1.4.3  Using nutrients to produce energy

When you turn on the engine of a car, the petrol combines with oxygen and ‘burns’ to make energy. The energy makes the car move, and it also makes the engine warm. Similarly, the body ‘burns’ nutrients to make energy. Sometime people are surprised to learn that nutrients are ‘burning’ inside their bodies. Nutrients do really burn – but in a different way from a fire so that there is no fire or smoke.

Starch, sugar and fat are made of the elements carbon, hydrogen and oxygen. When they ‘burn’ in the cells, they combine with oxygen from the air that we breathe in. They release energy, and they change into carbon dioxide and water, which we breathe out. Table 1.4 shows the different ways our body uses energy.

Table 1.4  Different uses of carbohydrates in our body.
FunctionReason
To keep aliveOur bodies are ‘turned’ on and use energy from the moment of conception until we die. For example, energy is used to keep the heart and kidneys working.
To keep warmOur bodies are warm, even if we are asleep. Keeping warm uses energy.
To build tissuesThe body uses nutrients such as starch to provide the energy for building.
To secrete fluidsThe body uses energy to secrete fluids such as saliva and breastmilk.
To repair tissuesAfter injury or illness, the body uses energy to repair damaged tissues.
To move and workWe need energy to move muscles, to move our bodies, to walk, to talk, to play, to run and to work.

  • List some of the ways the body uses nutrients to produce energy. Which population group in your community needs the most energy and why?

  • The body uses nutrients to produce energy to keep alive, build and repair tissues, secrete fluids, keep warm, move and work. The population group that needs a lot of energy is children because they are very active (they run and play a lot) and their energy needs, based on their body weight are high.

Table 1.5 below provides you with a summary of the way our body uses nutrients.

Table 1.5  How the body uses nutrients in food we eat.
NutrientUse
Carbohydrates (starches and sugars)For energy
Fibre

To keep gut healthy

To help digestion

Fats

For energy

To build cells

Stored for use as energy when needed

Proteins

To build cells

To make fluids

For chemical processes

For energy

To protect against infection

Minerals

To build cells

To make fluids

For chemical processes

Vitamins

For chemical processes

To build cells

To protect against infection

Water

For chemical processes

For building cells

To make fluids

1.4.2  Using nutrients to build the body

1.5  Food and nutrition: cultural and religious taboos