WHAT A HEALTH
D ehydration and Sports Drinks
trenuous exercise in hot weather can cause a loss of up to
2 liters or about 68 fluid ounces of water per hour through
sweating and evaporation through
the lungs. Such losses can
lead to dehydration and
elevated body tem-
peratures if fluids
are not replaced.
the loss of fluid
to 1% of body
weight. In some
such as football,
soccer, or tennis,
lead to a 5% loss in
body weight. Symptoms of simple dehydration include irritability,
fatigue, headache, and loss of appetite.
To prevent dehydration under such conditions, you should
drink plenty of water. But what about sports drinks? Are they any
better than plain water? Sports drinks have three basic compo-
nents that help combat dehydration. Water is the most impor-
tant. In addition, you lose some salts or electrolytes when you
sweat, so sports drinks contain potassium salts. Finally, exercis-
ing muscles require carbohydrates as energy sources. Sports
drinks contain generous amounts of sugars such as glucose, fruc-
tose, or sucrose. Although sports drinks are designed to replace
all the fluid components lost through sweat, water is the most
essential component. So, if you don't have a sports drink handy,
drink plenty of water when exercising or in hot weather.
1. W hen young children get sick and
vom it frequently, pediatricians recom m end that parents
adm inister Pedialyte to prevent dehydration. The com -
position of Pedialyte is sim ilar to that of a sports drink.
W hat substances are children losing when they vom it?
2. W hat steps m ight you take prior to intensive exercise
to prevent dehydration?
One important example of a buffer system in the hu-
man body is the
carbonic acid-bicarbonate buffer.
It is based
(HCO3-), a weak base, a significant
anion in both intracellular and extracellular fluids, and
(H2CO3), a weak acid. If there is an excess of
strong acid (H+), HCO3- can function as a weak base and
remove it as follows:
Conversely, if there is an excess of strong base (a
shortage of H+), carbonic acid can function as a weak acid
and increase the amount of H+:
You will learn more about the carbonic acid-bicarbonate
buffer system, which helps regulate the pH of the blood
and other body fluids, in Chapter 15. For more informa-
tion on dehydration and how to prevent it see
Health Provider Sees.
Carbohydrates Are Major Energy
Sources for the Body
hydrogen, and oxygen in a ratio of
1:2:1. For example, the molecular formula of the simple
carbohydrate glucose is C6H12O6. Carbohydrates are di-
vided into three categories, based on size:
= sugar) or simple sugars are the building
blocks of carbohydrates (Figure 2.10). They include
glucose, galactose, fructose, ribose, and deoxyribose.
In your body, glucose is the main source of chemical
energy. As you will see later, chemical energy is captured
in a molecule called
adenosine triphosphate (ATP)
fuels metabolic reactions. Two monosaccharide sugars,
and deoxyribose, make
up ribonucleic acid
(RNA) and deoxyribonucleic acid (DNA), two nucleic
acids important to human body functions that are
described later in the chapter.
A compound that
34 CHAPTER 2