The study of food, its composition, the
amounts needed by the body and its
effects on the body
© PDST Home Economics
Food: any substance, solid or liquid, that contains
Nutrients: substances that can be digested and used by
Elements: All nutrients are made up of elements. They are
simple substances that cannot be broken down into
Diet: the selection of food each person eats
Balanced diet: contains all the nutrients in the correct
amount for the needs of the body.
RDA: Recommended dietary allowance
GDA: Guideline daily amount
There are 6 nutrients
Fats / Lipids
Macronutrients: needed in large amounts by the
body i.e. protein, fat and carbohydrate.
Micronutrients: Needed in small amounts by the
body i.e. vitamins, minerals
Composition: the elements that make up the
Classification: dividing things into groups or
Sources: foods that supply a large amount of a
Functions: Uses of nutrients in the body
Protein - Composition
Made up of the elements:
Protein is the only nutrient with nitrogen which
is needed for growth
The elements join to form Amino Acids
The amino acids link together in long chains
Protein - Composition
Protein - Classification
There are 2 classes of protein
1. HBV protein (High Biological Value)/ First
class protein / Animal protein.
2. LBV protein (Low Biological Value ) / Second
class protein / Plant protein.
Both classes of protein are needed in the diet
Protein - Sources
Animal protein: meat, poultry, fish, eggs, cheese,
Plant protein: Lentils, Beans, Peas, nuts, cereals
Plant protein foods contain:
Less saturated fat
Cheaper to produce
Protein - Sources
Protein - Functions
The growth of all body cells
For repair of worn or damaged cells
To make hormones, enzymes and antibodies in
Protein - functions
Protein – RDA and Energy value
RDA for protein is 1g per day per Kg of body
1 gram of protein can release 4 kilocalories or 17
kilojoules of energy
Test on Protein
Atoms of which elements make up protein?
What’s special about Nitrogen?
Name the small units that form proteins
Name the 2 classes of protein
List 5 food sources for each class
Give 2 functions for protein
What are the effects of protein deficiency
Are proteins micro or macro nutrients?
How much protein do we need per day?
What is the energy value of 1 gram of protein?
Lipids (fats & oils)- Composition
Lipids are called fats when solid at room temperature
and oils when they are liquid at room temperature.
Made of 3 elements:
The elements make units called glycerol and fatty acids
Each glycerol joins to 3 fatty acids to form a lipid
Lipids - structure
Lipids - Classification
There are 2 classes of lipids
1. Saturated lipids: animal fats, solid at room
2.Unsaturated lipids: plant and fish oils, liquid at
Lipids - Sources
1. Saturated fats are found in: butter, suet, lard,
meat, cheese, eggs, milk, yoghurt.
2. Unsaturated fats are found in: fish, nuts,
seeds, cereals, soya beans, olives, avocado pears,
some margarines, cooking oils.
Unsaturated fat sources
Lipids - Function
Releases heat and energy for the body
Insulates the body
Protects delicate organs e.g. kidneys
Source of fat soluble vitamins A, D, E, K
Adds flavour to foods
Overweight or obesity
Saturated fats raise blood cholesterol. This
causes high blood pressure, strokes and heart
Benefits of saturated lipids
Help reduce cholesterol
Omega 3 and omega 6 fatty acids reduce risk of
heart disease and improve brain function. They
are found in oily fish, seeds and nuts
Carbohydrates - Composition
Made of 3 elements:
The elements form single sugar units e.g. glucose
The sugar units link up to form other
There are 3 classes of carbohydrates
Cellulose (fibre, roughage)
Carbohydrates - Sources
1. Sugars are found in: fruit, honey, table sugar,
cakes, biscuits, sweets, fizzy drinks, jam
2. Starches are found in: bread, potato, pasta,
3. Cellulose is found in: Fruit, vegetables, wholecereals, seeds, nuts, beans, brown bread, brown
rice, high fibre breakfast cereals
Carbohydrate - functions
To supply the body with energy
Extra carbohydrate is changed to body fat and
Cellulose is needed to keep the digestive system
healthy and lower cholesterol
Not digested, just passes through our digestive
Helps to push food through the intestine and
prevent constipation, diverticulosis and cancer of
We need to eat 30g of fibre a day to be healthy
most people only eat 15g
Sugar is a food we need to eat less of
Too much sugar is causing obesity, tooth decay
A lot of sugar is hidden in foods that don’t really
taste sweet especially convenience foods e.g.
spaghetti hoops, check label for ingredients
Reducing Sugar in your Diet.
Replace sugary snacks with healthy fruit , nuts,
Drink water instead of fizzy drinks
Sweeten breakfast cereals with fresh or dried
fruit e.g. raisins, banana
Check sugar content on food labels and choose
low sugar foods
Vitamins – (micronutrients)
Essential for good health
Each vitamin has its own job to do in the body
If a vitamin is missing from the diet a deficiency
disease can occur
Vitamins - Classification
1. Fat –Soluble (dissolve in fat) Vitamins: A,D,E,K.
2. Water – Soluble (dissolve in water) Vitamins:B, C
If more of the fat soluble vitamins is eaten than the
body needs it is stored in the liver.
If an overdose of these vitamins is eaten it causes
hypervitaminosis which is harmful to the body.
Water soluble vitamins are not stored in the body, if too
much is eaten they are removed in the urine.
It is therefore important to eat water soluble vitamins
Fat soluble vitamins
Oily fish, cod liver oils
(changed to vitamin A
in the body)
e.g. cabbage, spinach
Sunlight oily fish, cod liver oil, tinned salmon/sardines,
margarine, butter eggs,
of the body
Unhealthy membranes /linings
Healthy bones and teeth
Water Soluble Vitamins
Meat, fish, eggs, cereals, flour, yeast, nuts,
pulses, Brown bread, supplements
release of energy from food.
a healthy nervous system
For growth of healthy foetus during pregnancy
Healthy skin & gum
Fruit, esp. blackcurrants, citrus fruit
e.g. oranges, strawberries. Veg. esp.
Strengthens blood vessels
Test on Vitamins
Are vitamins micro or macro nutrients?
What are the two classes of vitamins and name the
vitamins in each class
List (a) 3 sources of vitamin A (b) 2 sources of carotene
What is the functions of vitamin D?
What happens if you are deficient in Vitamin B?
List 4 functions for vitamin C
What vitamin can be got from sunshine?
Which vitamin prevents scurvy?
What is hyper-vitaminosis?
Which vitamin works with calcium in the body?