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The Wonders of Water
Water is one of the most basic
elements of life but figuring out how much we ought
to drink hasn't always been so simple.
By Kathleen M. Zelman, MPH
WebMD Feature
Most
of us grew up thinking we needed to drink eight
glasses of water each day, in addition to any other
drinks we might choose. But the latest
recommendations say that we no longer need to worry
about drinking specific amounts of water. Instead,
we can simply satisfy our thirst with any beverage.
As
it turns out, there really was no scientific
evidence for the 64-ounce daily recommendation that
was based on survey data of usual consumption.
Of
course, water -- clean, refreshing, and calorie-free
-- is an ideal beverage of choice but studies have
shown that you can be just as hydrated with coffee,
soft drinks, or even beer.
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"Trust your thirst instinct to make sure you get
enough fluids and, of equal importance, void
frequently" |
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And some folks swear by its
weight loss powers, including Mireille
Guiliano, author of the best-selling book
French Women Don't Get Fat. To help make the
facts about water crystal clear, WebMD asked
experts for the skinny on just how much
water we need, and whether drinking water
can really help keep those extra calories at
bay.
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The New Fluid Guidelines
A
2002 study published in the American Journal of
Physiology questioned the old recommendation of 8
ounces of water, eight times a day. After a thorough
review, researcher Heinz Valtin concluded there was
inadequate evidence that healthy adults -- living in
temperate climates and not engaged in rigorous
activities -- need large amounts of water.
For
normal, healthy adults, Valtin recommended simply
drinking when thirsty. And he reported that even
caffeinated drinks can count toward satisfying our
fluid requirements.
In
February 2004, the Institute of Medicine (IOM)
issued new recommendations that agree with Valtin's
findings. The new guidelines remove the
eight-glasses-a-day recommendation, and say healthy
adults may use thirst to determine their fluid
needs. Exceptions to this rule include anyone with a
medical condition requiring fluid control; athletes;
and people taking part in prolonged physical
activities or whose living conditions are extreme.
How Much Is Enough?
The
IOM report did not specify requirements for water
but made general fluid intake recommendations based
on survey data of 91 ounces (that's 11-plus cups a
day) for women and 125 ounces (15-plus cups a day)
for men. Remember, these guidelines are for total
fluid intake, including fluid from all food and
beverages.
Approximately 80% of our water intake comes from
drinking water and other beverages, and the other
20% comes from food. Assuming these percentages are
accurate for most of us, the recommended amount of
beverages, including water, would be approximately 9
cups for women and 12.5 cups for men.
While 20% may seem like a lot of fluid to get from
food, many common food items are mostly water. Here
are some foods with high water content, according to
the American Dietetic Association:
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Food |
% Water |
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Lettuce (1½ cup) |
95% |
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Watermelon (1½ cup) |
92% |
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Broccoli (1½ cup) |
91% |
|
Grapefruit (1½ cup) |
91% |
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Milk (1 cup) |
89% |
|
Orange juice (3/4 cup) |
88% |
|
Carrot (1½ cup) |
87% |
|
Yogurt (1 cup) |
85% |
|
Apple (one medium) |
84% |
When
You Need More
Physical activity, heat, and humidity can increase
our fluid needs. In these situations, keep water
bottles close at hand and drink frequently to avoid
dehydration. If you're going to be physically active
for long periods, consider sports drinks that
hydrate and provide easily usable sugar and
electrolytes.
Illnesses accompanied by increased body temperature,
excessive perspiration, vomiting, frequent
urination, or diarrhea can also increase our fluid
needs. Be sure to drink plenty of liquids if you
have one of these conditions, and see a doctor if
your fluid losses are excessive or prolonged.
How Much Is Too Much?
Scientists on the IOM panel did not set an upper
limit for water.
"Water intoxication is very rare, although it has
been seen in fraternity pranks. That can be very
serious and result in death" says David Perlow, MD,
an Atlanta-based urologist.
One
recent study of Boston Marathon runners showed that
one in three marathon runners was drinking too much
water during a race -- probably because they were
following recent advice to drink as much as
tolerated.
If
you follow your thirst, you won't go wrong, Perlow
says. He notes that pre-modern man never ran around
sipping on a water bottle. A dry mouth indicated it
was time to run to the stream for a drink.
"Trust your thirst instinct to make sure you get
enough fluids and, of equal importance, void
frequently," suggests Perlow.
Perlow says the bladder is like a balloon. When you
make infrequent trips to the bathroom, it can become
overstretched -- which can result in problems with
incomplete emptying, he explains.
He
recommends 7-12 trips to the toilet daily for most
healthy people.
Water and Weight Control
For
years, drinking water has been recommended for
weight loss -- despite the fact that fluids
generally satisfy thirst and not hunger. Barbara
Rolls, PhD, an expert on thirst and satiety, points
out that thirst and hunger are regulated by entirely
different mechanisms.
A
recent study by Rolls and colleagues at Penn State
University looked at whether people who drank water
with lunch took in fewer calories than those who
drank other low-calorie beverages. They found that
drinking water had little effect on total calorie
consumption at the meal.
"In
all of our research, we have never been able to show
that water can cause weight loss," says Rolls. The
only way drinking water can help you lose weight is
if you substitute it for higher-calorie beverages or
foods, she explains.
However, eating foods with high water content can
help dieters, by increasing the fullness factor.
"When you add water to a bowl of vegetables as in
soup, the soup has greater satiety than when the
vegetables are eaten alone with a glass of water,"
explains Rolls, author of The Volumetrics Eating
Plan and The Volumetrics Weight Control Plan. "When
water is incorporated into food or shakes, satiety
is increased and subjects ultimately eat less food."
The
weight loss benefits of water stem from several
facts:
Foods that incorporate water tend to look larger.
The
higher volume of these foods provides greater oral
stimulation.
Most
important, when water is bound to food, it slows
down absorption and lasts longer in the belly.
If
you want to lose weight, Rolls recommends an eating
plan that includes plenty of high-volume foods such
as fruits, vegetables, broth-based soups, and
oatmeal, along with adequate fluids to satisfy your
thirst.
Bottom Line
The
experts agree: Drinking water -- either sparkling or
flat and perhaps with a twist of citrus -- is a
great, non-caloric way to satisfy your thirst. But
if you prefer 100% fruit juice, low fat milk,
coffee, or other flavored beverages, they too can
keep you well hydrated. Water is calorie free, which
makes it a great choice for weight control, but we
also need the calcium and especially the vitamin D
in low-fat milk.
Bottom line, make your beverage choices work to
satisfy your nutritional needs, fluid preferences,
and hydration needs.
©
WebMD. All rights reserved.
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