Table of Contents
IGCSE Biology Topic 8.1 – Understanding what we need to eat and why it matters for our health
What is Diet? Your diet is all the food and drink you consume every day. A good diet provides your body with everything it needs to work properly – energy for movement, materials for growth and repair, and substances that keep you healthy. Understanding diet helps you make smart food choices that keep your body strong and healthy.
Food is not just about filling your stomach – it’s the fuel and building material your body needs to survive and thrive. Every nutrient in food has a specific job to do. Some give you energy to run and play, others help build strong bones and muscles, and some protect you from getting sick. Learning about nutrition helps you understand why eating a variety of foods is so important.
The Seven Components of a Healthy Diet #
A healthy diet contains seven essential components: carbohydrates, lipids (fats and oils), proteins, vitamins, mineral salts, fibre, and water. Each component plays a different role in keeping your body healthy. You need all seven components in the right amounts – too much or too little of any component can cause health problems.
IMAGE NEEDED: Diagram showing the seven components of a balanced diet with simple icons for each nutrient
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Carbohydrates #
What Are Carbohydrates? #
Carbohydrates are the body’s main source of energy. They are made up of sugar molecules. Some carbohydrates are simple (like the sugar in sweets), while others are complex (like the starch in bread and rice). Your body breaks down carbohydrates into a simple sugar called glucose, which your cells use for energy.
Two Types of Carbohydrates: Simple carbohydrates (sugars) give you quick energy but don’t last long. Complex carbohydrates (starches) release energy slowly over a longer time, keeping you energized throughout the day. Complex carbohydrates are usually better for your health.
Principal Sources of Carbohydrates #
Foods Rich in Carbohydrates:
- Starchy foods: Rice, bread, pasta, potatoes, cereals
- Sugary foods: Sweets, chocolate, cakes, biscuits, soft drinks
- Fruits: Bananas, apples, oranges (contain natural sugars)
- Vegetables: Sweet potatoes, corn, peas
IMAGE NEEDED: Photo collage showing common carbohydrate food sources like bread, rice, pasta, potatoes, and fruits
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Dietary Importance of Carbohydrates #
Why Your Body Needs Carbohydrates:
- Main energy source: Provides energy for all body activities including movement, breathing, and thinking
- Brain fuel: The brain uses glucose (from carbohydrates) as its only energy source
- Physical activity: Gives you energy for sports, exercise, and daily activities
- Energy storage: Excess carbohydrates can be stored in the liver and muscles as glycogen for later use
Real-Life Example: Athletes often eat pasta or rice before a big competition. These starchy carbohydrates provide long-lasting energy that helps them perform well during their event. This is why marathon runners often “carb-load” before a race.
Lipids (Fats and Oils) #
What Are Lipids? #
Lipids is the scientific name for fats and oils. Fats are solid at room temperature (like butter), while oils are liquid at room temperature (like olive oil). Both are types of lipids and have similar roles in the body. Lipids are made up of fatty acids and glycerol molecules joined together.
Understanding Lipids: Although people often talk about “fats” being bad for you, lipids are actually essential for health. The key is eating the right types in the right amounts. Your body needs some fat – but not too much, and preferably from healthy sources.
Principal Sources of Lipids #
Foods Rich in Lipids:
- Animal sources: Butter, cheese, milk, cream, meat (especially fatty meat), fish
- Plant sources: Vegetable oils (olive oil, sunflower oil), nuts, seeds, avocados
- Processed foods: Margarine, fried foods, pastries, chocolate
IMAGE NEEDED: Photo showing various lipid sources including butter, oils, nuts, avocado, fish, and cheese
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Dietary Importance of Lipids #
Why Your Body Needs Lipids:
- Energy source: Provides more than twice as much energy per gram compared to carbohydrates
- Energy storage: Stored under the skin as body fat to use when food is scarce
- Insulation: Fat under the skin keeps you warm by reducing heat loss
- Protection: Fat surrounds and protects delicate organs like kidneys and heart
- Cell membranes: Lipids are an essential part of all cell membranes
- Vitamin absorption: Helps your body absorb vitamins A, D, E, and K (fat-soluble vitamins)
Why Some People Have More Body Fat: Your body stores excess energy as fat under your skin. This fat acts like a savings account – your body can use it for energy when you haven’t eaten for a while or when you’re doing lots of physical activity. However, storing too much fat can lead to health problems.
Proteins #
What Are Proteins? #
Proteins are large molecules made up of smaller units called amino acids. Think of amino acids as building blocks – they join together in different combinations to make thousands of different proteins. Your body uses proteins as the main building material for growth and repair. Every cell in your body contains protein.
Why Proteins Are Special: Unlike carbohydrates and lipids, proteins contain nitrogen as well as carbon, hydrogen, and oxygen. This nitrogen is essential for making new proteins in your body. Proteins are especially important for children and teenagers because you are still growing.
Principal Sources of Proteins #
Foods Rich in Proteins:
- Animal sources: Meat, fish, eggs, milk, cheese, yogurt
- Plant sources: Beans, lentils, peas, nuts, seeds, tofu
- Other sources: Soya products, quinoa
Animal vs Plant Proteins: Animal proteins are called “complete proteins” because they contain all the amino acids your body needs. Most plant proteins are “incomplete” – they lack some amino acids. Vegetarians need to eat a variety of plant proteins to get all the amino acids they need.
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Dietary Importance of Proteins #
Why Your Body Needs Proteins:
- Growth: Building new cells and tissues, especially important for children and teenagers
- Repair: Fixing damaged tissues and healing wounds
- Enzymes: Making enzymes that control chemical reactions in your body
- Antibodies: Producing antibodies that fight diseases and infections
- Hormones: Making some hormones that control body processes
- Hair and nails: Building hair, nails, and skin
- Emergency energy: Can be used for energy if carbohydrates and lipids are not available (though this is not their main job)
Why Athletes Need Extra Protein: People who do lots of exercise need more protein to repair muscle tissue that gets damaged during workouts and to build stronger muscles. This is why athletes often drink protein shakes or eat high-protein meals after training.
Vitamins #
What Are Vitamins? #
Vitamins are special chemicals that your body needs in very small amounts to stay healthy. You only need tiny amounts of vitamins, but without them, you can become seriously ill. There are many different vitamins, and each one has a specific job to do in your body. For IGCSE, you need to know about vitamins C and D in detail.
Understanding Vitamins: Unlike carbohydrates, lipids, and proteins, vitamins don’t provide energy or building materials. Instead, they help your body use other nutrients properly and keep your body systems working correctly. Each vitamin prevents specific diseases.
Vitamin C (Ascorbic Acid) #
Vitamin C is a water-soluble vitamin, which means it dissolves in water and cannot be stored in your body for long. This means you need to eat foods containing vitamin C every day. Your body uses vitamin C for several important jobs, especially in keeping tissues healthy and helping wounds heal.
Principal Sources of Vitamin C #
Foods Rich in Vitamin C:
- Citrus fruits: Oranges, lemons, limes, grapefruits
- Other fruits: Strawberries, kiwis, blackcurrants, mangoes
- Vegetables: Peppers (especially red and green peppers), broccoli, Brussels sprouts, tomatoes
- Potatoes: Contain some vitamin C, especially in the skin
Important Note About Vitamin C: Vitamin C is easily destroyed by heat and by storing food for a long time. Fresh fruits and raw vegetables contain more vitamin C than cooked ones. This is why it’s good to eat some raw fruits and vegetables every day.
IMAGE NEEDED: Photo showing vitamin C rich foods including oranges, strawberries, peppers, broccoli, and kiwi fruit
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Dietary Importance of Vitamin C #
Why Your Body Needs Vitamin C:
- Connective tissue: Helps make collagen, a protein that holds cells together and keeps skin, gums, and blood vessels healthy
- Wound healing: Helps cuts and wounds heal properly
- Immunity: Helps your immune system fight infections
- Iron absorption: Helps your body absorb iron from food
- Antioxidant: Protects cells from damage
Vitamin C Deficiency: Scurvy #
What is Scurvy? Scurvy is a disease caused by not eating enough vitamin C. It used to be common among sailors on long sea voyages because they had no fresh fruits or vegetables. Today it’s rare, but it can still occur in people with very poor diets.
Symptoms of Scurvy:
- Bleeding gums: Gums become swollen, soft, and bleed easily
- Loose teeth: Teeth may become loose and fall out
- Skin problems: Rough, dry skin and easy bruising
- Slow wound healing: Cuts and wounds take a long time to heal
- Weakness and tiredness: Feeling tired and weak all the time
- Joint pain: Pain and swelling in joints
- Anaemia: May develop because vitamin C helps absorb iron
Why These Symptoms Occur: Without enough vitamin C, your body cannot make collagen properly. Collagen is the “glue” that holds cells together. When this glue weakens, blood vessels break easily (causing bleeding), skin becomes weak, and wounds cannot heal properly. This explains all the symptoms of scurvy.
IMAGE NEEDED: Medical diagram showing symptoms of scurvy including bleeding gums, skin problems, and wound healing issues
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Historical Example: In the 1700s, British sailors often got scurvy on long voyages. A doctor named James Lind discovered that eating citrus fruits prevented scurvy. This is why British sailors were given lime juice – and why they were nicknamed “limeys”!
Vitamin D (Calciferol) #
Vitamin D is unusual because your body can make it when your skin is exposed to sunlight. However, you can also get it from food. Vitamin D is fat-soluble, which means it can be stored in your body fat and liver. This is different from vitamin C, which cannot be stored.
Principal Sources of Vitamin D #
Sources of Vitamin D:
- Sunlight: Your skin makes vitamin D when exposed to sunlight (this is the main source for most people)
- Fatty fish: Salmon, mackerel, sardines, tuna
- Fish liver oils: Cod liver oil
- Dairy products: Milk, cheese, butter, yogurt (some are fortified with extra vitamin D)
- Eggs: Especially the yolk
- Fortified foods: Some cereals and margarine have vitamin D added
The Sunlight Connection: When UV rays from sunlight hit your skin, they trigger a chemical reaction that makes vitamin D. You need about 10-30 minutes of sunlight exposure a few times a week. However, people with darker skin need more sun exposure to make the same amount of vitamin D.
IMAGE NEEDED: Diagram showing vitamin D sources including sunlight, fish, eggs, dairy products, and fortified foods
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Dietary Importance of Vitamin D #
Why Your Body Needs Vitamin D:
- Calcium absorption: Helps your body absorb calcium from food in the intestines
- Bone health: Works with calcium to build strong bones and teeth
- Bone maintenance: Keeps bones strong throughout life
- Muscle function: Helps muscles work properly
The Vitamin D and Calcium Partnership: Vitamin D and calcium work as a team. Without vitamin D, your body cannot absorb calcium properly from food, even if you eat lots of calcium-rich foods. Without calcium, your bones cannot become strong, even if you have plenty of vitamin D. You need both!
Vitamin D Deficiency: Rickets #
What is Rickets? Rickets is a disease that affects bone development in children. It happens when children don’t get enough vitamin D, which means their bodies cannot absorb enough calcium to make strong bones. The bones become soft and weak, causing them to bend under the child’s weight.
Symptoms of Rickets:
- Soft, weak bones: Bones don’t harden properly and become soft
- Bowed legs: Leg bones bend outward, causing a bow-legged appearance
- Knock knees: Knees bend inward
- Curved spine: Spine may develop abnormal curves
- Delayed growth: Children may be shorter than expected
- Delayed tooth development: Teeth may come through late
- Weak muscles: Muscles become weak, causing delayed walking
- Bone pain and tenderness: Bones may hurt when touched
- Frequent fractures: Bones break easily
Why These Symptoms Occur: Without enough vitamin D, the body cannot absorb calcium from food. Without calcium, bones don’t harden properly – they stay soft and bendy. When a child stands and walks, their weight pushes down on these soft bones, bending them into abnormal shapes. This is why rickets mainly affects the leg bones – they carry the child’s weight.
IMAGE NEEDED: Medical diagram comparing normal bone structure with rickets, showing bowed legs and skeletal deformities
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Who is at Risk of Rickets?
- Children who don’t get enough sunlight exposure (especially in winter)
- Children with darker skin living in countries with less sunshine
- Children who don’t eat foods containing vitamin D
- Babies who are only breastfed (breast milk is low in vitamin D)
Modern Rickets: Rickets is less common today because many foods are fortified with vitamin D, and doctors recommend vitamin D supplements for babies. However, it still occurs in some children who spend too much time indoors or cover their skin completely when outside.
Mineral Salts #
What Are Mineral Salts? #
Mineral salts are simple chemical elements that your body needs in small amounts. Unlike vitamins, minerals are not made by living things – they come from rocks and soil. Plants absorb minerals from soil, and we get minerals by eating plants or animals that have eaten plants. For IGCSE, you need to know about calcium and iron in detail.
Calcium #
Calcium is the most abundant mineral in your body. About 99% of your body’s calcium is found in your bones and teeth, where it provides strength and hardness. The remaining 1% is found in blood and other body fluids, where it has other important jobs.
Principal Sources of Calcium #
Foods Rich in Calcium:
- Dairy products: Milk, cheese, yogurt (these are the best sources)
- Leafy green vegetables: Broccoli, cabbage, spinach
- Fish with bones: Sardines, salmon (if you eat the soft bones)
- Fortified foods: Some cereals, bread, and plant-based milks have calcium added
- Nuts and seeds: Almonds, sesame seeds
- Tofu: If made with calcium
IMAGE NEEDED: Photo showing calcium-rich foods including milk, cheese, yogurt, leafy greens, and sardines
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Dietary Importance of Calcium #
Why Your Body Needs Calcium:
- Bone formation: Building strong bones, especially important during childhood and teenage years
- Tooth formation: Making strong, hard teeth
- Bone maintenance: Keeping bones strong throughout life
- Blood clotting: Helping blood clot when you cut yourself
- Muscle contraction: Helping muscles contract and work properly
- Nerve function: Helping nerves send messages around the body
Calcium and Growing Bodies: Children and teenagers need lots of calcium because their bones are still growing and getting stronger. Your teenage years are especially important for building bone strength that will last your whole life. Peak bone mass (maximum bone strength) is usually reached by age 20-25.
Calcium Deficiency: Rickets #
Calcium and Rickets: As mentioned in the vitamin D section, rickets can also be caused by calcium deficiency. Even if you have enough vitamin D, you can still develop rickets if you don’t eat enough calcium-rich foods. This is because both calcium and vitamin D are essential for building strong bones.
The Connection Between Calcium and Vitamin D: Remember that vitamin D helps your body absorb calcium from food. So rickets can be caused by: (1) not enough vitamin D (can’t absorb calcium properly), or (2) not enough calcium in the diet (nothing to absorb), or (3) both. The symptoms are the same regardless of which deficiency causes the rickets.
Symptoms of Rickets (Same as Vitamin D Deficiency):
- Soft, weak bones that bend easily
- Bowed legs or knock knees
- Delayed growth and development
- Bone pain and muscle weakness
- Delayed tooth development
Prevention of Rickets: To prevent rickets, children need BOTH adequate vitamin D (from sunlight and food) AND adequate calcium (from diet). One without the other is not enough. This is why milk is such a good food for children – it contains both calcium and vitamin D.
Iron #
Iron is a mineral that your body needs to make haemoglobin, the red substance in red blood cells that carries oxygen around your body. Without enough iron, you cannot make enough haemoglobin, and your cells don’t get enough oxygen. This causes a condition called anaemia.
Principal Sources of Iron #
Foods Rich in Iron:
- Red meat: Beef, lamb (contains easily absorbed iron)
- Liver and kidney: Very rich in iron
- Fish: Sardines, tuna
- Eggs: Especially the yolk
- Leafy green vegetables: Spinach, cabbage, broccoli
- Dried fruits: Raisins, apricots
- Pulses: Beans, lentils, chickpeas
- Fortified cereals: Many breakfast cereals have iron added
Two Types of Iron: Iron from meat (called haem iron) is absorbed much more easily by your body than iron from plants (called non-haem iron). However, eating vitamin C-rich foods with plant sources of iron helps your body absorb the iron better. For example, drinking orange juice with your cereal helps you absorb more iron from the cereal.
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Dietary Importance of Iron #
Why Your Body Needs Iron:
- Haemoglobin formation: Making haemoglobin in red blood cells
- Oxygen transport: Haemoglobin carries oxygen from lungs to all body cells
- Respiration: Cells need oxygen for aerobic respiration to release energy
- Myoglobin formation: Making myoglobin, which stores oxygen in muscles
- Enzyme function: Some enzymes need iron to work properly
Who Needs More Iron? Some people need extra iron: (1) Teenage girls and women need more iron because they lose blood during menstruation, (2) Pregnant women need more iron for the growing baby, (3) Growing children and teenagers need iron for increasing blood volume, (4) Athletes need iron because exercise increases the need for oxygen transport.
Iron Deficiency: Anaemia #
What is Anaemia? Anaemia is a condition where you have too few red blood cells or too little haemoglobin in your blood. The most common cause of anaemia is iron deficiency. Without enough iron, your body cannot make enough haemoglobin, so your blood cannot carry enough oxygen to your cells.
Symptoms of Anaemia:
- Tiredness and weakness: Feeling tired all the time, even after rest
- Breathlessness: Getting out of breath easily during normal activities
- Pale skin: Skin looks paler than normal
- Pale inner eyelids and gums: The inside of the lower eyelid looks pale instead of pink/red
- Dizziness: Feeling dizzy or lightheaded, especially when standing up
- Rapid heartbeat: Heart beats faster to try to deliver more oxygen
- Headaches: Frequent headaches
- Difficulty concentrating: Hard to focus on schoolwork or tasks
- Cold hands and feet: Extremities feel cold
Why These Symptoms Occur: When you don’t have enough haemoglobin, your blood cannot carry enough oxygen to your cells. Cells need oxygen for aerobic respiration to release energy. Without enough oxygen, cells cannot produce enough energy, which makes you feel tired and weak. Your body tries to compensate by making your heart beat faster (to pump blood more quickly) and making you breathe faster, but you still feel breathless because the problem is not how fast blood moves, but how much oxygen it carries.
IMAGE NEEDED: Diagram comparing normal red blood cells with anaemic blood cells, showing reduced haemoglobin
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Real-Life Impact: A student with anaemia might struggle to stay awake in class, find it hard to concentrate on homework, and feel too tired to participate in sports. These symptoms improve quickly once the person starts eating more iron-rich foods or taking iron supplements.
Fibre (Roughage) #
What is Fibre? #
Fibre, also called roughage, is the part of plant foods that your body cannot digest. This might sound like it’s not useful, but fibre is actually very important for keeping your digestive system healthy. Even though your body cannot break down fibre and absorb it, it plays a crucial role as it passes through your intestines.
Understanding Fibre: Fibre is mainly cellulose from plant cell walls. Humans don’t have the enzymes needed to digest cellulose, so it passes through the digestive system unchanged. However, this “undigested” material is what makes fibre so useful for keeping your gut healthy.
Principal Sources of Fibre #
Foods Rich in Fibre:
- Whole grains: Wholemeal bread, brown rice, oats, wholegrain cereals
- Vegetables: Carrots, broccoli, potatoes with skin, peas, beans
- Fruits: Apples with skin, pears, oranges, berries
- Pulses: Lentils, chickpeas, kidney beans
- Nuts and seeds: Almonds, flax seeds, chia seeds
Whole vs Processed Foods: Whole grains (like brown bread) contain much more fibre than processed grains (like white bread) because processing removes the outer layers where most fibre is found. This is why wholemeal bread is better for your digestive health than white bread.
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Dietary Importance of Fibre #
Why Your Body Needs Fibre:
- Adds bulk to faeces: Makes waste material in the intestines larger and softer
- Prevents constipation: Helps waste move through the intestines more easily
- Stimulates peristalsis: The bulk stretches intestine walls, triggering muscle contractions that push food along
- Reduces bowel disease risk: May help prevent conditions like bowel cancer
- Helps you feel full: Makes you feel satisfied after eating, which can prevent overeating
- Slows sugar absorption: Helps prevent rapid increases in blood sugar levels
How Fibre Works: Fibre absorbs water as it moves through your intestines, making the waste material soft and bulky. This bulk stretches the intestine walls, which triggers peristalsis (wave-like muscle contractions that push food along). Without enough fibre, waste becomes hard and dry, making it difficult and painful to pass – this is called constipation.
Real-Life Impact: People who eat lots of fibre typically have regular, easy bowel movements. People who eat very little fibre often experience constipation and may develop digestive problems over time. Adding more fruits, vegetables, and whole grains to your diet increases your fibre intake naturally.
Water #
What is Water’s Role in the Body? #
Water is not usually thought of as a nutrient, but it’s absolutely essential for life – you can survive weeks without food but only days without water. About 60-70% of your body weight is water. Every cell, tissue, and organ in your body needs water to work properly.
Water is Essential: Water is the most important component of your diet. You lose water constantly through breathing, sweating, and urination, so you need to replace it regularly by drinking water and other fluids and by eating foods that contain water.
Principal Sources of Water #
Sources of Water:
- Drinking water: Plain water, the best source
- Other drinks: Milk, fruit juice, tea, soup
- Watery foods: Fruits (watermelon, oranges, grapes), vegetables (cucumber, lettuce, tomatoes)
- Metabolic water: Small amounts produced by cells during respiration
How Much Water Do You Need? Most people need about 6-8 glasses (about 1.5-2 litres) of fluid per day. However, you need more water when: it’s hot, you exercise, you’re ill with fever or diarrhea, or you’re pregnant or breastfeeding. A good sign that you’re drinking enough is if your urine is pale yellow.
IMAGE NEEDED: Diagram showing water-rich foods and drinks including water, milk, fruits, and vegetables
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Dietary Importance of Water #
Why Your Body Needs Water:
- Chemical reactions: All chemical reactions in cells occur in water
- Transportation: Blood (which is mostly water) transports substances around the body
- Waste removal: Dissolves waste products so they can be excreted in urine
- Temperature regulation: Sweating helps cool you down when you’re hot
- Digestion: Makes digestive juices and helps break down food
- Lubrication: Keeps joints lubricated and protects organs
- Cell structure: Helps cells keep their shape
Dehydration: When you don’t drink enough water, you become dehydrated. Mild dehydration causes headaches, tiredness, and difficulty concentrating. Severe dehydration is dangerous and can cause dizziness, confusion, rapid heartbeat, and even unconsciousness. This is why it’s important to drink water regularly throughout the day.
Signs of Dehydration: Dark yellow urine, feeling thirsty, dry mouth and lips, tiredness, dizziness, and not urinating very often. If you notice these signs, drink more water. Athletes and people exercising in hot weather need to be especially careful to drink enough water.
A Balanced Diet #
What is a Balanced Diet? #
A balanced diet is a diet that contains all seven components of nutrition in the correct proportions to keep you healthy. It’s not just about eating lots of food – it’s about eating the right variety of foods in the right amounts. A balanced diet provides everything your body needs for energy, growth, repair, and good health.
The Concept of Balance: “Balanced” means eating the right amounts of each nutrient – not too much and not too little. Eating too much of some nutrients (like lipids or sugar) can cause health problems like obesity. Eating too little of other nutrients (like vitamins or minerals) can cause deficiency diseases. Balance is key.
What Makes a Balanced Diet? #
A Balanced Diet Should Provide:
- Carbohydrates: For energy (about 50-60% of total energy intake)
- Lipids: For energy and other functions (about 20-30% of total energy intake)
- Proteins: For growth and repair (about 10-15% of total energy intake)
- Vitamins: In adequate amounts to prevent deficiency diseases
- Minerals: In adequate amounts for specific body functions
- Fibre: To keep the digestive system healthy
- Water: To maintain hydration and body functions
IMAGE NEEDED: Balanced diet plate diagram showing proportions of different food groups
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Factors Affecting Dietary Needs #
Not everyone needs exactly the same diet. Your dietary needs depend on several factors including your age, sex, activity level, and health status. Understanding these factors helps you understand why different people need different amounts of nutrients.
Age:
- Babies and children: Need proportionally more protein and calcium for growth, more energy per kilogram of body weight
- Teenagers: Need extra protein and calcium during growth spurts, girls need extra iron after periods start
- Adults: Need balanced nutrition to maintain health
- Elderly people: Need less energy (less active), but still need protein, vitamins, and minerals
Activity Level:
- Very active people/athletes: Need more carbohydrates for energy, more protein for muscle repair, more water to replace losses from sweating
- Manual workers: Need more energy from carbohydrates and lipids
- Sedentary people: Need less energy but same amount of vitamins, minerals, and protein
Sex:
- Males: Generally need more energy because they tend to have more muscle mass and higher metabolic rates
- Females: Need more iron (especially after menstruation starts) to replace iron lost in blood, pregnant women need extra nutrients for baby’s growth
Health Status:
- During illness: May need extra protein for repair and recovery
- Pregnant women: Need extra protein, calcium, iron, and vitamins for baby’s development
- Breastfeeding mothers: Need extra energy and nutrients to produce milk
IMAGE NEEDED: Diagram comparing dietary needs of different groups (child, teenager, athlete, pregnant woman, elderly person)
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The Importance of Variety #
Why Variety Matters: No single food contains all the nutrients you need in the right amounts. Eating a variety of foods ensures you get all the nutrients your body needs. Different foods provide different nutrients, so eating many different foods is the best way to achieve a balanced diet.
Practical Example of a Balanced Daily Diet:
- Breakfast: Wholegrain cereal with milk (carbohydrates, protein, calcium), orange juice (vitamin C)
- Lunch: Chicken sandwich with salad (protein, carbohydrates, fibre, vitamins), apple (fibre, vitamin C)
- Dinner: Fish with brown rice and vegetables (protein, lipids, carbohydrates, fibre, vitamins, minerals)
- Snacks: Nuts, yogurt, fruit (various nutrients)
- Throughout the day: Water (hydration)
Problems with Unbalanced Diets #
Too Little Food (Malnutrition):
- Starvation: Not eating enough energy (carbohydrates and lipids) causes weight loss, weakness, and eventually death
- Deficiency diseases: Not eating enough specific nutrients causes diseases like scurvy, rickets, and anaemia (as described earlier)
- Poor growth: Children who don’t eat enough protein don’t grow properly
Too Much Food (Overnutrition):
- Obesity: Eating too much energy (especially lipids and carbohydrates) causes excess weight gain
- Type 2 diabetes: Often linked to obesity and eating too much sugar
- Heart disease: Eating too much saturated fat can lead to heart problems
- Tooth decay: Eating too much sugar damages teeth
Energy Balance: To maintain a healthy weight, the energy you eat (in food) should equal the energy you use (for movement and body processes). If you eat more energy than you use, the excess is stored as fat, causing weight gain. If you eat less energy than you use, your body uses stored fat for energy, causing weight loss.
IMAGE NEEDED: Diagram showing energy balance – energy in from food equals energy out from activity and metabolism
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Summary: Key Points to Remember #
The Seven Essential Dietary Components:
- Carbohydrates: Main energy source (rice, bread, pasta)
- Lipids: Energy, insulation, protection (butter, oils, nuts)
- Proteins: Growth and repair (meat, fish, eggs, beans)
- Vitamins C and D: Specific health functions (fruits, vegetables, dairy, sunlight)
- Minerals – Calcium and Iron: Bone health and oxygen transport (dairy, meat, leafy greens)
- Fibre: Digestive health (wholegrain foods, fruits, vegetables)
- Water: All body functions (drinking water, watery foods)
Four Deficiency Diseases You Must Know:
- Scurvy (Vitamin C deficiency): Bleeding gums, loose teeth, poor wound healing
- Rickets (Vitamin D or Calcium deficiency): Soft bones, bowed legs, poor growth
- Anaemia (Iron deficiency): Tiredness, breathlessness, pale skin
- Note: Rickets can be caused by EITHER vitamin D deficiency OR calcium deficiency (or both)
Understanding Balanced Diet: A balanced diet contains all seven dietary components in the correct proportions for your individual needs. The proportions depend on your age, sex, activity level, and health status. Eating a variety of foods from all food groups is the best way to achieve a balanced diet and stay healthy.
Exam Tips:
- Always give specific food examples when asked about nutrient sources
- Link nutrients to their functions – explain WHY the body needs them
- For deficiency diseases, describe symptoms AND explain why they occur
- Remember that rickets can be caused by EITHER vitamin D OR calcium deficiency
- Understand that a balanced diet is not the same for everyone – explain how needs vary
- Be ready to explain the consequences of eating too much or too little
Real-World Application: Understanding nutrition helps you make healthy food choices every day. You now know why it’s important to eat fruits and vegetables (vitamins, minerals, fibre), why dairy products matter (calcium, protein, vitamin D), why you shouldn’t skip meals (energy needs), and why variety in your diet is essential. This knowledge will help you stay healthy throughout your life.
