Principles of Nutrition and Balanced Diet
Principles of Nutrition and Balanced Diet
This domain tests nutrient classes, energy values, recommended intakes, deficiency diseases and the construction of a balanced diet for different groups. Questions often ask you to calculate meal energy or identify a missing food group.
Core rules and concepts
- Energy values: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g. Alcohol supplies 7 kcal/g but is not a nutrient.
- A balanced diet supplies energy and all nutrients in appropriate proportions; no single food is complete except breast milk for infants.
- Five food group approach: cereals and millets; pulses, legumes and nuts; vegetables and fruits; milk and meat products; fats and sugars.
- Water-soluble vitamins (B-complex, C) are not stored appreciably; fat-soluble vitamins (A, D, E, K) need dietary fat and can be toxic in excess.
- Dietary fibre aids bowel function and glycaemic control but is not digested by human enzymes.
Worked example
A meal has 60 g carbohydrate, 20 g protein and 10 g fat. Energy = (60 × 4) + (20 × 4) + (10 × 9) = 240 + 80 + 90 = 410 kcal. If the person needs 2,000 kcal, this meal provides about 20.5% of daily energy. The protein contributes 80 kcal, or about 19.5% of the meal's energy.
Traps
Do not use 9 kcal/g for protein or 4 kcal/g for fat. Do not count fibre as 4 kcal/g in ordinary exam calculations unless a source specifies a value. Deficiency signs are specific: vitamin A with night blindness, vitamin D with rickets, iron with anaemia. Excess fat-soluble vitamins are not harmless.