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CHAPTEr 3
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WHY IS THIS IMPOrTANT?
Nutrition is one of the most important factors affecting
the health and individual human development of
Australia’s youth. Adequate nutrition is required for many
aspects of youth development. Nutrition has a direct
relationship to aspects of individual human development
such as bone and organ development. It also affects
development indirectly by, for example, providing energy
that allows the youth to concentrate at school, thereby
promoting intellectual development. In recent decades,
the nutritional status of Australia’s youth has declined and
is contributing to health and developmental issues. To
develop a deep knowledge of these issues, it is important
to learn about the nutrients, the roles they play in
optimising health and development, and the short- and
long-term consequences of nutritional imbalance. A range
of food selection models exist to assist youth in food
selection. Understanding these models can assist youth
in achieving a balanced nutrient intake and in achieving
optimal health and individual human development.
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Nutrition
during youth
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KEY KNOWLEDGE
2.1 the function of major nutrients for the development of hard tissue,
soft tissue, blood tissue and energy (pages 74–94)
2.2 the consequence of nutritional imbalance in a youth’s diet on shortand long-term health and individual human development (pages 95–8)
2.3 food selection models as tools to promote healthy eating during
youth (pages 99–104).
KEY SKILLS
• explain the functions of major nutrients for the development of hard
tissue, soft tissue, blood tissue and energy during youth
• explain the possible consequences of nutritional imbalance in a
youth’s diet on short- and long-term health and individual human
development
• explain how food models can be used as a tool to promote health.
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FIgUrE 3.1 As youths gain
independence, their food choices
become particularly important for
future health and development.
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KEY TERM DEFINITIONS
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anaemia a condition characterised by a reduced ability of the
body to deliver enough oxygen to the cells due to a lack of
healthy red blood cells
basal metabolic rate (BMR) the amount of energy required to
sustain basic functioning of the human body
bone matrix the structure of bone that allows calcium and
phosphorus to be deposited, therefore making the tissue hard.
The bone matrix consists mainly of collagen.
cartilage connective tissue that protects and cushions the
joints, and provides structure and support to various body tissues
cell differentiation the process in which body cells take on
their specialised function (e.g. skin cells or muscle cells)
cell membrane the outer layer of a cell that provides structural
support for the cell and allows nutrients, gases and waste into
and out of the cell
cellular respiration the process whereby oxygen and fuel are
converted into energy
cholesterol a type of fat required for optimal functioning of
the body that in excess can lead to a range of health concerns
including the blocking of arteries (atherosclerosis). Can be ‘bad’
low-density lipoprotein (LDL) or ‘good’ high-density lipoprotein
(HDL).
co-enzyme usually a vitamin or mineral that binds with protein
to allow chemical reactions such as metabolism to occur
collagen fibrous protein found in connective tissue that is
the main component of cartilage, ligaments, tendons, bone
and skin
connective tissue tissue that is involved in the structure and
support of body cells and systems
dental caries decay of teeth caused by a breakdown in the
tissues making up the tooth
discretionary foods includes foods and drinks not necessary to
provide the nutrients the body needs, but that may add variety.
However, many of these are high in saturated fats, sugars, salt
and/or alcohol, and are therefore described as energy dense.
fortified having a nutrient artificially added to increase
nutritional value
glycaemic index (GI) a scale from 0 to 100 indicating the
effect on blood glucose of foods containing carbohydrates
haemoglobin a component of blood, largely consisting of iron
and protein, that transports oxygen throughout the body
hard tissue tissues in the body that form hard substances such
as bones, teeth and cartilage
kilojoule (kJ) a unit for measuring energy intake or expenditure
macronutrients nutrients that are required in large amounts
(protein, carbohydrates and fats)
micronutrients nutrients that are required in small amounts
(vitamins and minerals)
ossification the process whereby bones are hardened by laying
down the minerals calcium and phosphorus
osteoporosis a condition characterised by a reduction in bone
mass that makes bones more likely to break and fracture
peak bone mass the maximum bone mass (i.e. density and
strength) reached in early adulthood
soft tissue organs and tissues in the body that connect,
support or surround other structures. They include skin, muscles,
tendons, ligaments, collagen and organs.
vegan a type of vegetarianism that excludes foods of animal
origin including eggs and dairy
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3.1
Introduction to the nutrients required during
youth: carbohydrates, protein and fats
KEY CONCEPT Understanding the major nutrients required
during youth
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When we eat, the foods are broken down in the process of digestion to release the
nutrients. These nutrients are then used by the body for many functions related
to health and development including the production of energy and blood and the
development of hard and soft tissues.
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Figure 3.2 Eating a range of foods is the best way to ensure adequate nutrition.
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Some foods have more nutrients in them than others, and some have nutrients
that other foods may not have at all. The best way to maintain a balanced diet is to eat
a wide variety or many different types of foods (figure 3.2). There are six categories
of nutrients that are needed for optimal health and individual human development.
They are:
• carbohydrates (including fibre)
• protein
• fats
• vitamins
• minerals
• water.
Carbohydrates, protein and fats are needed by the body in large amounts and are
often called macronutrients, while vitamins and minerals are called micronutrients
because they are only needed in very small quantities. Regardless of the quantity
needed by the body, each nutrient has a different role to play and all are important
for health and individual development.
Carbohydrates
Interactivity:
Time Out: ‘Food sources of nutrients’
Searchlight ID: int-1423
The main function of carbohydrates is to provide fuel for energy. As youth are
growing at a rapid rate, a lot of energy is required for metabolism and growth. Glucose
is the preferred fuel for energy in the human body and carbohydrates are rich
in glucose, and as a result should provide the majority of an individual’s energy
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needs. Carbohydrates allow an individual to maintain
high activity levels, which can provide opportunities to
develop motor skills and also the energy to concentrate
at school and therefore develop intellectually.
Carbohydrates are broken down and the glucose
molecules are absorbed into the bloodstream, from
where they are taken into the cells and stored, ready
for use. In terms of energy production, one gram of
carbohydrates will produce 16 kJ of energy.
Glucose (and therefore carbohydrates) that is not
used by the body is stored as adipose (or fat) tissue.
If a person eats too much carbohydrate, they can gain
weight because this increases the amount of glucose
stored as fat. This process can be reversed if glucose is
needed by the body.
Most carbohydrates are found in foods of plant origin. Common examples
are vegetable (including potatoes), rice, pasta, most breakfast cereals and fruit
(figure 3.3).
However, carbohydrates are also found in sugar and foods containing added
sugar such as soft drinks, cordial, lollies and chocolate. These foods contain few
other nutrients besides carbohydrates so are not considered to be good food
sources of this nutrient.
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FIgUrE 3.3 Pasta is a good source of
carbohydrates.
Fibre
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Fibre is a type of carbohydrate that is required for the optimal health and individual
human development of youth. Found in all foods of plant origin, fibre does not
get absorbed by the body. Rather, it travels through the digestive system, acting
like a cleaner as it moves. The benefits of fibre in the diet are numerous for youth:
• Fibre acts to reduce the amount of glucose that is absorbed by the digestive
system, thereby reducing the energy provided by the foods eaten. It also provides a feeling of fullness (satiety), so decreases the amount of energy consumed
from other foods. Both of these characteristics of fibre assist
in weight maintenance.
• Fibre reduces the amount of cholesterol that is absorbed
by the body, which reduces the risk of cardiovascular
disease later in life.
• Foods containing fibre are generally high in a range of
vitamins and minerals, which improves overall nutrient
intake. This is particularly important for youth as their
nutritional requirements increase due to the growth they
experience.
• Fibre absorbs water, which adds bulk to the faeces. This
assists in regular bowel movements, which decreases the
chances of becoming constipated.
According to the National Health and Medical Research
Council, youths should be consuming around 22–28 grams
of fibre per day. Examples of foods that contain fibre are:
• 3/4 cup bran flake cereal (4.5 grams of fibre)
• two slices wholemeal bread (4.5 grams of fibre)
• one apple and one orange (5.5 grams of fibre)
• two cups mixed raw vegetables (10 grams of fibre)
• 1/4 cup baked beans (3 grams of fibre).
As fibre absorbs water, increased fibre intake should be
accompanied by increased water consumption.
FIgUrE 3.4 Grains and seeds are an
excellent source of fibre.
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3.1 Introduction to the nutrients required during youth: carbohydrates, protein and fats
Protein
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Protein has two main functions in the body. Its main function (and probably the
most important for youth development) is to build, maintain and repair body cells.
This includes the cells required to build soft tissues such as muscles and organs,
hard tissue such as bone and the production of blood tissue (figure 3.5). The second
function of protein is to act as a fuel for producing
energy. If a person does not have enough glucose
(from carbohydrates) to use for energy production,
protein can be used as a secondary source of energy.
In times of starvation, muscle and other body cells
may be broken down so the protein contained within
them can be used for energy. Protein yields about
17 kJ per gram when being used for energy. If eaten in
excess, protein may be stored as adipose or fat tissue
and can contribute to obesity in the long term.
Protein is made up of smaller building blocks
called amino acids. There are 20 different types of
amino acids that humans need to function properly.
Eleven of these, called the non-essential amino acids,
can be synthesised (or made) in the body from other
amino acids. The other nine, called essential amino
acids, cannot be synthesised in the body and must
therefore be consumed (figure 3.8). To ensure that
all amino acids are being consumed regularly, protein
Figure 3.5 Protein is a key component of all body tissues, like these
from a range of different sources should be eaten.
muscle fibres.
Many people get much of their protein requirements
from meat, which is often rich in essential amino acids. Vegetarians must ensure
they consume a large variety of non-meat protein sources to ensure that their
nutritional needs are being met. These foods include nuts, beans, lentils and tofu.
Some food sources are termed ‘complete proteins’ because they contain all the
essential amino acids in the quantities required for individual human development.
They are usually found in vast amounts in animal products (figure 3.6). Some
proteins can also be found in many foods of plant origin (figure 3.7). These are
usually incomplete proteins and need to be eaten with other protein sources to
ensure that all required amino acids are consumed.
Protein content of selected foods
of animal origin (g of protein
per 100 g of food item)
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Protein content of selected foods
of plant origin (g of protein
per 100 g of food item)
Beef
Pork
Tuna
Chicken (thigh)
Salmon
Cheddar cheese
Lamb
Chicken breast
Egg
Milk
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Pumpkin seeds
Peanut butter
Almonds
Pistachios
Tofu
Oats
Cashews
Hazelnuts
Lentils
Wheat bread
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20
30
g per 100 g
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Figure 3.6 The protein content of selected
foods of animal origin
0
10
20
30
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g per 100 g
Figure 3.7 The protein content of selected
foods of plant origin
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Protein
Non-essential
amino acids
Can be made in the
body from essential
amino acids
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Incomplete proteins
Do not contain all
essential amino acids
FIgUrE 3.8 Proteins can be classified
as essential and non-essential amino
acids.
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Complete proteins
Contain all essential
amino acids
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Essential amino
acids
Fats
Fats (lipids)
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Fats (sometimes referred to as lipids) play a number of roles in youth health and
individual human development. Although fats are often associated with negative
effects on the body, they are required for adequate health and development
throughout the lifespan and are an essential part of a balanced food intake.
Like carbohydrates, the main function of fats is to act as a fuel for energy. Fats
are a richer source of energy than carbohydrates and protein, yielding 37 kJ per
gram. This is why foods packed with fat but little else are referred to as ‘energy
dense’ foods. How much fat to include in the diet should be determined by the
amount of energy required by the individual. Balance is the key here. Remember
that most of an individual’s energy should come from carbohydrates.
Fats are required for a number of other processes including the development and
maintenance of cell membranes. Cell membranes form an important component of
body cells and therefore blood and soft tissues. They are responsible for maintaining
the structure of cells and allowing the transport of nutrients, gases and waste into
and out of cells. Fats are a key component of the cell membrane and are required
throughout life for adequate cell function.
Fats are an important part of a balanced diet for youths, but there are different
types of fats and some are healthier than others (see figure 3.9). Some fats can
actually lead to poor health and should be kept to a minimum in the diet.
Monounsaturated
Omega-3
Polyunsaturated
Saturated
Trans
Omega-6
FIgUrE 3.9 There are four
different categories of fats.
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3.1 Introduction to the nutrients required during youth: carbohydrates, protein and fats
Interactivity:
Time Out: ‘Which fat?’
Searchlight ID: int-1424
Based on their chemical make-up, fats can be classified into four broad categories:
monounsaturated, polyunsaturated, saturated and trans fats. Total fat intake should
account for around 25 per cent of the total energy requirement (with carbohydrates
and protein making up the other 75 per cent). Of this 25 per cent, the majority should
come from monounsaturated fats. Approximate recommended percentages of total
energy intake from the different types of macronutrients are shown in figure 3.10.
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Fats 25%
Monounsaturated
10%
Polyunsaturated
5%
Saturated 9%
Trans fats 1%
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Carbohydrates 55%
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Protein 20%
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FIgUrE 3.10 Macronutrients (with a breakdown of fats), and the average percentage of
total energy intake each should make up (approximate values only)
Monounsaturated and polyunsaturated fat
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Monounsaturated and polyunsaturated fats are considered the ‘good fats’. They
carry out the necessary functions of fats and also have some health benefits such
as reducing levels of cholesterol and promoting the health of the heart and blood
vessels. The greatest health and development gains for youth can be achieved by
replacing saturated and trans fats with monounsaturated and polyunsaturated
fats. This can help reduce the risk of diet-related diseases later in life, such as
heart disease. Because all fats contain 37 kJ of energy per gram, the total fat intake
should not increase because all types will lead to weight gain and the associated
effects on health if eaten in excess.
FIgUrE 3.11 Nuts are a great source
of the ‘good’ fats.
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Monounsaturated fats are liquid at room temperature and begin to solidify if
placed in the refrigerator. Foods rich in monounsaturated fats include olive oil,
avocado, canola oil and canola-based margarine, nuts such as peanuts, hazelnuts,
cashews and almonds, peanut butter and other nut butters.
There are two main categories of polyunsaturated fats: omega-3 and omega-6.
Polyunsaturated fats are generally liquid at room temperature and when refrigerated.
Food sources for these fats include:
• omega-3 — fish (particularly oily fish such as mackerel, trout, sardines, tuna
and salmon), canola and soy oils, and canola-based margarines
• omega-6 — mainly nuts such as walnuts and Brazil nuts, seeds and oil made
from corn, safflower and soy.
Many people in Western countries consume too many omega-6 fats which, like
all fats, can increase the risk of obesity and associated conditions including heart
disease.
Saturated and trans fats
Figure 3.12 Fats that come from
animals and are solid at room
temperature are normally saturated.
This pork fat is one example.
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Saturated and trans fats are sometimes known as ‘bad fats’
because they increase cholesterol levels in the blood and
can therefore contribute to heart disease in the long term.
Although consuming saturated and trans fats will satisfy the
energy and other requirements provided by other types of
fats, they should be replaced where possible.
Saturated fats are generally found in foods of animal origin
(figure 3.12) and are often solid at room temperature. You
can see saturated fat in fatty cuts of meat as the marbling
throughout the meat or the fat that forms along the ends
of cuts of red meat. Other foods containing high levels of
saturated fat include full-cream milk, cream and cheese,
some fried takeaway food, and most commercially baked
goods such as pastries and biscuits.
Although small amounts of trans fats are found naturally in certain foods, most
trans fats are created when liquid oil is converted into solid fat by a process
called hydrogenation. For this reason, they are generally found in processed
foods such as pies, pastries and cakes (figure 3.13). Margarines and solid spreads
made for cooking are sometimes high in trans fats, as are the products made
from them.
Figure 3.13 Trans fats are often
present in baked goods such as
doughnuts, biscuits and cakes.
Nutrition during youth • CHAPTER 3 87
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3.1 Introduction to the nutrients required during youth: carbohydrates, protein and fats
APPLY your knowledge
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10 Explain how eating insufficient carbohydrates could
affect the physical, social, emotional and intellectual
development of youth.
11 Discuss the possible short- and long-term effects on
a youth who does not consume adequate amounts
of fibre.
12 Using mind mapping software, or by copying
figure 3.14, complete a mind map summarising
information relating to the functions and food
sources of carbohydrates, including fibre.
13 Create a table that summarises the health and
individual human development impacts of
carbohydrates (including fibre), protein and fat.
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1 What are the six categories of nutrients?
2 List the main function of carbohydrates.
3 How much energy does one gram of carbohydrate
produce?
4 Outline the main functions of fibre.
5 Does fibre contribute to energy intake? Explain.
6 (a) What is the main function of protein?
(b) How can protein enhance the physical
development of youth?
7 (a) Is fat required in the diet? Explain.
(b) Which fats are considered the ‘good’ fats? Why?
(c) Which fats are considered the ‘bad’ fats? Why?
8 Why should overall fat intake be limited?
9 (a) What percentage of energy should come from
each of the macronutrients?
(b) Explain why most of our energy needs should
come from carbohydrates instead of fats and
protein.
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TEST your knowledge
Function
Functions
Fibre
Carbohydrates
Food sources
FIgUrE 3.14 Concept map summarising the functions and food sources of carbohydrates
(including fibre)
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Food sources
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3.2
Introduction to the nutrients required
during youth: water, calcium and iron
KEY CONCEPT Understanding the major nutrients required
during youth
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Although it has no nutritional value, water is the most important nutrient for
human survival. Water makes up around 55 to 75 per cent of body mass and is
needed for numerous functions within the body, including:
• as a medium for all chemical reactions required to provide energy and produce
soft tissue
• as a key component of many cells, tissues and systems
• as a key component of blood.
Being adequately hydrated allows chemical reactions in the body to occur
effectively, which is important for periods of rapid development such as the youth
stage of the lifespan. Sufficient water intake allows the body’s systems to function
adequately and the body as a whole to function properly. This means an individual
can effectively go about their day-to-day activities. Water intake can also assist in
weight maintenance as it helps to reduce hunger while contributing no kilojoules
or energy. When dehydrated, a person will often lack alertness and the ability to
concentrate. They may not have the energy to participate in physical activities,
which can impact on motor skill development. They may not be able to concentrate
at school, which can directly impact on intellectual development.
All foods have some water content (figure 3.15) and contribute to total water
intake, as do fluids such as milk. Water should also be consumed in its pure form
(i.e. from the tap or in bottled form) to meet hydration needs. Although they
contain a large percentage of water, softdrinks and sports drinks often contain high
amounts of sugar and other additives, so their consumption should be limited.
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Water
Figure 3.15 Foods such as fruits and
vegetables have a high water content,
but water should also be consumed in
its pure form.
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3.2 Introduction to the nutrients required during youth: water, calcium and iron
Calcium
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Figure 3.16 Changes in bone mass
with age
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Bone mass
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Calcium is one of the key nutrients required for the building of bone and other
hard tissues (such as teeth and cartilage) and is therefore extremely important
during periods of rapid growth such as during youth.
The youth stage signifies the greatest increase in bone density and contributes
significantly to achieving optimal peak bone mass. It is therefore vital that youth
get enough calcium during these years to build as much bone density as possible.
The greater the bone density during this stage, the less chance the individual will
have of developing osteoporosis later in life (figure 3.16).
Calcium is found in most dairy products (figure 3.17). Milk, cheese and yogurt
are all rich sources of calcium. Other sources include sardines and salmon (with
bones), green leafy vegetables (broccoli, spinach), fortified soy milk, tofu made
with calcium sulfate and fortified
Men
orange juice.
Women
Oxalic acid is present in
spinach and binds to the calcium
molecules, preventing all of the
calcium from being absorbed.
In fact, if oxalic acid is present
when calcium is eaten, only 5 per
cent of the available calcium may
be absorbed. For this reason, it
is important to obtain calcium
from other sources as well, such
20
40
60
80
100
as dairy (which does not contain
Age (in years)
oxalic acid).
Figure 3.17 Dairy products such as milk are a rich source of calcium and help to build peak
bone mass.
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Case study
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When Tracy Spark’s daughter shed 15 kilograms in four
months her mother knew something was drastically
wrong.
The teenager’s school results had gone downhill
because she couldn’t concentrate, her hair had begun to
fall out and she was icy to touch.
The physical effects of anorexia were shocking, but
it was only when routine blood tests were carried out
during treatment that Ms Spark learnt the full horror
of what was happening to her daughter, then 14, on the
inside.
Tests showed the girl’s bones were being leached
of calcium to feed a body deprived of the essential
mineral.
‘At a time when she should have been laying down
calcium in her bones for later on, her body was actually
taking calcium out of her bones to survive,’ Ms Spark
said.
‘I work in the field and I was lost. I assumed eating
disorders were an issue when you became skeletal.
I didn’t realise people get very ill a long time before
they get to that stage.’
On the eve of National Healthy Bones Week,
Ms Spark, now a nutrition coordinator for Healthy
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By Angela Thompson
Cities Illawarra, is telling her daughter’s story in the
hope it will help arrest a worrying trend towards poor
nutrition among a body image-conscious generation of
adolescent girls.
According to Wollongong nutritionist Anita
Needham, those who fail to achieve peak bone
mass during adolescence are more likely to develop
osteoporosis.
‘While we’re young it’s good to stockpile the calcium
we get from dairy products so that you offset the effect
of ageing on bone loss and therefore you reduce the
risk of osteoporosis,’ she said.
‘Unfortunately many people exclude dairy foods
when trying to lose weight, and in doing so miss out
on valuable sources of calcium and other essential
nutrients.’
‘Recent clinical studies show that including three
dairy serves in a weight-reducing diet may in fact result
in more weight and body fat loss,’ she said.
At the Sparks household, it was a lesson learnt the
hard way.
‘She does focus on eating healthily now,’ Ms Sparks
said of her daughter, who did not want to be named.
‘I’m a big believer in your body knowing what it
needs and she absolutely adores dairy food.’
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Strong bones key to health
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Case study review
Source: Illawarra Mercury, 2 August 2008.
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Iron
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1 How was the development of Ms Sparks’ daughter affected by not consuming
enough calcium?
2 Why do a lot of people cut dairy products out of their diet?
3 Explain why getting adequate calcium in the diet is very important during the
youth stage of the lifespan.
Iron is an essential part of blood. As blood volume increases during
youth, iron is needed in greater quantities (figure 3.18).
Iron forms the ‘haem’ part of haemoglobin, which is the oxygencarrying part of blood. A person who does not get enough iron
may develop anaemia, a condition characterised by tiredness and
weakness. Individuals with anaemia struggle to generate enough
energy to complete daily tasks such as school work, sport and
socialising.
Red meat is a rich source of iron but it often contains high
levels of saturated fat. As a result, leans cuts of meat should be
chosen and iron should also be gained from other sources. A
balanced, varied diet is the best way to get adequate amounts of
iron.
Figure 3.18 As blood volume increases during the
youth stage of the lifespan, iron is required in higher
amounts to make red blood cells.
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3.2 Introduction to the nutrients required during youth: water, calcium and iron
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Foods providing iron include:
• lean red meat
• turkey and chicken
• fish, particularly oily fish (e.g. mackerel, sardines and pilchards), fresh, frozen
or canned
• eggs
• nuts (including peanut butter) and seeds
• brown rice
• tofu
• bread, especially wholemeal or brown bread
• leafy green vegetables, especially curly kale, watercress and broccoli.
Iron from meat is usually absorbed best, although vegetarians can still get enough
iron if they eat a variety of foods. Vitamin C changes the chemical make-up of
iron from non-meat sources and increases the amount absorbed. Vitamin C should
therefore be eaten if iron absorption needs to be maximised.
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Anaemia is a condition characterised by a deficiency in
the number or quality of red blood cells.
Red blood cells are responsible for transporting
oxygen to cells around the body to allow them to carry
out their normal functions. One of the components
of red blood cells is a protein called haemoglobin.
Each red blood cell contains a haemoglobin molecule
and it is this molecule that gives red blood cells their
red colour. When transported to the lungs, oxygen
molecules attach themselves to the haemoglobin and
are carried through the network of blood vessels until
they are absorbed by a cell.
Anaemia occurs when there is a reduced level of red
blood cells or haemoglobin in the blood.
In those with anaemia, the heart pumps harder in
an attempt to ensure adequate levels of oxygen are
delivered to the cells. During exercise, meeting the
demands of the cells becomes increasingly difficult and
the individual can become exhausted.
Anaemia isn’t a disease itself, but the result of a
malfunction somewhere in the body. Females are
particularly susceptible to anaemia, with some estimates
suggesting that around one in five menstruating females
and half of all pregnant females are anaemic. Youth
experiencing puberty are also at an increased risk as
blood volume increases, which increases the demand
for red blood cells and haemoglobin.
How are blood cells produced?
Blood cells are constantly being produced in the
bone marrow, at a rate of millions per second. Bone
marrow is a spongy tissue in the cavities of bones that
is responsible for generating the key components of
blood, including red blood cells. Bone marrow requires
certain nutrients, including iron, folate and vitamin
B12, to be able to create red blood cells.
In Australia, iron deficiency is one of the most
common causes of anaemia. If there is not enough iron
in the diet, the body will use stored supplies from the
liver. Once this reserve is used up, the bone marrow
will not be able to make enough haemoglobin and
anaemia may result.
PA
G
A close up on anaemia
E
Case study
What causes anaemia?
Anaemia can have many causes, and although
commonly associated with a deficiency in iron, folate
and/or vitamin B12, anaemia can also occur as the
result of:
• malabsorption — this occurs when the nutrients
that are consumed are not able to be used. It can be
caused by conditions such as coeliac disease.
• inherited disorders — some blood disorders such as
thalassaemia and sickle cell disease can be inherited
from parents and can lead to anaemia
• chronic conditions — conditions such as
rheumatoid arthritis and tuberculosis can contribute
to anaemia
• bone marrow conditions — such as cancer or
infection
• blood loss — due to injury, surgery, cancer, stomach
ulcers, heavy periods or giving blood frequently
• rapid growth or times during which large amounts
of energy are required — such as puberty or while
pregnant.
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PR
O
O
FS
How can anaemia be prevented?
Anaemia caused by deficiencies in dietary intake can
be prevented by making sure that certain foods are
consumed on a regular basis, including lean meats, nuts
and legumes, fruit and vegetables and dairy products.
Those who do not consume any animal products (known
as vegans) may have to increase their intake with
fortified foods or vitamin and mineral supplements.
Anaemia caused by an underlying health condition
may not be able to be prevented as it is caused by a fault
in the cell-making process. Treatments are available to
relieve the symptoms in these cases.
PA
G
How is anaemia treated?
Treatment for anaemia depends on the severity and the
cause of the condition. In any case, the cause must be
addressed in addition to treating the symptoms.
Vitamin and mineral supplements may be required
in the case of dietary deficiency. Iron injections may
be required if iron levels are particularly low. Note
that iron supplements should be used only under the
direction of a doctor. The human body does not excrete
iron efficiently, which can contribute to iron poisoning
if the dose is not monitored.
E
What are the symptoms of anaemia?
Depending on the severity, the symptoms of anaemia
can include:
• pale skin
• tiredness
• weakness
• shortness of breath
• blood pressure drops on standing up suddenly —
sometimes caused by blood loss, such as during a
heavy menstrual period
• headaches
• fast pulse
• irritability
• difficulty concentrating
• cracks or redness of the tongue
• appetite loss
• strange food cravings (including the desire to eat dirt
or rice, a condition known as pica).
TE
D
Case study review
Source: Adapted from www.betterhealth.vic.gov.au.
O
R
R
EC
1 Briefly explain anaemia.
2 Discuss haemoglobin and the role it plays in the body.
3 How might someone know if they are anaemic?
4 Research the blood disorders that can cause anaemia and prepare a brief
summary of each.
5 Explain how anaemia could impact on the health and development of youth.
6 Discuss why female youth are more susceptible to anaemia than male youth.
7 Discuss why youth is a higher risk lifespan stage for anaemia than adulthood.
C
TEST your knowledge
U
N
1 (a) List three functions of water.
(b) Why would it be a good idea to replace most
drinks with plain water?
2 Why is calcium required in the body?
3 (a)List three foods that contain high levels of
calcium.
(b) Even though spinach has a lot of calcium, it is
not considered the best food source of dietary
calcium. Explain why this is so.
4 Describe the role of iron in the body.
5 Why is iron required in greater amounts during the
youth stage of the lifespan?
6 Refer to figure 3.16.
(a) Identify two trends evident in the graph.
(b) Use the graph to help you explain a possible
difference in health outcomes between males
and females in older age.
APPLY your knowledge
7 Explain how being dehydrated could affect the four
dimensions of development in youth.
8 List the likely symptoms of not getting enough
calcium.
9 Which other stages of the lifespan would require
higher rates of:
(a)calcium?
(b)iron?
Nutrition during youth • CHAPTER 3 93
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3.3
Introduction to the nutrients required
during youth: vitamins A, B, C and D
KEY CONCEPT Understanding the major nutrients required during youth
Vitamin A
FS
Vitamin A is required for cell division and is therefore an important aspect of any
growth that occurs in the body. There are many aspects of physical development
that involve growth during the youth stage of the lifespan, so requirements for
vitamin A increase at this time. Skin, muscle, organ, bone
and blood cells all divide rapidly during youth and therefore
require vitamin A.
Vitamin A also plays a role in cell differentiation. Due to
the rapid speed of growth during youth, cell differentiation
occurs at a rapid rate and contributes to the increased need for
this vitamin. Vitamin A has also been shown to promote the
development of bones.
Vitamin A assists with the development of immune system
function by promoting mucus development in the lungs and
airways. This lining of mucus is a defence mechanism against
bacteria and viruses. Vitamin A also helps in the development
of antibodies required to fight infection.
The best sources of Vitamin A can be found in red, yellow
and orange coloured fruits and vegetables including raw
carrots, sweet potatoes, squash, spinach and rockmelon
(figure 3.19).
TE
D
PA
G
E
PR
O
O
Interactivity:
Time Out: ‘Vitamins and folate’
Searchlight ID: int-1425
Figure 3.19 Yellow, orange and
red fruit and vegetables are good
sources of vitamin A.
Vitamin D
U
N
C
O
R
R
EC
The main role of vitamin D is in the absorption of calcium from the intestine
into the bloodstream. Lack of vitamin D can lead to low levels of calcium being
absorbed and bones becoming weak.
Most Australians get enough vitamin D from exposure to sunlight (figure 3.20),
during which UV rays are converted to
vitamin D in the skin. However, there
is growing evidence to suggest that
some groups in Australia are deficient in
vitamin D because they rarely go out into
the sun. Youth with dark skin or those
who always cover up when outdoors can
become deficient in vitamin D. While
moderate exposure without any degree
of sunburn is healthy, excessive exposure
leading to sunburn is a major risk factor
for skin cancer and should always be
avoided.
In terms of food sources, fish
(particularly tuna, salmon, mackerel,
sardines and herring) is the best source
of vitamin D. Small amounts can also be
found in beef liver, cheese and egg yolks.
Some brands of milk, breakfast cereals and
orange juice are fortified with vitamin D,
Figure 3.20 Most Australians get enough vitamin D from exposure to sunlight, but
those with restricted access to sunlight might be deficient.
but it is important to check the packaging.
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O
U
N
C
O
R
R
EC
TE
D
PA
G
E
PR
O
Vitamin C is important for the structure of tissues within the body and is required
for building collagen. Collagen is a protein that is required for the formation of
skin, scar tissue, connective tissue, bone, tendons, ligaments, and blood vessels
(figure 3.21). In this role, vitamin C allows the other components of tissues to be
held together.
Vitamin C is important in promoting the absorption of iron and is therefore an
important nutrient in the production of blood.
Humans can neither make their own vitamin C in the body nor store it effectively
(as other animals can do). Therefore, a daily intake of vitamin C is important for
normal individual human development and functioning.
Vitamin C is found in many fruits and vegetables including kiwi fruit, broccoli,
blackcurrants, citrus fruits such as oranges, and strawberries. It is easily destroyed
when exposed to heat and air, so fresh fruit and vegetables provide the best source
of vitamin C.
FS
Vitamin C
Figure 3.21 Collagen is a key component
of these tendons.
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3.3 Introduction to the nutrients required during youth: vitamins A, B, C and D
B-group vitamins
Vitamins B1, B2 and B3
Folate (vitamin B9)
E
Folate is a B-group vitamin that is essential for growth and development. It plays
an important role in DNA synthesis and is therefore required for cells to duplicate
in periods of growth. (It also occurs in periods of maintenance, but not to the same
degree.)
Folate also plays a role in the development of red blood cells, and a deficiency
in folate can lead to anaemia. Note that anaemia can be caused by a deficiency in
iron (called iron-deficiency anaemia) or in folate (called folate-deficiency anaemia).
Anaemia is characterised by tiredness, so the youth might no longer participate in
daily activities. This in turn can affect all types of individual human development
(figure 3.23).
Folate is found in green leafy vegetables, citrus fruits, poultry and eggs. Many
cereals, breads and fruit juices are fortified with folate. The form of folate added to
foods is a synthetic form of folate known as folic acid.
EC
Figure 3.23 A lack of folate can
lead to folate-deficiency anaemia and
therefore tiredness. This can have
numerous effects on the development
of youth.
TE
D
PA
G
Figure 3.22 Vegemite is one of
the world’s richest sources of B-group
vitamins.
PR
O
O
FS
The B-group vitamins include vitamins B1, B2 and B3 (also known as thiamine,
riboflavin and niacin respectively). These vitamins are essential in the process of
metabolising or converting the fuels (carbohydrates, fats and protein) into energy.
A lack of these nutrients can lead to a lack of energy. As energy is essential for
growth, a lack of the B-group vitamins can contribute to slowed growth of hard
and soft tissues.
Rich sources of the B-group vitamins include Vegemite, wholegrain cereals
and breads, eggs, meats, fish, dark-green leafy vegetables and milk. The B-group
vitamins are very delicate and easily destroyed through cooking and processing.
Getting enough of these vitamins from whole grains and unrefined sources is the
best way to ensure that the recommended intake is met.
Vitamin B12
U
N
C
O
R
R
Vitamin B12 is another B-group vitamin that is required for adequate development
during youth. Although it has a number of roles in the body, its main function during
the youth stage is for the formation of
red blood cells. It works with folate in
this capacity, ensuring the red blood
cells are not only the correct size but
also the correct shape to enable oxygen
to be transported throughout the body.
A deficiency of vitamin B12 can increase
the chance of becoming anaemic. Having
this condition can prevent youths from
participating in normal activities and
therefore have a wide range of effects on
their development.
Most foods of animal origin contain
some vitamin B12 but particularly good
sources include meat, eggs and cheese.
Because vitamin B12 is found only in
food sources of animal origin, vegans
are at particular risk of being deficient in
Figure 3.24 Foods from animal sources are good sources of vitamin B12.
this vitamin.
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APPLY your knowledge
1 (a) What is cell differentiation?
(b) Explain the difference between cell
differentiation and cell division.
2 What is the main role of vitamin D in the body?
3 Why are vegans at particular risk of vitamin B12
deficiency?
4 Explain the role of the following nutrients and
why each is important for youth health and/or
development:
(a) vitamin A
(b) vitamin C
(c)folate
(d) vitamins B1, B2 and B3.
5 Describe the effects on development of youth who
are deficient in:
(a) vitamin A
(b) vitamin D
(c) vitamin C
(d) B-group vitamins.
6 Create a mind map that summarises the function
and food sources of the vitamins covered in this
chapter.
U
N
C
O
R
R
EC
TE
D
PA
G
E
PR
O
O
FS
TEST your knowledge
Nutrition during youth • CHAPTER 3 97
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3.4
The interrelationship of major nutrients
KEY CONCEPT The function of major nutrients for the development of
hard tissue, soft tissue, blood tissue and energy
PR
O
O
FS
Although all the key nutrients have their specific functions, they must work
together or interrelate to carry out four major processes in the body:
1.provision of energy
2.production of blood
3.formation of soft tissue
4.formation of hard tissue.
Each nutrient is like a piece of the puzzle, so although its role may be minor in
the process, without it, the process cannot be carried out effectively. The four major
processes and the nutrients required for each will be explored in more detail in the
following section.
Provision of energy
O
R
R
EC
TE
D
PA
G
E
Energy is required in all cells so they can carry out their functions. Cells without
energy — like cells without oxygen — will die. As well as being needed for physical
activity, energy is essential to sustain life and keep body systems functioning
adequately. The amount of energy needed to sustain life (i.e. to keep the major
organs functioning) is known as the basal metabolic rate (BMR).
About 70 per cent of an individual’s total energy expenditure is devoted to BMR
requirements such as temperature controll and cell replacement. The other 30 per
cent is needed for physical activity and digestion.
A number of factors influence BMR. They include:
• age — BMR generally decreases with age, mainly due to lower muscle mass.
The effect of ageing decreases BMR by about 2 per cent per decade after the
age of 20.
• growth — individuals undergoing growth (such as in youth) require more energy
to build tissues and increase blood volume.
• body size — larger people have a higher BMR as they have more cells which in
turn require more energy to maintain their function.
• body type — muscle requires a higher BMR than fat as muscle cells are more
active and therefore require more energy to maintain their function.
• dieting — can cause the body to conserve energy. This lowers the BMR.
• sex — males tend to have a higher BMR. The higher muscle mass in most males
contributes to this difference.
• environmental temperature — the body has to work harder to maintain
temperature in hot or cold environments, therefore raising the BMR.
In Australia, energy is measured in kilojoules (kJ). A kilojoule contains one
thousand joules. The exact meaning of a joule is quite technical but some examples
of how much energy is used in specific activities will help put it into perspective.
The approximate amount of energy used in certain activities is shown in table 3.1.
As the energy required for physical activity only makes up a fraction of a person’s
total energy requirement, it is useful to look at total energy requirements. The
approximate total energy requirement per day (kJ) based on an individual with
moderate physical activity levels is shown in table 3.2.
The amount of energy contained in food is also measured in kilojoules. This
makes it easier to compare energy intake with energy output. The amount of energy
contained in certain foods is shown in table 3.3. If more energy is consumed than is
needed for metabolism, digestion or physical activity, it is stored as fat and contributes
to weight gain. If more energy is used than is consumed, the individual will lose
weight. In either case, health and individual human development are affected.
U
N
Activity
C
Table 3.1 The energy used in
selected activities (kJ per kg per hour)
Energy
(kJ/kg/h)
Sitting quietly
1.7
Writing
1.7
Standing relaxed
2.1
Driving a car
3.8
Vacuuming
11.3
Walking rapidly
14.2
Running
29.3
Swimming (4 km/hour)
33.0
Rowing in a race
67.0
Source: Better Health Channel,
www.betterhealth.vic.gov.au.
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Females
Energy requirement
Age
Energy requirement
13
11 200
13
10 000
14
11 900
14
10 300
15
12 600
15
10 600
16
13 200
16
10 700
17
13 700
17
10 800
18
14 000
18
10 900
Approximate
kilojoules
Food
White bread (1 slice)
290
Wholemeal bread (1 slice)
270
Egg (boiled)
330
Egg (Fried)
417
Skim milk (250 mL)
Yoplait Creamy Original Yogurt (175 g)
Butter (1 tsp)
Source: Adapted from www.nhmrc.gov.au.
Hamburger mince (1 patty)
TE
D
EC
R
Blood production
R
O
C
120
1070
1050
Chicken breast (with skin, roasted
without fat, 100 g)
920
1 medium T-bone steak (trimmed
of fat)
960
E
605
Sausages (pork, grilled)
Lettuce (1 cup)
1015
20
Broccoli (1/2 cup)
115
Carrot (1 medium)
170
Potatoes (boiled, 100 g)
340
Apple (1 medium)
230
Banana (1 medium)
390
Popcorn (air-popped, no oil, 1 cup)
115
Ice-cream (vanilla, 1 scoop)
375
Snickers Bar (1 bar)
1175
Potato chips (50 g)
990
Pasta (1 cup, cooked)
French fries (small serve, 100 g)
Blood needs to be produced on a constant basis and even more
1 sausage roll
so when growth is occurring at a rapid rate. As youths are in a
Domino’s Supreme Deep Pan Pizza
period of rapid growth, their need for the nutrients required for
(1 slice)
blood production increase significantly. Blood is made up of three
McDonald’s Big Mac
main components:
Hungry Jack’s Whopper Cheese
• plasma — makes up approximately 55 per cent of blood and
KFC nuggets (6 pieces)
contains clotting material and transports nutrients, gases,
Subway (six inch sub, roasted chicken)
hormones and waste
Drinks
• red blood cells — make up around 44 per cent of blood and
contain haemoglobin, which carries oxygen, carbon dioxide and
Cola softdrink (375 mL)
other gases
Apple juice (125 mL)
• white blood cells — make up around 1 per cent of blood and are
Orange juice (250 mL)
important for fighting disease and infection.
Water (250 mL)
Blood cells are made in the bone marrow, which is a spongy
tissue found inside the large bones of the legs, hip, spine and skull.
Protein forms a major part of all three components of blood. In the case of red
blood cells, iron binds with protein to form haemoglobin. Haemoglobin makes up
around 33 per cent of the weight of red blood cells and is responsible for carrying
oxygen around the body.
U
N
380
745
Chicken breast (no skin, roasted
without fat, 100 g)
PA
G
The provision of energy involves two groups of nutrients —
those nutrients required for fuel (the sources of energy), and
those nutrients that enable the fuel to be converted or changed into
energy.
As discussed earlier in this chapter, carbohydrates, fats and
protein are the fuel or sources of energy. These fuels are broken
down into simpler forms and then transported to the cells for
immediate use or stored in various sites around the body (e.g. the
liver and fat cells). The nutrients needed for energy production to
occur are shown in figure 3.25 (page 90).
Thiamine, riboflavin and niacin (the B-group vitamins) form
co-enzymes that bind to other substances and convert the fuels
into forms that can be used by the cells. The B-group vitamins are
transported to the cells by water, and many of the chemical reactions
that occur in producing energy take place in water.
Oxygen is required in the process of energy production. It is
transported to the cells by haemoglobin, which is largely made up
of iron and protein. The process whereby energy is released and
used by the body is known as cellular respiration.
PR
O
Roast beef (lean, 150 g)
O
Males
Age
Table 3.3 The approximate energy content of
selected foods
FS
Table 3.2 Average energy requirements for individuals of selected ages,
by sex and based on moderate physical activity levels
830
1510
1500
835
2060
3184
1090
1240
655
210
335
0
Nutrition during youth • CHAPTER 3 99
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3.4 The interrelationship of major nutrients
Carbohydrates,
fats and protein
Are the fuel for
energy
PR
O
O
FS
B-group vitamins
Allow the release
of energy
PA
G
E
Iron
Forms a part of
haemoglobin, essential
for carrying oxygen
around the body
R
EC
TE
D
Water
Transports the
B-group vitamins and
is also required for
chemical reactions
to take place
U
N
C
O
R
FIgUrE 3.25 The nutrients required for energy production
100
c03NutritionDuringYouth
Vitamin C plays a number of roles in blood formation. It helps in the
absorption of iron from plant sources, making more iron available for haemoglobin
production.
It is also important in the formation of healthy blood cells. Red blood cells
live for only 100 to 120 days and therefore require constant regeneration. The
human body produces around two million new red blood cells per second. In
order for this volume of red blood cells to be produced, cell division must occur
at a rapid rate. Vitamin A is essential for cell division and is therefore required for
this process.
When a cell divides, the DNA must be replicated so each cell has a complete
set of DNA. Although a mature red blood cell does not contain DNA (as it has
no nucleus), immature blood cells do contain DNA. Folate and vitamin B12 are
required for DNA synthesis and so are vital for red blood cell development. Water
is the main component of blood plasma and many of the chemical reactions that
produce the components of blood need water.
The nutrients required for the production of blood are outlined in figure 3.26.
UNIT 1 • The health and development of Australia’s youth
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Protein
Main building material
for blood components
and also forms the ‘globin’
part of haemoglobin
FS
Vitamin C
Assists in
iron absorption
PR
O
O
Fats
Required for the
formation
of cell membranes
E
Plasma
55%
PA
G
Vitamin A
Required for cell division
Red
blood cells
44%
EC
TE
D
Iron
Required for ‘haem’
part of haemoglobin
production
Water
The main component
of blood
FIgUrE 3.26 The components of
blood and the nutrients required for
blood production
U
N
C
O
R
R
B6, folate and B12
Required for DNA
synthesis and red blood
cell formation
White
blood cells
1%
Formation of soft tissue
Soft tissue includes skin, muscles, tendons, ligaments, collagen and organs. They
are categorised as soft tissue because they are soft compared to the other tissues
that make up the human body (hard tissue).
The development of soft tissue needs many nutrients for maintenance
throughout the lifespan but, when the size of the soft tissue expands during times
of growth, greater amounts of nutrients are needed. These nutrients are summarised
in figure 3.27.
Protein is the main building material for soft tissue, as it is for all body cells.
Protein is broken down into amino acids through the process of digestion and
then rebuilt into protein required by the body. This process requires the nutrient
folate.
Nutrition during youth • CHAPTEr 3
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101
1 July 2015 7:54 PM
3.4 The interrelationship of major nutrients
Protein
Main building material
O
FS
Folate
Promotes cell
division and tissue
growth
E
Muscles
TE
D
PA
G
Fats
Maintains and develops
cell membranes
PR
O
Vitamin C
Forms connective tissue
R
R
EC
Vitamin A
Required for cell division
Water
Medium for chemical
reactions and present in
soft tissue cells
Organs
Tendons
Ligaments
Skin
U
N
C
O
FIgUrE 3.27 The nutrients required
for soft tissue formation
Vitamin C plays an important role in the process of soft tissue development by
providing collagen. Collagen is like glue for the body’s cells and tissues, holding
them together and giving them structure.
Fats are required for the maintenance and development of cell membranes,
which are the outer layer of all human cells. When soft tissues grow, more cells are
created, thus increasing the need for fats.
Vitamin A is required for cell division. It is therefore required for the generation
of new soft tissue cells.
Formation of hard tissue
Hard tissue includes bones, teeth and cartilage, which contain minerals and
vitamins. Hard tissue can break if it is not strong enough.
102
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The body cannot store all of the nutrients needed to make hard tissue, so these
nutrients are required throughout the lifespan. They are needed in greater amounts
during periods of growth such as during youth.
The nutrients required for hard tissue development are summarised in
figure 3.28.
O
FS
Protein
Main building material
PR
O
Vitamin C
Forms connective tissue
PA
G
E
Vitamin A
Required for cell division
TE
D
Calcium
Works with phosphorus (another
mineral) to produce the hardening
material for hard tissues
EC
Vitamin D
Required for the absorption
of calcium
Teeth
Cartilage
R
Bones
R
FIgUrE 3.28 The nutrients required for hard tissue formation
U
N
C
O
Protein, vitamin C and vitamin A play similar roles in hard tissue development
as they do in soft tissue development.
Protein is the main building material for hard tissue development and, with
vitamin C, forms collagen, which is the main component of the bone matrix
(sometimes referred to as the collagen matrix). The bone matrix is like a framework
for the bone structure. On its own, the bone matrix is spongy and would not
support the weight of a person, but it provides the shape of the bone and allows
the hardening agents to provide the structure with strength.
Once the bone matrix has formed, calcium and phosphorus bind together to
form calcium phosphorus, the hardening agent for the bone matrix. Crystals of
calcium phosphate attach to the matrix, making the tissue strong and hard. This
process is known as ossification. Ossification is much like dipping a sponge into a
bucket of plaster. The once-soft sponge maintains its shape but becomes very hard
as the plaster dries. The matrix is like the sponge and the calcium phosphate is like
the plaster. They are both needed for adequate bone formation (figure 3.29).
Vitamin D assists the absorption of calcium in the small intestine. A lack of this
vitamin can result in weak bones.
Calcium
phosphate
Bone
matrix
FIgUrE 3.29 The bone matrix
provides the form of the bone and
calcium phosphate provides the
strength.
Nutrition during youth • CHAPTEr 3
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103
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3.4 The interrelationship of major nutrients
The 24-hour intake of food and drink for Chris, a
17-year-old male, is shown below.
• 2 fried eggs on white toast with 2 tsp of butter
• 175 g yogurt
• 250 mL orange juice
• 1 sausage roll
• 500 mL water
• 1 Big Mac
• 1 small serving French fries
375 mL cola
1 apple
300 mL water
2 slices of leftover pizza
1 medium T-bone steak
200 g potatoes
1 carrot
1 banana
250 mL apple juice
2 scoops of vanilla ice-cream
O
•
•
•
•
•
•
•
•
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Energy
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Case study
Case study review
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1 Using table 3.3, calculate the total energy intake for Chris.
2 Chris weighs 70 kilograms, has a BMR of around 7200 kJ/day and uses around
1200 kJ/day for digestion. Using table 3.1, calculate the extra energy that Chris
will expend by engaging in each of the activities below in one day. You will need
to multiply the amount of energy the activity uses (in kJ/kilogram/hour) by Chris’s
weight (in kg) by the amount of time he performed the activity (in hours). An
Excel spreadsheet can be used to do this.
(a) Writing at school and at home for a combined total of four hours
(b) Running around at football training for one hour
(c) Sitting at home quietly for a total of five hours
(d) Walking rapidly to and from school for a total of 30 minutes
(e) Taking a one-hour driving lesson
3 Calculate the total energy requirement for Chris for this day.
4 Calculate the energy balance for Chris during this day (subtract the energy used
from the energy consumed).
5 (a)If 37 000 kJ result in around one kilogram of excess weight, calculate
how much weight Chris would lose/add if he maintained this intake and
expenditure of energy for a full year.
(b) Discuss how this weight gain/loss might affect Chris’s health and development.
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TEST your knowledge
1 (a)Which nutrients are required for more than one
process in the body?
(b) Do they play the same role in all processes?
2 (a)Design a silly sentence or acronym to remember
the nutrients required for energy provision, blood
production and hard and soft tissue formation.
(b) Share your response with other students and
decide on the best ones.
APPLY your knowledge
3 Which lifespan stages would require higher
amounts of the nutrients needed for each of the
following processes? Explain each answer.
(a) Energy provision
(b) Blood production
(c) Soft tissue formation
(d) Hard tissue formation
4 In small groups, select one of the processes (hard
tissue, soft tissue, energy or blood production) and
design a poster, multimedia presentation or video
that could be used to educate youth about the
nutrients required for the process and examples of
foods that may supply these nutrients.
5 Use the Bone mass links in the
Resources section of your
eBookPLUS to find the weblink
and questions for this activity.
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3.5
Consequences of nutritional imbalance
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Youth is the third-fastest period of growth in the lifespan. During the adolescent
growth spurt, the average female youth can expect to grow 16 centimetres in height
and gain 16 kilograms in weight, and the average male youth can expect to grow
20 centimetres and put on 20 kilograms in weight. For this physical development
to occur, all of the nutrients required for the four processes — soft and hard tissue
formation and the production of energy and blood — must be eaten in appropriate
proportions. When nutrient intake is balanced (figure 3.30), appropriate levels of
nutrients are available to carry out these processes effectively and the development
of youth is optimised.
FS
KEY CONCEPT Understanding the consequence of nutritional
imbalance in a youth’s diet on short- and long-term health and
individual human development
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FIgUrE 3.30 A balanced diet doesn’t
mean eating the same amount of
everything.
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The importance of food intake during youth is not limited to ensuring that
optimal individual human development occurs. Balanced nutrient intake also plays
a significant impact in promoting the health of youth.
If the nutritional intake of youth is not balanced and nutrients are not consumed
in appropriate proportions, the risk of a range of consequences for health and
individual human development increases. These consequences can occur as a result
of the over- or under-consumption of specific nutrients and can occur in both the
short and long term.
Short-term consequences
The consumption of a variety of nutrients is required regularly to carry out various
processes including the production of energy. If these nutrients are not present, or
are in incorrect proportions, these processes may not occur effectively.
Carbohydrates are broken down and the glucose molecules that result are
absorbed into the bloodstream, from where they are taken into the cells and stored,
ready for use. The amount of glucose contained within carbohydrate-rich foods,
and how much such foods affect the levels of blood glucose, is measured using a
system called the glycaemic index (GI). The glycaemic index rates foods from 1 to
100 based on how quickly they cause blood-glucose levels to rise. Foods that cause
blood glucose to increase sharply are called high GI (with a score of more than 70)
while those that have a more sustained impact on blood glucose are called low GI
Nutrition during youth • CHAPTEr 3
c03NutritionDuringYouth
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1 July 2015 7:54 PM
3.5 Consequences of nutritional imbalance
(with a score less than 55). Those in-between these numbers are
termed medium GI. Eating foods with a low GI rating gives a more
sustained energy release and can therefore assist in carrying out the
biological processes required during the day. In contrast, high GI
foods give a quick rush of glucose that then drops off just as quickly
(figure 3.31). As blood glucose levels decrease, hunger increases. As
a result, high GI foods can contribute to overeating.
In addition to carbohydrates, B-group vitamins and iron also
contribute to the production of energy. If these nutrients are not
0
1
2
3
consumed on a regular basis, energy levels may decrease, impacting
Time after meal (hours)
physical health. Reduced energy levels also impact on an individual
in many ways such as not having the energy to:
Figure 3.31 The effect on blood
• socialise — which impacts social health
glucose of high and low GI foods
• exercise — affecting fitness, an aspect of physical health
• concentrate at school — affecting intellectual development.
Fibre is a type of carbohydrate made up of the indigestible parts of plant matter.
Fibre assists in regulating bowel movements and providing feelings of fullness.
Adequate fibre intake can reduce the risk of constipation and overeating in the
short term. Fibre also reduces the absorption of glucose and cholesterol into the
blood stream. This acts to decrease blood glucose and blood cholesterol levels in
the short term.
Water is essential for the optimal functioning of body systems throughout the
lifespan. Dehydration can affect many processes within the body and contribute
to a range of short-term impacts as a result. Common symptoms of dehydration
include thirst, dry mouth, headaches, decreased blood pressure, dizziness, fainting,
tiredness and constipation. In the most severe cases, dehydration can lead to
unconsciousness and death.
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Blood glucose level
High GI
Low Gl
Figure 3.32 Foods like cakes,
biscuits and donuts have a high GI
that gives a quick rush of glucose.
Long-term consequences
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As well as contributing to short-term consequences, nutrient imbalance is associated
with many long-term consequences impacting on health and development,
including dental caries; underweight, overweight and obesity; chronic conditions
such as cardiovascular disease, colorectal cancer and osteoporosis; slowed growth;
anaemia; and increased risk of infection.
Sugars are a type of carbohydrate found naturally in some foods such as fruit
and honey, and added to many processed foods such as cakes and soft drinks.
As well as providing a fuel for energy production, sugars provide a food source
for bacteria in the mouth. These bacteria produce acids which can contribute to
dental decay and the development of dental caries. Dental caries can impact mental
health as a result of reduced self-esteem if the individual’s appearance is altered.
Intellectual development may also be affected if the individual misses school as
a result of ongoing treatment. If left untreated, diseases such as periodontitis can
occur. Periodontitis is a condition characterised by inflammation and infection of
the tissues that support the teeth. In the long term, periodontitis can lead to the
loosening and loss of teeth.
Although required as a fuel for energy production, if eaten in excess,
carbohydrates, fats and protein are stored as adipose (fat) tissue. Over time, this can
lead to weight gain, overweight and/or obesity. The most immediate consequences
of overweight and obesity in youth are social discrimination (associated with poor
self-esteem and depression), negative body image and eating disorders. Overweight
youth are more likely to develop sleep apnoea, have a reduced ability to exercise,
and show early signs of metabolic consequences, such as hypertension, high blood
glucose and high blood cholesterol.
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Overweight and obesity rates have been steadily increasing for youth over time
(see figure 3.33). Overweight youth are more likely to be overweight or obese as
adults, which increases the risk of a range of conditions including type 2 diabetes,
cardiovascular disease, some cancers and arthritis.
30
Obese
Overweight
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25
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Per cent
20
15
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10
0
1985
1995
Males
2011–12
1995
Females
2011–12
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* Figures are for 12–17 years
1985
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Figure 3.33 Prevalence of overweight and obesity among males and females aged
7–15 years, 1985, 1995 and 2011–12
EC
Source: Adapted from Australian Institute of Health and Welfare 2004, Risk factor monitoring, a rising epidemic: obesity in
Australian children and adolescents and ABS, Australian health survey: updated results, 2011–12.
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When consumed in excess, protein can reduce the ability of the body to absorb
calcium. This can contribute to reduced bone density and osteoporosis later in life.
Fibre provides feelings of fullness without contributing significantly to energy
intake. As a result, adequate fibre intake can assist with weight management in the
long term. It also assists with regulating bowel movements and has been linked to
lower rates of colorectal cancer in the long term.
Saturated and trans fat increase the process of atherosclerosis by increasing
levels of low density lipoprotein (LDL) in the blood. Low density lipoprotein is
a type of cholesterol that can stick to the walls of blood vessels which causes the
blood vessels to narrow. This process can eventually restrict blood flow or stop it
completely. Atherosclerosis is the underlying cause of many types of cardiovascular
disease, including heart attack and stroke. Monounsaturated and polyunsaturated
fats work to reduce levels of LDL cholesterol in the blood and can therefore assist in
reducing the risk of cardiovascular disease in the long term. Like all fats, however,
over-consumption can contribute to obesity and its associated effects.
Although overweight and obesity are significant issues for youth, underweight
is also a concern. Underweight often indicates undernourishment in which the
nutrients required for optimal health and development are not present.
Severe undernourishment, as occurs in many individuals with an eating disorder,
can contribute to long-term developmental problems. Growth may be slowed as
the nutrients required for hard tissue formation are not present. Although peak
bone mass is not reached until early adulthood, bone density increases significantly
during youth. Calcium, phosphorus and vitamin D are all essential nutrients for
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3.5 Consequences of nutritional imbalance
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this process. If intake is deficient in these nutrients, weakened bones may be the
result. In many cases, this will develop into osteoporosis later in life.
Soft tissues are constantly repaired and replaced, and nutritional balance is
needed to ensure the nutrients required to carry out this process are present in
appropriate levels. Protein, vitamin C, vitamin A, folate, fats and water are all
required for the growth and repair of soft tissues. Without adequate amounts of
these nutrients, muscles and organs may not develop to their full potential.
As blood cells are produced constantly, adequate intake of the nutrients required
to make blood, such as iron, folate and vitamin B12, are required to ensure the
amount of blood produced meets the needs of the growing youth. Vitamin C is also
important as it assists with iron absorption. If these nutrients are under-consumed,
anaemia can occur. Anaemia is characterised by an inability of the blood to carry
adequate oxygen around the body. Symptoms of anaemia include tiredness and
weakness, so the youth might no longer be able to participate in daily activities.
Anaemia may affect development by creating:
• an inability to participate in the weight-bearing activities that are needed to
increase bone density, which can result in reduced bone mass
• an inability to participate in physical activity, which can impair motor skill
development
• insufficient energy to have a part-time job, which can affect social development
such as learning the role of an employee
• constant feelings of tiredness, which may generate a range of negative emotions
such as helplessness and isolation.
As well as providing energy and aiding in the formation of hard tissue, soft tissue
and blood, nutrients are required to keep all bodily systems functioning correctly.
The immune system, for example, requires a nutritional balance to function
effectively. Protein and vitamin A are key nutrients in immune system function. If a
person is deficient in protein or vitamin A, their immune system may not function
correctly, increasing the risk of disease or infection.
APPLY your knowledge
1 (a) Explain the glycaemic index.
(b) Outline the consequences that a high GI diet can
have on the health of youth.
2 (a)Discuss how nutritional imbalance may
contribute to low energy levels.
(b) Explain three ways in which this could impact on
youth health and/or development.
3 Outline the role that fibre can play in optimising
health in the short term.
4 (a)Explain how nutritional imbalance may contribute
to dental health problems among youth.
(b) Discuss how dental caries could impact on
youth:
i.health
ii.development.
5 Explain anaemia.
6 Explain how carbohydrate, protein and fat intake
can contribute to obesity.
7 Discuss how youth could reduce the risk of
developing osteoporosis in later life.
8 Explain how being underweight could impact on
youth health and development.
9 Discuss how anaemia could impact on youth health
and development.
10 Design a poster or short video outlining the
possible short- and long-term effects of nutritional
imbalance among youth.
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TEST your knowledge
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3.6
Food selection models as tools to promote
healthy eating during youth
KEY CONCEPT Understanding food selection models as tools to
promote healthy eating during youth
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The Australian Dietary Guidelines
and the Australian Guide to
Healthy Eating
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To assist youth in consuming a balanced diet and reducing the risk of short- and
long-term consequences associated with nutritional imbalance, a number of food
selection models have been produced. Food selection models are tools that help
youth to select foods that will meet their nutritional needs, without consuming
too many energy dense foods. Examples include the Australian Guide to Healthy
Eating and the Healthy Eating Pyramid.
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The Australian Dietary Guidelines and the Australian Guide to Healthy Eating
are federal government initiatives that provide nutrition advice with the aim of
reducing the short- and long-term consequences associated with nutritional
imbalance.
The guidelines are targeted towards health professionals, including dietitians,
nutritionists, general practitioners (GPs), nurses, educators, government policy
makers, the food industry and other interested parties. Guidelines 2 and 3 provide
advice on which foods should be consumed regularly and which ones should be
consumed in moderation.
GUIDELINE 2
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GUIDELINE 3
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Enjoy a wide variety of nutritious foods from these five groups every day:
• Plenty of vegetables, including different types and colours, and legumes/beans
• Fruit
• Grain (cereal) foods, mostly wholegrain and/or high cereal fibre varieties, such as breads, cereals, rice, pasta, noodles,
polenta, couscous, oats, quinoa and barley
• Lean meats and poultry, fish, eggs, tofu, nuts and seeds, and legumes/beans
• Milk, yoghurt, cheese and/or their alternatives, mostly reduced fat
And drink plenty of water.
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Limit intake of foods containing saturated fat, added salt, added sugars and alcohol.
a. Limit intake of foods high in saturated fat such as many biscuits, cakes, pastries, pies, processed meats, commercial burgers,
pizza, fried foods, potato chips, crisps and other savoury snacks.
• Replace high fat foods which contain predominantly saturated fats such as butter, cream, cooking margarine, coconut
and palm oil with foods which contain predominantly polyunsaturated and monounsaturated fats such as oils, spreads,
nut butters/pastes and avocado.
b.Limit intake of foods and drinks containing added salt.
• Read labels to choose lower sodium options among similar foods.
• Do not add salt to foods in cooking or at the table.
c. Limit intake of foods and drinks containing added sugars such as confectionary, sugar-sweetened soft drinks and cordials,
fruit drinks, vitamin waters, energy and sports drinks.
d.If you choose to drink alcohol, limit intake.
Serving numbers and sizes from each of the five food groups and healthy fats and
oils are included in the Australian Dietary Guidelines to assist youth in planning
their daily food intake (table 3.4).
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3.6 Food selection models as tools to promote healthy eating during youth
Table 3.4 Australian Dietary Guidelines recommended serves from the five food groups for 12–18 year olds
Recommended number of serves per day
Age (years)
Vegetables
and legumes/
beans
Fruit
Grain (cereal) foods per day,
mostly wholegrain and/or
high cereal fibre varieties
Lean meats, poultry, fish,
eggs, tofu, nuts and seeds,
and legumes/beans
Milk, yoghurt, cheese
and/or alternatives
mostly reduced fat
12–13
14–18
5½
5½
2
2
6
7
2½
2½
3½
3½
Females
12–13
14–18
5
5
2
2
5
7
2½
2½
3½
3½
Pregnant (up to
18 years)
5
2
8
3½
Breastfeeding
(up to 18 years)
5½
2
9
2½
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Males
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3½
4
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Note: Additional amounts of the Five Food Groups or unsaturated spreads and oils or discretionary food choices are needed only by people who are taller or more active to
meet additional energy requirements.
14–18
2
12–13
1½
14–18
2
Pregnant (up
to 18 years)
2
Breastfeeding
(up to 18 years)
2
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75 g (½ cup) cooked green or Brassica or cruciferous vegetables
75 g (½ cup) cooked orange vegetables
75 g (½ cup) cooked dried or canned beans, chickpeas or lentils, no added salt
75 g (1 cup) raw green leafy vegetables
75 g starchy vegetables (e.g. ½ medium potato, or equivalent of sweet potato,
taro, sweet corn or cassava)
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1½
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Girls
12–13
Fruit
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Boys
Vegetables and
legumes/beans
75 g other vegetables, e.g. 1 medium tomato
150 g (1 piece) of medium-sized fruit, e.g. apple, banana, orange, pear
150 g (2 pieces) of small fruit, e.g. apricots, kiwi fruit, plums
150 g (1 cup)
diced, cooked or
canned fruit
125 mL (½ cup) 100% fruit juice
Grain (cereal)
foods per
day, mostly
wholegrain and/
or high cereal
fibre varieties
1 slice of bread or ½ a medium roll or flat bread (40 g)
R
Age (years)
Unsaturated
spreads and
oils per day
Table 3.6 Examples of single serves
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Table 3.5 Australian Dietary
Guidelines recommended fat intake
for youth
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Fats play an important part in many processes such as the development of cell
membranes, fuel for energy production and regulation of cholesterol. Unsaturated
fats are the healthiest options and should be included in the food intake of youth.
The amount of unsaturated fats recommended by the guidelines for youth are
shown in table 3.5.
Information is also included in the guidelines to provide youth with examples of
foods that make up a single serve (table 3.6).
30 g dried fruit, e.g. 4 dried apricot halves, 1½ tablespoons of sultanas
½ cup cooked rice, pasta, noodles, barley, buckwheat, semolina, polenta, bulgur
or quinoa (75–120 g)
½ cup cooked porridge (120 g), 2/3 cup wheat cereal flakes (30 g) or ¼ cup
muesli (30 g)
3 crispbreads (35 g)
1 crumpet (60 g) or 1 small English muffin or scone (35 g)
¼ cup flour (30 g)
Lean meats,
poultry, fish,
eggs, tofu, nuts
and seeds, and
legumes/beans
65 g cooked lean red meats (e.g. beef, lamb, pork, venison or kangaroo) or ½ cup
of lean mince, 2 small chops, 2 slices of roast meat (about 90–100 g raw weight)
80 g cooked poultry (about 100 g raw weight) e.g. chicken, turkey
100 g cooked fish fillet (about 115 g raw weight) or 1 small can of fish, no
added salt, not in brine
2 large eggs (120 g)
1 cup (150 g) cooked dried beans, lentils, chickpeas, split peas, or canned beans
170 g tofu
30 g nuts or seeds or nut/seed paste, no added salt*
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Milk, yoghurt,
cheese and/
or alternatives,
mostly reduced
fat
1 cup (250 mL) milk — fresh, UHT long life or reconstituted powdered
1/2 cup (120 mL) evaporated unsweetened milk
3/4 cup (200 g) yoghurt
40 g (2 slices or 4 x 3 x 2 cm piece) hard cheese, e.g. cheddar
1/2 cup (120 g) ricotta cheese
1 cup (250 mL) soy, rice or other cereal drink with at least 100 mg of added
calcium per 100 mL
FS
10 g polyunsaturated spread
10 g monounsaturated spread
10 g tree nuts, peanuts or nut pastes/butters
7 g polyunsaturated oil, e.g. olive or canola oil
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Unsaturated
spreads and oils
per day
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The Australian Guide to Healthy Eating is a food selection model that provides a
visual representation of guidelines 2 and 3 from the Australian Dietary Guidelines.
Presented in poster form (see figure 3.34), the main section of the Australian
Guide to Healthy Eating is a pie chart that shows the proportions of foods that
should be consumed from each of the five food groups according to Australian
Dietary Guideline number 2 — vegetables, fruit, grain, lean meats (or alternatives),
and milk, yoghurt and cheese products.
Grain foods such as bread, cereal, rice and pasta should
account for around 30–35 per cent of total daily food intake.
These foods are high in carbohydrates, which provide fuel for
energy production, and high in fibre, which assists with weight
management and maintains digestive health.
Vegetables and legumes/beans are the second biggest section
and should account for around 30 per cent of daily food intake.
These foods include fresh, frozen and tinned vegetables, legumes
such as lentils and chickpeas, and beans such as kidney beans.
These foods are high in vitamins and minerals, which assist in
promoting optimal health and development among youth. They
are also high in fibre and low in energy, which can assist with
weight management.
Meats and meat alternatives should account for around
15 per cent of total food intake. These foods provide much of the
protein that is required for the development of hard tissues, soft
tissue, energy and blood. They also contain iron and vitamin B12,
which are required for the production of red blood cells.
Although fruit contains many of the vitamins and minerals
required for optimal health, it can also contain high amounts
of high GI carbohydrates that can contribute to weight gain if
not used for energy. As a result, fruit should make up around
10–12 per cent of total food intake.
Milk and other dairy products should also account for around
10–12 per cent of total food intake. These foods are rich in
calcium and are required for optimal bone development.
The Australian Guide to Healthy Eating recommends that
people consume plenty of water, represented in the poster by a glass being filled
from a tap. Water is required for many body processes but does not contribute any
energy and so can assist in maintaining healthy body weight.
The healthier fats are shown in the bottom left corner of the Australian Guide
to Healthy Eating poster and include foods such as margarine and canola spray.
These foods contain monounsaturated and/or polyunsaturated fats and can assist
in reducing the risk of cardiovascular disease.
Figure 3.34 The Australian Guide
to Healthy Eating
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3.6 Food selection models as tools to promote healthy eating during youth
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Discretionary foods are shown in the bottom right corner of the Australian
Guide to Healthy Eating poster and consumers are advised to use these foods only
sometimes and in small amounts. They are not necessary to provide the nutrients
the body needs, but may add variety. Many of these foods are high in saturated fats,
sugars, salt and/or alcohol, and are therefore described as energy dense. Examples
of discretionary foods include pies and other pastries, cakes, processed meats, soft
and sports drinks, cordial, alcohol, potato chips, chocolate and biscuits.
With the information provided by the Australian Dietary Guidelines and the
Australian Guide to Healthy Eating, it is possible to evaluate the daily food intake
of an individual.
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Applying the Australian Dietary
Guidelines and the Australian Guide
to Healthy Eating
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If the food and drinks consumed in a 24-hour period are recorded, it is possible
to evaluate that particular day’s intake against the recommended number of
serves within the Australian Dietary Guidelines. This information can then give
some indication as to the adequacy of both the amount of food consumed and
the proportion of different food groups consumed. It is important to remember
that individual differences exist and the foods eaten in a 24-hour period do not
necessarily reflect overall dietary patterns. The following foods were consumed by
Scott, a 16-year old male, in a 24-hour period:
Table 3.7 Scott’s food consumption for one day
Morning tea
Lunch
Afternoon tea
Bowl of wheat
flake cereal (60 g)
with full-cream
milk (1 cup).
¾ cup of
yoghurt
1 medium
roll with
salad (75 g
total)
Cooked pasta
dish (1½ cups
of cooked pasta)
3 slices of roast meat
75 g mashed potato
2 slices of bread with
monounsaturated
margarine (20 g total)
75 g of cooked peas
75 g of cooked carrots
2 slices of
toast with
monounsaturated
margarine (20 g),
and 2 slices of
cheese
Small can of
tuna
1 vanilla
slice
Milkshake
(3 cups of full
cream milk,
chocolate
topping)
Fruit salad (150 g)
250 mL freshly
squeezed orange
juice
1 can of soft
drink
Water
1 apple
250 mL pineapple juice
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Breakfast
Dinner
1 banana
These foods can be broken down into their parts in order to classify them into
the five food groups. Creating a table like table 3.8 can be useful for doing this.
Refer to table 3.6 to see how many serves are present in each food item. For
example, the bowl of wheat cereal with milk would contribute two serves to the
‘grain’ group and one serve to the ‘milk’ group. Including a column for unsaturated
fats and discretionary food items is important as, even though these foods are
not considered a food group, they can have significant impacts on health. The
breakdown for Scott’s 24-hour food intake is shown in table 3.8.
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Instead of having to write each food in the table (as was done in table 3.8),
ticks or marks can be placed under each food group as you go through each item
consumed (as shown in table 3.9).
Table 3.8 Scott’s food consumption, broken down into the five food groups
Grain (cereal) foods
per day, mostly
wholegrain and/
or high cereal fibre
varieties
Fruit
Lean meats, poultry,
fish, eggs, tofu,
nuts and seeds, and
legumes/beans
Milk, yoghurt,
cheese and/or
alternatives, mostly
reduced fat
Unsaturated
spreads and
oils
margarine
from toast
salad from
roll
orange
juice
wheat flake cereal
small can of tuna
full-cream milk from
cereal
2
mashed
potato
orange
juice
wheat flake cereal
roast meat
cheese slices from
toast
3
peas
banana
toast
roast meat (1/2 serve)
yoghurt
margarine
from bread
4
carrots
apple
toast
full-cream milk from
milkshake
margarine
from bread
7
fruit
salad
pasta
9
pasta
bread from dinner
11
bread from dinner
Total
serves
4
7
11
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Grain (cereal) foods
per day, mostly wholegrain
and/or high cereal fibre
varieties
2½
Lean meats, poultry,
fish, eggs, tofu,
nuts and seeds, and
legumes/beans
6
Milk, yoghurt, cheese
and/or alternatives,
mostly reduced fat
4
3
Unsaturated
spreads and
oils
Discretionary
foods
O
R
Fruit
EC
Table 3.9 Vegetables
and legume/
beans
full-cream milk from
milkshake
TE
D
10
chocolate
topping
full-cream milk from
milkshake
pasta
8
PR
O
pineapple roll from lunch
juice
vanilla slice
E
6
margarine
from toast
soft drink
PA
G
pineapple roll from lunch
juice
O
1
5
Discretionary
foods
FS
Vegetables
and
legume/
beans
U
N
C
In order to do this accurately, you need to know how much of each food group
was in each item. If no amounts are given, you can base your judgements on what
an average serve might be (but some accuracy will be sacrificed). You may be able
to do this more accurately for foods that you have eaten yourself.
Once the number of serves from each group has been estimated, they can be
compared with the recommendations for someone of Scott’s age (males, 14–18,
from table 3.4).
Table 3.10 Scott’s intake compared to the recommended intake from the Australian Dietary Guidelines
Vegetables
and
legume/
beans
Fruit
Grain (cereal) foods
per day, mostly
wholegrain and/or high
cereal fibre varieties
Lean meats, poultry,
fish, eggs, tofu,
nuts and seeds, and
legumes/beans
Milk, yoghurt,
cheese and/or
alternatives, mostly
reduced fat
Unsaturated
spreads and
oils
Discretionary
foods
Males
14–18
5½
2
7
2½
3½
2
‘Limit intake’
Scott’s
intake
4
7
11
2½
6
4
3
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3.6 Food selection models as tools to promote healthy eating during youth
PA
G
E
PR
O
O
FS
Although Scott’s diet is varied, he may be consuming too many of some food
groups. Some specific observations include:
• he ate adequate amounts from the meat group
• he consumed only 4 serves of vegetables and should be consuming 5½
• he consumed 7 serves of fruit and should be consuming 2 serves
• he consumed 11 serves from the grain group, which is 4 serves above the
recommended amount
• he consumed 6 serves of dairy foods instead of the recommended 3½ serves
• he consumed more unsaturated fats than recommended for someone his age
• he may be consuming too many ‘discretionary’ foods.
Some advice regarding Scott’s diet could include:
• ensure that the amount of foods from the meat group is not decreased
• increase the amount of vegetables consumed
• reduce the amount of fruit being consumed — even though fruit contains many
important nutrients, it also has a relatively high amount of natural sugar, which
adds to the total kilojoules
• drink water instead of fruit juice in the morning and with dinner
• replace soft drink with a glass of water
• replace the vanilla slice at lunch with carrot and celery sticks
• replace the discretionary food items with healthier alternatives.
U
N
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O
R
R
EC
TE
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The Healthy Eating
Pyramid
FIgUrE 3.35 The Healthy Eating Pyramid
© The Australian Nutrition Foundation Inc.
114
c03NutritionDuringYouth
The Healthy Eating Pyramid was developed by
Nutrition Australia, a nongovernment organisation.
Based on the Australian Dietary Guidelines, the
pyramid represents foods from the five basic food
groups and arranges them into four levels, indicating
the proportion of different types of food that should
be consumed (see figure 3.35).
The Healthy Eating Pyramid promotes youth health
and development by encouraging food variety and a
diet with minimal fat, adequate fibre, limited salt and
sufficient water.
The ‘foundation’ layers (the bottom two layers)
contain food of plant origin: vegetables and legumes,
fruits and grains. These foods should make up the
majority of any meal. These foods are nutrient dense
and low in fat. They assist in providing youth with
optimal amounts of carbohydrates, fibre, vitamins
and minerals.
The middle layer includes the milk, yoghurt, cheese
(and alternatives) and lean meat, poultry, fish, eggs,
nuts, seeds and legumes food groups. These foods
provide protein, minerals (particularly calcium and
iron) and B-group vitamins.
The top layer presents foods that contain
monounsaturated and polyunsaturated fats, which
youth should consume in small amounts to support
heart health and brain function. Health benefits can
occur when consumers choose foods that contain
these healthier fats instead of foods that contain
saturated fats and trans fats.
UNIT 1 • The health and development of Australia’s youth
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O
FS
The pyramid encourages individuals to drink water because it provides the best
source of hydration for the body without adding extra sugar and therefore energy
to the diet.
It also recommends that salt intake should be limited. Salt is a rich source of
sodium, which is an essential nutrient, but many Australians consume excess
amounts and this can contribute to hypertension.
The Health Eating Pyramid provides youth with a simple visual tool that
promotes healthy food intake. However, serving sizes and provisions for composite
foods (such as pizza or casserole) are not included, and this may make following
the model difficult.
Consider the following food intake of Dallas, a
13-year-old female.
Snack:
1 banana
1 glass of water
PA
G
Breakfast:
Lunch:
A toasted sandwich (2 pieces of bread, 2 slices of
cheese, 10 g of monounsaturated margarine)
1 can of soft drink
E
Food intake
PR
O
Case study
Snack:
1 small carton of yoghurt (200 g)
3 tablespoons of sultanas
Dinner:
½ cup of cooked rice with 65 g of cooked beef, 1 cup
of cooked vegetables and 7 g of olive oil
1 cup of fruit salad
EC
Case study review
TE
D
2 pieces of toast with 10 g of monounsaturated
margarine
1 cup of orange juice
U
N
C
O
R
R
1 Complete a table similar to table 3.8 for Dallas’ food intake.
2 Compare Dallas’ intake to the guidelines given in tables 3.4 to 3.6.
3 (a)Of which food groups did Dallas consume the optimal amount?
(b) Explain how consuming an optimal amount of these foods might promote
Dallas’ health.
4 (a)Which food groups did Dallas not consume enough of?
(b) Explain how not consuming enough of these foods might affect Dallas’ health.
5 (a)Of which food groups did Dallas consume too much?
(b) Explain how consuming too much of these foods might affect Dallas’ health.
6 Why might it be more accurate to assess food intake over three days instead of
only one?
7 Explain the changes Dallas could make to her diet to more closely reflect the
recommendations of the Australian Guide to Healthy Eating and the Australian
Dietary Guidelines.
TEST your knowledge
APPLY your knowledge
1 Explain what is meant by a ‘food selection model’.
2 Identify two food selection models that can be used
by youth to promote health and individual human
development.
3 Explain the similarities and differences between the
Australian Guide to Healthy Eating and the Healthy
Eating Pyramid.
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3.6 Food selection models as tools to promote healthy eating during youth
PR
O
O
FS
(b) Prepare an analysis of your intake. Be sure to
include the following:
i.Identify food groups where intake was
adequate.
ii.Identify food groups where consumption was
deficient.
iii.Identify food groups where consumption was
excessive.
iv.Discuss the possible short- and long-term
consequences of your diet if it continued over
time.
v.Suggest changes that could be made to
minimise the risk of any short- or long-term
consequences identified in part iv.
(c) i.Discuss any difficulties you had in classifying
each food item.
ii.Explain how these challenges could be
overcome.
U
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C
O
R
R
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TE
D
PA
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4 (a)Identify the five food groups identified in the
Australian Guide to Healthy Eating.
(b) Identify the key nutrients provided by each group.
(c) Explain how these nutrients can impact on youth
health and development.
5 Outline the short- and long-term consequences that
may occur for Scott if he continues consuming the
foods shown in table 3.7 on a daily basis.
6 Describe how one of the food selection models
discussed in this chapter could promote healthy
eating among youth.
7 Explain how the Australian Guide to Healthy Eating
could reduce the short- or long-term consequences
of nutritional imbalance among youth.
8 Record your own food and drink intake over a
24-hour period.
(a) Estimate the number of serves consumed from
each food group using a similar method to that
outlined in table 3.8.
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KEY SKILLS Nutrition during youth
KEY SKILL Explain the functions of major nutrients
for the production of hard tissue, soft tissue, blood
tissue and energy during youth
FIgUrE 3.36 How energy is produced in the body
+
O
PR
O
+
Iron — forms
a part of
haemoglobin,
essential for
carrying oxygen
around
the body
Water —
transports the Bgroup vitamins and
is also required for
chemical reactions
to take place
=
Energy
production
E
+
B-group
vitamins —
allow the
release of
energy
PA
G
Carbohydrates,
fats and
protein —
provide the
fuel for energy
FS
This key skill requires knowledge of the nutrients needed to carry out different
functions in the body, namely the development of hard and soft tissue, blood
production and the provision of energy. As well as knowing which nutrients are
required for these processes, knowledge of the role each one plays is essential.
Visual tools such as concept maps, flow charts and equation diagrams can be used
to consolidate this information. The following example relates to the production of
energy:
R
EC
TE
D
In the following example, the nutrients required to produce bone (a hard tissue)
and the role each plays are outlined:
Protein❶: the main building material for hard tissue. Protein binds with vitamin C
to produce the collagen matrix, the outline for hard tissues.❷
Vitamin C: binds with protein to form the collagen matrix.
Vitamin A: assists in the division of the new cells needed by both the collagen
matrix and the hardening materials.
Calcium and phosphorus: bind together to form calcium phosphate, the hardening
material for bones.
Vitamin D: assists in the absorption of calcium in the small intestine. A lack of
this vitamin can result in weak bones.❸
❶
The nutrient is named.
❷
The function of the nutrient
is outlined and its role in the
development of hard tissue is
identified.
❸
The roles of a range of nutrients
required for hard tissue development
are discussed.
R
PrACTISE the key skills
U
N
C
O
1 Devise a summary diagram outlining the roles of the major nutrients required for
soft tissue production.
2 Discuss the roles of the nutrients required for blood production.
KEY SKILL Explain the possible consequences of
nutritional imbalance in a youth’s diet on short- and
long-term health and individual human development
Each nutrient has a role to play in the body, but both under- and over-consumption
of nutrients can contribute to a range of short- and long-term consequences for
youth. It is important to understand the effect that too little, or too much, of
each nutrient can have on the body. By understanding the role of the nutrients,
predictions can be made about the likely consequences on health and development.
Most of the short-term effects will be on physical health and development; it will
then be possible to predict the potential impact of these effects on the other areas
of health and development. For example, insufficient carbohydrates (which are a
Nutrition during youth • CHAPTEr 3
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1 July 2015 7:54 PM
Key skills Nutrition during youth
Possible short- and long-term
consequences of over-consumption
O
Nutrient
Possible short- and long-term
consequences of underconsumption
FS
fuel for energy) could make an individual feel tired (physical health). Feeling tired
can have other implications for health and development, such as not wanting to
go to school (intellectual development and social health could be affected by this).
Long-term consequences can occur in all areas of health and development, as
a result of nutritional imbalance over an extended period of time. The role the
nutrients play in these consequences must be understood. A summary table can
be useful for brainstorming the possible short- and long-term consequences of
nutrient imbalance.
PR
O
Consider the following example, which discusses the possible short- and longterm consequences on the health and development of youth who consume a diet
high in fibre.
Fibre assists in the removal of waste products in the digestive tract and promotes
regular bowel movements. In the short term❹, this can prevent constipation
(physical health). If an individual is not constipated, they may be able to concentrate
better at school, which can enhance intellectual development.❺
Fibre is made up of the indigestible parts of plant matter. As a result, fibre
provides feelings of fullness without adding excess kilojoules. In the short term, this
can prevent overeating. In the long term❻, this can assist with weight management
and prevent the risk of overweight and obesity. Decreased risk of obesity can
enhance self-esteem (mental health). Individuals of optimal body weight may
be more able to exercise and promote fitness (physical health) and motor skill
development (physical development). Fibre has also been shown to decrease the
risk of colorectal cancer in the long term (physical health).❼
❹ Short-term consequences are
❺ Possible consequences for
development are included.
❻ Long-term consequences are also
included.
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D
❼ Consequences on different areas
PA
G
E
addressed.
of health and development are
explored.
3 Explain the possible short-term consequences of a high-GI diet on youth health
and development.
4 Explain the possible long-term consequences of a low-GI diet on youth health
and development.
5 Explain the possible short- and long-term consequences on health and
development for a youth consuming low levels of:
(a)iron
(b)calcium.
U
N
C
O
R
R
EC
PRACTISE the key skills
KEY SKILL Explain how food models can be used as
a tool to promote health
In order to become proficient in this skill, knowledge of different food selection
models is necessary. The Australian Guide to Healthy Eating and the Healthy
Eating Pyramid are two food selection models that can be used by youth as tools
to promote health. Understanding how they can be used is an important aspect of
this skill. Using these tools to analyse and plan food intake can assist in developing
a deeper understanding of each model.
A typical scenario in which food selection models could be used to assist in
promoting the health of youth is explored in the following case study. ‘Simon is a
16 year old who enjoys playing football. He recently made the representative side
in his region and is now committed to training three nights a week and playing
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FS
❽ The food selection model is
O
identified.
❾ The food selection model is explained
in greater detail.
❿ Key aspects of the Australian Guide
to Healthy Eating are included. It is
important to avoid being too general
and to provide examples specific to
Simon where possible.
⓫ Aspects of the model that may limit
Simon’s ability to follow it are also
discussed.
⓬ Ways of increasing Simon’s
understanding of the model and so
improve his diet.
U
N
C
O
R
R
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TE
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PA
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PR
O
every Sunday. He also trains in the gym at school twice a week. He has been
purchasing his lunch from the school canteen most days of the week and buys food
from takeaway outlets on his way home from football training. Simon is unsure
whether he is consuming all the foods he should be to provide the nutrients he
needs to maintain optimal health and development’. To discuss a possible solution
to Simon’s eating challenges, one approach might be to identify a food selection
model, describe it, and then discuss how it could be used to assist Simon in
consuming a healthy food intake.
An initiative established to promote healthy eating is the Australian Guide to
Healthy Eating.❽ The Australian Guide to Healthy Eating is a food selection model
devised by the federal government. It is comprised of a poster that breaks the five
food groups into the proportions in which they should be consumed on a daily
basis.
The largest section of the graph, and therefore the food group that should be
consumed in the greatest proportion, is the grain group. This includes food items
such as cereals, breads and rice. Around a third of all foods should come from this
group.
The next section is the vegetables and legumes/beans group. Around a third of
all foods should come from this group.
The third group is the lean meats and poultry, fish and eggs. Around one-seventh
of all foods should come from this group.
The fruit group and dairy products such as milk, yoghurt and cheese are the
final two food groups. Each of these should account for around one-eighth of all
foods consumed.
The guide recommends drinking plenty of water, using only small amounts of
healthy fats such as canola and olive oils, and limiting discretionary foods such as
those containing alcohol or high levels of saturated fat, salt and/or sugar.❾
The Australian Guide to Healthy Eating can assist Simon in adopting a healthy
diet, but some of his circumstances may reduce his ability to follow it closely. The
guide is in graphical form, which might make it easier for Simon to understand it
and make changes to his diet.❿ The Australian Guide to Healthy Eating does not
include serving sizes, which might make it hard for Simon to consume adequate
amounts from each food group.⓫ He would have to consult the Australian Dietary
Guidelines to access this information. As Simon purchases a lot of his foods, he
will have to learn to break composite foods down into their parts so he can classify
them into one of the five food groups. He may be able to do this by keeping a
food diary of all the food and drink he consumes. He can then take some time to
practise breaking these items down to their primary components. If Simon gains
an understanding of the components of different items available from the canteen
and takeaway outlets, he may be able to choose foods that more closely reflect the
proportions outlined in the guide.⓬
PRACTISE the key skills
6 Identify two similarities between the Australian Guide to Healthy Eating and the
Healthy Eating Pyramid.
7 Obesity rates among youth in Australia have been steadily increasing over the
past 20 years. Explain how the Healthy Eating Pyramid could be used to assist
individuals in reducing their energy intake.
8 Jackie is 14 and has just become a vegetarian. Identify one food selection
model and explain how it could assist Jackie in consuming foods that will
provide her with the nutrients she needs to maintain optimal health and human
development.
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CHAPTER 3 review
Chapter summary
• There are six categories of nutrients required for optimal health and individual human
development; carbohydrates, protein, fats, water, vitamins and minerals.
Interactivities:
Chapter 3 crossword
Searchlight ID: int-2895
• Youth require a balance of the six categories of nutrients in order to maintain optimal
health and individual human development.
Chapter 3 definitions
Searchlight ID: int-2896
• Fibre is a type of carbohydrate that is indigestible. It has numerous health benefits, such
as reducing hunger, and decreasing cholesterol and glucose absorption. This can assist
in weight maintenance. Fibre also acts to clean the digestive system and reduce the
chance of colorectal cancer later in life.
O
FS
• The main function of carbohydrates is as an energy source.
PR
O
• Protein is required for the growth, maintenance and repair of body cells and structures.
It can also be used as an energy source.
• The main function of fats is as a fuel for energy production. They are also a key
component of cell membranes.
• Monounsaturated and polyunsaturated fats are a better choice than saturated and trans
fats because the latter increase the risk of cardiovascular disease.
PA
G
E
• Water is required for many body processes, including functioning as a medium
for all chemical reactions in the body and forming an important part of blood and
soft tissues.
• Calcium is an important component of hard tissues and is required to achieve optimal
peak bone mass.
• Iron is required for haemoglobin in blood and a deficiency can lead to anaemia.
• Vitamin A is required for cell division and cell differentiation.
TE
D
• Vitamin D is required in order for calcium to be absorbed in the small intestine and
therefore assists in building hard tissue.
• Vitamin C is required for collagen production and assists with the absorption of iron.
• The B-group vitamins are required to release energy from carbohydrate, protein and fat.
• The key nutrients interact to produce energy, blood, hard tissue and soft tissue.
EC
• If energy intake and expenditure are not roughly the same, weight gain or loss will
result.
U
N
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O
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R
• Nutrient imbalance can result in a range of short- and long-term consequences for
youth.
• Short-term consequences include lack of energy, a spike in blood glucose levels,
overeating and constipation.
• Long-term consequences include dental caries, periodontitis, overweight and obesity,
type 2 diabetes, cardiovascular disease, sleep apnoea, arthritis, osteoporosis, colorectal
cancer, anaemia and increased risk of infection.
• The short- and long-term consequences can impact on all areas of the health and
development of the individual.
• Food selection models can be used as tools to assist youth in preventing nutritional
imbalance.
• The Australian Guide to Healthy Eating presents the five food groups in the proportions
in which they should be consumed.
• The Healthy Eating Pyramid contains four layers relating to the proportions of different
foods that should be consumed.
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Food sources
APPLY your knowledge
U
N
C
O
R
R
EC
TE
D
PA
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3 Prepare a booklet that outlines the considerations
for youth food intake, with a focus on providing the
nutrients required for the production of hard tissue,
soft tissue, energy and blood.
4 Comment on the likely short- and long-term
consequences that may occur if youth consume too
much/too little of the key nutrients.
FS
Function/s
O
Nutrient
PR
O
1 What is the difference between macronutrients and
micronutrients?
2 Draw up a table similar to the one below and
complete it for each key nutrient.
5 Play a game of ‘nutrient celebrity head’. Three
players are selected and assigned a nutrient each
(the nutrient can be written above their head if they
sit with their back to the whiteboard) but are not
told which nutrient they have. They then take turns
at asking questions. Each time the answer to the
question is ‘no’, they lose their turn and the next
player asks a question. Play continues until a correct
guess is made. Incorrect guesses are counted as a
‘no’ and the player loses their turn.
6 (a)Conduct a survey of current nutritional intake
and trends in your school.
(b) Collate the results and comment on the
nutritional adequacy of the sample group’s diet.
(c) What are the possible short- and long-term
consequences if these trends continue?
(d) Use a food selection model to suggest changes
that the students could make to improve their diet.
E
TEST your knowledge
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