April 16, 2001 -- You'd think we were suffering a nationwide
drought, the way Americans go around clutching bottles of water these days.
Forget American Express cards: The one thing many of us would never dream of
leaving home without is our bottled water.
By all rights, that should be good news. For years
nutritionists have been warning us about the dangers of dehydration. Quaff at
least eight 8-ounce glasses of water, the common wisdom goes, or you'll suffer
the consequences: flagging energy, dry skin, lowered disease resistance, even
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And don't count the coffee, tea, or other caffeinated beverages
you drink. Anything with caffeine, we've long been told, actually increases the
risk of dehydration because it flushes water out of the system.
Nor can you rely on thirst. By the time you're thirsty, you're
well on your way to being dehydrated.
There's only one problem with all these warnings. Almost none
of them hold water. Here's why:
Myth No. 1: We need to drink at least eight 8-ounce glasses of water a day
Researchers aren't sure where this familiar advice came from,
but most agree there's very little solid scientific evidence to support it. The
average adult loses only about 1 liter of water a day through sweating and
other bodily processes -- the equivalent of only four 8-ounce glasses. We
typically get that much water just in the foods we eat. Drinking an
additional eight tall glasses of H20 is probably more fluid
than most of us need.
What about older people? For years, experts have warned that
elderly people are especially prone to dehydration because they lose their
sense of thirst. But even this may be overstated, according to a report in the
July 2000 Journal of Gerontology. Robert Lindeman, MD, professor
emeritus of medicine at the University of New Mexico, surveyed fluid
consumption among 833 elderly volunteers.
"People who drank less than four glasses of water a day
were no more likely to show signs of dehydration than those who drank six or
more," says Lindeman. "We found absolutely no difference between those
who drank a little and those who drank a lot when we looked at all the standard
markers for dehydration."
Of course, that doesn't mean you shouldn't drink plenty
of water a day. In fact, there's at least one reason to think it's a very good
idea. In a 1999 study published in The New England Journal of Medicine,
researchers found that the more liquids men consumed, the lower their risk of
bladder cancer. Men who drank more than 10 8-ounce servings of fluids had a 49%
lower incidence of the disease than those who drank only half that much.