Carbohydrate:
Carbohydrates (sugar and starches) are the most efficient sources of energy and are known as the “fuel of life.” They are abundantly found in most plant food sources. Complex carbohydrates (starches) are in breads, cereals, pasta, rice, dry beans and peas, and other vegetables, such as potatoes and corn. Simple carbohydrates are found in sugars, honey, syrup, jam, and many desserts.
Each
gram of carbohydrate yields 4 calories in the process of
its metabolism.
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.
Protein:
Proteins
are the “building blocks” of the body and provide important
required nutritive elements.
Proteins are
needed for
- growth,
maintenance, and replacement of
body cells, and
- they
form hormones and enzymes used to regulate body processes.
Extra
protein is either used to supply energy or is changed into body fat. Found in both the animal and plant
kingdoms, all proteins are composed of amino acids. Some amino acids are
absolutely essential to maintain life and are necessary for repair, growth,
and body development. Of the
approximately 20 amino acids, our body can produce all but nine. These nine
amino acids are termed “essential amino acids.”
We must get them from food, and we need all nine at one time so our body
can use them effectively.
Each gram (g) of protein
yields 4 calories in the process of metabolism.
Fats:
The chief functions of fats are to supply energy and transport fat-soluble vitamins.
Each gram of fat yields 9 calories.
Fats provide the most concentrated source of calories (and, therefore, energy) of all the food nutrients.
Fats are found in both the animal and vegetable kingdoms. Fatty acids and glycerol are the end products of the digestion of fats.
Many fats
act as
- carriers for
the fat-soluble
vitamins A, D,
E, and K.
- a
padding for vital organs, particularly the kidneys, and as subcutaneous
tissue to help conserve body heat.
- Fat
is stored as
adipose (fatty) tissue
to form a
reserve supply in time
of need.
Dietary fats
delay gastric emptying and promote a feeling of
fullness. Excess calories from fats may
produce obesity, the forerunner of arteriosclerosis, hypertension, gallbladder
disease, and diabetes. A diet high in fat, especially saturated fat and cholesterol, contributes
to elevated blood cholesterol levels in many
people.
Minerals:
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 organic compounds.
- Minerals form
an integral part
of basic cell structure and
circulate in body
fluids.
- They also 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.
Vitamins:
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 diseases.
Vitamins are so widely
distributed in food that a properly
prepared normal diet
usually provides an adequate amount
Water:
Water is sometimes
included in a listing of nutrients
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