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Macronutrients
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Macronutrient is defined as a nutrient that is needed in large amounts and has lots of
functions in our bodies.
Three of the essential nutrients our bodies need are called macronutrients.
These macronutrients are also the energy producing nutrients.
The Three macronutrients are Carbohydrates, Fats, and Protein.
CARBOHYDRATES
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are the sugars, starches and fibres in your diet.
Are made up of three common chemical elements: carbon, hydrogen and oxygen.
When these elements are bonded together they form what are called sugar units or
saccharides.
The way these elements are bonded together determines the type of sugar/saccharide unit
achieved. It also dictates the level at which the carbohydrates are able to be broken
down. Simple patterns or Complex patterns.
The three saccharide groups are:
1. Monosaccharides
2. Disaccharides
3. Polysaccharides
1. Monosaccharides
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are the smallest carbohydrate molecules, they are made up of one single sugar
unit.
Single sugar units/monosaccharides are easily digested and absorbed across the
intestinal wall and available for energy.
There are three monosaccharides: glucose, fructose and galactose. Glucose and
fructose stand alone but galactose is always bonded to glucose.
Glucose – is our body’s major source of energy.
Fructose – is found naturally in honey and fruits
Galactose – always bonded with glucose and this bonding can be problematic for
individuals that don’t have the enzyme necessary to break the bond that allows
digestion. (see next overhead)
2. Disaccharides
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Disaccharides are made up of double sugar units.
The body uses enzymes to breakdown down these sugar units, once the action of
the enzymes occurs the disaccharides are turned into monosaccharides so they can
be digested and absorbed into the body as a source of energy.
There are three different disaccharides: sucrose, maltose, and lactose.
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Sucrose – is the sugar we use in our baking or in our coffees it is also found in
many foods like molasses and maple syrup. It is made up of two bonded
monosaccharides – glucose and fructose.
Lactose – is found in milk, again it is made up of two bonded monosaccharides –
glucose and galactose.
Maltose – is found in some grain products but is also produced when the body
breaks down starch. It is made up of to identical and bonded monosaccharides glucose and glucose.
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3. Polysaccharides
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Polysaccharides are made up of many bonded monosacchrides.
Again it is necessary for our body to breakdown these bonded units in order for us
to digest them. This is done by the secretion of enzymes used to break the bonds
that connect the monosacchrides.
 There are two types of polysaccharides: starch and fibres
 Starch – starch is found in grains and pastas as well as starchy vegetables. Starch
is made up of many bonded glucose molecules. Starch is actually formed in plants
through the process of photosynthesis. Starch is a plants fat source, in other
words a plant stores its excess energy as starch.
 Fibres – are only found in plants. During the digestion process there is no enzyme
that is successful in breaking down these polysaccharides. Because they are not
successfully digested, fibres provide almost zero energy to our bodies. Some of
the most significant fibres are Cellulose, gums and pectin.
Why is fibre important in our diets
 Helps promote normal digestion and elimination of body wastes.
 Fibre not only moves things through the intestinal track more quickly because of its
absorption of water, this absorption also makes us feel full and reduces our desire to over
eat.
 Fibre also reduces the risks of gastro intestinal track diseases like colon cancer
 Dietary fibre can prevent appendicitis and helps control diabetes.
 Fibrous diets may be a proponent in lowering the risk of heart disease and artery disease.
Two Types of Fibre
1. Soluble fibre – these fibres are easily dissolved in water and becomes gel-like as it
travels through the intestines to be eliminated – Some sources are oat bran, legumes, and
citrus fruits.
2. Insoluble fibre – these do not dissolve and are often pushed through our systems whole –
some sources are wheat bran, pea pods, wheat stalks, corn.
Simple and Complex Carbohydrates
(Chart on Page 78)
1. Simple Carbohydrates: these are described as simple because the bonds are easily broken
down by our enzymes. All monosaccharides and disaccharides are considered simple
carbohydrates. Some simple carbohydrates are candy, syrups, and soft drinks
2. Complex Carbohydrates: these are described as complex because of the complexity and
intricate bond structures. All polysaccharides are considered complex carbohydrates.
Some complex carbohydrates are breads, cereals, pastas and vegetables.
So why know this??????
 Because complex carbohydrates require more work for our bodies to digest and convert
to energy and are also much more nutritious for us.
The Functions of Carbohydrates
1. Our bodies major source of energy – in order for our bodies to get energy from
carbohydrates(CHO), the CHO has to be converted to Glucose during digestion. Recall
that glucose is a monosaccharide.
The Process
 Glucose is absorbed by the cell then splits in half – this splitting results in the
release of energy.
 Once splitting occurs the left over fragments can re-join and make more glucose
or they can breakdown even further where even more energy is released. Once
the fragments further breakdown they can no longer re-join to make more
glucose. The cell must then find more glucose to absorb in order to get more
energy.
Glucose Absorbed by cell and splits resulting in:
1) fragments can be put back together to make glucose again
or
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fragments can be broken down even further, where they release more energy – here they
are no longer capable of gathering to make more Glucose.
2. Necessary cells require CHO – Three cells in our bodies absolutely require
carbohydrates. The three cells are red blood cells, brain cells, and nerve cells. Because
of their requirement of CHO these cells are called obigate CHO users.
3. Spares the use of Protein – Protein has its own functions related to tissue building and
cell construction it doesn’t really have time to waste making energy for you…but it will.
If you deprive your body of CHO it will use protein and your lean body tissue to form
glucose for energy. Ingesting CHO ultimately spares the use of protein so it can stay busy
doing what it is meant to do.
4. Helps break down FAT – excess glucose is stored as fat in the body…but this process
cannot be reversed. Once glucose is turned to fat it cannot become glucose again. Fat
cannot breakdown properly without CHO, in order to produce energy, carbohydrates
need to combine with fat…if CHO is not available fat remains as ketone bodies(unusual
products of fat breakdown) in the blood. Ketosis is the result. Ketosis is a very unusual
acid-base imbalance. If Ketosis is present during pregnancy it can cause brain damage to
the unborn fetus.
Helps make us feel full – creates bulk – it is CHO’s that help keep our intestinal track healthy
and disease free. Review : Why is fibre important in our diets
Sources:
Simple Carbohydrates
1. Natural sugars: fresh fruit, honey, lactose in milk
2. Refined sugars: chocolate, candy, soft drinks, baked goods, some cereals.
Buyers beware: just because a product says fat free it doesn’t mean your body won’t take the
added calories from sugar and make fat.
Complex Carbohydrates
1. Starchy foods: potatoes, rice, pastas, breads, cereals
2. Fibres: whole grain breads and cereals, bran, vegetables, fruits, dry beans, legumes and
lentils.
What is the required intake of CHO for our diet???
 We should be receiving 45-60 percent of our daily intake of calories should come from
CHO’s and most of this should be from complex carbohydrates instead of simple
carbohydrates.
Problems with excess Carbohydrates
1. Excess of simple CHO – can result in weight gain, but consumption of complex CHO
does not pose any major problems. To reduce overall calorie intake in a diet reducing fat
works better. Recall Calorie Calculations.
2. Dental Caries – excess refined sugar in a diet can cause some problems with cavities.
Research has produce clear evidence in a correlation between excess sugars and tooth
decay. There are other CHO that can cause problems as well – on of the biggest cavity
causing products is actually raisins. Any product that sticks to teeth is likely to result in
an increase in tooth decay.
3. CHO do not cause hyperactivity as previously suggested – much research has tried to
draw a connection between sugars and hyperactivity – but no correlation really exists.
4. Diabetes Mellitus – is a disease where one’s body does not use insulin properly. Type I
is insulin dependant while Type II can be treated effectively with diet restructuring and
an exercise plan. In the late stages of Type II insulin may be necessary. Individuals that
are overweight have a higher likelihood of developing Type II Diabetes.
5. Hypoglycemia – this is described as a low blood glucose level. This again is a problem
with insulin levels – overproduction of insulin results in low blood sugar which impacts
the central nervous system.
6. Lactose Intolerance: individuals that suffer here do not have the enzyme necessary to
breakdown this disaccharide and are therefore unable to digest the lactose.