Food Studies and Nutrition
What is tested
Nutrient classes, functions, food sources, energy values, digestion and absorption, the effect of cooking on nutrients, and dietary needs across life stages. Questions ask you to justify choices, not just name nutrients.
Core rules
- Macronutrients (carbohydrate, protein, fat) supply energy; vitamins, minerals and water do not supply energy.
- Atwater values: carbohydrate 4 kcal/g (17 kJ), protein 4 kcal/g (17 kJ), fat 9 kcal/g (37 kJ), alcohol 7 kcal/g (29 kJ).
- Functions: carbohydrate is the main energy source; protein supports growth and repair; fat gives concentrated energy, insulation and essential fatty acids; vitamin C builds collagen and aids iron absorption; calcium builds bone and teeth; iron forms haemoglobin; water transports nutrients and controls temperature.
- Deficiency signs: scurvy (vitamin C), beriberi (thiamin), pellagra (niacin), anaemia (iron), rickets (vitamin D/calcium), night blindness (vitamin A), goitre (iodine).
- Cooking losses: B-group and C vitamins are water-soluble and leach into cooking water; vitamin C is also heat-labile. Fat-soluble A, D, E, K are more stable. Use little water, short times and skins where suitable.
Worked example
A portion has 60 g carbohydrate, 20 g protein and 15 g fat. Energy = (60 × 4) + (20 × 4) + (15 × 9) = 240 + 80 + 135 = 455 kcal. In kJ: 455 × 4.184 ≈ 1 904 kJ. Reasoning: multiply each macronutrient mass by its Atwater factor and add. Fat gives 135 kcal from only 15 g, showing high energy density.
Traps
- Saying vitamins supply energy.
- Mixing kcal and kJ: 1 kcal = 4.184 kJ.
- Confusing water-soluble and fat-soluble cooking losses.
- Naming a deficiency without its nutrient, or giving a food that lacks it (citrus is not an iron source).