Nutrition, Diet and Healthy Eating
This domain tests nutrient classes and their functions, energy values, the balanced diet, diet-related diseases, and simple nutritional calculations.
Core rules
- Macronutrients: carbohydrates (main energy source), proteins (growth and repair) and fats (concentrated energy, fat-soluble vitamin absorption).
- Energy values: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g.
- Micronutrients: vitamins and minerals are needed in small amounts; deficiency causes specific diseases.
- A balanced diet supplies energy, protein, vitamins, minerals, fibre and water in suitable proportions. Limit free sugars, salt and deep-fried foods.
- Deficiency examples: vitamin C - scurvy; vitamin D/calcium - rickets; iron - anaemia; iodine - goitre; vitamin A - night blindness. Kwashiorkor shows oedema and poor growth; marasmus shows severe wasting.
- BMI = mass in kg ÷ (height in m)². Adult healthy range is about 18.5–24.9; children and adolescents are judged against age- and sex-specific growth charts.
Worked example
A meal contains 60 g carbohydrate, 20 g protein and 10 g fat. Energy = (60 × 4) + (20 × 4) + (10 × 9) = 240 + 80 + 90 = 410 kcal. Reasoning: use 4 kcal/g for carbohydrate and protein, but 9 kcal/g for fat. A common error is using 4 for fat, which gives 370 kcal and loses the mark.
Traps that cost marks
- Fibre is not a nutrient that supplies energy; it aids digestion and prevents constipation.
- Fruit juice has less fibre than whole fruit.
- Fat-free does not mean calorie-free.
- BMI units must be kg/m², with height converted from centimetres to metres.