Lesson focus: A balanced diet supplies energy, raw materials, micronutrients, fibreThe part of plant food we cannot digest, which helps food move through the gut. and water in amounts that match an individual’s needs.
Describe the functions and sources of the seven main nutrientA useful substance in food that your body needs, such as protein or vitamins. groups and explain why requirements vary.
Build on earlier learning
Structure–function chainsYear 7 linked organ systems to cell needs. This lesson identifies the materials that digestion and circulation must make available to cells.
You will be successful when you can…
- Name the seven nutrient groups.
- Distinguish energy-providing nutrients from micronutrients.
- Link nutrients to functions and food sources.
- Explain why a balanced diet varies between people.
Words that carry the science
- nutrient
- A substance in food needed for energy, growth, repair or healthy body function.
- carbohydrate
- A nutrient group including sugars and starches, used mainly in respiration.
- lipid
- A nutrient used in membranes, insulation and long-term energy storage.
- protein
- A nutrient digested to amino acids for growth, repair and making cell proteins.
- vitamin
- An organic micronutrient needed in small amounts for normal body processes.
- mineral
- An inorganic nutrient element needed in small amounts, such as iron or calcium.
- fibre
- Mostly indigestible plant material that supports movement through the gut.
Link each nutrient to a biological role
01Macronutrients provide fuel and building material
carbohydrateA nutrient that gives us energy, found in foods like bread, rice and pasta. provide glucose for respiration. lipidA fat or oil, used by the body to store energy and keep warm. form part of cell membranes and act as concentrated energy stores and insulation. proteinA nutrient made of chains of amino acids, used for growth and repair of cells; found in meat, fish, eggs and beans. supply amino acids used to make body proteinA nutrient made of chains of amino acids, used for growth and repair of cells; found in meat, fish, eggs and beans., including enzymes.
These roles overlap. Protein can release energy, but describing it only as an energy source misses its major structural and functional roles.
02Micronutrients have specific functions
vitaminA nutrient the body needs in small amounts to stay healthy, such as vitamin C. and mineralA nutrient such as iron or calcium that the body needs in small amounts. are required in smaller amounts but remain essential. Vitamin C supports connective tissue, vitamin D helps calcium absorption, iron forms part of haemoglobin and calcium contributes to bones and cell signalling.
A deficiency results from too little of a particular nutrientA useful substance in food that your body needs, such as protein or vitamins. over time. More is not always better because excessive intake of some micronutrients can also cause harm.
03Fibre and water support the whole system
fibreThe part of plant food we cannot digest, which helps food move through the gut. adds bulk and helps material move through the large intestine. Water acts as a solvent, transports substances and supports temperature control.
A balanced diet provides appropriate amounts and variety. Age, body size, activity, pregnancy, health and environmental conditions can alter needs, so one fixed menu cannot define balance for everyone.
Nutrients in food
A balanced diet has carbohydrates, proteins, fats, vitamins, minerals, fibre and water. Different foods are good sources of different nutrients. Compare what is in 100 g of each food.
Controls
Approximate values. Water and other includes vitamins and minerals, which are needed only in tiny amounts.
Improve a low-variety lunch
A lunch contains only white bread and a sugary drink. Suggest two justified additions.
- Identify what the meal already provides: mainly carbohydrate and water.
- Notice likely gaps such as protein, fibre and a wider range of micronutrients.
- Add beans, egg or another protein-rich food to supply amino acids.
- Add fruit, vegetables or wholegrain food for fibre and varied vitamins and minerals.
How to make the reasoning visible: The additions improve nutrient variety; they do not make a universal claim that one food is always healthy or unhealthy.
Build nutrient–function chains
Use each example as evidence about the main role, while recognising that real foods contain mixtures.
| Nutrient | Example source | Important role | Possible issue if intake is persistently low |
|---|---|---|---|
| Carbohydrate | Rice or potato | Substrate for respiration | Low available energy |
| Protein | Beans, fish or egg | Growth and tissue repair | Poor growth or repair |
| Lipid | Seeds or oils | Membranes and energy store | Reduced supply of essential fatty acids |
| Iron | Beans, meat or fortified cereal | Haemoglobin production | Iron-deficiency anaemia |
| Fibre | Wholegrains, fruit and vegetables | Supports gut movement | Constipation risk |
| Water | Drinks and water-rich foods | Solvent and transport | Dehydration |
Why can one food appear in more than one nutrient category?
Explain why a very active person may need a different intake from a less active person of similar size.
Check your understanding
Answer from memory, then check against the suggested answer.
Which nutrient is digested to amino acids?
What is a major role of fibre?
Why is iron needed?
A cereal provides carbohydrate, fibre, iron and vitamin D. Explain why listing these nutrients does not prove the whole diet is balanced.
Explain why calling vitamins “energy-giving nutrients” is scientifically inaccurate.
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A growing teenager needs a varied diet containing carbohydrate, protein, lipid, vitamins, minerals, fibre and water.
Give the main use in the body of carbohydrate, protein and lipid.
(3)Explain why vitamins, minerals, fibre and water are also needed.
(2)Total for this question: 5 marks
Command word: For explainA command word: say how or why something happens, giving reasons with words like "because" or "so"., attach a biological function to each named nutrient rather than writing a food list.