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Science

Diet and digestion

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Food provides the energy needed by living things. Food undergoes both physical digestion and chemical digestion so that it can be absorbed into the bloodstream.

Carbohydrates and fats are high energy sources. Protein, meanwhile, is needed for growth and repair. Protein deficiency leads to diseases such as kwashiorkor.

A balanced diet

The table below summarises the three main nutrients in food, what they are made from, and why they are needed.

The main nutrients in food

nutrientmade frommain uses
potato, banana, pasta carbohydratessimple sugars such as glucosehigh energy source
cheese fatsfatty acids and glycerolhigh energy source
meat proteinsamino acidsgrowth and repair

Proteins are also used as an 'emergency' energy source if the diet has insufficient carbohydrates and fats in it.

A balanced diet will also include nutrients that do not provide energy, such as:

  • minerals, like iron, to make haemoglobin
  • vitamins, such as vitamin C, which prevents a disease called scurvy
  • fibre, which prevents constipation
  • water

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