Diet and ExerciseBy Kashmala

Energy Resources

❖ Carbohydrates for Energy❖ Proteins for Growth and Repair in Cells❖ Fats for Energy and Making Cell Membrane❖ Vitamins and Minerals for Keeping us Healthy❖ Fibre to Keep the Digestive System working❖ Water to Transport other Nutrients

Metabolism

Metabolism rate is the rate at which Chemical Reactions take place in your body.

❖ Different Bodies have different rates❖ Males usually have faster metabolic rate compared to Female❖ Younger people have faster Metabolic rate than older people❖ The greater the Proportion of Muscle:Fat in the body, the higher

the metabolic rate❖ Can be Affected by your genes

Vitamin C

Vitamin C (ascorbic acid) is needed to help heal wounds and maintain healthy connective tissue (which gives support to other tissues and organs).

Good sources of vitamin C include:● citrus fruits (such as oranges, lemons and limes)● leafy green vegetables (such as sprouts and broccoli)

Vitamin C deficiency leads to scurvy. The symptoms of scurvy include bleeding and swelling of the gums, loss of teeth, tiredness and muscle and joint pain.

Vitamin D

The human body can make vitamin D when our skin is exposed to sunlight.

Good dietary sources of vitamin D include:● eggs● margarine and breakfast cereals fortified with vitamin D● oily fish

Vitamin D is needed to maintain healthy bones and teeth. Vitamin D deficiency leads to rickets and bone pain.

Vitamin A

Vitamin A is needed to maintain good vision, healthy skin and strong immunity against infection.

Good sources of vitamin A include:● milk, and dairy products (such as cheese and yoghurt)● mackerel and other oily fish

Vitamin A deficiency leads to night blindness, which is when a person finds it difficult to see well in dim light.

The body can convert beta-carotene (found in carrots, spinach and mangoes, for example) into vitamin A.

Calcium

Calcium is needed to maintain healthy bones and teeth, for normal blood clotting and to control muscle contractions.

Good sources of calcium include:● cheese● eggs● milk● green leafy vegetables such as broccoli and cabbage

The symptoms of calcium deficiency include weak bones and teeth, poor clotting of the blood and muscle spasms.

Irons

Iron is needed to produce haemoglobin, found in red blood cells.Good sources of iron include:● liver● red meat● beans and nuts● dried fruits such as dried apricots

Iron deficiency causes anaemia. People with anaemia become tired and weak because their blood does not transport enough oxygen.

Water

Water and dietary fibre (roughage) are also important components in the diet.

About two-thirds of the human body is water. It is found in the cytoplasm of our cells and in body fluids like blood.

Sources of water include:● food● drinks● metabolic processes - such as aerobic respiration

Dietary Fibre

Dietary fibre consists of material in food that cannot be digested, in particular cellulose from plant cell walls.

Sources of fibre include:● fruit● vegetables● cereals

Dietary fibre is important because it provides bulk, which helps the walls of the intestine move food and faeces along the gut. Lack of dietary fibre can lead to constipation.

Balanced Diet

A balanced diet is a diet in which all the components needed to maintain health are present in appropriate proportions.

The ‘eatwell plate’ shows the proportions of the different components that should be eaten daily in a well-balanced diet.

A balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.

Energy Requirements:AgeThe amount of energy we need tends to increase as we approach

adulthood.

The energy needs of adults go down as they age. For example, people in their 50s need about 17% less energy in their diet than people in their 30s.

ER:Activity Levels

People who are active tend to need more energy than sedentary people. For example, an adult office worker might need 10,000 kJ per day, but a manual worker might need 15,000 kJ per day.

ER:PregnancyIn general, the greater a person’s mass, the more energy they need. Men tend to need more energy than women, and a woman’s energy needs increase when she is pregnant. This is mainly because she is carrying extra mass.

Calorimetry

The energy content in a food sample can be measured using simple calorimetry.

To carry out this experiment, you need to:1. pour cold water into a boiling tube2. record the starting temperature of the water3. record the mass of the food sample4. heat the food until it catches fire5. heat the water using the flame from the burning food6. record the final temperature of the water

Calculations

energy transferred (J) = mass of water (g) × 4.2 (J/g°C) × temperature increase (°C)

Question:When 0.5 g of food is burned, 10 cm3 of water warms up by 20°C.What is the energy content of the food in J/g?

Answer:1 cm3 of water has a mass of 1 genergy transferred to water = 10 × 4.2 × 20 = 840 Jenergy content of food = 840 ÷ 0.5 = 1680 J/g

Fair Testing

When comparing different foods, it is important to carry out a fair test. Several variables should be kept constant:

● the starting temperature of the water● the temperature increase● the distance of the flame from the boiling tube

More reliable results can be obtained by repeating the experiment. The biggest source of error in calorimetry is usually unwanted heat loss to the surroundings.

Food Additives

Food may contain additives. These are substances intended to improve the properties of the food.

E NumbersAdditives with an E number have been licensed by the European

Union. Some are natural and some are artificial. They have all been safety tested and passed for use. The UK Food Standards Agency sets strict limits on the amounts allowed in food.

Hazards of Food AdditivesThere are health hazards associated with certain food additives. For

instance, some additives:● cause allergic reactions in some people● may cause hyperactivity and behavioural problems in some

children● have been associated with an increase in childhood asthma in

recent years

Glossary

KeyPoints

❖ Most people eat a varied diet which includes everything needed to keep the body healthy

❖ Different people need different amounts of energy❖ The Metabolic rate varies from person to person❖ The more Exercise you do, the more food you need❖ The temperature where you live also affects how much energy you

need to take in❖ Malnourished is the condition when the body doesn’t get balanced

diet