7.1 Diet

2026 Syllabus Objectives

  1. Describe what is meant by a balanced diet
  2. State the principal dietary sources and describe the importance of:
    • (a) carbohydrates
    • (b) fats and oils
    • (c) proteins
    • (d) vitamins, limited to C and D
    • (e) mineral ions, limited to calcium and iron
    • (f) fibre (roughage)
    • (g) water
  3. State the causes of scurvy and rickets

Diet refers to the food an animal eats every day. For humans to maintain good health and function properly, the diet must contain specific types of nutrients in appropriate amounts and proportions.

Balanced Diet 🔑

Key Definition: A balanced diet is a diet that contains all of the required nutrients, in suitable proportions, and the right amount of energy.

Humans need six types of nutrients in their diet:

  • Carbohydrates
  • Proteins
  • Fats
  • Vitamins
  • Minerals
  • Water

In addition to these nutrients, the diet should contain fibre (roughage). Fibre is not technically a nutrient because it is not absorbed into the body. Instead, it passes straight through the digestive system and is eliminated in the faeces. However, it plays an important role in maintaining digestive health.


Energy Requirements ⚡

Every day, a person uses up energy. The amount of energy required depends on several factors:

  • Age: Energy needs vary throughout life stages
  • Sex: Males and females have different energy requirements
  • Occupation/Activity level: Physical activity increases energy needs
  • Physiological state: Pregnancy and lactation increase energy requirements

The energy used each day comes from the food consumed. The body's energy balance is important:

  • Eating too much food: Excess energy is stored as fat, leading to weight gain
  • Eating too little food: Insufficient energy causes tiredness and fatigue

Energy Content of Nutrients

Different nutrients provide different amounts of energy:

  • One gram of fat contains about twice as much energy as one gram of protein or carbohydrate

Changing Energy Needs Throughout Life

A person's diet may need to change at different times of their life:

During pregnancy: A woman needs to eat a little more each day and ensure extra intake of calcium and iron to help build the baby's bones, teeth, and blood.

During breastfeeding: Increased energy intake is required to support milk production.

As people age (50s and 60s): Most people need to eat less because their metabolism slows down.

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