonable substitutes for glasses of the plain
stuff, Valtin says.
Yet, while the origins of the 8 x 8 myth are murky, the booming
bottled water industry is clearly a driving force behind its promotion.
which boasts of being "the first e-commerce site for the
purchasing and delivery of high quality spring water."
A "Live Healthy" section of the site, part of the
Suntory Water Group in Atlanta, declares that "most experts
agree that eight 8-ounce glasses is a good rule of thumb. But
every individual has his or her own needs, and the amount of water
needed from person to person varies, depending on their weight
and level of activity."
However, it seems the only variable is how much more
than 64 ounces a day you need. On a water intake calculator water.com
provides, a 160-pound person who got no exercise is advised to
drink 80 ounces, or between six and seven 12-ounce glasses, a
day. Adding a 20-minute workout to the routine ups that figure
to 84 ounces.
Stephen Kay, a spokesman for the International Bottled Water
Association, says the 8 x 8 recommendation "certainly was
not invented by the bottled water industry, nor is it a bottled
water issue only. The issue overall is really water and water
consumption" for proper hydration.
While a variety of foods have fluids, Kay says water is the
"most direct source" of, well, water. It also happens
to be free of calories, caffeine and other potentially undesirable
substances. A statement on the group's Web site in response to
Valtin's paper says it "remains supportive" of the 8
x 8 guidelines.
The Food and Nutrition Board is now reviewing daily water consumption.
Its recommendations should be released in March 2003, says Paula
Trumbo, a nutritionist who's in charge of the project.
Trumbo says her group is not relying on Valtin's paper, since
it's a review not a study. However, she adds she agrees so far
with his conclusion that there's little data supporting the conventional
"No one really knows the scientific basis for" the
8 x 8 rule, Trumbo says. "It's kind of hard to say whether
it's credible or not."
The panel is conducting a study to clear up the question of
how much water a person needs. Whatever answer emerges is sure
to vary by weight or climate, for example, she says.
They're also looking at how, if at all, water intake affects
certain health outcomes, from kidney stones to heart ailments,
and whether the fluid in foods such as fruits and vegetables is
an adequate source of H2O.
"We will be very specific in saying what this value is
for," Trumbo says.
What To Do
For more on water and health, try the
University of Iowa. For the water industry's perspective,
International Bottled Water Association.
Reference Source 89