Welcome to Macronutrients and Micronutrients!
Food does far more than just stop your stomach rumbling — it provides the chemical building blocks your body needs to grow, repair itself, stay warm, and fight off illness. For your CCEA GCSE Home Economics: Food and Nutrition (Component 1) exam, you need to understand exactly what our food is made of and how our bodies use it.
Don't worry if nutrition science feels overwhelming with all its chemical names. We will break everything down step-by-step into two main groups: macronutrients (nutrients we need in large amounts) and micronutrients (nutrients we need in tiny amounts), plus essential dietary fibre and water.
---Part 1: The Macronutrients
The word macro means large. Macronutrients are nutrients that the body needs in large quantities every day (measured in grams, \(g\)). They provide our bodies with energy and raw materials for growth.
1. Protein
Think of proteins as the bricks and mortar of your body. Everything from your muscles to your hair, skin, and nails is built from protein.
Chemical Structure: Proteins are made up of long chains of smaller units called amino acids. These chains contain the elements carbon, hydrogen, oxygen, and nitrogen.
Biological Value of Protein
There are certain amino acids that our bodies cannot make from scratch; these are called essential amino acids and must come from the food we eat. Based on this, proteins are split into two groups:
• High Biological Value (HBV) Proteins: These contain all the essential amino acids our bodies need.
Sources: Meat, poultry, fish, eggs, milk, cheese, soya, and quinoa.
• Low Biological Value (LBV) Proteins: These lack one or more of the essential amino acids.
Sources: Cereals (wheat, oats, rice), pulses (peas, beans, lentils), nuts, and seeds.
Protein Complementation & Alternatives
• Protein Complementation: If you eat two LBV foods together in the same meal, the amino acids missing in one food are provided by the other. This gives you a complete, high-quality protein meal!
Everyday Examples: Baked beans on wholemeal toast, hummus with pita bread, lentil dahl served with rice.
• Alternative/Novel Protein Sources: These are meat-free alternatives often used by vegetarians or vegans, such as Textured Vegetable Protein (TVP), tofu, tempeh, and mycoprotein (such as Quorn).
Functions of Protein
• Growth: Building new cells and tissues during childhood, adolescence, and pregnancy.
• Repair and Replacement: Fixing damaged tissues after injury and replacing worn-out cells.
• Maintenance: Keeping body tissues healthy and functioning.
• Body Chemicals: Making vital enzymes, hormones, and antibodies for the immune system.
• Secondary Energy: Acts as an emergency backup energy source if carbohydrates and fats are not available.
Deficiency and Excess
• Deficiency (Not enough): Slow or stunted growth in children, loss of muscle mass (wasting), thin/brittle hair and nails, poor immune defence, and in severe cases, a malnutrition condition called kwashiorkor.
• Excess (Too much): Extra protein is broken down (deamination), which puts strain on the liver and kidneys. Any surplus energy is stored as body fat (adipose tissue).
Quick Takeaway on Protein: Remember that protein's primary job is growth and repair. It is only used for energy as a last resort!
---2. Fats (Lipids)
Fats often get a bad reputation, but healthy fats are absolutely essential for life!
Chemical Structure: Fats are made of triglycerides. One triglyceride unit consists of 1 glycerol molecule attached to 3 fatty acid chains.
Types of Fats
• Saturated Fatty Acids: These have no double bonds between carbon atoms (\(C–C\)). They are usually solid at room temperature and mostly come from animal sources.
Sources: Butter, lard, suet, fatty cuts of meat, palm oil, and coconut oil.
• Unsaturated Fatty Acids: These contain one or more double bonds in their carbon chains (\(C=C\)) and are usually liquid at room temperature (oils):
- Monounsaturated Fatty Acids (MUFAs): Have exactly one double bond. Found in olive oil, rapeseed oil, avocados, and almonds.
- Polyunsaturated Fatty Acids (PUFAs): Have two or more double bonds. Found in sunflower oil, corn oil, and oily fish (which provide essential omega-3 and omega-6 fatty acids).
Functions of Fats
• Concentrated Energy: Fat is our most concentrated energy source, providing \(9\text{ kcal}\) (\(37\text{ kJ}\)) per gram.
• Thermal Insulation: A layer of fat under the skin keeps our bodies warm.
• Protection: Surrounds and cushions vital internal organs (like the kidneys) from physical shocks.
• Fat-Soluble Vitamin Carrier: Necessary for absorbing and carrying vitamins A, D, E, and K.
• Cell Structure: Helps build cell membranes.
Deficiency and Excess
• Deficiency: Weight loss, difficulty absorbing fat-soluble vitamins, and a shortage of essential fatty acids.
• Excess: Weight gain leading to obesity, high blood cholesterol (especially LDL cholesterol from excess saturated fats), which increases the risk of coronary heart disease (CHD), stroke, and type 2 diabetes.
3. Carbohydrates
Carbohydrates are your body's main and preferred source of fuel, providing \(4\text{ kcal}\) (\(17\text{ kJ}\)) per gram.
Classification of Carbohydrates
1. Simple Carbohydrates (Sugars): Fast-acting sugars that taste sweet.
• Monosaccharides (Single sugar units): Glucose, fructose, and galactose.
• Disaccharides (Two sugar units joined together):
- Sucrose = Glucose + Fructose
- Lactose = Glucose + Galactose
- Maltose = Glucose + Glucose
• Free/Added Sugars vs Intrinsic Sugars: Free sugars are added to foods (like table sugar, sweets, syrups, honey, and unsweetened fruit juices) and should be limited. Intrinsic sugars are naturally locked inside the intact cell walls of whole fresh fruits and vegetables.
2. Complex Carbohydrates (Polysaccharides): Long chains of sugar units joined together that take longer to digest.
• Starch: Plant energy storage found in potatoes, bread, rice, pasta, and cereals.
• Dietary Fibre (NSP): Indigestible plant material.
Functions of Carbohydrates
• Primary Energy Source: Converted to glucose to fuel daily activities.
• Brain Fuel: Glucose is the primary fuel required by the brain and nervous system.
• Protein-Sparing Action: When you eat enough carbohydrate, your body uses it for energy instead of breaking down dietary protein.
Deficiency and Excess
• Deficiency: Fatigue, lack of energy, weakness, and ketosis (where the body is forced to break down its own fat and muscle stores for energy).
• Excess: Surplus carbohydrates are converted to glycogen and stored as body fat; eating too many free sugars causes tooth decay (dental caries) and increases the risk of type 2 diabetes and obesity.
Part 2: Dietary Fibre and Water
Dietary Fibre (Non-Starch Polysaccharide / NSP)
Dietary fibre is the part of plant foods that human digestive enzymes cannot break down. It passes through our digestive system, keeping our gut healthy.
Daily Target: Adults should aim for \(30\text{ g}\) of fibre each day.
Types of Fibre
• Insoluble Fibre: Does not dissolve in water. It absorbs moisture like a sponge, bulking up bowel waste and stimulating peristalsis (the muscular wave-like contractions of the intestines). This helps prevent constipation, diverticular disease, and haemorrhoids.
Sources: Wholemeal bread, brown rice, wholewheat pasta, wheat bran, and the skins of fruit and vegetables.
• Soluble Fibre: Dissolves in water to form a soft gel. It slows down digestion, helping control blood sugar levels and helping lower blood cholesterol levels.
Sources: Oats, beans, lentils, peas, barley, apples, and pears.
Water and Hydration
Water makes up about \(60\%\) of our body weight. It is essential for life!
• Key Functions: Transports nutrients and waste products around the body, regulates body temperature through perspiration (sweat), acts as a medium for all chemical reactions in cells, and lubricates joints.
• Recommendation: Drink \(6–8\) glasses (\(1.5–2\text{ litres}\)) of fluid daily under normal conditions.
Part 3: The Micronutrients
The word micro means small. Micronutrients are required in tiny quantities (measured in milligrams, \(\text{mg}\), or micrograms, \(\mu\text{g}\)). They do not provide energy directly, but they are essential for keeping chemical processes running smoothly.
1. Fat-Soluble Vitamins (A, D, E, K)
Memory Trick: Remember "ADEK" — these vitamins dissolve in fat and can be stored in the liver and fatty tissues. Because they can be stored, you do not need them every single day, but extreme excess can build up and become harmful.
• Vitamin A (Retinol / Beta-Carotene):
- Function: Helps vision in dim light (produces a pigment called rhodopsin), keeps skin and mucous membranes healthy, supports immunity, and acts as an antioxidant.
- Sources: Retinol (liver, oily fish, egg yolk, fortified spreads); Beta-carotene (carrots, sweet potatoes, dark leafy greens, apricots).
- Deficiency: Night blindness, xerophthalmia (dry eyes/corneal damage), and lowered immunity.
• Vitamin D (Cholecalciferol):
- Function: Helps the body absorb calcium and phosphorus to build and maintain strong bones and teeth.
- Sources: Direct sunlight on skin, oily fish, egg yolks, and fortified breakfast cereals/spreads.
- Deficiency: Rickets in children (soft, weak, bowed leg bones); Osteomalacia in adults (bone softening and bone pain).
• Vitamin E (Tocopherol):
- Function: A powerful antioxidant that protects cell membranes from damage.
- Sources: Vegetable oils, nuts, seeds, wheat germ, and leafy green vegetables.
• Vitamin K:
- Function: Essential for normal blood clotting (helping scabs form over cuts) and bone health.
- Sources: Green leafy vegetables (spinach, broccoli, kale), fermented foods, and made naturally by friendly bacteria in our gut.
2. Water-Soluble Vitamins (B-Group and Vitamin C)
These vitamins dissolve in water. They cannot be stored in large amounts because any excess is passed out in urine. Therefore, we need to eat foods containing them every day!
The B-Complex Vitamins
• Vitamin \(\text{B}_1\) (Thiamin): Helps release energy from carbohydrates; supports the nervous system.
Sources: Whole grains, pork, fortified cereals.
Deficiency: Beriberi (muscle weakness and nerve disorders).
• Vitamin \(\text{B}_2\) (Riboflavin): Helps release energy from food; keeps skin, eyes, and nervous system healthy.
Sources: Milk, eggs, mushrooms.
Deficiency: Ariboflavinosis (cracked corners of the mouth / cheilosis).
• Vitamin \(\text{B}_3\) (Niacin): Supports energy metabolism and nervous system function.
Sources: Meat, fish, wheat flour.
Deficiency: Pellagra (characterised by the 4 Ds: Dermatitis, Diarrhoea, Dementia, Death).
• Vitamin \(\text{B}_9\) (Folate / Folic Acid): Works with \(\text{B}_{12}\) to produce healthy red blood cells; essential for the development of the foetal neural tube during early pregnancy.
Sources: Green leafy vegetables, chickpeas, fortified breakfast cereals.
Deficiency: Megaloblastic anaemia; neural tube defects (e.g., Spina Bifida) in unborn babies. Note: Women planning pregnancy are advised to take a daily \(400\,\mu\text{g}\) folic acid supplement prior to conception and up to the 12th week of pregnancy.
• Vitamin \(\text{B}_{12}\) (Cobalamin): Maintains nerve fibres and helps make red blood cells.
Sources: Animal products only (meat, fish, eggs, dairy) or fortified vegan products.
Deficiency: Pernicious anaemia and nerve damage.
Vitamin C (Ascorbic Acid)
• Functions: Production of collagen (connective tissue for skin, blood vessels, and wound healing), acts as an antioxidant, boosts immunity, and greatly enhances the absorption of non-haem iron from plant foods.
• Sources: Citrus fruits (oranges, lemons), blackcurrants, kiwi fruit, strawberries, bell peppers, tomatoes, broccoli.
• Deficiency: Scurvy (bleeding swollen gums, loose teeth, poor wound healing, joint pain).
3. Minerals and Trace Elements
• Calcium:
- Functions: Building and maintaining strong bones and teeth, aiding normal blood clotting, and assisting muscle contraction and nerve transmission.
- Sources: Milk, cheese, yoghurt, fortified plant milks, canned fish eaten with bones (sardines), tofu, and leafy green vegetables.
- Deficiency: Weak bones, failure to reach peak bone mass, leading to Osteoporosis (brittle, porous bones) in later life, and rickets in children.
• Iron:
- Functions: Needed to produce haemoglobin in red blood cells, which carries oxygen around the body to all cells.
- Forms of Iron:
1. Haem Iron: Easily absorbed by the body. Found in animal sources such as red meat, liver, and poultry.
2. Non-Haem Iron: Less easily absorbed. Found in plant sources like spinach, lentils, beans, dried fruit, and fortified cereals.
- Absorption Boosters & Inhibitors: Vitamin C increases non-haem iron absorption (e.g., drinking orange juice with fortified cereal). Tea/coffee (tannins), phytates in grains, and oxalates in spinach reduce iron absorption.
- Deficiency: Iron-deficiency anaemia (tiredness, fatigue, pale complexion, breathlessness, dizziness).
• Sodium (Salt / \(\text{NaCl}\)):
- Functions: Controls body water and fluid balance; supports nerve signaling.
- Guideline: Maximum of \(6\text{ g}\) of salt per day for adults (which equals \(2.4\text{ g}\) of sodium).
- Excess: Hypertension (high blood pressure), increasing the risk of strokes and heart attacks.
• Other Key Minerals:
- Phosphorus: Works with calcium to build strong bones and teeth.
- Iodine: Needed by the thyroid gland to produce hormones regulating metabolic rate. Deficiency causes a swelling in the neck called a goitre.
- Fluoride: Strengthens tooth enamel against acid attacks and prevents dental caries.
Exam Pitfalls to Avoid
• Pitfall 1: Saying "Protein's main job is energy."
Correction: Always write that protein's main roles are growth, repair, maintenance, and making enzymes/hormones. It is only an emergency backup for energy.
• Pitfall 2: Forgetting to distinguish Haem vs Non-Haem iron.
Correction: State clearly that haem iron (from meat) is easily absorbed, whereas non-haem iron (from plants) is harder to absorb and needs Vitamin C to boost absorption.
• Pitfall 3: Thinking all fats are harmful.
Correction: Explain that unsaturated fats (MUFAs and PUFAs) provide essential fatty acids, protect organs, insulate the body, and carry fat-soluble vitamins (A, D, E, K).
• Pitfall 4: Believing vegetarians cannot get all essential amino acids.
Correction: Mention protein complementation (pairing two LBV foods like beans and toast) or HBV plant sources like soya and quinoa.
Quick Revision Summary Checklist
Can you explain these key ideas to a friend or write them down without looking?
1. The difference between Macronutrients (Protein, Fat, Carbohydrate) and Micronutrients (Vitamins, Minerals).
2. What HBV and LBV proteins are, and how protein complementation works.
3. The structure of a fat molecule (\(1\text{ glycerol} + 3\text{ fatty acids}\)) and the difference between saturated and unsaturated fats.
4. The daily fibre target for adults (\(30\text{ g}\)) and the difference between soluble and insoluble fibre.
5. The Fat-Soluble vitamins (A, D, E, K) vs the Water-Soluble vitamins (B-group and C), including their storage rules, functions, and deficiency diseases.
6. How Vitamin C helps the body absorb non-haem iron from plant foods.