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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. Proteins

2. Fats

3. Carbohydrates

4. Vitamins

5. Minerals

6. 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:

1. Proteins

2. Fats

3. 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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FATS 9 Cal/g

ALCOHOL 7 Cal/g

CARBOHYDRATES 4 Cal/g

PROTEINS 4 Cal/g

Calorie Densities of Various Energy Sources

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Proteins Found in every living cell

Act as structural components for:

1. Muscles

2. Bones

3. Blood

4. Enzymes

5. Some hormones

6. Cell membranes

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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. Histidine2. Isoleucine3. Leucine4. Lysine

5. Methionine6. Phenylalanine7. Threonine8. Tryptophan9. 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. Provide a source of energy

2. Insulate the body

3. Cushion organs

4. Aid the absorption of fat-soluble vitamins

5. 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. Saturated2. Monounsaturated3. 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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