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Topic 3.1: Nutrition
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Sports,
Exercise and
Health Science
Topic 3.1: Nutrition
Proper nutrition is important to athletes and non-athletes. Nutritional requirements depend on
health, activity levels and the internal & external environment (Fig. 1). Optimal
nutrition results in normal development, good health and a high quality of life,
whereas under-nutrition (hunger), malnutrition (lack of particular types of nutrients) and
over-nutrition (obesity) all have detrimental effects.
Fig. 1 The relationship between nutrition, health and environment.
The type, quality and quantity of nutrient intake is important in sports science as it
impacts an athlete’s performance as it largely determines energy levels, performance
and recovery. We will begin by examining the various types of nutrients and discussing
the proportions of nutrients required in the diets of different individuals. We will
then examine metabolism, the process by which nutrient molecules are broken down to
provide energy, and assess the contributions of different energy systems during
exercise.
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3.1.2
Outline the functions of macronutrients and micronutrients
Macronutrients are defined as nutrients that are needed in larger quantities whereas
micronutrients are defined as nutrients that are needed in smaller quantities (Fig. 2).
 Dietary fiber
Fig. 2 Micronutrients and macronutrients.
Macronutrients (Table 3) include water, lipids, carbohydrates and proteins.
 Water serves as a solvent for many other chemical compounds & a medium for
chemical reactions.
 Carbohydrates, lipids and proteins (in that order) can be utilized by the body as
substrates for energy production during cellular respiration (KIV: Sections 2.2, 2.3 and 2.4).
Macronutrients
Water
Carbohydrate
Lipids
Protein
Main functions
Solvent to dissolve & transport chemical compounds
Medium for chemical reactions
Thermoregulation (through its’ evaporation in sweat); osmoregulation &
excretion; lubrication
Energy store & primary energy source
Sugars used to synthesize DNA, RNA & components of the cell
membrane
Main energy store in humans; secondary energy source
Conservation of body heat; cushioning of vital organs; buoyancy; fats
used to synthesize components of the cell membrane, hormones & bile
acids
Energy source after depletion of carbohydrates & fats
Proteins carry out the majority of cell functions, including structural
support, transport and enzymatic functions
Main food sources
Beverages, fruits,
vegetables
Cereals, leafy & root
vegetables, fruit, dairy
products
Meat, fish oils, eggs,
milk & dairy products,
nuts, vegetable oils
Meat, fish, milk & dairy
products, eggs, cereals,
dried beans
Table 3 Summary of the main functions & food sources of macronutrients.
Micronutrients include dietary fibre, vitamins and minerals.

Dietary fibre (Fig. 4) consists of indigestible plant polysaccharides such as cellulose.
 Soluble dietary fibre can be fermented by intestinal bacteria to produce flatulence.
It serves to slow down the movement of food through the digestive tract.
 Insoluble dietary fibre bulks up waste material by absorbing water, and
eases defecation.
Fig. 4 Sources of soluble
& insoluble dietary fibre.
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
Vitamins are organic compounds that play important roles in regulating metabolic
processes. They serve as cofactors to allow enzymes to fit specifically with and
act on their substrates. For example, some enzymes involved in macronutrient
breakdown use vitamin-derived cofactors (Fig. 5).
Fig. 5 Many enzymes need a cofactor
(vitamin or mineral) to activate them.
Without the cofactor, the enzyme
cannot fit well with the reacting
substance (substrate) at its’ active
site, so the reaction cannot take place.
Most vitamin deficiency diseases
happen in this way.
 Vitamins are divided into water-soluble (C, B1-B12) and fat-soluble (A, D, E, K)
types.
 Water-soluble vitamins are excreted in the urine, hence overdoses are usually
not toxic. However, fat-soluble vitamins are stored in adipose (fat-containing)
tissue and in the liver; overdoses can lead to poisoning.
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A list of vitamins, their functions and food sources is shown in Table 6. Note that two
vitamins can be synthesized by our bodies: vitamin D can be synthesized in the presence of
sunlight, and vitamin B3 (niacin) can be synthesized from the amino acid tryptophan.
(thiamine)
(riboflavin)
(niacin)
(pantothenic
acid)
(pyridoxine)
(biotin)
(folic acid)
(cobalamin)
Table 6 Summary of the main functions & food sources of vitamins.
Micronutrients
Table 7 summarizes the main functions and food sources of micronutrients.
Main functions
Fibre
Slow down food movement in gut, bulk up stools, ease defecation
Vitamins
(organic)
Minerals
(inorganic)
Cofactors / prosthetic groups for enzyme & protein function
Fat soluble vitamins include A (vision & immunity), D (calcium
absorption & bone growth), E (antioxidant) & K (blood clotting).
Water soluble vitamins include B1-B12 (metabolism), C (collagen)
Cofactors / prosthetic groups for enzyme & protein function
Include sodium & potassium (muscle & nerve function), calcium
(muscle & nerve function and bone formation) iron (oxygen transport),
phosphorus (ATP & bone formation) and others.
Table 7 Summary of the main functions & food sources of micronutrients.
Main food sources
Dried beans,
vegetables, fruit
Various sources for the
different vitamins &
minerals
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You are sports scientists working for a pharmaceutical company that specialises in nutrition
for elite athletes. An athlete has come to you and asked you for 2 things;
•
The perfect daily diet plan for a training day (food)
•
What performance enhancing drugs are available that may help them in their quest for
glory
3.1.1
List and outline the role of the macronutrients and micronutrients
required by the body
Research and fill out the following……
Macronutrient Role
Carbohydrate
Fat
Protein
Water
Micronutrient
Vitamins
Minerals
Fibre
Role
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3.1.3
3.1.4
3.1.5
State the chemical composition of a glucose molecule
Identify a diagram representing the basic structure of a glucose
molecule.
Explain how glucose molecules can combine to form disaccharides and
polysaccharides
Carbohydrates are a large group of chemical compounds that have a basic chemical
formula of (CH2O)n (i.e. they are made up of the elements carbon, oxygen and
hydrogen in a 1:2:1 ratio). They can be classified on the basis of size (Fig. 10) into
simple sugars (small, soluble sweet-tasting compounds) and complex carbohydrates
(larger molecules made by joining simple sugars via condensation reactions).
Single
I.
Monosaccharides
Fig. 10 Classification of carbohydrates.

The basic unit of simple sugars and complex carbohydrates is a single sugar unit,
known as a monosaccharide. Glucose (Fig. 11), a six-carbon sugar, is an
example of a monosaccharide. Other examples of six-carbon monosaccharides are
galactose and fructose (Fig. 13).
(a) Full drawing of glucose
molecule. Note the chemical
formula of C6H12O6.
(b) Simplified representation
– carbons in the ring are not
shown.
(c) Simplified representation
– carbons in the ring and
hydrogens are not shown.
Fig.11
Diagrammatic
representations
of glucose, a sixcarbon
monosaccharide.
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


Monosaccharides are the monomers (i.e. building blocks) of larger carbohydrates
such as disaccharides and polysaccharides.
In order to join monosaccharides together, a condensation reaction occurs. This
results in the removal of a water molecule, as well as the formation of a covalent
bond known as a glycosidic bond between the monosaccharides (Fig. 12).
Larger carbohydrates can also be broken down to give monosaccharides by the
reverse reaction, hydrolysis. Hydrolysis requires a water molecule to break the
glycosidic bond (Fig. 12).
Fig. 12 Condensation and hydrolysis reactions are the reverse of one another.
II. Disaccharides
 Disaccharides are formed by one condensation reaction between two
monosaccharides (Fig 12).
 Some common disaccharides (Fig. 13) are maltose (glucose+glucose, found in
cereals & grains), sucrose (glucose+fructose, found in fruit) and lactose
(glucose+galactose, found in milk).
Fig. 13 The common disaccharides. (A) Maltose is made up of two glucose molecules. (B) Sucrose is made up
of one glucose and one fructose molecule. (C) Lactose is made up of one glucose and one galactose molecule.
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

III.



Monosaccharides and disaccharides share the properties of being small, sweet and
soluble and are considered simple sugars.
Disaccharides can be hydrolysed into monosaccharides by our digestive enzymes.
These monosaccharides can then be used as substrates for ATP production during
cellular respiration.
Oligosaccharides & Polysaccharides
Additional monosaccharides can be added to disaccharides by further
condensation reactions to form larger carbohydrates.
Carbohydrates of 3-9 monomers are termed oligosaccharides, whereas those of 10
monomers or larger are termed polysaccharides.
Oligosaccharides and polysaccharides are known as complex carbohydrates. Being
larger than simple sugars, they do not taste sweet. Furthermore, some of them are
not soluble and/or not easily digestible.
 Digestible polysaccharides can be hydrolysed by digestive enzymes into
monosaccharides, which are then used for energy production. Such polysaccharides
form part of our carbohydrate intake.
 Indigestible polysaccharides (e.g. cellulose) make up our dietary fibre
intake.
Some important polysaccharides made up of glucose (Fig. 14) include:
(a) Cellulose, an indigestible polysaccharide which comprises most of our dietary
fibre intake. It plays a structural support role in plant cell walls.
 Cellulose consists of long, straight, unbranched chains that are arranged in
parallel bundles. In order to allow the chain to be straight, alternating glucose
monomers are inverted.
 The bundles are linked to form cellulose fibers. Many layers of cellulose fibers
make up the plant cell wall.
(b) Starch, a digestible plant polysaccharide in plants which serves as their glucose
store.
 Starch is composed of amylose, which forms long unbranched helical chains,
as well as amylopectin, which forms branched helical chains.
 The branching of amylopectin allows for more compact packing, as well as
providing more free ends for (and thus increasing the rate of) hydrolysis when
glucose is needed.
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(c) Glycogen is a digestible polysaccharide which is used as a glucose store in
animals.
 Glycogen has a very similar structure to amylopectin, but is even more
branched. Hence, it can be more compactly packed, and release glucose
even more rapidly by hydrolysis.
 Excess glucose from our food intake is stored as glycogen granules in the
cytoplasm of liver and muscle cells. However, the total amount of glycogen
forms a very small percentage of our body weight, and serves mainly to allow a
short-term, rapid release of glucose. Most of our stored energy resources are
in the form of fats (KIV: Section 2.3).
Fig. 14 The polysaccharides starch, glycogen and cellulose. Note that only the
amylose component of starch is shown.
The main functions of digestible polysaccharides are to act as energy stores.


When necessary, these energy stores are broken down to rapidly release glucose
to be used as a substrate for ATP production by cellular respiration.
Carbohydrates are hence an important energy source during intense and prolonged
periods of exercise.
The complete breakdown of 100 grams of carbohydrates yields 1760 kilojoules
(kJ) of energy.
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3.1.4
3.1.5
Draw a diagram representing the basic structure of a glucose
molecule.
Explain in your own words, how a glucose molecules can combine to
form disaccharides and polysaccharides.
Condensation reactions
3.1.6
State the composition of triacylglycerol (triglycerides).
Click on this video link to see how they are formed
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The term lipid, or fat, is used to refer to a large variety of hydrocarbon compounds (i.e.
containing mostly carbon and hydrogen with very little oxygen). Lipids include
triglycerides, phospholipids and sterols (Fig. 15).
Fig. 15 Classification of
Dietary fat is found in a variety of plant and animal sources. The fats that we ingest are
mainly made up of triglycerides / triacylgylcerols, with smaller proportions of
phospholipids and cholesterol.
Triglycerides consist of three fatty acids joined to one molecule of glycerol (Fig. 16).
 Glycerol is a three-carbon compound with three OH (alcohol) groups.
 Fatty acids are long hydrocarbon chains with a COOH (carboxylic acid) group at
one end.
 A condensation reaction (with the removal of a molecule of water) occurs
between an OH group of glycerol and the COOH group of a fatty acid to form an
ester bond. Three such condensation reactions result in the formation of a triglyceride.
The distinction between fats and oils is based on their melting points – fats are solid at
room temperature, while oils are liquid.
Fig. 16 Glycerol and three fatty acids are joined by condensation reactions to form a triglyceride.
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3.1.7
Distinguish between saturated and unsaturated fatty acids.
The three fatty acids attached to the glycerol may differ in their numbers of carbon atoms
(usually an even number from 12 to 24) and the number, position & orientation of C=C
double bonds present.


Fatty acids with no C=C double bonds are known as saturated fatty acids, as all
carbons have been maximally saturated with hydrogens.
Fatty acids with C=C double bonds are known as unsaturated fatty acids and
have relatively less hydrogen atoms than a saturated fatty acid with the same number
of carbon atoms.
The differences between saturated and unsaturated fatty acids are summarized in Table 17.
Saturated fatty acids (SFA)
Unsaturated fatty acids (UFA)
C=C
bonds
Absent; all carbons are bonded to maximum
number of hydrogens
Structure
Melting
point
Straight chain with no kinks
Higher melting point as the straight-chained
SFAs can be packed more closely together.
Usually solid at room temperature, hence
referred to as fats.
Present; may be mono-unsaturated (MUFA, one
C=C) or poly-unsaturated (PUFA, more than one
C=C).
PUFA are classified based on the distance of the first
C=C bond from the CH3-bearing end of the chain into
omega-3 and omega-6 fatty acids.
Kinks present in chain
Lower melting point as kinked UFAs cannot be
packed very closely together. Usually liquid at
room temperature, hence referred to as oils.
Sources
Usually from animal sources e.g. meat, poultry,
full-fat dairy products and tropical oils, such as
palm and coconut oils.
Usually from plant sources e.g. olive oil, olives,
avocado, peanuts, cashew nuts, canola oil and seeds,
sunflower oil and rapeseed.
Table 17 Summary of the differences between saturated and unsaturated fatty acids.
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Draw a Saturated and an Unsaturated fat:
Watch this video link
Saturated
Unsaturated
3.1.8 State the chemical composition of a protein molecule.
3.1.9 Distinguish between an essential and non-essential amino acid
Proteins are the second most abundant type of compound in the body, after water. In the
same way that polysaccharides are polymers of monosaccharides, proteins are polymers of
monomers known as amino acids (Fig. 19).
Fig. 19 Polysaccharides are polymers of
monosaccharides,
and
proteins
are
polymers of amino acids. Trigylcerides, while
not polymers, are composed of smaller units
of glycerol and fatty acids.
The general structure of an amino acid is shown in Fig. 20.
All amino acids consist of a central carbon
atom (the -carbon), which is attached to:
(i)
H atom
Constant for all
(ii)
Amine (NH2) group
amino acids
(iii)
Carboxylic acid (COOH) group
(iv)
Variable side chain, known as the R
group. There are 20 different R
groups, which distinguish the 20 amino
acids from one another. The sequence
and number of amino acid R groups in
a protein determine its’ structure &
function.
Fig.20 The general structure of an animo acid.
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The chemical composition of amino acids (and hence of proteins) is carbon, hydrogen,
oxygen and nitrogen.
Amino acids can be joined together by condensation reactions to form proteins. The bond
joining amino acids is known as a peptide bond (Fig. 21).
Condensation
reactions
Formation of many peptide bonds
Fig. 21 Condensation reaction between amino
acids to form peptide bonds.
Many
condensation reactions result in the formation of
a polypeptide / protein.
Adult humans lack enzymes to synthesize sufficient quantities of 10 out of the 20 amino
acids, which are termed essential amino acids (Table 22). Hence, the only source of such
amino acids is from our diet.
 Humans are able to synthesize histidine and arginine, but in insufficient quantities;
these must be supplied through our diet as well.
 Complete protein sources contain sufficient quantities and correct proportions of all
the essential amino acids to support human functioning.
 Non-essential amino acids can be synthesized from essential amino acids; hence,
our diet does not need to contain them.
Essential amino acids
Phenylalanine, valine, threonine, tryptophan, lysine,
isoleucine, methionine, histidine*, arginine*, leucine
* synthesized in insufficient quantities
Non-essential amino acids
Alanine, asparagine, aspartic acid, glutamic acid,
serine, cysteine, glutamine, glycine, proline, tyrosine
Table 22 Essential and non-essential amino acids.


Proteins serve many functions within the body, as shown in Table 23. Hence,
although the amino acids obtained from protein breakdown can be used as energy
sources, they are only utilized as such under extreme circumstances (e.g.
prolonged under-nutrition).
The complete breakdown of 100 grams of proteins yields 1720 kJ of energy,
slightly less than that of carbohydrates.
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Table 23 Functions
of proteins in the
human body.
Draw a diagram representing the basic structure of a protein acid.
In your own words explain the following:
Essential amino acid
Non-essential amino acid
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3.1.10
Describe the current recommendations for a healthy balanced diet.
A balanced diet is defined as one that provides all the nutrients in the right amount
in order to maintain heath and prevent nutrient excess or deficiency diseases.
Factors affecting the nutritional intake of individuals are varied and complex (recall Fig.
1). They include:
1. External factors
 socioeconomic factors
 food availability (whether a country in question grows / imports / exports certain
food types, which is influenced by its’ geographical conditions including soil type &
weather)
 food access (whether the population is able to afford certain food groups / types)
 access to clean water (which can affect food preparation techniques)
 food distribution (which can be affected by infrastructure & geopolitical
situation, as well as government programmes)
 cultural / religious preferences & traditions
 food choices & dietary restrictions (e.g. certain religions advocate
vegeterianism)
 food storage & preparation methods, which can affect the bioavailability of
nutrients (e.g. preservation / cooking methods destroy or make nutrients less
accessible to digestive enzymes).
2. Internal factors
 Genetic factors determining nutritional needs
 Diseases (genetic or otherwise) causing defects in nutrient digestion,
absorption, distribution & storage
 Life situations (e.g. age, gender, diseased vs healthy state, athlete vs non-athlete,
pregnancy & lactation etc) that affect individuals’ energy expenditure
Though these factors means that actual dietary requirements can differ greatly
between individuals, the governments & health authorities of many nations issue dietary
recommendations & guidelines for their populations. These guidelines are meant to set
standards for what constitutes an adequate intake of essential nutrients, and
should be based on scientific evidence regarding the needs of the population / population
subgroup.

Dietary recommendations refer to the recommended amounts of essential
nutrients in the diet.
 Guidelines for total energy intake are chosen such that the needs of 50% of the
population are met (i.e. the estimated average requirement, EAR), as even a
small excess of energy intake over energy expenditure can lead to overnutrition and
obesity over time.
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 Guidelines for recommended daily allowances for nutrient intake are chosen
such that the needs of 95 - 97.5% of the population (i.e. the EAR + 2SD) are met.
 Some nutrients which may cause toxicity (e.g. fat soluble vitamins) also have a
recommended upper limit.

As dietary recommendations may be abstract for the majority of the population, dietary
guidelines which give recommended amounts of foods / food groups & portion
sizes are commonly used.
Internationally, there is no agreement about dietary recommendations & guidelines. These
may differ due to the external & internal factors mentioned above that are relevant to the
country’s population, as well as the methods used to garner and apply research data in
different countries. The World Health Organization (WHO) and Food & Agriculture
Organization (FAO) of the United Nations maintain a list of dietary recommendations &
guidelines from various countries, as well as a set of international dietary goals aimed at
preventing long-term nutritional diseases in both developed & developing countries
(Table 26).
Dietary factor
Total fat
Saturated fatty acids (SFA)
Polyunsaturated fatty acids (PUFA)
Omega-6 polyunsaturated fatty acids
Omega-3 polyunsaturated fatty acids
Trans fatty acids
Monounsaturated fatty acids (MUFA)
Total carbohydrate
Sugars
Dietary fibre
Protein
Sodium chloride (salt)
Dietary recommendation (% of total energy or g/day)
15-30%
< 10%
6-10%
5-8%
1-2%
< 1%
Total fat – (SFA + PUFA + trans fatty acids)
55-75%
< 10%
>25g
10-15%
<5g
Table 26 FAO international dietary recommendations for carbohydrate, fat, protein & salt (2003).
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The visual presentation of dietary guidelines and advice given differs between different
countries. Most countries utilize graphical images to illustrate proportions of fluids, fruits,
vegetables, cereals, milk, dairy products, meat, eggs, fish and oils and sweets in the diet. The
images chosen usually represent conmmon food types available in that country, and
the overall visual presentation can range from the dietary pyramid in Singapore, to a food
plate (US & UK) or a food circle (Australia) (Figs. 27-30).
Fig. 27
(USA)
MyPlate
Fig. 28 Eatwell
Plate (UK)
Fig.
29
(Singapore)
Food
pyramid
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Fig. 30 Food circle
(Australia)
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Fig. 31 shows the average total energy requirements (in calories; 1 calorie = 4.2 joules) and
requirements for each of the nutrient groups across different age groups and genders. Values
for males are typically higher than those for females of the same age group, due to their
higher percentage of muscle mass.
Fig. 31 Average daily requirements for males and females of different age groups.
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FYI: Understanding Food Labels
Food labels can aid us in choosing foods that provide the right amount & proportion of
nutrients.
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Describe the current recommendations for a healthy balanced diet.
Macronutrient Advice
Carbohydrate
Fat
Protein
Water
Salt
Fibre
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3.1.11
State the energy content per 100 g of carbohydrate, lipid and
protein.
Table 24 shows a summary of the functions and properties of carbohydrates, lipids and
proteins.
Chemical
composition
Basic units
Bond formed
Carbohydrates
Made up of C, H & O in
1:2:1 ratio
Monosaccharides e.g.
glucose
Lipids (triglycerides)
Made up mostly of C & H;
very small amounts of O
Glycerol & 3 fatty acids
Proteins
Made up of C, H, O & N.
Amino acids
Fatty acids can differ in their
20 different types of amino
length, number & position of
acids that differ in their R
double bonds.
groups
Glycosidic bond
Ester bond
Peptide bond
All bonds are formed by condensation reactions, with the removal of a molecule of water for
each reaction. In order to break these bonds, a hydrolysis reaction occurs, which requires a
molecule of water (Fig. 25).
Fig. 25 Hydrolysis and condensation reactions
Polymer
formation
Main functions
in humans
Main storage
site in humans
Energy yield per
100g
Yes; polysaccharides
include cellulose, starch
(amylose+amylopectin) &
glycogen
Glycogen serves as energy
store; it can be rapidly
broken down to give
glucose, the substrate for
ATP production by cellular
respiration.
Glycogen granules in liver
and muscle tissue
1760kJ
No
Yes
Energy store
Various other functions include
thermal insulation, cushioning
against physical impact,
transport of fat-soluble
substances and phospholipid,
cholesterol & steroid hormone
synthesis
Adipose tissue & muscle
Not intended as primary
energy store / energy source.
Various functions in body
include structural, support,
transport, storage, enzymatic,
hormonal, immune defense
etc.
4000kJ
1720kJ
Table 24 Summary of the functions and properties of carbohydrates, lipids and proteins.
All cells & tissues
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Now in your own words state the energy content per 100 g of carbohydrate, lipid
and protein.
Carbohydrate
3.1.12
Lipid
Protein
Discuss how the recommended energy distribution of the dietary
macronutrients differs between endurance athletes and non-athletes.
In comparison to non-athletes, athletes generally have increased dietary requirements,
especially with respect to the energy-providing macronutrients. These increased dietary
requirements depend on energy expenditure of the sport involved, as well as the
intensity & duration of training undertaken.
1. Increased total nutrient intake
The total intake should increase by a factor of up to 2-3x.
2. Increased carbohydrate intake (Table 32 & Fig. 33)
 Carbohydrates provide the main
energy
source
for
ATP
production
by
cellular
respiration.
 With an increased carbohydrate
intake, (e.g. due to carbo loading)
glycogen stores increase. During
exercise, glycogen is broken
Fig. 33 Glycogen levels can be
replenished by high-carbohydrate
down to provide glucose for
meals.
cellular respiration. Hence, the more
the stored glycogen, the better the athlete’s performance, especially in endurance
events.
 The absolute carbohydrate intake increases by a factor of about 2-3x; hence, the
proportion of total intake that is made up of carbohydrates also increases.
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3. Increased fat intake (Table 32)
 Fats can also serve as an energy source, and hence the absolute intake of fats
should be higher in an athlete.
 However, due to the disproportionately large increase in carbohydrate intake, the
proportion of energy intake that is made up by fat actually decreases.
 An increased fat intake is also beneficial to athletes as fats are important in the
synthesis of steroid hormones, as well as the transport and storage of fatsoluble vitamins.
4. Increased protein intake (Table 32)
 Protein is usually not used as an energy source. However, the absolute intake
of protein should be higher in an athlete (though protein as a proportion of the
diet actually decreases) as proteins are required for muscle building as well as the
synthesis of protein hormones.
Table 32 Comparison of the recommended proportions of dietary carbohydrates, fat and protein in non-athletes vs
endurance athletes.
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5. Increased water intake (Fig. 34)
 As athletes lose a large amount of water through sweating, especially during
intense competition, adequate water intake (i.e. hydration) is crucial in maintaining
optimal performance.
 Dehydration is a contributing factor to muscle cramps, fatigue and heat exhaustion.
Fig. 35 shows the proportions of carbohydrate, fat & protein used as fuel sources during different exercises.
Fig. 34 Water balance.
Fig. 35 Proportion of energy intake obtained from carbohydrate, fat & protein for sports of different intensities.
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The timing of nutrient intake is also important in optimizing performance.
Timing
Pre-exercise
During
exercise
Post-exercise
(recovery)
Nutrient intake
 Carbo loading begins up to 6 days before an event. Foods high in starch are eaten and
physical activity is minimized, to maximize muscle glycogen content.
 The last meal should be taken 3-4 hours before competition to allow sufficient time
for digestion, as well as for the effects of transient hypoglycemia (KIV: Section 5.1) to
pass.
 Easily digestible carbohydrates (e.g. those in gels & sports drinks) are used to
maintain blood glucose levels, especially for endurance events.
 Adequate hydration is maintained with water & sports drinks.
 During this time period, protein synthesis is increased in order to repair damaged
muscle tissue, & glycogen stores are replenished.
 A small meal containing carbohydrates, fats and proteins should be taken within 30
minutes.
 Replace fluid lost during exercise with water & sports drinks
Discuss how the recommended energy distribution of the dietary macronutrients
differs between endurance athletes and non-athletes.
Carbohydrate
Nonathlete
Athlete
Fat
Protein
IB
Sports,
Exercise and
Health Science
Topic 3.1: Nutrition
Review Questions
SUMMARY QUESTIONS FOR CARBOHYDRATES
Name the carbohydrate type that
when consumed in excess
contributes to diabetes
List 3 functions of carbohydrates in
1.
the body
2.
3.
List 2 types of polysaccharides
1.
2.
Define hypoglycaemia and
hyperglycemia
Give two benefits of exercise to an
obese individual
Explain the difference between
glycemic index and glycemic load
Give an example of a food with a
high fibre content
Write the chemical formula for
glucose
1.
2.