broken down and released as glucose at the exact rate
needed by the body.
This latter mechanism is
controlled largely by insulin from the pancreas.
During fasting, liver glycogen is rapidly depleted,
leading the body to use its fat for energy.
hydrates that are not needed for energy are converted to
and stored as adipose (fat) tissue.
The main functions of carbohydrates are to
furnish the main source of energy for
muscular work and nutritive processes,
help maintain body temperature,
form reserve fuel,
assist in oxidation of fats, and
spare protein for growth and repair.
Although mineral elements constitute only a small
portion of the total body weight, they enter into the
activities of the body to a much greater degree than
their weight would indicate. Certain mineral elements
are essential for specific body functions. While it is not
yet known exactly how many of the mineral elements
are indispensable to the body functions, seemingly
small changes of mineral concentration can be fatal.
These essential inorganic elements contribute
overwhelmingly to the skeletal framework of the body
and teeth, and they are an essential part of many
Minerals form an integral part of basic cell
structure and circulate in body fluids.
exercise specific physiologic influences on the
function of body tissues. For mineral needs to be met
satisfactorily, consumption of each element must be
sufficient to cover body tissue requirements and to
meet changing physiological needs. At one time, it
was erroneously believed that any diet adequate in
other respects would also provide an adequate intake
of essential minerals.
This is not so.
greatly in their mineralas well as their overall
nutritionalcontent, depending on growing
conditions, storage, and preparation procedures.
Among the major minerals are calcium, phosphorus,
iron, potassium, zinc, and magnesium. Table 91 lists
the essential elements, the foods that contain them, and
Vitamins are essential compounds that are present
in food in minute quantities. Although vitamins do not
furnish energy or act as tissue-building materials, they
do act as catalysts in many body chemical reactions
and are necessary for normal metabolic functions,
growth, and the health of the human body. Their
absence results in malnutrition and specific deficiency
Vitamin chemistry is complex and
nutritional experimentation is difficult, so our
knowledge of them is being continually supplemented
It is quite possible that additional
vitamins will be discovered or that some of those
already recognized may prove to contain more than
Vitamins are so widely distributed in food that a
properly prepared normal diet usually provides an
adequate amount. Vitamins can be destroyed during
the preparation or preservation of certain foods;
however, manufacturers frequently add vitamins to
their products to replace those destroyed or removed in
processing. Since fat-soluble vitamins can be stored in
the body, it is possible to develop hypervitaminosis by
consuming excessive amounts of these nutrients, and
death may result in extreme cases.
vitamins include A, D, E, and K.
Vitamin A is involved in the formation and
maintenance of healthy skin, hair, and mucous
membranes. Vitamin A helps us to see in dim
light and is necessary for proper bone growth,
tooth development, and reproduction.
sources of vitamin A include yellow, orange, and
dark green vegetables; fruits; and liver, eggs,
cheese, butter, and milk.
Vitamin D promotes calcium and phosphorus
absorption and is required for the formation of
healthy bones and teeth. Good sources include
fortified milk, egg yolk, liver, tuna, and cod liver
Vitamin D is produced in the body on
exposure to sunlight.
Vitamin E protects vitamin A and essential fatty
acids from oxidation in the body cells and
prevents breakdown of body tissues.
sources include vegetable oils, fortified cereals,
whole-grain cereals and bread, nuts, wheat
germ, and green leafy vegetables.
Vitamin K includes a group of vitamins that
promote normal clotting of the blood and helps
maintain normal liver functions. Good sources