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NUTRITION |
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Human
Nutrition, study of how food affects the health and
survival of the human body. Human beings require food
to grow, reproduce, and maintain good health. Without
food, our bodies could not stay warm, build or repair
tissue, or maintain a heartbeat. Eating the right foods
can help us avoid certain diseases or recover faster
when illness occurs. These and other important functions
are fueled by chemical substances in our food called
nutrients. Nutrients are classified as carbohydrates,
proteins, fats, vitamins, minerals, and water. |
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we eat a meal, nutrients are released from food
through digestion. Digestion begins in the mouth
by the action of chewing and the chemical activity
of saliva, a watery fluid that contains enzymes,
certain proteins that help break down food.Nutrients
are absorbed from the inside of the small intestine
into the bloodstream and carried to the sites
in the body where they are needed. |
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At
these sites, several chemical reactions occur that ensure
the growth and function of body tissues. The parts of
foods that are not absorbed continue to move down the
intestinal tract and are eliminated from the body as
feces.
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Once
digested, carbohydrates, proteins, and fats
provide the body with the energy it needs to
maintain its many functions. Scientists measure
this energy in kilocalories, the amount of energy
needed to raise 1 kilogram of water 1 degree
Celsius. In nutrition discussions, scientists
use the term calorie instead of kilocalorie
as the standard unit of measure in nutrition.
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ESSENTIAL
NUTRIENTS |
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Nutrients
are classified as essential or nonessential. Nonessential
nutrients are manufactured in the body and do not need
to be obtained from food. Examples include cholesterol,
a fatlike substance present in all animal cells. Essential
nutrients must be obtained from food sources, because
the body either does not produce them or produces them
in amounts too small to maintain growth and health.
Essential nutrients include water, carbohydrates, proteins,
fats, vitamins, and minerals.
An individual needs varying amounts of each essential
nutrient, depending upon such factors as gender and
age. Specific health conditions, such as pregnancy,
breast-feeding, illness, or drug use, make unusual demands
on the body and increase its need for nutrients. Dietary
guidelines, which take many of these factors into account,
provide general guidance in meeting daily nutritional
needs. |
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"Human
Nutrition."Microsoft® Encarta® Encyclopedia
2001. © 1993-2000 Microsoft Corporation. All rights
reserved. |
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