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3 ExploRING CengoHyDRATES
NUTRIENTS:
You Just
Cant Live Without'Em
"Do you want fries
with that cheeseburger?"
"Sure, and alar$e
soda, please."
You've ordere d a
An lndian family enjoys dinner.
{reat-tasting lunch,
but is it a healthy
meal? The good news
is that you're getting
many of the nutrients
you need. The bad
news is that you're
also about to eat a lot
of stuff that you don't
need-like extra salt
and fat.
When you choose
what to eat, you need
to think about more
than your taste buds.
You need to know
what your body
needs and what foods
will give it to you.
You need to know
about nutrients.
What are nutrients?
They are the fuels
your body needs to
keep you going. They
are used for growth
and repair. They help
fight disease.
There are six types
of nutrients: carbohydrates, proteins, fats,
vitamins, minerals,
and water. The first
three<arbohydrates,
proteins,' andfatsmake up the three
basic food types.
Foods are part of cultural traditions.
All foods, however, contain one or
more of the same essential nutrients.
Can you tell which of the foods that
you see in the first three photographs
of this article are high in carbohydrates? Fat? Protein?
Tortillas, beans, and trimmings are popular foods in Mexico and
many other countries.
20
STCA{STM Huueu Boov SvsrEMS
LEssoN
g ExploRrNG CenBoHyDRATES
carbohydrate. It is
m-ade of
the same
-
raw matenals as
su$ars:
carbon,
hydrogen,
and oxygen. But
you can't
digest fiber.
Rice and vegetables are mainstays of this Asian family's diet.
So what
good is it?
Garbohydrates:
Energy to Burn
The two most important kinds of carbohydrates are su$ars and
starches. The simplest
carbohydrate is a
sugar called glucose.
Glucose is your body's
first choice for fuel.
Complex carbohydrates are called
starches. When you
eat complex carbohydrates such as pasta,
bread, or rice, your
body breaks them
apart to get the simple sugars that it
needs for fast fuel.
But your body
doesn't waste the leftovers. It turns most
of the extra $ucose
into a substance
called glycogen and
saves it in your muscles and liver. If you
eat more food than
you need at the
moment, some of the
glucose gets turned
into fat. Your body
stores fat to make
sure it has fuel for
its future energy
needs. (It's like
putting the fat away
in a warehouse.)
But watch out: the
warehouse carTget
too full. If you continually eat too much
Fiber provides bulk
that helps move food
through your intestines. Fruits provide
fiber called pectin.
Whole -{rain breads
and cereals cont ain
cellulose, the fiber
that forms a plant's
cell walls.
Proteins: The Body
Builders
Proteins are at work
in every cell of your
body. You need pro-
teins to build tissue
(muscle tissue contains alot of protein).
Your body also uses
proteins to repair
dama{e and to make
substances such as
hemoglobin, which
carcies oxy$en
through your blood.
When your body
digests food, it breaks
the protein down into
simpler substances
called amino acids.
sugar-such as the
su$ar in corn syrup,
candy, and soft
drinks-you
can
quickly put on extra
pounds. What's more,
candy bars and soft
drinks usually don't
contain other nutrients, like minerals
and vitamins that you
can $et from fruits
These foods are good sources of carbohydrates.
and vegetables.
Can
Fiber is another
you name them? Do you know any other
foods that are high in carbohydrates?
STCA{STM HuueN Booy SysrEMS 21,
LEssoN
3 ExpLoRrNG CensoHYDRATES
such as obesity and
heart disease. But fat
isn't all bad news. It
has more energy than
proteins or carbohydrates. A gram of fat
supplies about twice
as much energy as a
gram of protein or
carbohydrates.
For many people, meat is an important source
of protein. Other protein-rich foods include nuts,
egg whites, and cheese.
You might compare
amino acids with
letters in the alphabet. There are 20
amino acids, and
they combine to
create millions of
different protein
"words." Your body
also builds some
amino acids from
scratch by combining
carbon, hydrogen,
oxygen, and nitro$en.
There are nine
amino acids that you
can get only from the
food you eat. Your
body can't build them
on its own. These are
called the essential
amino acids. A food
that has all nine
essential amino acids
is called a complete
protein. Food that
comes from animals
(for example, meat,
eggs
, and milk) has
complete proteins.
22
STCA4STM
F'oods that do not
have all the essential
amino acids are
called incomplete
proteins. Foods that
come from plantsfor example, ve$etables, fruit, wheat, and
rice-contain incomplete proteins.
If you don't want to
eat meat or animal
products, you catr still
get your essential
amino acids. Just
make sure you combine foods that have
dffirent incomplete
proteins. For example,
a meal that combines
black beans and rice,
or lentil soup and
corn bread, will grve
you the complete proteins that you need.
What else is good
about fat? Thin layers
of fat act as protective
padding around your
heart and other
organs. Fat helps
insulate your body,
too, so you don't have
to burn too much fuel
to stay warrn.
There are two kinds
of fats: saturated and
unsaturated. Most
fats that come from
animals are saturated
fats. Inside your
body, saturated fats
cart turn into cholesterol-a substance
that may collect
inside your blood vessels and place an
extra burden on your
heart. Most fats that
come from plants (for
example, from nuts
andvegetables) are
unsaturated fats.
Even though your
body cart convert
carbohydrates into
f at, you still need to
eat some foods that
contain fat. Why?
Because your body
can't build some of
the unsaturated fats
that you need.
But be careful. You
need only a small
amount, and the fatty
foods you eat should
contain mostly unsaturated, rather than
Fats: What's the
Skinny?
Tbo much f.at can
Eat only small quantities of foods such as these,
cause health problems
which are high in fat.
HuueN Botv SvsrEMS
LEssoN
saturated, fat. Meat,
cheese, and butter
have saturated f.at.
Sweet baked goods
like cookies and cakes
also have saturated
fat. Fish, avocados,
and most
liquid cook-
ing oils are sources of
unsaturated fats.
Vitamins: The ABCs
of Health
Vitamins are chemicals that have been
made by living orgartisms. Scientists discovered the first vitamin (B-1, or thiamin)
about 100 years ago.
They have now
identified a total of
13 vitamins. Each of
these vitamins has an
essential role in the
chemi cal reactions
that $o on in our
bodies. Vitamins help
build blood cells and
chemicals that control
the neryous system.
You only need tiny
amounts of vitamins
but your body cart't
manuf.acture them.
The best sources of
most vitamins are
fresh fruits and
vegetables.
Minerals: Little
Things That Mean
a Lot
Minerals are chemicals that occur
naturally in the environment. They do
not need to be made
by a living orsanism.
You need minerals to
build bones, teeth,
and blood cells.
Minerals also regulate
the chemical and
electrical signals that
control the way your
body works. Minerals
come from the earth.
They are absorbed by
plant roots as they
grow, and they are
passed on to animals
that eat plants.
You $et minerals
from many foodsfruits, ve$etables, and
$rains, 4s well as
meat and milk.
You need only tiny
amounts of some minerals (for example,
copper, iodifl€, iron,
and zinc). Thes e are
called trace minerals.
You need more of
other minerals such
as calcium, ma$nesium, potassium, and
sodium. Thes e are
the macrominerals.
Calcium, found in
milk
and cheese, is
especially important
for children wh o are
still growing. Your
body uses calcium to
build the hard, strong
parts of your bodybones and teeth, for
example. Older
3 ExpLoRING CeneoHYDRATES
people need calcium
too, to keep bones
stron$. Iron is a mineral component of
hemo$obin. Because
women lose blood
during their menstrual
cycle, they need more
iron than men. Beef,
tttna, and chickert are
$ood sources of iron.
Water: Where lt All
Comes Together
How can water be a
nutrient? There's
nothing in it! There
may not be much
nutrition in water,
but there's an awful
lot of water in you.
Your brain and muscles are three-fourths
water, and bone is
20 percent water.
Every cell in your
body is packed with
water. Your body
needs
replace some of
it
with food, but be
sure to drink six to
eight glasses of liquid
each day to maintain
your water supply.
When you're thirstyand even when
you're not-have
some water.
So What's for
Dinner?
The best way to get
the nutrients you
need is to eat good,
fresh food. Get
enough of the right
stuff, and you won't
have to worry about
vitamin or mineral
pills. Knowin$ about
nutrients can help
you choose foods that
give your taste buds
what they want and
the rest of your body
what it needs. tr
it to
transport
nutrients
and wastes,
control
your temperature,
and carry
out chemical teactions.
Each
your
body loses
more than
2liters of
duy,
water. You
Copper is a trace mineral. You need
just
a tiny bit of it in your diet. ln fact, if this
penny were pure copper, it would contain enough of this mineral to meet your
daily needs for three and a half years!
STCA4STM Huu^rN
Bonv SvsrEMS 23
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