Balanced diet

A balanced diet is the different components present in appropriate proportions needed to maintain a healthy body. It should inlude carbohydrates, lipids, proteins, vitamins a,c,d, iron, calcium, dietary fibre and water.

Carbohydrates: Constructed mostly of starch and glucose hence it is a source of immediate energy. Found in cereal, potatoes, rice and pasta. Note that starch is a store of glucose.

Proteins: Constructed of a unique sequence of amino acids. They are required for the growth and repair of tissue. Found mostly in eggs, lentils, pork and soy.

Lipids: Constructed of fatty acids and glycerol. This is used as a store of energy in the long term. It is primarily used to insulate the body and stop the loss of heat i.e. homeostasis. It is found in dairy products, cheese, milk, fish etc.

Vitamin A: Essential for the reproduction of cells - maintains immune system. It is an antioxidant found in fatty fish, milk, cheese and mango.

Vitamin C: Another antioxidant that helps fight infection. Found in orange, grapefruit and kiwi.

Vitamin D: Maintains healthy bones and teeth by aiding the absorption of calcium. Remember that absorption is the taking in of minerals, ions and other soluble molecules into the bloodstream. It is found in milk and other dairy products i.e. yoghurt. Eggs and fish are also rich in vitamin d. Sunlight is helpful in encouraging the body to produce vitamin d.

Calcium: Is essential to the growth and repair of bones and heart function. Found in dairy products.

Iron: A component of haemoglobin in red blood cells. This is what oxygen binds to. It is common in red meats.

Water: Useful in the chemical reactions of cells. Found in the sea, clouds, me, you, in glaciers and in your tap.

Dietary fibre: Keeps the bowels functioning well and reduces the risk of bowel cancer. Found in cereals and rice.

Activity levels, age and pregnancy requirements for energy:

When people are young, they are more active and are growing. As a result they require more energy than an elderly person who is less active and no longer grows. With an active lifestyle, more energy is utilised in movement and the development of cells. As a result, more energy is required as the cells are respiring more.

When a woman is pregnant, she is supporting not only her life but her baby's. Therefore she needs to consume the appropriate amount of energy for both of them. The baby's growth and development requires significant amounts of energy.

An experiment to investigate the energy content in a food sample

1. Get a food sample.
2. Weigh the food sample and record the mass.
3. Fill a boiling tube with 10cm^3 of cold water.
4. Using a thermometer, measure the temperature of the water.
5. Burn the food sample using a bunsen burner until it catches fire.
6. Hold the burning food under the water for 2 minutes.
7. Extinguish the fire.
8. Measure the new temperature of the water using the thermometer and calculate the temperature rise.
9. Using the equation [mass of water x 4.2J/oC x temperature rise] calculate the total energy transferred.
10. Divide the total energy transferred by the original mass of the sample to calculate the energy present in one gram.