A balanced diet and the main nutrients

Human nutrition · Diet · note 1 of 2

Spec 7.1.1, 7.1.2Download all Diet notes (PDF)Download all notes (PDF)4 pages

A balanced diet and the main nutrientsSpec 7.1.1, 7.1.2

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 balanced diet contains all the nutrients the body needs, in the correct proportions, and gives the right amount of energy for the person. The amount of energy needed depends on age, sex and how active the person is.

You need to know the main source of each nutrient and why the body needs it. Vitamins are limited to C and D, and mineral ions are limited to calcium and iron.

Nutrients: sources and importance
Nutrient	Main dietary sources	Importance in the body
Carbohydrates	Bread, rice, pasta, potatoes	Provide energy
Fats and oils	Butter, cooking oils, fatty meat, nuts	Provide energy, act as an energy store and give insulation (keeping the body warm)
Proteins	Meat, fish, eggs, beans	Growth and repair of tissues
Vitamin C	Citrus fruits, fresh fruit and vegetables	Needed for healthy skin and gums; prevents scurvy
Vitamin D	Oily fish, eggs, margarine (also made in the skin in sunlight)	Helps the body absorb calcium, so bones and teeth are hard; prevents rickets
Calcium	Milk, cheese, yoghurt	Making bones and teeth
Iron	Red meat, liver, green leafy vegetables	Making haemoglobin in red blood cells
Fibre (roughage)	Wholemeal bread, fruit, vegetables	Provides bulk for the muscles of the gut to push food along, which helps prevent constipation
Water	Drinks and most foods	Needed as a solvent and for the reactions in cells; forms the blood plasma, sweat and urine

A plate divided into food groups: fruit and vegetables (vitamins, minerals, fibre, e.g. oranges, carrots), carbohydrates (e.g. bread, rice), proteins (e.g. meat, fish, beans) and a small section of fats and oils (e.g. butter, cooking oil), with a glass of water beside it. — A balanced diet contains all the nutrients in the correct proportions, plus fibre and water.

Common mistake:

Do not say fibre 'gives energy' or is digested. Fibre is not digested by humans; it adds bulk to the food.

Exam tip:

Give a specific use, not just 'for health'. Write 'iron for making haemoglobin' or 'calcium for strong bones and teeth'.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

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.

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