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.
Proteins, which promote tissue growth and
renewal, have long been recognized as the main
structural unit of all living cells. Each gram (g) of
protein yields 4 calories in the process of metabolism.
Although proteins yield energy, they are an expensive
source. If sufficient carbohydrates are not supplied,
the body will use protein for energy requirements.
This protein may be obtained from muscle tissue,
producing the wasting effect of long-term starvation
and some diseases.
A constant protein source is required in the daily
diet. The normal daily protein intake for adults should
be 0.8 gram per kilogram (g/kg) (2.2 lbs) of body
weight, or 12 percent of the total caloric intake.
Pregnant women require an additional 10 grams of
protein a day over the normal daily intake.
Proteins play an important role in recovering from
fractures, burns, and infections.
They are also
important in healing wounds and recovering from
surgical procedures. In cases of recovery, protein
intake should be increased in accordance with the
severity of the condition, and carbohydrates and fats
can be added liberally. While proteins can supply
energy, they are not a main source of energy like
carbohydrates and fat.
Ideally, the patient should receive protein by
mouth; however, it is sometimes necessary to meet the
minimum requirements parenterally.
parenteral solution, given during an acute emergency
period, will prevent some loss of protein. Protein
deficiency may stunt growth, promote a secondary
anemia, or induce nutritional edema. Dietary sources
of protein and the nine essential amino acids are milk,
yogurt, eggs, meats, fish, cheese, poultry, peanut
butter, legumes, and nuts. Protein from plant sources is
best when combined with animal protein, such as milk
plus peanut butter, or when legumes are combined with
grains, such as Navy beans plus rice.
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
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. They also act both as 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. Adults over the age
of 30 should have a serum cholesterol level of less than
200 mg/dl. Health experts agree that less than 30
percent of our total calories per day should come from
fat. Saturated fat intake should be no more than 10
percent of the total calories.
Reducing dietary fat is also a good way to limit
calories. Decreased fat intake results in fewer calories
without a reduction of most nutrients. Too little fat in
the diet may lead to being underweight, having
insufficient padding for the vital organs, and lowered
energy. Butter, margarine, cream cheese, fatty meats,
whole milk, olives, avocados, egg yolks, nuts,
commercial bakery products, and vegetable oils are all
sources of dietary fat.
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
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. The new nutritional guidelines
established by the Food and Drug Administration
(FDA) recommend that complex carbohydrates and
naturally occurring sugars (found primarily in fruit)
make up approximately 50 percent of ones total
caloric intake. The FDA also recommends that refined
and processed sugars make up no more than 10 percent
of the calories in ones diet.
Each gram of carbohydrate yields 4 calories in the
process of its metabolism. Carbohydrates must be
reduced to glucose before the body can use them.
Carbohydrates are stored in the muscles to fuel their
movement, and in the liver as glycogen, which is then