the best and earliest indicator that you need more water. Urine should
be clear, except for the first urine in the morning because you’re mild-
ly dehydrated then and drinking water should be one of the first
things you do upon awakening. If your urine has a yellow color, it
probably means you need more water. The darker the yellow the
more water you need.
Water input must balance water loss, which occurs from several
areas of the body. Most water is lost through the kidneys. This water
is used to help eliminate waste products from the body. But during
vigorous activity, such as exercise, the body attempts to conserve
water, and loss through the kidneys is very limited. Evaporation from
the skin, important for controlling body temperature, is also a major
source of water loss. Even under cool, resting conditions, about 30
percent of water loss occurs here. But sweating, from exercise or nor-
mal daily activity, increases this amount dramatically — during exer-
cise, it’s about 300 times the amount lost during rest! Water loss in
exhaled air is also significant. The air going in and out of your lungs
needs to be humidified. And a small but significant water loss (about
5 percent) occurs through the intestine.
The amount of water loss is determined in part by air tempera-
ture (the higher the temperature the more water loss), humidity (drier
climates result in more water loss) and body size (the larger the per-
son the more water loss). If you’re dehydrated, just drinking a glass
of water won’t solve the problem. Complete water replacement
throughout the body may take 24 to 48 hours no matter how much
you drink at one time. Unfortunately, the human body does not func-
tion like that of many other animals. By drinking a large volume of
water, dehydrated animals can consume 10 percent of their total body
weight in a few minutes, and rehydrate. Humans need to drink water
in smaller amounts much more frequently to correct dehydration and
maintain proper hydration.
What should you do to prevent dehydration and maintain prop-
er hydration? Here are some general everyday guidelines:
- Don’t wait until you’re thirsty to drink water. Drink
water every day, throughout the day.
120 • IN FITNESS AND IN HEALTH