CIE iGCSE Biology-7.1 Diet- Study Notes- New Syllabus
CIE iGCSE Biology-7.1 Diet- Study Notes – New syllabus
CIE iGCSE Biology-7.1 Diet- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- Describe what is meant by a balanced diet
- State the principal dietary sources and describe the importance of:
(a) carbohydrates
(b) fats and oils
(c) proteins
(d) vitamins, limited to C and D
(e) mineral ions, limited to calcium and iron
(f) fibre (roughage)
(g) water - State the causes of scurvy and rickets
What is a Balanced Diet?
Definition
A balanced diet is one that includes the right amounts of all the essential nutrients that the body needs to stay healthy, grow properly, and carry out all vital functions.
“A balanced diet provides the right nutrients, in the right amounts, to the right person.”
🥗 Why Is a Balanced Diet Important?
- Maintains healthy body weight
- Supports growth and development
- Strengthens the immune system
- Repairs damaged cells and tissues
- Provides energy for activity
- Prevents deficiency diseases (e.g., anemia, rickets)
🔎 What Should a Balanced Diet Contain?
| Nutrient | Function | Main Sources |
|---|---|---|
| Carbohydrates | Provide energy | Rice, bread, potatoes, pasta |
| Proteins | Growth and repair of body tissues | Meat, fish, eggs, dairy, beans |
| Fats | Energy storage, insulation | Oils, butter, nuts, cheese |
| Vitamins | Support body functions | Fruits, vegetables, dairy |
| Minerals | For bones, blood, muscles | Milk (Ca), spinach (Fe), bananas (K) |
| Fiber | Helps digestion | Whole grains, vegetables, fruits |
| Water | Vital for life processes | Water, fruits, juices |
🎯 What Affects a Person’s Balanced Diet?
- Age: Children need more protein and calcium.
- Sex: Nutritional needs vary slightly between males and females.
- Activity level: Athletes need more carbohydrates and protein.
- Health status: Diabetics may need to avoid certain sugars.
- Pregnancy: Increased need for iron, calcium, folic acid.
🧪 Consequences of an Unbalanced Diet
| Too Little | Result |
|---|---|
| Iron | Anaemia |
| Vitamin C | Scurvy |
| Calcium | Weak bones (Rickets) |
| Protein | Kwashiorkor |
| Fibre | Constipation |
| Too Much | Result |
|---|---|
| Fat | Obesity, heart disease |
| Sugar | Diabetes, tooth decay |
| Salt | High blood pressure |
Principal Dietary Sources and Importance of Key Nutrients
(a) Carbohydrates
Sources: Rice, pasta, bread, potatoes, cereals, fruits, sugar
Importance:
- Main source of energy for body functions
- Broken down into glucose and used in respiration
- Excess is stored as glycogen in liver or converted to fat
(b) Fats and Oils
Sources: Butter, oil, cheese, nuts, oily fish, red meat, avocado
Importance:
- Provide more energy than carbohydrates
- Act as insulation and protect organs
- Needed for cell membranes and vitamin absorption (A, D, E, K)
(c) Proteins
Sources: Meat, fish, eggs, dairy, beans, lentils, soy, nuts
Importance:
- Growth and repair of tissues
- Make enzymes, hormones, body chemicals
- Used as energy source during starvation
(d) Vitamins
Vitamin C
Sources: Citrus fruits, strawberries, broccoli, peppers
Importance:
- Wound healing, iron absorption, prevents scurvy
Vitamin D
Sources: Sunlight, oily fish, eggs, fortified milk
Importance:
- Calcium absorption, bone strength, prevents rickets
(e) Mineral Ions
Calcium
Sources: Milk, cheese, green vegetables, tofu
Importance:
- Strong bones/teeth, muscle and nerve function
Iron
Sources: Red meat, spinach, beans, liver, fortified cereals
Importance:
- Makes hemoglobin, prevents anemia
(f) Fiber (Roughage)
Sources: Whole grains, fruits (with skin), vegetables, seeds, bran
Importance:
- Aids digestion and bowel movement
- Prevents constipation
- Lowers bowel cancer risk
(g) Water
Sources: Water, fruits, vegetables, soups, milk
Importance:
- Makes up ~70% of the body
- Helps transport substances and regulate temperature
- Needed for chemical reactions and waste removal
📝Summary:
- Carbs, fats, proteins: Provide energy and structure
- Vitamins and minerals: Maintain body functions, bone and blood health
- Fiber and water: Support digestion, transport, and metabolism
Causes of Scurvy and Rickets
1. Scurvy
What is Scurvy?
Scurvy is a nutritional deficiency disease caused by a lack of vitamin C (ascorbic acid). It affects the skin, joints, gums, and blood vessels.
Cause:
Deficiency of Vitamin C. Common in people who do not eat enough fresh fruits and vegetables, especially citrus fruits.
Role of Vitamin C:
- Helps make collagen for connective tissues
- Important for wound healing and immune function
- Aids in iron absorption
Symptoms:
- Swollen, bleeding gums
- Loose teeth
- Fatigue, joint pain, bruising
- Poor wound healing
- Red/purple spots under the skin
At Risk Groups:
- People with poor diets
- The elderly, alcoholics
- Children in famine
Sailors in the past
2. Rickets
What is Rickets?
Rickets is a bone disease in children caused by deficiency of vitamin D, and sometimes calcium. It results in soft, weak, and deformed bones.
Cause:
- Lack of Vitamin D in diet or insufficient sunlight
- Low calcium intake or poor absorption
Role of Vitamin D:
- Helps absorb calcium and phosphate
- Builds strong bones and teeth
Symptoms:
- Soft or brittle bones
- Bowed legs, knock-knees
- Bone pain, delayed growth
- Weak muscles, dental deformities
At Risk Groups:
- Children with little sun exposure
- People with dark skin in low-sunlight areas
- Poor diets low in dairy
- Exclusively breastfed infants without supplements
Summary Table
| Disease | Caused by Deficiency of | Main Symptoms | At Risk |
|---|---|---|---|
| Scurvy | Vitamin C | Bleeding gums, fatigue, joint pain | Poor diet, no fruits/veg |
| Rickets | Vitamin D (and calcium) | Soft/bent bones, growth issues | Children, low sunlight |