April 8, 2008
There have been recent reports that question the need to
drink eight 8-ounce glasses of water throughout the day.
For years people have been told that this is
important, but no one seems to know why.
"Scientists say there's no clear health benefit to chugging
or even sipping water all day. So where does the standard
advice of drinking eight glasses each day come from?
'Nobody really knows,' says Dr. Stanley Goldfarb, a kidney
expert at the University of Pennsylvania."
This doesn't mean that people should stop drinking water.
"All living things must have water to survive, whether they
get it from a water fountain, a rain cloud, or a little
bottle attached to the side of a hamster cage. Without
water, your body would stop working properly. Water makes
up more than half of your body weight and a person can't
survive for more than a few days without it. Why? Your body
has lots of important jobs and it needs water to do many of
them. For instance, your blood, which contains a lot of
water, carries oxygen to all the cells of your body.
Without oxygen, those tiny cells would die and your body
would stop working. Water is also in lymph (say: limf), a
fluid that is part of your immune system, which helps you
fight off illness. You need water to digest your food and
get rid of waste, too. Water is needed for digestive
juices, urine (pee), and poop. And you can bet that water
is the main ingredient in perspiration, also called sweat.
In addition to being an important part of the fluids in
your body, each cell depends on water to function
It makes sense: the bigger the person, the more water they
need for their body to function properly. On the other
hand, if a person is smaller, they can lose less water
before they begin to suffer from dehydration.
"Dehydration sets in when a person has lost 2 percent of
his or her body weight. So for a 200-pound man, this means
losing 4 pounds of water. Marathon runners, bikers and
hikers all need to recognize the signs of dehydration. 'It
is also obvious that individuals in hot, dry climates have
increased need for water,' says Goldfarb."
Whatever the size of the person, the amount of water
consumed needs to make up for the amount of water used by
the body. Otherwise, dehydration becomes a problem.
"Dehydration occurs when you lose more fluid than you take
in and your body doesn't have enough water and other fluids
to carry out its normal functions. If lost fluid remains
unreplenished, you may suffer serious consequences. ...
Mild dehydration can cause symptoms such as weakness,
dizziness and fatigue. Severe dehydration is a
life-threatening medical emergency. You can usually reverse
mild to moderate dehydration by increasing your intake of
fluids, but severe cases need immediate medical treatment.
The safest approach is not to become dehydrated in the
first place. You can do that by monitoring your fluid loss
during hot weather, illness or exercise, and drinking
enough liquids to replace what you lose."
Drinking enough to replace what you lose is important, but
water is not the only drink. Water is often the recommended
drink of choice because it contains no calories. When
people get their liquids from soda, or even juice, these
drinks can contain excess calories and simple sugars.
"When selecting a juice, buyer beware: many so-called
juices contain little real juice and have more added sugar
than anything else. So read the label carefully. Your best
choice is one that is 100% fruit or vegetable juice -- not
a 'juice drink,' 'fruit flavored drink' or a sugar-heavy
'blend.' And even when it is 100% juice, remember that
juices lack the fiber of whole fruit. ... Don't get me
wrong -- pure fruit juice is nutritious as well as
delicious, containing a whole host of vitamins, minerals,
antioxidants, and phytochemicals. It's much better than
drinking a soda. But even pure fruit juices are high in
naturally occurring simple sugars. So unless you eat them
along with other foods, they can send your blood sugar
soaring... And those natural sugars can add up to lots of
calories. A glass of fruit juice ranges from 100 (orange,
grapefruit, apple) to 170 (grape and prune) calories for an
Water is not the only drink, and drinking is not the only
way that people get the fluids they need.
"Your body doesn't get water only from drinking water. Any
fluid you drink will contain water, but water and milk are
the best choices. Lots of foods contain water, too. Fruit
contains quite a bit of water, which you could probably
tell if you've ever bitten into a peach or plum and felt
the juices dripping down your chin! Vegetables, too,
contain a lot of water. Think of slicing into a fat tomato
from the garden or crunching into a crisp stalk of celery."
Getting enough fluids is important, but, as with anything,
too much of a good thing can be bad.
"Hyponatremia is an abnormally low concentration of sodium
in your blood. When your blood sodium is too low, your
cells malfunction -- causing swelling. In chronic
hyponatremia, sodium levels drop gradually over several
days or weeks -- and symptoms are typically moderate. In
acute hyponatremia, sodium levels drop rapidly -- resulting
in potentially dangerous effects, such as rapid brain
swelling, which can result in coma and death. Hyponatremia
occurs when the sodium in your blood is diluted by excess
water. Hyponatremia may result from medical conditions that
impair excretion of water from your body, or by a
significant increase in water consumption, such as by
athletes competing in marathons and other high-endurance
Questions of the Week:
How does the amount of fluids that you need to consume to
keep your body healthy vary from day to day? What might
make it higher on one day and less on another? How does the
amount of liquids you need to consume vary from the
quantity needed by another person? From what sources can
you get the fluids that you need? In what ways are some
sources better than others? How can you tell when you are
getting enough to drink and when you are not?
Please email me with any ideas or suggestions.
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