Lesson overview
A balanced diet: Is this a balanced diet?
Pack the food crate of a polar station for a 16-week winter, run the winter and watch which nutrients run out. Find out what too little vitamin C, vitamin D, calcium or fibre does to the body, then repack the crate until every nutrient lasts and none is far more than needed. Learn where each kind of nutrient comes from, why the body needs it, and what causes scurvy and rickets.
Suggested sequence
- Lesson 1 · Nutrients and what they do. The seven kinds of nutrient: carbohydrates, fats and oils, proteins, vitamins C and D, calcium and iron, fibre and water; their main sources and why the body needs each. Read together and discuss (15–20 min), practise with self-checking (20–25 min).
- Lesson 2 · A balanced diet. A balanced diet: every nutrient in the right amount; the polar station's crate; scurvy from too little vitamin C and rickets from too little vitamin D or calcium; sunlight and vitamin D. Read together (10–15 min), show or explore the experiment (10 min), practise with self-checking (15–20 min).
- End of module · final check. 6 new questions, 20–30 min, without hints or notes; pupils check their answers once they have answered them all.
- One to two weeks later · return questions. 8 questions, 15 min, lesson closed.
Learning goals
Part 1: Nutrients and what they do
- State the principal dietary sources of carbohydrates, fats and oils, proteins, vitamins C and D, calcium, iron, fibre and water (7.1.2)
- Describe the importance of carbohydrates, fats and oils, and proteins (7.1.2 a–c)
- Describe the importance of vitamins C and D and of the mineral ions calcium and iron (7.1.2 d–e)
- Describe the importance of fibre (roughage) and water (7.1.2 f–g)
Part 2: A balanced diet
- Describe what is meant by a balanced diet (7.1.1)
- State the causes of scurvy and rickets (7.1.3)
- Use what each nutrient does and where it comes from to judge whether a diet is balanced and which foods would fill a gap (7.1.1–7.1.2)
Misconceptions to listen for
- “Protein is mainly for energy.” — The body can respire protein, but its main job is growth and repair: new cells are built from it.
- “Iron makes bones hard.” — Calcium makes bones hard. Iron is needed to make haemoglobin in red blood cells.
- “Meat contains fibre.” — Fibre comes from plant cell walls. Meat, fish, eggs and milk contain none.
- “Milk is the best source of vitamin D.” — Milk is rich in calcium. It has little vitamin D unless vitamin D has been added to it (fortified milk).
- “Fat has no use in the body.” — Fat is a nutrient: it is a source and store of energy, insulates the body and is part of every cell membrane.
- “Vitamin D makes bones hard by itself.” — Calcium is what makes bones hard. Vitamin D helps the body take calcium in from food.
- “Iron makes muscles strong.” — Iron is needed for haemoglobin, which carries oxygen in the blood.
- “Only meat contains iron.” — Beans, lentils and dark green leafy vegetables contain iron too.
- “Fibre is useless because it is not absorbed.” — Fibre does its job inside the gut: it adds bulk so food keeps moving.
- “Fibre gives us energy.” — We cannot digest fibre, so it releases no energy for us.
Scope
What is meant by a balanced diet (7.1.1); the principal dietary sources and the importance of carbohydrates, fats and oils, proteins, vitamins C and D, calcium and iron, fibre and water (7.1.2); the causes of scurvy and rickets (7.1.3). Energy values, portion sizes and body weight are left out; food tests are in Food tests, digestion in the gut modules. The amounts of each nutrient in the experiment come from a teaching model.