Nutritional Requirements:
Types and Sources of Nutrients
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Nutrition

The science of food and
how the body uses it in
health and disease
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Essential Nutrients
1.
2.
3.
4.
5.
6.
Proteins
Fats
Carbohydrates
Vitamins
Minerals
Water

In this context,
‘essential’ refers to
nutrients that the body
is unable to
manufacture (or not in
sufficient quantities)

They must be obtained
from the diet
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Essential Nutrients

Necessary for energy

Needed for the building and maintenance
of tissues

Relied upon for the regulation of body
functions
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Energy-Providing Nutrients

Three nutrients provide the body with energy:
Proteins
1.
2.
3.
Fats
Carbohydrates
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Energy Measurements

Energy is expressed in ‘kilocalories’

1 kilocalorie = 1000 calories

Kilocalorie = Calorie (note capital ‘C’)

1 kilocalorie = heat required to raise the temperature of 1kg of
water 1°C

An average person requires approximately 2000 kilocalories per
day
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Calorie Densities of Various Energy Sources
FATS
9 Cal/g
ALCOHOL
7 Cal/g
CARBOHYDRATES
4 Cal/g
PROTEINS
4 Cal/g
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Proteins

Found in every living cell

Act as structural components for:
Muscles
Bones
Blood
Enzymes
Some hormones
Cell membranes
1.
2.
3.
4.
5.
6.
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Proteins

Composed of chains of amino acids

20 commonly recognized amino acids

Nine essential (can not be synthesized) amino
acids
1.
2.
3.
4.
Histidine
Isoleucine
Leucine
Lysine
5.
6.
7.
8.
9.
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Methionine
Phenylalanine
Threonine
Tryptophan
Valine
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Protein

Individual sources of protein are
‘complete’ if they supply all nine essential
amino acids

Complete protein sources include animal
products such as meat, cheese, fish,
eggs, poultry and milk
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Protein

‘Incomplete’ protein sources
include those foods that do not
contain all nine essential amino
acids

Usually from plant sources such
as grains, beans, peas, and nuts

Still good sources of amino acids

Foods must be combined to get
all amino acids (rice and beans
for example)
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Protein

Protein should
comprise 10-15% of
total caloric intake

Protein consumed in
excess of needs is
stored as fat

Inadequate protein
consumption can lead
to muscle wasting
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Fats



Also known as lipids
Concentrated source of energy
Fat serves to
1.
2.
3.
4.
5.
Provide a source of energy
Insulate the body
Cushion organs
Aid the absorption of fat-soluble vitamins
Add flavour and texture to foods
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Fats

Fats in food are mostly triglycerides

Include a glycerol (an alcohol)

Three fatty acid molecules
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Fats

Fats can be classified as
1. Saturated
2. Monounsaturated
3. Polyunsaturated

Based on the degree of saturation or number of
double bonds that exist between carbon atoms

No double bonds = saturated

One double bond = monounsaturated

Two or more double bonds = polyunsaturated
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Saturated Fat
Monounsaturated Fat
Polyunsaturated Fat
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Saturated Fats

Food usually contains more than
one type of fat

The dominant fat determines the
characteristics of the fat

Saturated fats are solid at room
temperature

Saturated fat is found predominantly
in animal products

Saturated fat has also been linked to
cardiovascular disease
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Unsaturated Fats

Monounsaturated and polyunsaturated fats
usually come from plant sources

Unsaturated fat is liquid at room temperature
(oil)

More desirable, not linked to cardiovascular
disease

Unsaturated fats appear to lower blood
cholesterol

Also shown to reduce the risk of heart
disease
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