2015-03-29 08:38:25
Water is essential to good health, yet needs vary by individual. These
guidelines can help ensure you drink enough fluids.
By Mayo Clinic Staff
How much water should you drink each day? It's 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.
Although 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 and makes up about 60 percent
of your body 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. Even mild
dehydration can drain your energy and make you tired.
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.
So how much fluid does the average, healthy adult living in a temperate climate
need? The Institute of Medicine determined that an adequate intake (AI) for men
is roughly about 13 cups (3 liters) of total beverages a day. The AI for women
is about 9 cups (2.2 liters) of total beverages a day.
What about the advice to drink 8 glasses a day?
Everyone has heard the advice, "Drink eight 8-ounce glasses of water a day."
That's about 1.9 liters, which isn't that different from the Institute of
Medicine recommendations. Although the "8 by 8" rule isn't supported by hard
evidence, it remains popular because it's easy to remember. Just keep in mind
that the rule should be reframed as: "Drink eight 8-ounce glasses of fluid a
day," because all fluids count toward the daily total.
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. If you exercise or engage in any activity that makes you sweat, you
need to drink extra water to compensate for the fluid loss. An extra 1.5 to 2.5
cups (400 to 600 milliliters) of water should suffice for short bouts of
exercise, but intense exercise lasting more than an hour (for example, running
a marathon) requires more fluid intake. How much additional fluid you need
depends on how much you sweat during exercise, and the duration and type of
exercise.
Intense exercise. 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. Also, continue to replace fluids after you're finished
exercising.
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 8,200 feet (2,500 meters)
may trigger increased urination and more rapid breathing, which use up more of
your fluid reserves.
Illnesses or health conditions. When you have fever, vomiting or diarrhea, your
body loses additional fluids. In these cases, you should drink more water. In
some cases, your doctor may recommend oral rehydration solutions, such as
Gatorade, Powerade or CeraLyte. You may also need increased fluid intake if you
develop certain conditions, including bladder infections or urinary tract
stones. On the other hand, some 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 pregnant or breast-feeding need
additional fluids to stay hydrated. Large amounts of fluid are used especially
when nursing. The Institute of Medicine recommends that pregnant women drink
about 10 cups (2.3 liters) of fluids daily and women who breast-feed consume
about 13 cups (3.1 liters ) of fluids a day.
Beyond the tap: Other sources of water
You don't need to rely only on what you drink to meet 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. For example, many fruits
and vegetables, such as watermelon and spinach, are 90 percent or more water by
weight.
In addition, beverages such as milk and juice are composed 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 still your best bet because it's calorie-free, inexpensive and
readily available.
Staying safely hydrated
Generally, if you drink enough fluid so that you rarely feel thirsty and your
urine is colorless or light yellow and measures about 6.3 cups (1.5 liters)
or more a day if you were to keep track your fluid intake is probably
adequate. If you're concerned about your fluid intake or have health issues,
check with your doctor or a registered dietitian. He or she can help you
determine the amount of water that's right for you.
To ward off dehydration and make sure your body has the fluids it needs, make
water your beverage of choice. It's also a good idea to:
Drink a glass of water or other calorie-free or low-calorie beverage with each
meal and between each meal
Drink water before, during and after exercise
Although 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 low sodium levels in the blood, a condition
called hyponatremia. 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 eat an average American
diet.
http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/in-depth/
water/art-20044256