Explain a balanced diet
Relate a varied nutrient supply to the needs of the organism.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall large and small nutrient molecules, cell membranes and enzyme specificity.
- Use the stated diagram keys and evidence; models are not to scale.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which component supports tissue growth and repair?
What you will learn
- Relate a varied nutrient supply to the needs of the organism.
- Evaluate a menu without treating balance as equal masses.
Several components, different functions
| Component | Examples of sources | Role |
|---|---|---|
| Carbohydrate | Rice, bread, potatoes | Energy source for respiration |
| Fats / oils | Vegetable oil, nuts, butter | Energy store; insulation; membranes |
| Protein | Eggs, beans, lentils | Amino acids for growth and repair |
| Vitamin C | Citrus fruit, peppers | Connective tissue; deficiency: scurvy |
| Vitamin D | Oily fish; labelled fortified foods | Calcium use; deficiency: rickets |
| Calcium | Dairy; labelled fortified sources | Bones and teeth |
| Iron | Meat, pulses, fortified cereal | Needed for haemoglobin |
| Fibre | Wholegrains, fruit, vegetables | Bulk and movement through the gut |
| Water | Drinks; water-containing foods | Solvent, transport and reaction medium |
Meet several needs
A balanced diet supplies the nutrients needed in appropriate amounts and proportions: carbohydrate, fat, protein, vitamins and minerals, together with fibre and water. It must support energy needs, growth, repair and normal body functions rather than maximise one nutrient.
Balanced does not mean equal masses of every nutrient. Energy needs vary with activity and other circumstances. A food commonly supplies several nutrients, so a label such as protein food is not a claim that it contains only protein.
Evaluate the evidence supplied
Compare a proposed menu with the named nutrient sources and functions. A single energy total does not show whether vitamins, minerals, fibre and water are adequate. A photograph of one meal does not establish a person’s whole dietary pattern.
In written school questions, identify a missing category using the stated information and explain its function. These comparisons teach biology; they do not prescribe a personal diet or diagnose a deficiency.
Sources for this lesson
Pause and explain
Which claim best describes balance?
Worked example
A supplied menu provides enough energy and protein but is stated to contain very little fibre. Explain why the energy total alone does not establish balance.
Show the worked solution
- Identify the missing category.
- Connect fibre to movement of material through the gut.
- Explain that energy is only one dietary need.
Answer Adequate energy does not replace fibre or the other required components.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
List the seven named dietary categories in this syllabus.
Give me a hint
Include fibre and water as well as nutrients.
Compare my reasoning
- Name carbohydrate, fat, protein, vitamins and minerals.
- Add fibre and water.
Carbohydrates, fats/oils, proteins, vitamins, mineral ions, fibre and water.
Look for these in your work
- All seven categories.
- Do not omit water.
Two menus have the same energy value. Menu A is stated to lack vitamin C; menu B provides all named components in suitable amounts. Which has stronger evidence of balance, and why?
Give me a hint
Compare more than energy.
Compare my reasoning
- Use the stated vitamin information.
- Vitamin C has a function that energy does not replace.
Menu B; equal energy does not compensate for missing vitamin C.
Look for these in your work
- Use the supplied evidence.
- Explain the nutrient distinction.
A student calls a meal unbalanced because protein, fibre and water do not have equal masses. Evaluate the reasoning.
Give me a hint
Needs differ between components.
Compare my reasoning
- Balance concerns suitable amounts and proportions.
- Equal masses are not required.
- A full intake record would be needed.
The unequal masses do not prove imbalance; adequacy for each required function must be considered.
Look for these in your work
- Reject the equal-mass rule.
- State the evidence needed.
Common mistakes
- Balanced is not equal portions by mass.
- One meal cannot establish a complete daily intake.
What can you explain now?
Which claim best describes balance?
Compare with the explanation
Appropriate amounts and proportions of required components.
Several functions must be supported.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain why an energy total cannot establish dietary balance.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.