Unfortunately, hydration needs vary widely from person to
person, so there is no one-size-fits-all answer.
The easiest method I have found to gauge my own hydration
level is to be aware of my pee. It may not be the sort of conversation I want
to have over dinner, but I want to be sure I’m going at least every two hours,
going with some volume, and that the color is always a nice pale yellow
(colorless is even better).
Why does water matter?
Water is the most important single component of the human
body. It makes up more than 60% of your body weight (75% of muscle tissue and
10% of fat cells). It cushions your organs, helps you maintain a constant body
temperature, and provides a waste transportation system to help each cell in
your body “take out the trash.”
You lose water through sweat when you exercise, especially
when exercising intensely or in hot weather. One design problem with the human
body is that we don’t feel thirsty until we are already on the way to
dehydration. So our goal is to stay ahead of thirst and drink before we need
to.
What is dehydration?
Symptoms of dehydration, or excessive water loss, include:
muscle fatigue, loss of coordination, lack of sweat, inability to control water
temperature, heat-related illness (like cramps, heat exhaustion or heat
stroke), and a loss of energy. Dehydration can be life-threatening if you
ignore it too long. Athletes and casual exercisers are likely to encounter heat
exhaustion and possibly heat stroke if we don’t stay ahead of the dehydration
curve.
How much do I need?
The old adage that everyone should drink eight eight-ounce
glasses of water per day falls just slightly short of The Institute of Medicine’s
recommendation that men drink about 13 cups of total beverages a day and 9 cups
a day for women. This is a good starting point, and it can be a useful baseline
if you emphasize “at least eight glasses,” or if you drink 10 ounce instead of
8-oz glasses.
Men require more water than women. Older people feel less
thirsty and can have more trouble regulating temperature than younger people
(the same is true of children). Heavy sweaters and salty sweaters (people whose
workout clothes are dripping wet and/or rimmed with salt after an exercise
session) require more hydration than those who sweat little.
The weight of it all
Try weighing yourself to see how much water you lose in a
day. Start off first thing in the morning, after the early-morning pee, and
weigh yourself buck naked. Then weigh yourself again after your workout. Don’t
get too excited if you lost several
pounds in just a few hours: weight lost in such a short time is almost all
water. For every pound lost during the workout, drink 20-24 oz within the next
few hours after your workout.
But what should I drink?
Water, tea, coffee, sports drinks, wine, beer, sodas…what
should you choose? Each type of beverage seems to have its own advocacy group.
However, for each there is a benefit and a caution. Sports drinks contain salt
and other electrolytes (sodium, chloride, potassium, magnesium and calcium) to
replace minerals lost through sweat. If not corrected after exercise,
electrolyte loss can lead to muscle cramps after exercise. Some people dislike
sports drinks because of the artificial colors, sugar and additives. However,
for an extended exercise event (like a long weekend run or a three-hour swing
dance in a non-air-conditioned summer dance hall) a sports drink will help your
body hold on to the fluids you’re taking in, and the sugar in the drink will
provide just enough energy to fuel your muscles with glycogen.
Coffee and tea both provide caffeine, which can give you a
tiny pre-performance boost. According to the American College of Sports Medicine,
moderate caffeine intake does not affect hydration status or urine output.
However, alcohol will increase your urine output and decrease hydration.
Sodas can also provide hydration and sugar, but they are
nutritional pariahs. Personally, I enjoy decaffeinated iced green tea, which I
make myself. I don’t put any kind of sweetener in it, just the tea leaves and
water on ice. It has just enough flavoring to be interesting and keep me
drinking in the hot months. I also like smoothies, which help replace fluids,
electrolytes and carbohydrate after workouts. I make mine with banana, orange
juice, frozen fruit, plenty of greens and a dab of yogurt. This smoothie is
fairly calorie-dense, so it takes the place of breakfast after a workout.
How much is too much?
It is possible to get too much of a good thing. Even too
much water, taken too fast and without enough salt, can lead to hyponatremia, or water intoxication.
According to the American Council on Exercise, symptoms of hyponatremia include
nausea, vomiting, muscle weakness, headache and disorientation, and bloating in
the face and hands. To avoid this unpleasant condition, avoid drinking more
than one liter of water per hour.
References
American College of Sports Medicine: Selecting and
Effectively Using Hydration for Fitness
MayoClinic.com: Water: How much should you drink every day?
American Council on Exercise: How much water is too much?
American Council on Exercise, Certified News: Electrolytes:
Understanding Replacement Options
American Council on Exercise, Fit Facts: Healthy Hydration: http://www.acefitness.org/acefit/healthy_living_fit_facts_content.aspx?itemid=173
Science Daily: How much water should you drink?
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