HUMAN NUTRITION
Nutrition is the taking in of nutrients which
include organic substances and ions, containing raw materials or energy for
growth and tissue repair, and then absorbing and assimilating them. A balanced
diet should consist of all six nutrients including fiber. These nutrients
should be in reasonable proportions. The total energy content of the food
should be about the same as the total energy the person uses each day. Energy
is measured in kilojoules.
Humans need the following nutrients:
- Carbohydrates
-
Fats
-
Proteins
-
Vitamins
-
Minerals
-
Water
Why do humans need
nutrients?
1.
Energy
2.
Building
materials to build the cells in our body
3.
To
provide us with chemicals used to help metabolic reactions
Carbohydrates
The carbohydrates with the smallest and
simplest molecules are sugars. A sugar molecule contains three elements –
carbon, hydrogen and oxygen. Glucose is an example of a simple sugar (monosaccharide)
meaning it is made up of a single ring of carbon atoms. Complex sugars
(disaccharides) are sugars with bigger molecules made up of two rings joined
together. Sugar molecules can link together to form huge molecules made up of
chains of hundreds of sugars. These big molecules are known as polysaccharides
and include starch, glycogen and cellulose.
Carbohydrates provide us with energy. The
carbohydrate molecules that we eat are taken into every cell in our bodies in
the form of glucose. Inside these cells the energy in the glucose is released
and changed into a form that our cells can use. This process is called
respiration.
Proteins are made up of many small molecules
called amino acids. Amino acids contain five elements. These are carbon,
hydrogen, oxygen, nitrogen and sometimes sulfur.
Proteins are needed to build new cells so they
are important for growth and repair. They build new tissues, antibodies,
enzymes, hormones and other compounds.
Fats
Fats are sometimes known as lipids. Fats that
are liquid at room temperature are known as oils. A fat molecule is made up of
two kinds of smaller molecules – glycerol and fatty acids. Like carbohydrates,
fats contain carbon, hydrogen and oxygen. 
Fat is needed for energy and for making cell
membranes. Fat is especially useful for energy as it contains twice as much
energy per gram as carbohydrates. The stored fat underneath your skin is useful
as heat insulation.
Saturated fats are found in animal products and processed foods, such
as meats, dairy products and chips. The chemical structure of a saturated fat
is fully saturated with hydrogen atoms, and does not contain double bonds
between carbon atoms. They are bad for your heart.
Unsaturated fats, on the other hand, are found foods such as
nuts, avocados, and olives. They are liquid at room temperature and differ from
saturated fats in that their chemical structure contains double bonds.
Additionally, studies have shown that unsaturated fats are also heart-healthy
fats.
Vitamins
Vitamins are organic substances that we need in
only very small amounts to help some of the chemical reactions inside our cells
take place. For example vitamin C and vitamin D. Vitamin C acts as an antioxidant, helping to protect cells from the damage caused
by free radicals. Vitamin D is needed for health and to maintain strong bones.
It does so by helping
the body absorb calcium from food and supplements.
Minerals
This
means that minerals are needed for the body to work properly, for growth and
development, and overall, for maintaining normal health. For example iron and calcium.
Iron is needed for making hemoglobin. Hemoglobin carries oxygen around our
bodies. Calcium is required for making teeth and bones as well as to help blood
clot.
Water
Fiber
Fiber is needed in our diet as well however it
is not considered as a nutrient. Fiber normalizes bowel movements, helps
maintain bowel health, lowers cholesterol levels and helps control blood sugar
levels. Insufficient amounts of fiber can lead to constipation. A
good example of food high in fiber are lentils.
Food tests
Deficiency diseases
Name
|
Lack of
|
Symptoms
|
|
Scurvy
|
Vitamin C
|
Bad gums (teeth can fall out), fatigue,
pain in joints
|
|
Rickets
|
Vitamin D and calcium
|
Delayed growth, muscle weakness,
pain in spine, pelvis and legs
|
|
Anemia
|
Iron
|
Fatigue, headaches, shortness of
breath
|
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