A balanced diet and the 7 food groups Aims: –To know why food is important –To know that a healthy diet consists of a balance of 6 groups of chemicals.

A balanced diet and the 7 food groups

• Aims:

– To know why food is important

– To know that a healthy diet consists of a balance of 6 groups of chemicals and water

– To be able to use chemical tests to identify proteins, carbohydrates and fats

Diet

• Your diet is the food you eat every day.

• You could have a poor diet or a healthy diet.

• Your food is a source of raw materials for your body.

• These raw materials are needed to make new substances for:– Energy– Growth– Health

Humans need to consume a balanced diet which contains a variety of different types of food.

The main nutrients the body needs are:

carbohydrates for energy;

proteins for growth and repair;

fats to store energy;

vitamins and minerals to keep the body healthy;

fibre to keep your intestines healthy and prevent constipation;

water is an important solvent in your body. It has many used.

Why do we need food?

The amount of each food type needed is related to theproportions in the food pyramid.

Which food type does the body need the most of?

Nutrients in food

What is a balanced diet?

Starchy foods contain carbohydrates which are made of long chains of identical small sugar molecules.

carbohydratemolecule

What are carbohydrates?

one sugar molecule

The long chains of carbohydrates are broken down into the smaller sugar molecules by the body.

The small molecules from carbohydrates are used by the body to release energy and make the body work.

Proteins, like carbohydrates, are made of long chains of small molecules. In proteins, these small molecules are not identical.

What are proteins?

protein molecule

one amino acid

Proteins are made up of chains of small molecules called amino acids. There are over 20 different kinds of amino acid.

Proteins are used by the body for growth and repair.

Fats are made up of fat molecules which contain fatty acids and glycerol.

What are fats?

fat molecule

glycerol

Fat molecules have to be broken down by the body so that they can be used for energy storage.

Fats are also used by the body to keep heat in and to make cell membranes.

fatty acids

Food typesTypeType Found inFound in UsesUses

Carbohydrates

Fats

Proteins

Vitamins

Minerals

Fibre

Water

Bread, potatoes, cereal

Cream, butter, milk, oil

Meat, fish, eggs

Vegetables, cereal

Meat, milk, cereal

Fruit + veg, cereal

Water!

Energy

A store of energy

Building and repairing cells

Keep things “ticking over”

Strong teeth etc

75% of the body is water

Keeps you regular!

What problems can diet cause?

• Too much food:– Weight gain– Heart disease

• Too little food:– Weight loss– Lack of energy

• Too little protein:– Muscle wastage– Kwashiorkor

What problems can diet cause?

• Too little vitamin C:– Scurvy

• Too little vitamin D:– Rickets

• Too little calcium:– Weak bones and teeth

Food tests 1To investigate what happens in digestion we need to be able to test for different foods. Here are two simple tests:1) The test for starch:

Drop some iodine onto the food. If the iodine turns BLUE/BLACK then STARCH is present.

2) The test for simple sugars (e..g glucose)

Boil the food with some Benedict’s solution. If an orange “precipitate” appears then the food contains simple sugars

Iodine

Food tests 21) The test for protein:

Place 1 cm of food at the bottom of a test tube. Add 5 drops of Biuret solution. If protein is present it will turn lilac/purple

2) The test for fats:

Shake the food with about 10cm3 of ethanol in a test tube. Pour some of the solution into a tube containing water. If fat is present the water will turn cloudy white.