ahe7042s chapter1

© Edco 2011 Lifewise

Lifewise

Home Economics for Junior Certificate


FOOD AND NUTRITIONChapter 1


Functions of food

• Food helps the body to grow

• Food provides the body with energy

and warmth

• Food protects the body against

disease


Nutrition: important terms

• Nutrient – a chemical in food that nourishes the body, e.g. protein

• Composition – what the nutrient is made of• Source – a food that contains the nutrient• Function – what the nutrient does in the body• Recommended dietary allowance (RDA) –

the amount of the nutrient we should eat each day

• Deficiency disease – ill effects that are caused by lack of the nutrient


Nutrients

• A nutrient is a chemical in food that nourishes the body

• Although water is not regarded as a nutrient, it is essential for life

• There are six types of nutrient:– proteins– vitamins– fats– minerals– carbohydrates– water


Macronutrients and micronutrients

• Proteins, fats and carbohydrates are macronutrients: they are needed in large amounts

• Vitamins and minerals are micronutrients: they are needed in small amounts


Proteins

• Proteins are made up of amino acids

• Amino acids are made up of carbon, oxygen, hydrogen and nitrogen


Classification of proteinsFoods containing high biological value protein

Foods containing low biological value protein

• Meat• Fish• Eggs• Milk and dairy produce• Soya beans• Quorn

• Peas• Beans• Lentils• Nuts• Whole cereals• Muesli


Functions of protein

• Helps body cells to grow• Helps the body repair damaged cells• Forms hormones and enzymes• Used for heat and energy when there are

not enough energy foods in the diet


Fats

• Fats are made from fatty acids and glycerol

• Each molecule of glycerol is attached to three fatty acids

• Glycerol and fatty acids contain carbon, hydrogen, oxygen

Composition of fats


Sources of fatsSaturated fats Unsaturated fatsMainly from animal sources From plant and marine sources• Butter• Meat• Milk and cream• Cheese• Eggs• Suet

• Sunflower oil• Olive oil• Nuts• Seeds• Polyunsaturated margarine• Fish oils• Oily fish


Functions of fats

• Provide heat and energy• Contain vitamins A, D, E, K• A layer of fat under the skin insulates the

body• Protect delicate organs• Delay the feeling of hunger


Carbohydrates

• Made up of simple sugars

• Simple sugars join to form starch

• Carbohydrates contain carbon, hydrogen and oxygen

• Composition of carbohydrates


Sources of carbohydratesSugars Starches Dietary fibre• Fruit (fresh and dried)• Milk• Cakes, biscuits• Soft drinks• Jam• Ice cream• Honey• Sugar

• Cereals• Potatoes• Root vegetables• Pulse vegetables

• Vegetables• Fruit• Brown rice• Brown bread


Fibre

• Fibre absorbs water and becomes bulky in the intestine

• This prevents constipation and other bowel diseases

• RDA for fibre: 30g for an average person


Vitamins

• Vitamins are needed in small amounts• They are divided into two groups:

– Water-soluble: vitamin B group and vitamin C– Fat-soluble: vitamins A, D, E and K


Minerals


Water

Sources of water• Tap or bottled water• Drinks such as milk, tea,

coffee• Most foods contain water

Functions of water• Satisfies thirst• Helps digestion• Helps remove waste

from the body• Source of fluoride and

calcium• Part of all body fluids


Energy

Energy from food• The body’s cells burn

food and produce energy. This is called oxidation

• Energy in food is measured in kilocalories or kilojoules

• 1 kcal = 4.2 kJ

Energy requirements depend on:

• Size• Age• Activity levels• Climate• Gender• Pregnancy


Energy balance

• Energy input should be equal to energy output

• Extra energy is stored in the body as fat

• Too little energy can lead to a person being underweight

ahe7042s chapter1

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