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3.1 Nutrients

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3.1 Nutrients

Summary: We all know that sweets should only be eaten as a treat, and you have probably heard many times that you should eat a balanced diet. But what does this mean, and why is it important? Tags: science oxford-science student-book-7 biology Created: 2026-05-19 Last Updated: 2026-05-19

After this topic, you will be able to:

  • define a balanced diet
  • name the seven parts of a balanced diet, giving examples
  • describe the role of each part of a balanced diet.

Think back

  1. Name the organ in the body where food is broken down.
  2. What is an organ system?
  3. Name the organ system in the body where food is broken down.

Key idea Eating a balanced diet helps us stay healthy. A balanced diet includes six nutrients: carbohydrates, lipids, proteins, vitamins, minerals, and water. A balanced diet also includes fibre. These substances help our bodies in different ways.

Key words nutrient, carbohydrate, lipid, protein, vitamin, mineral, fibre, balanced diet

We all know that sweets should only be eaten as a treat, and you have probably heard many times that you should eat a balanced diet. But what does this mean, and why is it important?

Nutrients are important substances that your body needs to survive and stay healthy. There are different types of nutrient. We get most of them from food. The types of nutrient are:

  1. carbohydrates – provide Energy
  2. lipids (fats and oils) – provide energy
  3. proteins – used for growth and repair
  4. vitamins – keep you healthy
  5. minerals – keep you healthy
  6. water – needed in all Cells and body fluids (liquids).

We also need fibre to help keep food moving through the gut (your digestive system).

To remain healthy, you must eat a balanced diet. This means eating food containing the right nutrients in the correct amounts.

A Name the two nutrients that provide the body with energy.

Carbohydrates

Carbohydrates are your main source of energy. They are found in sugary foods such as cake and fruit, where they provide a quick source of energy. They are also found in starchy foods, such as pasta and bread (see Figure 1). These foods have to be broken down by the body, so the energy is released more slowly.

Food items including pasta, spaghetti, wheat grains and a loaf of bread.

Figure 1These foods are a good source of carbohydrates.

Maths skills A 500 g yoghurt pot contains 55 g of sugar. A recommended serving is 100 g.

  1. Calculate how many servings of yoghurt are in the 500 g pot.
  2. Calculate how much sugar each serving contains.

Lipids

Lipids include fats and oils (see Figure 2). They have three important jobs. They:

  • provide you with a store of energy
  • keep you warm, by providing a layer of insulation under your skin
  • protect organs, like your kidneys and heart, from damage.

A tray served with burger, fries, onion rings, tortilla chips, wafers, pizza slices and ketchup.

Figure 2These foods have a high fat content.

Proteins

Proteins (see Figure 3) are needed to repair body tissues. They are also needed to make new cells for growth. Your muscles, organs, and immune system are mostly made of proteins.

Food items including a slice of cheese, a glass of milk, nuts, eggs, beans and lentils.

Figure 3These foods are a good source of protein.

B Give two examples of foods that have a high protein content.

Vitamins and minerals

Vitamins and minerals are essential substances for keeping you healthy. However, you only need tiny amounts. Vitamins are needed for you to grow, develop, and function normally. For example, vitamin A is needed for good eyesight. Vitamin D is needed with the mineral calcium to keep your teeth and bones healthy. Fruits and vegetables are a good source of vitamins and minerals.

Water

Your cells are made up of about 70% water. To keep them healthy, you need to keep replacing the water your body loses in sweat, tears, urine, faeces, and exhaling (breathing out). You should drink over a litre of water every day. This can come from drinking water, but tea, fruit juice, and squash all count.

C Explain why you need to drink more water on a hot day.

Fibre

Fibre is a type of carbohydrate, but it is not a nutrient. It is an important part of your diet because it adds bulk (roughage) to your food (see Figure 4). This means it keeps food moving through the gut, and waste is pushed out of the body more easily. This helps prevent constipation. Constipation is hard, dry faeces that are difficult to pass out of the body.

Food items including rice, pasta, multi-grain bread, broccoli, potato, bell peppers, beans, avocado, apples, grapes and walnuts.

Figure 4These foods are a good source of fibre.

Summary questions

  1. Match the nutrients to their role in the body. carbohydrates growth and repair lipids remain healthy protein provide energy vitamins and minerals provide bulk to food water energy store and insulation fibre needed in cells and body fluids
  2. Describe the role of lipids in the body.
  3. Explain how carbohydrates allow the body to function.Explain how eating a diet with lots of fibre helps prevent constipation.

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