FN1: Macronutrients
The three macronutrients — carbohydrates, proteins, and fats — their functions, sources, and role in a balanced diet.
Macronutrients
The three macronutrients — carbohydrates, proteins, and fats — their functions, sources, and role in a balanced diet.
Key Fact: Carbohydrates are the body's main source of energy. They are divided into sugars (simple, quick-release) and starches (complex, slow-release). Excess glucose is stored as glycogen in the liver and muscles, or converted to fat.
Key Fact: Proteins are essential for growth, repair, and maintenance of body tissues. They are made up of amino acids — there are 20 amino acids, 9 of which are essential (cannot be synthesised by the body and must come from food).
Key Fact: High biological value (HBV) proteins contain all 9 essential amino acids — found in animal sources (meat, fish, eggs, dairy) and soya. Low biological value (LBV) proteins lack one or more essential amino acids — found in plant sources (cereals, pulses, nuts).
Key Fact: Complementary proteins: combining LBV protein sources to provide all essential amino acids — e.g. rice and beans, hummus and pitta, toast and baked beans.
Key Fact: Fats (lipids) provide concentrated energy (9 kcal/g vs 4 kcal/g for carbs and protein), insulate the body, protect organs, carry fat-soluble vitamins (A, D, E, K), and provide essential fatty acids.
Key Fact: Saturated fats (mainly animal sources — butter, lard, cheese) are solid at room temperature and raise LDL cholesterol. Unsaturated fats (plant and fish sources — olive oil, oily fish) are liquid and can help lower cholesterol.
Key Fact: Trans fats are artificially hydrogenated fats found in processed foods; they raise LDL cholesterol and lower HDL cholesterol, increasing heart disease risk.
Key Fact: The Eatwell Guide recommends: carbohydrates should provide about 50% of energy, fats about 35%, and protein about 15%. Most people in the UK eat too much saturated fat and sugar, and not enough fibre.
Key Fact: NSP (non-starch polysaccharides) / dietary fibre is not digested but is essential for bowel health, preventing constipation, and reducing risk of bowel cancer. Recommended: 30g/day for adults.
Key Fact: Energy balance: energy in (calories consumed) vs energy out (BMR + physical activity). Positive energy balance = weight gain; negative = weight loss; neutral = weight maintenance.
Key Fact: Deficiency diseases: kwashiorkor (protein deficiency — swollen belly, poor growth), marasmus (severe calorie deficiency — extreme thinness), scurvy (vitamin C deficiency — bleeding gums).
Key Fact: Current UK dietary concerns: excess sugar, saturated fat, and salt intake; insufficient fibre, fruit, vegetables, and oily fish. These contribute to obesity, type 2 diabetes, heart disease, and certain cancers.
📋 Key Vocabulary and Concepts
For Macronutrients, you must know:
- Macronutrient
- Carbohydrate
- Protein
- Fat/Lipid
- Amino acid
- Essential amino acid
- HBV protein
- LBV protein
- Complementary protein
- Saturated fat
- Unsaturated fat
- Trans fat
- Glycogen
- Dietary fibre/NSP
- Energy balance
❓ Practice Questions
Q: What is the difference between HBV and LBV proteins?
Q: Explain why saturated and unsaturated fats have different health effects.
Q: Evaluate the importance of dietary fibre in the diet.
✅ Answers
- HBV (high biological value) proteins contain all 9 essential amino acids and come mainly from animal sources (meat, fish, eggs, dairy) and soya. LBV (low biological value) proteins lack one or more essential amino acids and come from plant sources (cereals, pulses, nuts). LBV proteins can be combined (complementary proteins) to provide all essential amino acids.
- Saturated fats (animal sources, solid at room temperature) raise LDL ('bad') cholesterol, increasing heart disease risk. Unsaturated fats (plant and fish sources, liquid at room temperature) can help lower LDL cholesterol and raise HDL ('good') cholesterol, reducing heart disease risk. Public health advice recommends replacing saturated with unsaturated fats.
- Fibre is essential for digestive health — it adds bulk to stools, prevents constipation, and feeds beneficial gut bacteria. It reduces risk of bowel cancer, heart disease, and type 2 diabetes. However, excessive fibre can interfere with mineral absorption. The UK average intake (14g/day) is well below the recommended 30g/day, making increased fibre consumption a public health priority.
🎯 Exam Tips
- Always give at least two specific food sources for each nutrient
- Link nutrient functions to health — not just 'energy' but 'provides glucose for brain function'
- Use the correct terminology: HBV/LBV, essential/non-essential amino acids, saturated/unsaturated
📝 Exam Technique
Food Preparation & Nutrition Exam Tips — Macronutrients:
1. For Macronutrients questions, show every step of your working clearly — method marks count even if the final answer is wrong
2. Check your answer makes sense in context (estimation, units, reasonableness)
3. Use correct mathematical notation and state formulae before substituting values
4. If a Macronutrients question asks you to 'prove' or 'show', write a logical chain of reasoning with a conclusion line
5. For problem-solving, identify the topic first, then recall the relevant method
1. For Macronutrients questions, show every step of your working clearly — method marks count even if the final answer is wrong
2. Check your answer makes sense in context (estimation, units, reasonableness)
3. Use correct mathematical notation and state formulae before substituting values
4. If a Macronutrients question asks you to 'prove' or 'show', write a logical chain of reasoning with a conclusion line
5. For problem-solving, identify the topic first, then recall the relevant method
⚠️ Common Errors
✗ All fats are bad for you. ✓ Fats are essential — they provide energy, carry fat-soluble vitamins, and provide essential fatty acids. The type of fat matters: unsaturated fats are beneficial while excess saturated and trans fats increase health risks.
✗ Plant proteins are inferior to animal proteins. ✓ Plant proteins are LBV (missing some essential amino acids) but can be combined to form complementary proteins that provide all essential amino acids. A varied plant-based diet can meet protein needs.
✗ Carbohydrates make you fat. ✓ Excess calories from any source cause weight gain. Carbohydrates are the body's preferred energy source. Complex carbohydrates (wholegrains) are particularly beneficial for sustained energy and fibre.
✍️ Model Answer
Full-Mark Response
Evaluate the role of macronutrients in maintaining a healthy diet. [12 marks]
Macronutrients — carbohydrates, proteins, and fats — each play essential roles in maintaining health, and balance between them is crucial. Carbohydrates provide the body's primary energy source. Glucose from carbohydrate digestion fuels the brain and muscles. Complex carbohydrates (wholegrains, pulses) also provide dietary fibre, essential for digestive health and reducing risk of bowel cancer and type 2 diabetes. Current UK guidelines recommend carbohydrates provide about 50% of dietary energy. Proteins are vital for growth, repair, and maintenance of body tissues. HBV proteins from animal sources provide all essential amino acids, while LBV plant proteins can be combined to achieve the same effect. Protein deficiency causes kwashiorkor and marasmus, though these are rare in developed countries. Fats provide concentrated energy and carry fat-soluble vitamins (A, D, E, K). However, the type of fat matters significantly: unsaturated fats (olive oil, oily fish) reduce cardiovascular risk, while excess saturated fats (butter, fatty meat) raise LDL cholesterol and increase heart disease risk. The balance between macronutrients is key. The Eatwell Guide recommends roughly 50% energy from carbohydrates, 35% from fats (mostly unsaturated), and 15% from protein. Most UK diets contain too much saturated fat and sugar, and insufficient fibre, contributing to obesity and chronic diseases. In conclusion, all three macronutrients are essential, but their type and proportion determine whether the diet promotes or undermines health.
📊 AO Deep Dive
Assessment Objective Analysis
AO1 (Knowledge & Understanding): Demonstrate knowledge and understanding of macronutrients, including nutritional principles, food science, and food safety regulations.
AO2 (Application): Apply knowledge and understanding of macronutrients to practical cooking contexts, recipe adaptation, and food choice decisions.
AO3 (Analysis & Evaluation): Analyse and evaluate macronutrients in relation to nutritional needs, food safety, sustainability, and cultural factors. Justify decisions with reasoned arguments and evidence.
📝 Exam Questions by Topic
- AQA Past Papers - Topic Questions -- AQA
- Edexcel Past Papers - Topic Questions -- Edexcel
- OCR Past Papers - Topic Questions -- OCR
- Eduqas Past Papers - Topic Questions -- Eduqas
🎬 Video Resources
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