Need to Guzzle All That Water
- Trying to do the "right" thing by drinking eight full glasses
of water a day may do little more than make a person run to the
bathroom, a researcher said on Friday.
health and beauty magazines all advise drinking at least 8 full
glasses of water a day totaling 64 ounces for optimal health --
an approach called "8x8" by proponents.
But Dr. Heinz
Valtin of Dartmouth Medical School in New Hampshire said there is
no scientific evidence to back up this advice, which has helped
create a huge market for bottled water.
"After 10 months
of careful searching I have found no scientific evidence that supports
'8x8'," Valtin, who has written textbooks on the subject of human
water balance, said in a telephone interview.
the American Journal of Physiology, Valtin, a kidney specialist,
said people forget that the food they eat also contains some water.
The Food and
Nutrition Board of the National Research Council has recommended
that people take in about one milliliter of water for each calorie
of food eaten.
This adds up
to two liters, or 74 fluid ounces on an average 2,000-calorie diet.
But the National Research Council also noted that much of this is
already contained in food.
"I did 43 years
of research on that system -- the osmoregulatory system. That system
is so precise and so fast that I find it impossible to believe that
evolution left us with a chronic water deficit," Valtin said.
LOW ON FLUID
If a person
gets low on fluid, the body compensates by bringing fluid back out
of the kidneys and by slowing the loss of water through the skin,
Valtin said. Thirst kicks in long before dehydration starts, he
"It does it
very quickly and very accurately and it does so in minutes," Valtin
He said he
and colleagues became concerned after seeing dozens of newspaper
and magazine articles urging people to sip water all day. "I started
talking to my colleagues and asking them 'Do you know of any evidence
for this?'. Invariably, they said, 'No I think it's a myth'," Valtin
asked him to review all the scientific studies he could find and
he concluded that someone misinformed has been telling people to
drink large amounts of water when most do not need to.
"I am referring
to healthy adults in a temperate climate leading a largely sedentary
existence," Valtin said. "Persons with certain diseases must have
large volumes of water -- kidney stones are probably the most common
The rest can
just drink enough to slake thirst -- and this includes coffee, tea,
and even beer -- despite their diuretic effects, Valtin said.
He hopes people
will be relieved of the guilt of not getting enough water, and of
the expense of buying bottled water to drink throughout the day.
"There is also
the possibility that if you drink a lot of water that happens to
be polluted then of course you get more pollutants," Valtin said.
is the inconvenience of constant urination, the embarrassment of
having to go to the bathroom all the time," he added.
of water can cause water intoxication that can lead to confusion
and even death. Water intoxication is one deadly effect of taking
the drug Ecstasy, for instance, because it makes people thirsty
beyond their physical needs.
Reference Source 89