Download Macro nutrients Fats

Macronutrients
Fats (lipids)
The functions of fats
Fats are needed for:
• Providing you with a concentrated source of energy –
1g of fat provides 9kcals of energy
• Making body cells
• Keeping the body warm (insulation)
• Protecting organs such as the kidneys
• Providing the fat soluble vitamins: A, D, E and K
• Providing the essential fatty acids
Sources of fat
Animal
Vegetable
Butter, ghee, lard, goose fat, suet, dripping
Vegetable and plant oils: olive, sunflower,
rapeseed, sesame, corn, almond
Meat/poultry: beef, lamb, pork, chicken,
bacon
Fruits: avocado, olives
Meat products: sausages, chorizo, burgers,
corned beef, salami
Nuts and nut products: cashew, pecan,
almonds, walnuts
Oily fish: mackerel, sardines, tuna, salmon,
herring, cod liver oil
Seeds: sesame, pumpkin, sunflower, peanuts
(peanut butter),
Milk, cream, yoghurt, cheese
Vegetable fat spreads, blended butter
spreads
Chocolate, pastries, biscuits, cake,
doughnuts, bread, ice cream, ready meals
and other processed foods
Ready meals and other processed foods:
curries, ice cream, salad dressing, sauces,
dips (humus)
Egg yolk
Visible and invisible fats
• Fats can be visible in some foods, such as the fat layer on
the outside of lamb or pork.
• The fat in meat may also be shown as marbling, which
appears as white streaks or flecks of fat within the meat flesh.
• Visible fat is also the butter on a slice of toast.
• Fats can be invisible and cannot be seen – for example, the
fat in pastries and cakes.
• Liquid foods such as sauces and gravy often contain invisible
fat.
Introduction to fats
• Eating fat is essential for a balanced diet.
• The term fats includes both fats and oils.
• Fats are solid at room temperature and oils are liquid at room
temperature.
• The functions of both fats and oils in the body are basically the
same.
Chemically, fat is a Triglyceride which consist of three fatty acids
combined with one glycerol molecule. The fatty acids are the most
important part of the molecule and the can be either saturated or
unsaturated
Types of fats
Depending on their chemical structure, fats are often classified into:
1. Saturated fatty acids/fats
2. Unsaturated fatty acids/fats
(a) Monounsaturated fatty acids
(b) Polyunsaturated fatty acids
3. Cholesterol
Fat-containing foods usually provide a range of different fatty acids. So, even
foods with a high saturated fat content, e.g. butter, also provide some
monounsaturates and polyunsaturates. But in simple terms, foods are often
categorised by the dominant type of fatty acid. For example, butter is often
described as a ‘saturated fat’ because it has more saturated fatty acids than
unsaturated fatty acids.
Most vegetable oils are described as ‘unsaturated fats’ as they have more
mono- and polyunsaturated fatty acids than saturated.
Types of fats and oils
1. Saturated
Saturated fats have single bonds between all the carbon atoms
in the fat.
•Melting point at about room temperature and are therefore
usually hard/solid
•Are usually from animal sources except Coconut and Palm Oil
•Sources: butter, meat fat, lard, suet, cheese, milk, egg
•Linked to heart disease – foods high in saturated farts will also
contain cholesterol. This combination can lead to a build-up of
fatty deposits in and around the heart
2. Unsaturated
Unsaturated fats have one or more double bonds between all
the carbon atoms in the fat. The double bond puts a bend or
curve in the carbon chain and this allows movement.
- Liquid at room temperature
- Sources:normally from plant sources, but also fish oils
- Research suggest they are healthier than saturated fats –
may lower blood cholesterol and heart disease
- Two types: Monounsaturated and Polyunsaturated
2a. Monounsaturated fatty acids
2b. Polyunsaturated fatty acids
- Monounsaturated fatty acids have one double bond in the
carbon chain– avocados, cashew, peanuts
- Polyunsaturated fatty acids have two or more double bonds in
the carbon chain – corn, soya, sunflower oil
Polyunsaturated fatty acids
Esential fatty acids
- Polyunsaturated fats can be sub-divided further into a omega group followed
by a number (n-3 and n-6). The number indicates the location of the first
double bond at one end of the carbon chain.
- Two well known polyunsaturated fats that are essential for health: omega 3
and omega 6 fats
- Essential fatty acids must be consumed in the diet as the body cannot
manufacture them. (When we eat foods containing fat, our body breaks up (digests) the
molecules and makes new fatty acids and molecules specifically for our body to use).
- Sources:
Omega 3 = The richest dietary source is oily fish (sardines, salmon, tuna)
therefore a weekly serving is recommended. They are also present in the
meat or eggs of animals fed with diets enriched with omega 3 fatty acids, but
in smaller amounts compared with oily fish. Rapeseed oil (canola), mustard
seeds, pumpkin seeds, linseed and linseed oil, soya bean, walnuts, green
leafy vegetables
Omega 6 = The main sources are vegetable oils and spreads made from
them: sunflower oil, corn soya , pumpkin , wheat germ, vegetables, chicken
3. Cholesterol
•
•
•
•
Cholesterol is a waxy substance and type of fat, but it does not produce any energy
75% of your cholesterol is made in your liver, the rest is absorbed from food
It is found in all animal cells and tissues, but not in vegetables or plants
Cholesterol is transported by complex proteins molecules around the body called
lipoproteins
• There are two main types of protein and cholesterol molecules:
High-Density Lipoproteins (HDL) and Low-Density Lipoproteins (LDL)
- LDLs tend to stick to damaged or inflamed areas of blood vessel walls and form
plaque buildup. Considered the ‘bad' cholesterol which can cause heart disease
- HDLs transport cholesterol from the tissues of the body to the liver, so the
cholesterol can be eliminated in the bile. Considered the ‘good' cholesterol which
can actually help to protect against heart disease.
• Where does cholesterol come from?
The Liver = Makes cholesterol and secretes it into the blood.
Genetics = genetic predisposition
Diet = High saturated fat intake
Hydrogenation
Hydrogenation is the chemical process when vegetable oils are hardened to
make them solid at room temperature.
Some oils are so unsaturated in the natural state that they need to be treated
to make them useful in food. A portion of the vegetable fat used in margarine is
hardened by hydrogenation to produce the required plasticity in the final
product before it is blended with the water.
Partially hydrogenated oil is widely used in baking and processed foods like fat
spreads, cakes, biscuits and some ready meals and may contain trans fats
Hydrogenated fat makes TRANS FATS which increases likelihood of cancer
and free radicals in the body. Like saturated fats, artificially created trans fats
have also been related to coronary heart disease. Several food manufacturers
use “free from hydrogenated fats” as a marketing claim, due to concerns about
the potential harmful effects of a high intake of trans fatty acids.
(It is carried out by heating the oil in large sealed vessels under pressure. Hydrogen is bubbled into the oil with finely
divided nickel (which acts as a catalyst and is subsequently removed by filtration). The oil blend is mixed with the water
phase, which is skimmed milk, soured under controlled conditions to give the right flavour to the product. Salt, vitamins A
and D and artificial colouring are then added. The mixture is then mixed to achieve an emulsion and cooled.)
Dietary Reference Values (DRV)
• The amount of fat we need is calculated as a percentage of
our total daily energy intake, rather than by weight.
Type of fat
% of food energy per day
Total fat of which:
No more than 35%
Saturated
11%
Monounsaturated
13%
Polyunsaturated
6.5%
Trans fatty acids
No more than 2%
Deficiency and Excess
Deficiency
-
Weight loss if carbohydrate intake is also reduced
Body feels cold quickly (not enough insulation)
Body bruises easily (not a thick enough cushion of fat to prevent damage to blood
vessels and bones)
Body will not receive enough Vit A, D, E, K (found in foods that contain fat)
Excess
- Weight gain or obesity
Being overweight or obese raises the risk of serious health problems such as
- Type 2 diabetes
- High blood pressure
- Heart disease
Foods containing fat are energy dense – fat provides 37kJ energy per gram. So foods high
in fat are high in energy too
Obesity develops if you combine eating too many energy rich foods with a lack of exercise.
If the energy from fatty foods is not all used in physical activity each day it will be stored by
the body under the skin and elsewhere around the organ.s