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In This Chapter:
Types and Sources of Nutrients
Macronutrients
Micronutrients
Water
Fibre
Nutrition Guidelines and Recommendations
Canada’s Food Guide to Healthy Eating
What Food Labels Tell You
Does All Food Fit?
Nutrition Questions and Answers
Are there foods that boost our health?
What are nutraceuticals?
Is vegetarianism a healthy alternative?
How bad is fast food, really?
How does aging affect nutrition?
Putting It All Together
CONNECTION
CHAPTER
THE NUTRITION
16
After completing this chapter you should be able to:

identify the nutrition requirements and components of a healthy diet;

outline the official nutrition advice provided to Canadians;

describe the effects of nutrition on general health and athletic performance;

answer some of the most common questions regarding nutrition and the unique
needs of various populations.
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N
“
To eat is a necessity, but to
eat intelligently is an art.
”
FRANÇOIS DE LA ROCHEFOUCAULD
ot all the factors associated with health can be controlled, but your
attitude and habits related to diet can influence your health in a
positive way. The role of diet in overall health is significant and has
profound effects on general well-being. Poor diets are often associated with
disease and illness, but healthy diets can be sources of energy and vigour.
Choosing foods that provide the necessary nutrients, while limiting those
associated with disease, can therefore significantly affect the course your life
and health will take. Furthermore, proper nutrition is essential for getting
the competitive edge that athletes require to win, since it allows the body to
perform at its best.
An understanding of what constitutes a healthy diet will allow you to
make informed decisions about your nutrition-related concerns. While you
should enjoy eating well and staying active, you must not assume that a
healthy diet needs to be restricted to fat-free, low-sugar, and high-fibre foods
all the time; in fact, the basics of a healthy diet are variety, balance, and
moderation. Following these basic rules will effectively guide
you to eating sensibly.
It is also important to understand that all foods are
good – with one distinction: that some are good to
have more often than others. There is nothing
wrong with eating ice cream or a chocolate bar
on occasion, just as long as it is on occasion.
Labeling foods as good or bad sends a negative
message about eating that should be avoided.
An overall pattern of healthy eating should be
your practical nutrition goal. We must not take
for granted the remarkable ability of our bodies to deal with foods and
substances over time, because it may catch up with us in the long run.
Clearly, many issues are related to your nutrition habits, and their impact
on your daily life is considerable. This chapter will attempt to outline the
dietary recommendations made for Canadians, helping you attain the tools
necessary to incorporate a healthy diet in your own life.
Types and Sources of Nutrients
T
he term nutrition, the science of food and how the body uses it in
health and disease, encompasses a wide variety of topics and issues.
When you consider what your diet is composed of, you probably think
about the foods you eat. Really, what is important is
what nutrients they contain. The nutrients are obtained
when the foods we eat are digested (broken down)
into compounds that can be absorbed and used by
the body. It is vital to consume a diet containing
adequate amounts of all essential nutrients, which
provide energy as well as the materials to build and
maintain tissues and regulate body functions. The
body requires three macronutrients (proteins, fats,
and carbohydrates) and a long list of micronutrients
(vitamins and minerals). Water and fibre complete
the picture of a healthy diet.
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16
The three nutrients that provide the body with energy are carbohydrates,
fats, and proteins. Fats are the most calorie dense, providing nine calories
per gram. In contrast, proteins and carbohydrates each provide four calories
per gram. Another source of energy (though not an essential nutrient) is
alcohol, which provides seven calories per gram. Alcohol has no nutritional
value, but its high caloric content creates the problem of excess calories
being consumed (which in heavy drinkers replace calories from nutritious
sources).
1 gram of fat provides 9 calories of energy.

1 gram of protein can provide 4 calories of energy if it is not used for
tissue building and repair.

1 gram of alcohol provides 7 calories of energy.
nutrients.

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1 gram of carbohydrate provides 4 calories of energy.
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A kilocalorie (commonly called a calorie) is the amount of energy that is
required to raise 1 kg of water 1 degree Celsius.
akes it the most c
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Macronutrients
Carbohydrates
The primary source of energy in our diets is carbohydrates, which should
make up 55 to 60 percent of our daily caloric intake. The body can use
carbohydrates easily and quickly, and so they are used first, before fats and
proteins. Sugars and starches are both carbohydrates.
Sugars The simplest of sugars (also known as monosaccharides and
disaccharides) include glucose, fructose, lactose, and sucrose. Glucose, also
known as dextrose, is a single sugar that makes up the body’s primary source
of energy (blood sugar). Fructose, also a single sugar, is known as fruit sugar.
Glucose tends to be found in foods such as vegetables, fruits, and honey,
whereas fructose is often found in fruits and berries.
Lactose and sucrose are double sugars. Lactose, also known as milk sugar,
is made by animals and is found in milk products. Sucrose, known as table
sugar, is refined from sugar beets or sugar cane. Sucrose is used as a table
sweetener and is found in candies and baked goods.
Although sugar itself does not make us
fat, sugary foods also tend to be high in
fat and calories, which can make us fat.
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DID YOU
KNOW
Unlike muscles, which have three
sources of energy for contraction, the
brain and nervous system have only
one source of fuel – the glucose that
circulates through the
bloodstream. Roughly
50 percent of the
food energy we
ingest is used to fuel
the brain’s activities.
Starches Starches are complex carbohydrates (polysaccharides).
They are found in vegetables, fruits, and grains (e.g., pasta, bread, and
rice). Starches are the recommended form of carbohydrate to eat because
in addition to energy, these foods provide vitamins, minerals, water, and
protein and are also a good source of dietary fibre.
Before starches and double sugars can be taken up and used for energy,
the body must digest them (break them down) into single sugar molecules
(such as glucose) for absorption. Once in the bloodstream, glucose is able to
provide cells with an energy source. The liver and muscles also store glucose
in the form of glycogen. When glycogen stores are
full, any carbohydrates consumed beyond
the body’s needs are synthesized into
fat and stored.
What's the Word on Glycemic Index?
Glycemic index (GI) ranks carbohydrates according to
their effect on blood glucose. Low-GI carbohydrates are
absorbed slowly and produce only small fluctuations in
blood glucose and insulin levels compared with high-GI
foods.
Low-GI foods have many health benefits, including
control of diabetes and blood cholesterol and reduction
of heart attack risk factors. Switching to eating mainly
low-GI carbohydrates that slowly trickle glucose into
your bloodstream keeps your energy levels balanced
and helps you feel fuller for a longer time between meals.
Eating a lot of high-GI foods can be detrimental to your
health because it pushes your body to extremes. This
is especially true if you are overweight and sedentary.
However, high-GI foods can play an important role in
refuelling carbohydrate stores after strenuous exercise.
Examples of foods that have a high GI are carbohydrates
that have been processed (i.e., have had their natural
nutrients and fibre removed) and many “starchy” foods.
These foods include white bread, white rice, French
fries, potatoes, white pasta, refined breakfast cereals,
soft drinks, and sugar. Examples of low-GI foods include
whole wheat bread, oats, bran, couscous, whole wheat
pasta, converted or parboiled rice, and sweet potatoes.
Most fruits, vegetables, and milk products have a low
glycemic index. Legumes such as chickpeas, beans, and
lentils have a low glycemic index and are an excellent
source of fibre. Meat and fish are also low-GI foods.
Fats
Although fat serves
important energy,
insulation, and protective
functions, fat consumption
must be closely monitored.
Fats (also known as lipids and fatty acids) are very important nutrients in
our diets for many reasons. Fat is a source of usable energy. It insulates
our bodies, cushions our organs, is involved in the synthesis of many
hormones, and aids in the absorption of the fat-soluble vitamins A, D,
E, and K (which would otherwise pass through our bodies). Further, the
presence of fat in foods adds important flavour and texture (palatability),
which is one reason many people find it difficult to cut down on some of
their favourite foods. Still, because it is the most concentrated source of
energy, fat consumption should be closely monitored. The main factor that
determines the healthfulness of a fat is its effect on blood cholesterol, a high
level of which is a precursor of cardiovascular diseases.
Saturated and Unsaturated Fats Fats are large molecules
made up of two kinds of smaller molecules – fatty acids and glycerol (an
alcohol). Three fatty acids are linked to one glycerol, which is why fats are
also called triglycerides. Fats that naturally occur in foods can be classified as
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16
Performance
Carbohydrate Loading
Studying the relationship between the
amount of stored glycogen in the muscle
and the ability to do work, exercise
physiologists found that sustained work
of two to three hours fully depleted
glycogen supplies and led to an inability
to work further. This means the amount of
glycogen present in muscle cells before
the start of exercise is very important.
Scientists determined that carbohydrate
loading could be accomplished by first
depleting the carbohydrate in the cells
with two to three hours of exhaustive
exercise, by then starving the muscles
of carbohydrate for two days (eating
high-protein meals with some fat and
little carbohydrate), and finally by eating
very large amounts of carbohydrate.
Under these conditions, the muscle cells
overcompensated in their demand for
carbohydrate and developed muscle
glycogen levels significantly higher than
normal.
Carbohydrate loading offers potential
benefits for endurance athletes (distance
runners, road cyclists, cross-country skiers,
rowers) and others who risk depleting
glycogen stores. The graph below shows
how diet and work influence the amount
of glycogen in the muscles. If a normal
mixed diet (fat, protein, carbohydrate) is
eaten, additional carbohydrate increases
Training
Heavy
Reduced
Diet
Mixed Diet
Fat and Protein
Light/Taper
Race Day
Glycogen (g/100 g muscle)
1.0
1
2
3
4
5
6
7
Manipulating the diet to store a “super”
load of glycogen can have negative
effects as well, such as gastrointestinal
discomfort and sluggishness. It can also
add body weight that might actually
negate the potential benefits of the
increased glycogen storage. Before trying
to achieve a super-compensation effect
before a race, long-distance athletes
are advised to first experiment with
carbohydrate loading.
The negative aspects of carbohydrate
loading can be reduced or eliminated
by following a less stringent loading
protocol. This protocol does not require
prior exercise to exhaustion. During the
first two days the athlete trains at about
75 percent of VO2max for about 1.5
hours. Training duration and intensity
are then gradually reduced, leading
into an exercise taper before the day of
the race. During the first three days, the
carbohydrate content in the diet should
represent about 50 percent of total calories
consumed. An increased carbohydrate
content, about 65-75 percent of total
energy intake, then follows during the
three days prior to competition. Research
has shown that this modified approach
to carbohydrate loading enhances
glycogen concentration in the muscle
without requiring the dramatic glycogen
depletion–loading protocol outlined
earlier.
2.0
0
Negative Aspects of Loading
Modified Carbohydrate Loading
Carbohydrate
3.0
0
muscle glycogen. Adding carbohydrate to
the depleted muscle (i.e., after work) loads
the muscle to a level higher than possible
on the normal mixed diet. Depleting the
muscle, eating fat and protein for two
days, then adding carbohydrate provides
even more glycogen – about 20 percent
higher than a mixed diet.
8
Days
saturated, monounsaturated, and polyunsaturated, based on the number of
double bonds between the carbon atoms of the fatty acid molecules. If no
double bonds exist, these are saturated fats. When one double bond exists,
the fatty acids are called monounsaturated fats, while those with two or
more double bonds are called polyunsaturated fats. Monounsaturated and
polyunsaturated fats are classified as unsaturated fats.
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Although most foods contain some combination of these fats, the
dominant type of fatty acid determines the characteristics of the fat.
Foods that contain an abundance of saturated fat are usually solid at room
temperature and are commonly found in animal products such as meats,
dairy products, eggs, and many baked goods. Since this type of fat is most
closely associated with numerous cardiovascular diseases such as heart
disease, it should be eaten less often.
Foods that contain large amounts of unsaturated fats usually come from
plant sources and are liquid at room temperature (so-called oils). These
unsaturated fats come in two forms, monounsaturated and polyunsaturated.
These fats are deemed more desirable because they are not linked to
cardiovascular disease; in fact, monounsaturated and polyunsaturated fats
may lower blood cholesterol levels and reduce the risk of heart disease.
Monounsaturated fats are found in large amounts in olive, canola,
sesame, and peanut oils. Sunflower, safflower, and corn oils contain
mostly polyunsaturated fats (Figure 16.1).
Canola Oil
5
Safflower Oil
Sunflower Oil
9
12
13
Olive Oil
13
Peanut Oil
24
9
4
32
46
26
18
4
33
11
82
6
87
Figure 16.1 Percentages of saturated,
monounsaturated, and polyunsaturated
fats in some common oils.
5
52
60
Monounsaturated
4
58
17
Coconut Oil
Foundations of Kinesiology
4
59
23
Palm Kernel Oil
346
4
74
Cocoa Butter (Chocolate)
Saturated
4
66
15
Cottonseed Oil
5
75
19
11
Corn Oil
Soybean Oil
28
62
Polyunsaturated
3
4
2
5
2
5
Other fatty substances
Trans Fat To extend the shelf life of fats (i.e., to keep them from breaking
down or turning rancid), a process called hydrogenation was invented. It
turns what were double bonds in unsaturated fats to single bonds, yielding
a more solid product. Until recently most packaged and mass-produced
baked goods (cakes, cookies, pies, crackers, snack foods) contained partially
hydrogenated vegetable oils. Another name for this manufactured product
is trans fat. The dangers of trans fats are now well known, and many food
companies have removed trans fats from their products. In fact, legislation
may be passed to ban the use of partially hydrogenated vegetable oils.
Hydrogenated oils and fats should be consumed sparingly. Read labels
carefully and avoid foods that contain palm, coconut, palm kernel, or tropical
oil; these cheaper oils are most likely to have undergone hydrogenation.
Cholesterol Another type of lipid that circulates in the blood is
cholesterol, an essential component of all human and animal tissues.
Cholesterol acts like a sort of cement, or mortar, strengthening and fortifying
the walls of the cells. It is also needed to make vitamin D, the coverings of
nerve fibres, and certain hormones. In healthy people, the body produces all
the cholesterol it needs.
However, excessive amounts of cholesterol in the bloodstream have been
implicated in the development of cardiovascular disease. Although there is
evidence to show that an elevated intake of saturated fats may increase the
levels of cholesterol in the blood, the relationship between the intake of
dietary cholesterol (from sources such as egg yolk and animal fat) and blood
cholesterol levels is less certain.
HDL and LDL Two protein particles called lipoproteins
act as cholesterol carriers: low-density lipoprotein (LDL) and
high-density lipoprotein (HDL). The responsibility of LDL
is to carry cholesterol to the body’s cells. However, any excess
cholesterol in the bloodstream is deposited in the blood vessels,
eventually causing artery clots and a narrowing and hardening
of the arteries (i.e., the arteriosclerosis that can lead to heart
attacks and strokes). Therefore, LDL is known as the “bad”
cholesterol.
On the other hand, HDL delivers cholesterol back to
the liver, where it is removed from the blood. Therefore,
HDL is known as the “good” cholesterol and is not linked to
cardiovascular disease.
16
C
holesterol is found in animal tissue, such as
meat, fish, and dairy products. Plants are
naturally cholesterol free.
“What else should I know
about HDL and LDL?”
Males
before puberty and females before menopause
have a high HDL level, after which the level drops and
they become more susceptible to heart disease.

Smokers, people with diabetes, and people who are obese
have low HDL levels.
 Dietary habits can raise or lower LDL and HDL.

Participation in regular vigorous physical activity increases
levels of HDL.
Triglycerides Free fatty acids, or triglycerides, make up most of the fat
in our diets and most of the fat that circulates in the blood. In combination
with cholesterol, triglycerides speed up formation of plaque in the arteries.
Triglycerides are carried in the bloodstream primarily by very low-density
lipoproteins (VLDL).
Performance
Pre-event Meals
To be fully ready to compete, athletes
need to follow certain nutrition
guidelines. First, meals eaten before
a competition should be high in
carbohydrates and low in fat, because
carbohydrate-containing foods leave
the stomach more quickly than other
foods (fats are slowest). Food in the
digestive system makes a demand
on the circulatory system, so it is
beneficial to have food move quickly
through the system to allow needed
oxygen to be supplied to the working
muscles. In stressful and competitive
CHAPTER
The Nutrition Connection
conditions, muscle damage can occur
if muscles are deprived of energyyielding oxygen. Second, only familiar
foods should be eaten before an event
to avoid any strange or surprising
reactions.
DID YOU
KNOW
All vegetable oils, butter, and regular
margarine are 100 percent fat and
contain up to 15 grams of fat (up
to 135 calories) per tablespoon,
equivalent to the fat in one scoop of
ice cream. Look for the Health Check
symbol on tubs of soft margarine. The
Heart and Stroke Foundation awards
this symbol to brands that have no
trans fat, are nonhydrogenated, and
are low in saturated fat.
Packed with an assortment of vitamins
and minerals, bananas make a great
snack to boost energy before, during,
and after a bout of exercise.
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