Nutrients are the parts of food that are
important for life and health. Nutrients are important for three reasons. First,
some nutrients provide fuel for energy. Second, some nutrients build and repair
body tissues. Third, some nutrients help control different processes of the body
like the absorption of minerals and the clotting of blood. Scientists think
there are 40 to 50 nutrients. These nutrients are divided into five general
groups: carbohydrates, fats, proteins, minerals, and vitamins.
The first group of nutrients is carbohydrates. There are two kinds of
carbohydrates: starches and sugars. Bread, potatoes, and rice are starches. They
have many carbohydrates. Candy, soft drinks, jelly, and other foods with sugar
also have carbohydrates. Carbohydrates are important because they provide the
body with heat and energy. Sugar, for instance, is 100 percent energy. It has no
other food value. Sugar does not build body tissues or control body processes.
If there are too many carbohydrates in the body, they are stored as body fat.
The body stores fuel as fat. There are two types of
fats: animal and vegetable. Butter, cream, and the fat in bacon are animal fats.
Olive oil, corn oil, and peanut oil are vegetable fats. The body has fat under
the skin and around some of the organs inside. The average adult has 10 to 11
kilograms (20 to 25 pounds) of body fat. If adults eat too many carbohydrate and
fats, they can add another 45 kilograms (100 pounds) to their bodies. Fat is
extra fuel. When the body needs energy, it changes the fat into carbohydrates.
The carbohydrates are used for energy. Fat also keeps the body warm.
The third group of nutrients is proteins. The word "protein" comes
from a Greek word that means "of first importance". Proteins are "of first
importance" because they are necessary for life. Proteins are made of amino
acids, which build and repair body tissue. They are an important part of all the
muscles, organs, skin, and hair. The body has 22 different amino acids.
Nutritionists call eight of these amino acids essential because the body does
not manufacture them. There are two kinds of proteins:
complete proteins and incomplete proteins. Complete proteins, which the body
needs for growth, have all the essential amino acids. Meat, fish, poultry, eggs,
milk, and cheese have complete proteins. The body needs complete proteins every
day. Incomplete proteins do not have all the essential amino acids. The proteins
in vegetables and grains, for instance, are incomplete proteins. Two ways to
form complete proteins from incomplete proteins are: (1) to mix vegetables and
grains correctly, or (2) to add a small amount of meat or milk to a large amount
of grains. The body can then use the complete proteins which result from the
mixtures. Extra protein in the body can be changed to
fat and stored as body fat. It can also be changed to carbohydrates and used for
energy. If people do not eat enough carbohydrates and fats for the energy that
they need, their body uses proteins for energy. Then the body does not have the
proteins that it needs to build and repair tissues. A nutritious diet includes
carbohydrates and fats for energy, and proteins for growth. One important source of fat is______.