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Water: How Much
Should You Drink Everyday?
Water is
essential to good health, yet
needs vary by individual. These
guidelines can help ensure you
drink enough fluids.
How much water
should you drink each day? — a
simple question with no easy
answers. Studies have produced
varying recommendations over the
years, but in truth, your water
needs depend on many factors,
including your health, how
active you are and where you
live.
Though no single formula fits
everyone, knowing more about
your body's need for fluids will
help you estimate how much water
to drink each day.
Health
benefits of water
Water is your body's principal
chemical component, comprising,
on average, 60 percent of your
weight. Every system in your
body depends on water. For
example, water flushes toxins
out of vital organs, carries
nutrients to your cells and
provides a moist environment for
ear, nose and throat tissues.
Lack of water can lead to
dehydration, a condition that
occurs when you don't have
enough water in your body to
carry out normal functions.
How
much water do you need?
Every day you lose water through
your breath, perspiration, urine
and bowel movements. For your
body to function properly, you
must replenish its water supply
by consuming beverages and foods
that contain water.
A couple of approaches attempt
to approximate water needs for
the average, healthy adult
living in a temperate climate.
Replacement approach. The
average urine output for adults
is 1.5 liters a day. You lose
close to an additional liter of
water a day through breathing,
sweating and bowel movements.
Food usually accounts for 20
percent of your total fluid
intake, so if you consume 2
liters of water or other
beverages a day (a little more
than 8 cups) along with your
normal diet, you will typically
replace the lost fluids.
Dietary recommendations.
The Institute of Medicine
advises that men consume roughly
3.0 liters (about 13 cups) of
total beverages a day and women
consume 2.2 liters (about 9
cups) of total beverages a day.
Even apart from the above
approaches, it is generally the
case that if you drink enough
fluid so that you rarely feel
thirsty and produce between one
and two liters of colorless or
slightly yellow urine a day,
your fluid intake is probably
adequate.
Factors
that influence water needs
You may need to modify your
total fluid intake depending on
how active you are, the climate
you live in, your health status,
and if you're pregnant or
breast-feeding.
Exercise. The more you
exercise, the more fluid you'll
need to keep your body hydrated.
An extra 1 or 2 cups of water
should suffice for short bouts
of exercise, but intense
exercise lasting more than an
hour (for example, running a
marathon) requires additional
fluid. How much additional fluid
is needed depends on how much
you sweat during the exercise,
but 13 to26 ounces (or about 2
to 3 cups) an hour will
generally be adequate, unless
the weather is exceptionally
warm.
During long bouts of intense
exercise, it's best to use a
sports drink that contains
sodium, as this will help
replace sodium lost in sweat and
reduce the chances of developing
hyponatremia, which can be
life-threatening. Fluid also
should be replaced after
exercise. Drinking 16 ounces of
fluid per pound of body weight
lost during exercise is
recommended.
Environment. Hot or humid
weather can make you sweat and
requires additional intake of
fluid. Heated indoor air also
can cause your skin to lose
moisture during wintertime.
Further, altitudes greater than
2,500 meters (8,200 feet) may
trigger increased urination and
more rapid breathing, which use
up more of your fluid reserves.
Illnesses or health
conditions. Signs of
illnesses, such as fever,
vomiting and diarrhea, cause
your body to lose additional
fluids. In these cases you
should drink more water and may
even need oral rehydration
solutions, such as Gatorade,
Powerade or Ceralyte. Certain
conditions, including bladder
infections or urinary tract
stones, also require increased
water intake. On the other hand,
certain conditions such as heart
failure and some types of
kidney, liver and adrenal
diseases may impair excretion of
water and even require that you
limit your fluid intake.
Pregnancy or breast-feeding.
Women who are expecting or
breast-feeding need additional
fluids to stay hydrated. Large
amounts of fluid are lost
especially when nursing. The
Institute of Medicine recommends
that pregnant women drink 2.4
liters (about 10 cups) of fluids
daily and women who breast-feed
consume 3.0 liters (about 12.5
cups) of fluids a day.
Beyond
the tap: Other sources of water
Although it's a great idea to
keep water within reach at all
times, you don't need to rely
only on what you drink to
satisfy your fluid needs. What
you eat also provides a
significant portion of your
fluid needs. On average, food
provides about 20 percent of
total water intake, while the
remaining 80 percent comes from
water and beverages of all
kinds.
For example, many fruits and
vegetables — such as watermelon
and cucumbers — are nearly 100
percent water by weight.
Beverages such as milk and juice
are also comprised mostly of
water. Even beer, wine and
caffeinated beverages such as
coffee, tea or soda can
contribute, but these should not
be a major portion of your daily
total fluid intake. Water is one
of your best bets because it's
calorie-free, inexpensive and
readily available.
Dehydration and complications
Failing to take in more water
than your body uses can lead to
dehydration. Even mild
dehydration — as little as a 1
percent to 2 percent loss of
your body weight — can sap your
energy and make you tired.
Common causes of dehydration
include strenuous activity,
excessive sweating, vomiting and
diarrhea.
Signs and symptoms of
dehydration include:
Mild to excessive thirst
Fatigue
Headache
Dry mouth
Little or no urination
Muscle
weakness
Dizziness
Lightheadedness
Mild dehydration rarely results
in complications — as long as
the fluid is replaced quickly —
but more-severe cases can be
life-threatening, especially in
the very young and the elderly.
In extreme situations, fluids or
electrolytes may need to be
delivered intravenously.
Staying
safely hydrated
It's generally not a good idea
to use thirst alone as a guide
for when to drink. By the time
one becomes thirsty, it is
possible to already be slightly
dehydrated. Further, be aware
that as you get older your body
is less able to sense
dehydration and send your brain
signals of thirst. Excessive
thirst and increased urination
can be signs of a more serious
medical condition. Talk to your
doctor if you experience either.
To ward off dehydration and make
sure your body has the fluids it
needs, make water your beverage
of choice. Nearly every healthy
adult can consider the
following:
Drink a glass of water with each
meal and between each meal.
Hydrate before, during and after
exercise.
Substitute sparkling water for
alcoholic drinks at social
gatherings.
If you drink water from a
bottle, thoroughly clean or
replace the bottle often. Refill
only bottles that are designed
for reuse.
Though uncommon, it is possible
to drink too much water. When
your kidneys are unable to
excrete the excess water, the
electrolyte (mineral) content of
the blood is diluted, resulting
in a condition called
hyponatremia (low sodium levels
in the blood). Endurance
athletes — such as marathon
runners — who drink large
amounts of water are at higher
risk of hyponatremia. In
general, though, drinking too
much water is rare in healthy
adults who consume an average
American diet.
If you're concerned about your
fluid intake, check with your
doctor or a registered
dietitian. He or she can help
you determine the amount of
water that's best for you.
By Mayo Clinic Staff
May 23, 2006
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