Unit 7 - Human Diet & Digestion

Balanced Diet

• A balanced diet includes all food groups in correct proportions
• Necessary food groups include carbohydrates, proteins, lipids, vitamins, minerals, dietary fiber, and water

Food Groups and Functions

• Carbohydrates: Source of energy
• Proteins: Growth and repair
• Lipids: Insulation and energy storage
• Dietary Fiber: Provides bulk for intestinal movement
• Vitamins: Needed in small quantities for maintaining health
• Minerals: Needed in small quantities for maintaining health
• Water: Needed for chemical reactions in cells

Food Sources

• Carbohydrates: Bread, cereals, pasta, rice, potatoes
• Proteins: Meat, fish, eggs, pulses, nuts
• Lipids: Butter, oil, nuts
• Dietary Fiber: Vegetables, whole grains, fruits
• Vitamins & Minerals: Fruits, vegetables, meats, dairy products, water, juice, milk

Vitamin and Mineral Requirements

• Vitamin C: Crucial part of collagen. Deficiency causes scurvy. Found in citrus fruit, strawberries, and green vegetables
• Vitamin D: Aids calcium absorption, key for strong bones and teeth. Found in oily fish, eggs, liver, dairy products, sunlight.
• Calcium: Needed for strong teeth and bones, blood clotting. Deficiency can lead to osteoporosis. Found in milk, cheese, eggs, leafy green vegetables
• Iron: Essential for hemoglobin production (carrying oxygen). Found in red meat, liver, leafy green vegetables

Varying Dietary Needs

• Age: Energy and protein needs vary with age (higher for growth)
• Activity Levels: Higher energy needs for more active individuals
• Pregnancy: Increased energy requirements for fetal growth, also higher calcium and iron needs
• Breastfeeding: Increased energy and calcium needs for milk production

Scurvy

• Severe Vitamin C deficiency
• Symptoms: Anemia, exhaustion, spontaneous bleeding, limb pain, swelling, gum ulcerations, tooth loss
• Caused by lack of Vitamin C in the diet over 3 months
• Treatable with oral or intravenous Vitamin C

Rickets

• Condition in children – poor bone development
• Symptoms: Bone pain, lack of bone growth, weak bones, deformities
• Caused by severe Vitamin D deficiency
• Vitamin D helps absorb calcium. Calcium is critical for normal bone development.
• Sources of Vitamin D are sunlight, oily fish, egg yolks

Digestive System (Organs)

• Alimentary Canal: Food passes directly through these organs: Mouth, Oesophagus, Stomach, Small Intestine (duodenum and ileum), Large Intestine (colon, rectum, anus)
• Accessory Organs: Salivary glands, Pancreas, Liver, Gallbladder

Digestive System Functions (Summary)

• Ingestion: Taking food and drink into the body
• Mechanical Digestion: Breaking food into smaller pieces (e.g., chewing, stomach churning)
• Chemical Digestion: Breaking down complex food molecules into simpler absorbable molecules (e.g., enzymes breaking down proteins)
• Absorption: Taking small molecules into the bloodstream
• Assimilation: Using absorbed nutrients for bodily functions
• Egestion: Removing undigested waste from the body

Enzymes in Digestion

• Amylases: Break down starch to simpler sugars
• Proteases: Break down proteins into amino acids
• Lipases: Break down lipids into fatty acids and glycerol

Hydrochloric Acid (HCl)

• Produced in the stomach
• Low pH needed for enzymes (e.g., pepsin) to work optimally
• Kills bacteria

Bile

• Produced by the liver, stored in the gallbladder
• Neutralises stomach acid, aiding small intestine enzymes
• Emulsifies fats (breaks down large fat droplets into smaller ones, increasing surface area for enzyme action)

Absorption (Summary)

• Occurs mainly in the small intestine (with villi and microvilli)
• Nutrients (glucose, amino acids, fatty acids, glycerol) transported to blood or lymph.

Adaptations of the Small Intestine

• Long, folded structure dramatically increases surface area for absorption.
• Villi and microvilli increase surface area for faster absorption.