8.1 Diet

2026 Syllabus Objectives

By the end of these notes, you should be able to:

  1. List the main sources of carbohydrates, lipids, proteins, vitamins C and D, mineral salts (calcium and iron), fibre, and water — and explain why each one is important in your diet.
  2. Name the diseases caused by deficiencies of vitamin C, vitamin D, calcium, and iron — and describe their symptoms.
  3. Understand what a balanced diet means.

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What is a Nutrient?

A nutrient is any substance that the body needs from food to survive, grow, and stay healthy. Different nutrients do different jobs. Eating a variety of foods gives your body everything it needs.

1. Carbohydrates

What they are: Carbohydrates are molecules made of carbon, hydrogen, and oxygen. They come in two main forms — sugars (like glucose and sucrose) and starch.

Principal sources (main food sources):

  • Bread, rice, pasta, noodles
  • Potatoes and sweet potatoes
  • Cereals (e.g. oats, corn flakes)
  • Sugar, sweets, honey, fruits

Dietary importance (why your body needs them):

  • Carbohydrates are the body's main and quickest source of energy.
  • When you eat carbohydrates, they are broken down into glucose. Glucose is used in respiration — the process that releases energy in every cell of your body.
  • Without enough carbohydrates, you would feel tired and lack energy for daily activities.

2. Lipids (Fats and Oils)

What they are: Lipids is the scientific word for fats and oils. Fats are solid at room temperature (e.g. butter), while oils are liquid (e.g. sunflower oil).

Principal sources:

  • Butter, ghee, lard
  • Cooking oils (olive oil, sunflower oil, palm oil)
  • Nuts and seeds
  • Oily fish (salmon, sardines)
  • Full-fat dairy products (cheese, cream, whole milk)
  • Meat (especially fatty cuts)
  • Avocados

Dietary importance:

  • Lipids provide energy — in fact, they store more than twice as much energy per gram as carbohydrates.
  • They form a layer of insulation under the skin, helping to keep your body warm.
  • They protect organs — a cushion of fat surrounds delicate organs like the kidneys.
  • Lipids are needed to absorb fat-soluble vitamins (such as vitamins A, D, E, and K), meaning these vitamins can only enter the body when fat is also present.
  • They are an important part of cell membranes (the outer layer of every cell).

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