Nutrition and Health
What you must understand
Food supplies nutrients: macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals), plus water and dietary fibre. Know the function of each, two or three rich sources, and the deficiency disease linked to it - for example protein-energy malnutrition (kwashiorkor and marasmus), iron-deficiency anaemia, vitamin A deficiency causing night blindness, vitamin C deficiency causing scurvy, iodine deficiency causing goitre, and calcium/vitamin D deficiency causing rickets.
Understand energy balance: energy comes from food (carbohydrate and protein about 4 kcal/g, fat about 9 kcal/g) and is used by basal metabolism, activity and growth. Positive balance stores fat; negative balance causes weight loss. Know the eatwell-style guidance: base meals on starchy staples, eat plenty of fruit and vegetables, moderate fat and sugar, choose unsaturated fats, limit salt and free sugars.
Traps in questions
- Confusing fat-soluble vitamins (A, D, E, K) with water-soluble ones (B group, C); water-soluble vitamins are easily lost in cooking water.
- Naming a source when asked for a function, or vice versa.
- Assuming more vitamins are always better - vitamin A and D excess is toxic.
- Forgetting that fibre is not a nutrient but is needed for healthy digestion.
- Mixing up anaemia (iron) with scurvy (vitamin C).
Worked rule of thumb
A snack supplies 20 g carbohydrate, 5 g protein and 10 g fat. Energy = (20×4) + (5×4) + (10×9) = 80 + 20 + 90 = 190 kcal. Always show the multiplication line - marks are usually for method, not just the answer.