726
UNIT FIVE
A
n endurance athlete and a sedentary indi-
vidual have dif
erent nutritional require-
ments, as the description oF cyclist Lance
Armstrong’s diet in the chapter opener indicates.
A diet that is predominantly complex carbohy-
drate supports a liFestyle that includes Frequent
strenuous activity. A distribution oF 60% or more
carbohydrate, 18% protein, and 22% Fat supports
Frequent, strenuous activity.
Macronutrients
Athletes should get the bulk oF their carbohydrates
From vegetables and grains to avoid cholesterol,
and they should eat Frequently, because the mus-
cles can store only 1,800 calories worth oF glycogen.
Athletes need to consume only slightly more
protein than less-active individuals. The American
Dietetic Association suggests that athletes eat 1
gram oF protein per kilogram oF weight per day,
compared to 0.8 gram For nonathletes. Athletes
should not rely solely on meat For protein,
because these Foods can be high in Fat. Protein
supplements may be necessary For only young
athletes at the start oF training, under a doctor’s
supervision. Too little protein in an athlete is
linked to “sports anemia,” in which hemoglobin
levels decline and blood may appear in the urine.
Water
A sedentary person loses a quart oF water a day
as sweat; an athlete may lose 2 to 4 quarts oF
water an hour! To stay hydrated, athletes should
drink 3 cups oF cold water two hours beFore an
event, then 2 more cups ±
Fteen minutes beFore
the event, and small amounts every FiFteen
minutes during the event. They should drink
aFterward too. Another way to determine water
needs is to weigh in beFore and aFter training.
²or each pound lost, athletes should drink a pint
oF water. They should also avoid sugary Fluids,
which slow water’s trip through the digestive
system, and alcohol, which increases ³
uid loss.
However, athletes should also avoid drinking
too much water during competition, which can
cause hyponatremia (too little sodium in the
bloodstream, see Clinical Applications 21.1 and
21.2 on pages 816–817 and 820 respectively).
Vitamins and Minerals
IF an athlete eats an adequate, balanced diet, vita-
min supplements are not needed. Supplements
oF sodium and potassium are usually not needed
either, because the active body naturally con-
serves these nutrients. To be certain oF enough
sodium, athletes may want to salt their Food; to
get enough potassium, they can eat bananas,
dates, apricots, oranges, or raisins.
A healthy pregame meal should be eaten
two to Five hours beFore the game, provide 500
to 1,500 calories, and include 4 or 5 cups oF ³
uid.
The pregame meal should also be high in carbo-
hydrates, which taste good, provide energy, and
are easy to digest.
Creatine
Creatine is advertised to increase energy stores
and provide a saFe alternative to steroids For bulk-
ing up muscles. This is deceptive.
Creatine may be obtained From Foods,
through supplements or by synthesis From the
amino acids arginine, glycine, and methionine.
Creatine, in the Form oF creatine phosphate, pro-
vides energy to muscle cells by phosphorylating
ADP to generate ATP. Creatine is converted to its
metabolite, creatinine, at such a constant rate
that the excretion oF creatinine in the urine is
used as a marker For normal kidney Function.
Do creatine supplements enhance perFor-
mance? The emerging picture suggests that during
peak exertion, especially repetitive peak exertion
(such as multiple sprints), conditions in which cre-
atine levels may become depleted, supplemental
creatine may be advantageous. Muscle mass may
appear to increase in athletes taking creatine sup-
plements because creatine draws water into muscle
cells by osmosis. However, the disturbance in water
distribution that creatine supplementation can
cause may create problems iF the athlete encounters
extreme heat—sweating becomes inadequate to
ef
ectively cool the body. Swelled muscle cells may
burst, causing a potentially Fatal condition called
rhabdomyolysis. The ²ood and Drug Administration
has received many adverse event reports oF muscle
cramps, seizures, diarrhea, loss oF appetite, muscle
strains, dehydration and even deaths, associated
with creatine use among athletes.
18.3
CLINICAL APPLICATION
Nutrition and the Athlete
Some starving children have protruding bellies. These
youngsters suffer from a form of protein starvation called
kwashiorkor
(kwash
-e-or
kor), which in the language of
Ghana means “the evil spirit which infects the first child
when the second child is born” (F g. 18.21
b
). Kwashiorkor
typically appears in a child who has recently been weaned
from the breast, usually because of the birth of a sibling.
The switch from protein-rich breast milk to the protein-
poor gruel that is the staple of many developing nations is
the source of this protein deF
ciency. The children’s bellies
swell with F ltered fl uid, lost from capillaries in greater than
normal volume due to a lack of plasma proteins. This con-
dition is called
ascites
(ah-si
te
ˉz). Their skin may develop
lesions. Infections overwhelm the body as the immune sys-
tem becomes depleted of its protective antibodies.
broken down to release amino acids used for the more vital
functioning of the brain, heart, and lungs. When the immune
system’s antibody proteins are dismantled for their amino
acids, protection against infection declines. Mouth sores and
anemia develop, the heart beats irregularly, and bone begins
to degenerate. After several weeks without food, coordina-
tion is gradually lost. Near the end, the starving human is
blind, deaf, and emaciated.
Marasmus and Kwashiorkor
Lack of nutrients is called
marasmus
(mah-raz
mus), and
it causes people to resemble living skeletons
(f g. 18.21
a
)
.
Children under the age of two with marasmus often die of
measles or other infections. Their immune systems become
too weakened to F
ght off normally mild viral illnesses.
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