Diet — Cambridge IGCSE Biology
A balanced diet, the sources and importance of each nutrient, and the causes of scurvy and rickets.
Revision notes
2 short notes, in the order of the specification. Each one in short:
A balanced diet contains all the nutrients the body needs, in the correct proportions, and gives the right amount of energy for the person. Carbohydrates and fats provide energy, proteins are needed for growth and repair, calcium makes bones and teeth, iron makes haemoglobin, and fibre provides bulk so the gut muscles can push food along.
A deficiency disease is caused by not getting enough of a particular nutrient over a long period. Scurvy is caused by a lack of vitamin C and causes bleeding gums and slow healing of wounds. Rickets is caused by a lack of vitamin D or calcium, so bones do not harden properly and may bend.
Exam questions
6 exam-style questions (15 marks), each with its mark scheme.
Answer the questionsFlashcards
8 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of human nutrition on one page, so you can see where this subtopic fits.
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Quick check questions
What is a balanced diet?
Show answer
A diet containing all the nutrients in the correct proportions, giving the right amount of energy for the person.
Which nutrient is needed for growth and repair?
Show answer
Protein.
What causes scurvy?
Show answer
A lack of vitamin C.
What causes rickets?
Show answer
A lack of vitamin D (or calcium).
Why does the body need iron?
Show answer
To make haemoglobin in red blood cells.
Frequently asked questions
What does each nutrient do in a balanced diet?
Each nutrient has a specific job. Carbohydrates provide energy; fats provide energy, an energy store and insulation; proteins are for growth and repair; vitamin C keeps skin and gums healthy; vitamin D helps absorb calcium; calcium makes bones and teeth; iron makes haemoglobin; fibre adds bulk; and water is a solvent.
Why is fibre important in the diet?
Fibre is important because it provides bulk for the muscles of the gut to push food along, which helps prevent constipation. Fibre, also called roughage, is not digested by humans and does not give energy. Good sources include wholemeal bread, fruit and vegetables. Always say it adds bulk, not that it gives energy.
What is the difference between scurvy and rickets?
Scurvy is caused by a lack of vitamin C and causes bleeding gums, slow healing of wounds and damaged skin. Rickets is caused by a lack of vitamin D or calcium, so bones do not harden properly and may bend, especially in children. Each is prevented by eating more of the missing nutrient.
Why does the body need vitamin D?
The body needs vitamin D because it helps absorb calcium from food, so bones and teeth become hard. Without enough vitamin D, bones stay soft and may bend, which is rickets. Vitamin D comes from oily fish, eggs and margarine, and it is also made in the skin in sunlight.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026