Describe the dietary importance of each of the main food groups and of water and dietary fibre.

7.1 Human Nutrition – Diet

Carbohydrates – The Energy Engine ⚡️

Carbohydrates are the body’s main fuel. Think of them as the batteries that power your brain, muscles and heart. Simple sugars (glucose, fructose) give quick energy, while complex carbs (starches) release it slowly.

• Sources: Bread, rice, pasta, potatoes, fruits.
• Key nutrient: Glucose – $C_6H_{12}O_6$.
• Analogy: Carbs are like the gasoline that keeps your car running.

Proteins – The Building Blocks 🏗️

Proteins repair tissues, make enzymes and hormones, and support immune function. They are made of amino acids, some of which the body cannot produce.

• Sources: Meat, fish, eggs, beans, nuts.
• Essential amino acids: Leucine, lysine, tryptophan.
• Analogy: Proteins are like the bricks used to build and rebuild your body.

Fats – The Long‑Term Energy Store 🛢️

Fats provide concentrated energy, protect organs, and help absorb fat‑soluble vitamins (A, D, E, K). They also form cell membranes.

• Sources: Oils, butter, avocado, oily fish.
• Types: Saturated, unsaturated, trans fats.
• Analogy: Fats are like the oil that keeps a machine running smoothly.

Vitamins & Minerals – The Micronutrient Toolkit 🧰

These tiny nutrients are essential for enzyme function, bone health, vision, and immune defence.

• Vitamins: A, C, D, E, K, B‑complex.
• Minerals: Calcium, iron, zinc, potassium.
• Analogy: Micronutrients are the screws that hold the body’s machinery together.

Water – The Life‑Sustaining Solvent 💧

Water makes up about 60 % of the body and is crucial for temperature regulation, waste removal, and transport of nutrients.

• Daily requirement: ~2–3 L for teens.
• Sources: Water, fruit, soup, tea.
• Analogy: Water is the highway that carries all the goods (nutrients) to where they’re needed.

Dietary Fibre – The Digestive Helper 🚂

Fibre adds bulk to food, slows digestion, and helps maintain healthy bowel movements. It also lowers cholesterol and stabilises blood sugar.

• Sources: Whole grains, fruits, vegetables, legumes.
• Types: Soluble (oats, beans) and insoluble (bran, wheat).
• Analogy: Fibre is like the train tracks that keep the digestive train on schedule.