Transcript Fat - Food a fact of life

Macronutrients
© Food – a fact of life 2009
Extension
Learning objectives
• To understand macronutrients are needed by the
body.
• To know the functions and sources of carbohydrate,
protein and fat.
• To understand the consequences of malnutrition of
carbohydrate, protein and fat.
© Food – a fact of life 2009
Macronutrients
The macronutrients are:
• Carbohydrate;
• Protein;
• Fat.
© Food – a fact of life 2009
Function and sources of carbohydrates
Carbohydrate provides the main source of energy for
the body.
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Further classification of carbohydrate
There are different ways to classify carbohydrate.
One method is into:
1) sugar;
2) carbohydrate.
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Classification of carbohydrates
Sugars
Monosaccharides are the simplest form of
carbohydrate molecules, e.g. glucose, fructose and
galactose.
Disaccharides are formed when two sugar molecules
join together, e.g. sucrose (glucose and fructose),
lactose (glucose and galactose) and maltose (2
molecules of glucose)
Starches
Polysaccharides are made up of many
monosacharides molecules joined together, e.g.
starch, glycogen, cellulose and pectin.
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Another classification systems for sugars
Intrinsic can be described as sugars incorporated into
the cellular structure of foods.
e.g. sugars in whole fruits and vegetables.
Extrinsic sugars can be described as not bound into
cellular structure.
e.g. lactose in dairy products.
Non-milk extrinsic sugars (NMES) are obviously sugars
not bound into cellular structure and also not found in
milk
e.g. honey, fruit juices, table sugar and confectionery
are all examples of foods containing NMES.
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Excessive consumption of carbohydrates
Decrease cholesterol levels
A positive effect is where some forms of complex
carbohydrates may reduce cholesterol which is
beneficial for health.
Increased body weight
When too much carbohydrate is consumed and not
used for energy over an extended period of time, it is
stored as fat. Building up too much fat will increase
body weight.
Increase dental caries
It is important that teeth are brushed twice a day and
sugary foods should be eaten with main meals, rather
than in between snacks to prevent dental caries.
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Lack of carbohydrates
The short term effects of a lack of carbohydrates are
weight loss and lethargy.
Kwashiorkor and Marasmus are two forms of deficiency
disease which can develop in extreme conditions.
These occur where energy and protein are lacking in
the diet over an extended period of time.
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Protein
Protein is needed for growth and repair of the body.
Excess protein can be broken down and used as a
source of energy.
Protein is made up of different combinations of amino
acids. These are the building blocks of protein. Amino
acids are compounds containing carbon, hydrogen,
oxygen, nitrogen and, in some cases, sulphur.
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Indispensable or dispensable?
The human body is able to make most amino acids
itself and these are known as non-essential or
dispensable amino acids.
There are some amino acids that cannot be made by
the body.
They are called indispensible amino acids (IAA) or
sometimes essential amino acids.
It is essential that these are provided in the diet as the
body cannot make them.
© Food – a fact of life 2009
Body needs
Adults only need 8 indispensible amino acids for
growth and repair.
Children need to obtain 10 indispensible amino acids.
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Biological value and complementation
It is not just the amount of protein, but the quality or
biological value of the protein that needs to be
considered.
If a protein contains all the indispensible amino acids it
is said to have a high biological value.
If a protein does not contain all the indispensible
amino acids it is said to have a low biological value.
The amino acid that is in the shortest supply in relation
to need is termed the limiting amino acid.
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High and low biological value
High biological value (HBV) proteins include:
Meat, fish, eggs, cheese, and milk.
Low biological value (LBV) proteins include:
Cereals, pulses, some nuts and vegetables.
In general, animal protein sources have a higher
biological value, than vegetable sources.
Vegetarians and vegans need to eat wisely to ensure
they are getting all the indispensible amino acids.
© Food – a fact of life 2009
Protein complementation
Complementation of low biological value (LBV)
protein sources ensures that all essential amino acids
are consumed.
Amino acids of one protein source can compensate
for the limitations of the other, resulting in a
combination to create a high biological value meal.
© Food – a fact of life 2009
An example of protein complementation
Two foods providing vegetable protein are eaten at a
meal e.g. a cereal (bread) and a pulse (baked
beans).
The amino acids of one protein compensates for the
limitations of the other.
This results in a combination of higher biological value.
© Food – a fact of life 2009
The body’s needs for protein
Babies and children have a high need for protein
because they are growing.
Adolescents need protein for their rapid growth spurt.
Pregnant women need more protein than normal
adults because of the growing baby.
Nursing mothers also need more protein for lactation.
© Food – a fact of life 2009
Protein deficiency
Protein deficiency is rare, but there is a condition
called PEM – protein energy malnutrition. This can be
seen in infants with stunted growth or thin arms and
legs, and large distended abdomens.
Marasmus - this condition mainly affects infants
causing them to become thin and weak. The body
adapts to the shortage of energy and nutrients. All
energy stores are depleted as it is used to supply vital
organs.
Kwashiorkor - this condition is known to be the body’s
adaption to shortage of energy and nutrients.
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Fat
Fat performs many functions in the body.
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A concentrated source of energy.
Surrounds and protects body organs.
Forms an insulating layer keeping us warm.
Provides fat soluble vitamins.
Fatty Acid 1
Fat is made up of
fatty acids and glycerol.
Fatty Acid 2
Fatty Acid 3
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Glycerol
Essential fatty acids
The body can make most fatty acids.
Essential fatty acids (EFA) are required for important
functions in the body. These must be provided by the
diet because our bodies cannot make them.
Foods which provide fat contain a mixture of fatty
acids but usually one type of a fatty acid.
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Sources of saturated and unsaturated fats
Saturated fat
Meat, coconut oil, palm oil, cakes and biscuits, lard.
Unsaturated fat
Mono unsaturated fat
Rapeseed oil, avocado and olive oil.
Polyunsaturated fat
Oily fish, sunflower oil and pine nuts.
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Over consumption of fat
Eating too much saturated fat has become a problem
in our society.
There are many health problems linked with too much
saturated fat in the diet, e.g. coronary heart disease,
and strokes.
© Food – a fact of life 2009
Review of the learning objectives
• To understand macronutrients are needed by the
body.
• To know the functions and sources of carbohydrate,
protein and fat.
• To understand the consequences of malnutrition of
carbohydrate, protein and fat.
© Food – a fact of life 2009
For more information visit
www.foodafactoflife.org.uk
© Food – a fact of life 2009