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Unit 12
FATS AND CHOLESTEROL
Objectives
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To recognise that the average Australian consumes too much fat
To understand that fat is an essential nutrient
To identify the 4 groups of fat types and their physiological effects
To recognise the hidden fats in the food we eat
To understand the risk factors of a high fat diet
To develop an understanding of the main types of blood cholesterol
To show food choices and cooking methods that promote good health
THE FACTS ON FAT
Fat. Cholesterol. Saturated fats. Poly-unsaturated fats. Mono-unsaturated fats.
Omega-3s. Fish oils. Olive oil. Trans fatty acids. Good fats. Bad fats. Over the past
few years, no other nutrient has had as much attention as fat. We all know we
should eat less of it, but it seems hard to do.
First, fat is ‘hidden’ in many foods so we may not actually be aware we are eating it.
Second, flavour and aroma tend to accompany fat, so low-fat meals can taste bland
unless you know how to be creative in the kitchen. Third, there is much confusion
about which type is the right type of fat; here are some ‘Facts on Fat’.
Few people set out to eat a fatty diet. Fat is surprisingly tempting! Think of the smell
of fat wafting from fried foods that sets the taste buds tingling. It is fat which draws
many magnet-like, into a take-away food shop. And it is fat many crave when they
reach for a chocolate, a luscious-looking piece of cream cake, a pastry, croissant or a
packet of savoury snacks5.
It is also fat which clogs up the arteries, forcing the heart to work harder to push
blood past the grease deposits. It is fat which makes life difficult for our livers and
gallbladders. And it is fatty deposits that bulge over the belt, hang under the chin,
obliterate the shape of our lean tissue and wobble when we walk5.
Body fat can arise out of any sort of excess. If you eat more protein, fat, or
carbohydrate than you use for energy, the excess is converted to body fat deposits 5.
Fats are such concentrated sources of calories/kilojoules that is difficult for the
average body to burn them all for energy. Fats provide 9 calories (38 kJ) per gram
compared to carbohydrate and protein, which supply 4 calories (17kJ) per gram. So
the body efficiently converts the excess fat we eat into fat stores around the body.
Some of these are important5.
Large fat deposits are not only unnecessary but are a burden for the body. To get
some idea of the extra effort which must be expended to cart around excess body fat,
try walking up a hill carrying a 10 or 20-kilogram load. You will soon understand why
heavy people do not move around as much as their leaner peers5.
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It has been estimated that for every 10 kilograms of extra body fat, there are some 29
kilometres of extra blood vessels through which blood must be pumped. With such
an increased burden to bear, it is little wonder that overweight people have a shorter
life expectancy5.
The opposite extreme, with minimal fat stores, is also unhealthy. The human body is
designed to have a small store of fat, but not too much5.
WHY IS FAT NECESSARY IN OUR DIET?
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Vital organs such as the kidneys, liver and nerves are protected by layers of fat1.
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A little is needed for the body’s cosmetic appeal 1.
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Women have extra fat deposits on breasts, hips, buttocks and thighs and these
should be regarded as normal. In fact it is physiologically undesirable for women
to reduce body fat levels too far. With the current vogue for extreme slimness,
many young women have so little body fat that their hormonal balance is affected
and they no longer menstruate. A small amount of body fat is also wise as a
reserve for unexpected illness. You cannot, however, rationalize obvious flab as
being essential5.
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Fat is needed to facilitate the absorption of the fat-soluble vitamins A, D, E and K.
as well as the carotenoid pigments, flavonoids and other fat-soluble
phytochemicals1,6.
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Fat slows digestion and provides satiety, adds flavour and palatability to food1.
The essential fatty acids are converted into very important substances vital for the
regulation of many body processes including the immune response, inflammatory
reactions, regulation of blood pressure and blood clotting, the maintenance of normal
blood cholesterol levels, and other important body functions.
TYPES OF FAT
According to their chemical structure, fats are described as saturated, monounsaturated or poly-unsaturated. Foods contain a mixture of all three types of fats.
There is usually one type of fat which predominates in foods, and most foods are
placed in a category according to their major type of fat5.
All types of fat contribute exactly the same number of calories/kilojoules and have the
same potential to increase body weight. Poly-unsaturated margarine is just as
fattening as butter5.
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Saturated fats
Saturated fats are the ‘bad guys’ in causing high levels of cholesterol in the blood 5.
Saturated fats are solid at room temperature, found predominantly in animal and
animal based foods, such as full-cream dairy products and meat (including chicken
and seafood). Two exceptions to this are palm and coconut oils (plant fats) 4.
These fats tend to increase the ‘bad’ cholesterol levels as well as total cholesterol
levels in the blood4.
Saturated fat from either animal or plant sources can trigger the body’s mechanism to
make cholesterol. Some people are more sensitive to saturated fat intake than
others.
A greater proportion than expected of our saturated fat intake can come from eating
foods such as fried foods, fast foods, many processed foods, biscuits, pies, cakes,
pastries and chocolate. Of course animal foods such as fatty meats, sausages,
salamis, bacon, processed meats, cream, butter, most cheeses and full cream dairy
products also contribute a lot of saturated fat. If you avoid only the obvious animal
fats in meats and dairy products, however, you can still consume a lot of saturated
fats which are present, but not necessarily visible, in processed foods5.
In our over-fed and under-exercised society eating too many fatty foods can
constitute a dietary hazard. A high fat diet can increase the risk of disease in several
ways. High fat intakes can be a contributing factor to becoming overweight. In turn
being overweight increases the chances of developing a number of diseases such as
diabetes (type 2), colon cancer, breast cancer, heart disease, stroke and high blood
pressure4.
Dietary guidelines for Australians recommend eating a diet low in fat, and in
particular, low in saturated fat. Certainly some fat is required in the diet, but dietary
surveys show that the amount eaten by most Australians exceeds the requirements
for good health4.
Mono-unsaturated fats
Mono-unsaturated fats are liquid at room temperature. (The name refers to the
chemical structure of the fat; mono meaning one, this fat has one double bond 1.)
These fats dominate the fatty acids present in olives and olive oil, canola oil,
avocados, peanuts and peanut oil. They also occur in eggs, chicken and some fish
(salmon, mackerel, sardines and tuna), macadamias and hazelnuts.
These fatty acids do not oxidize readily and are more stable than poly-unsaturated
fats.
For many years these fats were largely ignored. They were thought to have a neutral
effect on blood cholesterol levels. More recent research has shown that monounsaturated fatty acids are much more useful than was previously thought, because
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they reduce the undesirable LDL cholesterol, and actually raise the protective HDL
variety. (Only if they replace saturated fats in the diet) In addition, populations who
have eaten a high proportion of these fats for thousands of years, have very low
incidences of both heart disease and cancer.
The avocado is a good source of mono-unsaturated fat; it is also a source of vitamin
E. Criticism of the avocado as being one of the few fruits or vegetables to contain fat
should cease. Avocados certainly do not contain cholesterol, and even the type of fat
they contain is above suspicion. The major problem with avocados is that their
superb flavour encourages some people to eat too many and thus increase the total
fat intake.
Include some mono-unsaturated fats on a regular basis. Olive oil has an added
advantage in its range of valuable anti-oxidants.
Poly-unsaturated fats
Poly-unsaturated fats are liquid at room temperature. (The name refers to the
chemical structure of the fat; poly meaning many, this fat has more than one double
bond.)
Large quantities of these fats are found in vegetable oils and poly-unsaturated
margarines. Many nuts and seeds are also rich in poly-unsaturates.
Research has shown that poly-unsaturated fats tend to lower the level of ‘bad’
cholesterol in the blood while maintaining the ‘good’ cholesterol. These fats can be
divided into two categories omega-6 and omega-3. Both of these fats, omega-6 and
omega-3, are essential, as our bodies cannot make them. However to promote
health there is a desirable ‘balance’ between the two. Diets in Western countries are
often rich in omega-6 fats (found in poly-unsaturated margarines and oils, such as
sunflower and safflower oil) but too low in omega-3 fats. Therefore, health authorities
recommend that more omega-3 fats be consumed to help correct this imbalance4.
Research indicates that omega-3 fats may help to:
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Reduce blood triglyceride (blood fat) levels
Prevent the formation of blood clots
Reduce high blood pressure
Regulate heart rhythm
Reduce the occurrence of immune-related conditions, such as rheumatoid
arthritis and inflammatory bowel disease
Omega-3 fats are found in canola oils or margarines; linseeds; walnuts; soybeans;
certain soy products like So Good; dark green vegetables such as spinach, green
peas and beans; oily fish such as sardines, mackerel, Atlantic and red salmon 4.
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Trans-fats
Trans-fats are solid at room temperature and are treated by the body in the same
way as saturated fats. (Moderate to high intake of trans-fatty acids can elevate blood
cholesterol levels, while possibly lowering blood levels of HDL ‘good’ cholesterol)
Some of the fats in meats like beef and lamb as well as dairy products have transfatty acids occurring naturally. Trans-fats can also be created by chemically
hardening vegetable oils in the manufacture of margarines to make it spreadable.
This process is called hydrogenation. Many margarines have now been reformulated
to contain less trans-fats than they had previously. Trans-fats are used extensively in
the production of processed foods including biscuits, cakes, pastries and chocolate. 4
Triglycerides
After you have eaten a meal, fat is present in the blood in the form of triglycerides.
These should clear after a few hours. High levels can persist if you have taken in
more fat; sugar or alcohol than your body can use. Blood tests for triglyceride levels
should always be performed before breakfast. If the level of triglycerides is high,
even after you have had plenty of time for the previous meal to have been cleared
from the blood, your risk of heart disease is increased5.
BUTTER VS. MARGARINE
The fats in margarine and spreads are predominantly polyunsaturated or
monounsaturated fats, while those in butter are mainly saturated. In general,
margarines or spreads will have a lower amount of combined saturates and trans fats
than found in butter. This is important to note when choosing a spread, if you need to
reduce your blood cholesterol levels4.
The main sources of fat in our diets come from:
 The fats and oils used in cooking (both at home and commercially).
 The fat we use for spreads (butter, margarine etc.).
 Meat, poultry and dairy products4.
DIGESTION OF FAT
a. Fat in the diet is digested or broken down by an enzyme called lipase.
b. The duodenum is the main site of fat digestion. Bile is excreted into the
duodenum where it emulsifies the fat globules allowing lipase to act on smaller
particles of fat.
c. Lipase breaks down triglycerides. The free fatty acids can then pass into the
lacteals and are transported through the lymphatic system.
d. Dietary fat is poured into the blood stream through the thoracic duct near the neck
and circulates through the body via the heart1.
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FATS - HOW MUCH DO WE NEED4?
The Australian Dietary Guidelines and World Health Organisation recommend that fat
should provide no more than 30% of energy in the daily diet3,6. What does this
mean? It means that no more than 30% of the daily energy (calorie/kilojoule) intake
should come from fat.
30% or less of total daily calorie/kilojoule intake for people who are moderately
active, fairly healthy, with normal blood pressure and cholesterol represents:
Women and Children:
30 – 50 grams of fat per day.
Men:
40 – 60 grams
Very active teenagers:
70 grams.
For those wishing to lose weight it represents:
Men:
40 – 50 grams
Women:
30 – 40 grams
30 – 40 grams of fat is approximately what you’ll find in an average meat pie plus a
bar of chocolate4!
You can see visible fat and this makes it easier to limit or remove. However, you may
not see, or realise you’re eating invisible or hidden fats and there’s no way of
reducing it unless you avoid the food entirely.
The average Australian takes in 45% of energy as fat.
FAT CONTENT OF SOME COMMON FOODS4
Food
Apple pie - frozen 1/6 pie
Apple pie - individual pie - with cream
Apple - 1 medium
Bread, wholemeal – 2 slices
Bread, wholemeal – 2 slices with 2 tsp margarine
Chicken – rotisserie - leg quarter with skin
Chocolate-coated, cream-filled biscuit
Chocolate bar
Croissant
Dairy milk - full cream – 250 ml
Dairy milk - low fat (skim) – 250 ml
Fried egg
Lamb chops, 2 grilled & untrimmed
Meat pie – 175 g
Pizza, 1 slice
Plain donut
Potato crisps – 50 g
Potato – French fries - 100 g
Sanitarium So Good – 250 ml
Sanitarium So Good lite
Sanitarium Weet-Bix - 2 biscuits
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Grams of fat
18.5
29.0
0.0
2.0
12.0
18.5
5.5
11-17
16.5
9.5
0.5
22.0
30.0
24.0
20.0
10.5
16.0
17.0
8.5
1.3
0.5
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WAYS TO REDUCE TOTAL FAT IN THE DIET4
Shopping tips4
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Avoid buying or go easy with ‘junk foods’ and high-fat take-away foods, e.g.
pastries, pies, sweet biscuits, cakes, donuts, chocolate, potato crisps and rich
desserts.
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Limit intake of full-cream milk, high-fat cheeses and ice cream. Buy low-fat or fat
reduced dairy foods and alternatives, also salad dressings.
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Choose mono-unsaturated and omega-3 enriched margarines or spreads instead
of butter or use a small amount of olive oil as an alternative.
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Compare product labels for levels of fat and choose lower fat options whenever
possible, and also foods lowest in saturated fat.
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Fat may be listed on a product’s ingredient listing as shortening, milk solids,
tallow, lard, glycerides, diglycerides and hydrogenated vegetable oil.
Hints on cooking4
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Mostly, use cooking methods that require little added fat or oil rather than frying.
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Use a non-stick frying pan, brush the pan lightly with oil or use a cooking spray.
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Try steaming, grilling, baking or boiling, pressure-cooking, stir-frying or microwave
cooking.
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If you eat meat, bake the meat and poultry on a roasting rack to remove fat.
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Balance out a high-fat meal by following it with a low-fat meal such as fruit or
vegetable salad.
Food preparation ideas4
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Use minimal amounts of butter, margarine, oils, high oil salad dressings,
mayonnaise and cream.
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Spread less butter or margarine on bread or toast.
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Use reduced fat milk or Sanitarium So Good Lite in place of full-fat varieties.
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Use low-fat yoghurt or cultured buttermilk in place of cream and sour cream.
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Substitute where possible, cottage or ricotta cheeses.
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Use low-fat mozzarella cheese instead of hard cheeses on pizza, pasta and in
salads.
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Avoid the use of sausages, luncheon meats and salami.
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If you eat chicken and meat, trim all visible fat from the meat and remove skin
from poultry before cooking.
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If you use meat, reduce the amount used in soups, stews and casseroles.
Replace some meat with TVP (dehydrated ‘Vege-Mince’), legumes such as
lentils, tofu, nuts and other vegetarian protein foods.
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Herbs and spices do not contain fat. With a little imagination, think what some
fresh herbs and spices can do to basic foods!
CHOLESTEROL
Ever since it was first linked to heart disease cholesterol has been a buzzword 4.
Cholesterol is a fatty, waxy substance, which looks something like the wax which
accumulates in your ears. It should not be considered abnormal or even undesirable
since it has a vital role to play in making vitamin D and some of the body’s hormones
(including sex and adrenal hormones). Cholesterol is also found in nerve and brain
tissue and is an essential part of membranes which surround the body cells.
In spite of its vital role, we do not need to eat cholesterol since the body is quite
capable of making its own supplies5.
Most of the cholesterol in the body does not come from pre-formed cholesterol in
food, but is made within the body from saturated fats. Excess cholesterol can
accumulate in the arteries, especially the coronary arteries. These arteries are
branching structures with a diameter of about the size of a drinking straw. They carry
blood to the heart muscle itself. If the quantity of cholesterol in the blood rises, some
of the waxy fat is deposited with other substances around the inside of the arteries.
This means there is less room for the blood to pass through. As a consequence, the
heart must pump much harder to force blood through the coronary arteries. To make
matters worse, it will only take a small clot of blood to block a partially blocked artery
and shut off the blood supply, causing a heart attack5.
To prevent fatty cholesterol deposits from forming in the arteries, it is essential to
prevent the levels of cholesterol in the blood from rising; cholesterol in the blood
comes from two sources:
1. Eating foods that contain cholesterol (pre-formed cholesterol). This is found in
animal foods only and includes animal products like dairy products and eggs.
There is no pre-formed cholesterol in vegetable foods. Contrary to popular belief,
avocados or peanut butter do not contain cholesterol. The pre-formed cholesterol
occurs in lean meat as well as fatty meats since it is part of the structure of the
cells in animal flesh.
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The latest information on cholesterol suggests that pre-formed or dietary
cholesterol is only a problem when the basic diet is high in fat, or for individuals
who are sensitive to dietary cholesterol.
2. Eating foods which contain saturated fats. These fats are turned into cholesterol
in the liver. Saturated fats are found in both animal and vegetable foods. Major
dietary sources include most commercially fried foods, fast foods, fatty meats,
some processed meats such as sausages and salamis, butter, cream, most
margarines, ‘solid’ cooking oils, coconut and palm oil, pastries, biscuits, cakes,
most cheeses and full-cream dairy products5.
TYPES OF BLOOD CHOLESTEROL4
Cholesterol moves around our bodies attached to ‘carriers’ known as ‘lipoproteins’.
There are two major types – high-density lipoproteins (HDL) and low-density
lipoproteins (LDL).
LDL cholesterol is known as ‘bad cholesterol’ because of its artery clogging effect
when it is found in high concentrations. It moves around inside the arteries and
deposits fatty build-ups on the inside of the artery wall.
On the other hand, ‘good cholesterol’, HDL, actually collects cholesterol and takes it
back to the liver where it is then recycled4.
So what is the link between diet and blood cholesterol levels?
There are foods that have the potential to increase blood cholesterol levels. These
foods have a high proportion of saturated and trans-fats. These foods can trigger the
body’s mechanism to produce more cholesterol.
In some people, dietary cholesterol can also raise blood cholesterol. For this reason
the National Heart Foundation recommends that people with raised blood cholesterol
levels limit their consumption of cholesterol-rich foods4.
Foods that help lower blood cholesterol levels are:
Those high in mono-unsaturated and poly-unsaturated fats, such as olives, nuts,
seeds, avocados and oily fish.
Foods high in soluble fibre such as oats, barley, fruits and legumes. These foods,
which are low in saturated fat and full of other beneficial nutrients like soluble fibre,
can make a difference if eaten regularly. Research suggests that 2 to 3 serves of
soybeans, or soy drinks can help lower cholesterol levels4.
Evidence suggests that 30 grams of nuts, such as walnuts, almonds and
macadamias, peanuts and nut butters consumed most days each week will provide
protection against heart disease. These need to be eaten instead of less healthy
snacks like crisps, biscuits and chocolate. (Not as well as4!)
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THE FACTS
Dietary guidelines for Australians recommend eating a diet low in fat, and in
particular, low in saturated fat3.
Dietary surveys show that the amount of fat eaten by most Australians exceeds the
requirements for good health4.
So then, what shall we eat? Is it possible to control the amount of fat in our diet
without having to starve ourselves2?
A balanced vegetarian diet containing a variety of foods rich in fibre is an ideal way to
maintain a moderate fat intake, provided a lot of additional fat is not added2.
A decreased fat intake will decrease one’s risk of cancer, and a decreased animal fat
intake will decrease the risk of heart disease2.
REFERENCES:
1. Butler T, Butler D, Stanton H;
VEGETARIAN COOKING DEMONSTRATOR’S MANUAL –
2nd EDITION
Adventist Health Department &
Sanitarium Nutrition Education Service, 1995: E25-E33
2. Craig W;
NUTRITION AND WELLNESS
Golden Harvest Books Berrien Springs Michigan 1999: 33-42
3. National Health and Medical Research Council
DIETARY GUIDELINES FOR AUSTRALIANS
Australian Government Publishing Service Canberra 1992
4. Sanitarium Nutrition Education Service;
FACTS ON FATS
Sanitarium Health Food Company February 1999
5. Stanton R;
EATING FOR PEAK PERFORMANCE
Allen & Unwin Australia Pty. Ltd, North Sydney, NSW
1988:14-25
6. Wahlqvist M. L; FOOD AND NUTRITION – Australasia, Asia and the Pacific
Allen & Unwin Pty Ltd Crows Nest NSW 1997: 213
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