Nutrients Needed by the Body
A nutrient is a chemical that your body needs to stay healthy. The human body needs a large number of different nutrients. These can be divided into several groups:
- Carbohydrates
- Fats and oils
- Proteins
- Vitamins
- Minerals
- Fibre
In addition to these nutrients, the body also needs water. Water makes up about 70% of the body’s weight. It provides support for the body’s cells, carries dissolved materials around the body, and helps to control body temperature.
Carbohydrates
- Carbohydrates can be used as a store of energy in animals.
- Most of the carbohydrates you eat must be consumed in food.
- The three most common carbohydrates are starch, sucrose (which is table sugar), and glucose (which is used in respiration).
- Starch is a type of energy store found in plants.
- Glucose is a form of energy that easily travels in the blood plasma to the cells of the body.
- Plants also make another type of carbohydrate called cellulose, which they use to make their cell walls.
- Cellulose forms the part of our diet called fibre.
Extra Information
The Word “Carbohydrate”
- The word carbohydrate comes from two chemical elements.
- These elements are carbon and hydrogen.
- The suffix “-ate” means “having oxygen.”
- This shows that the name relates to the chemicals that make it up.
Theobromine in Chocolate
- Chocolate contains a substance called theobromine.
- Theobromine is harmless to humans because our bodies can easily break it down.
- However, dogs cannot break down theobromine.
- Because of this, if a dog eats chocolate, it could become very sick and possibly die.
Fats and Oils
- Fats can be used by animals as a store of energy.
- Animals must eat food to get fats.
- There are two types of fats: solid fats and liquid fats (oils).
- Solid fats are produced by animals. An example of a solid fat is lard, which is used in cooking and comes from pigs.
- Liquid fats or oils are produced by plants. An example is sunflower oil.
- Fat is also used by mammals for insulation. It is stored beneath the skin to help keep their bodies warm.
- Oils are energy stores in plants.
- Many mammals will increase their body fat in the autumn. This allows them to use the stored energy if there is little food available during the winter.
- Fats contain even larger amounts of energy than carbohydrates.
- However, the body cannot release the energy from fats as quickly as it can from carbohydrates.
The Fat Test
- Food that contains fat can leave a translucent mark on paper.
- A translucent mark is one that lets light pass through it but scatters it in all directions.
- Water also leaves a mark on paper.
- However, the water will evaporate from the paper, but the fat will not.
- This information can be used to create a fat test.
Extra Information
- Fats are made from the elements carbon and hydrogen.
- Lard is the fat from a pig, used in cooking.
- Insulation refers to protection against heat loss.
Proteins
- Proteins are a type of nutrient found in both plants and animals.
- They are the building materials that form most of the structures in our bodies.
- Examples of structures made from proteins include muscle and bone.
- Proteins are also necessary for the body to grow.
- They are also needed for repairing any damage caused by illness or an accident.
Did You Know?
- Proteins are made from four main elements: carbon, hydrogen, oxygen, and nitrogen.
- Some proteins also contain the element sulfur.
- Hair is an example of a structure made of protein. It is a protein that grows out from your skin.
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How the Body Uses Nutrients
Fibre
- Fibre is a carbohydrate that makes up the walls of plant cells.
- It is found in foods such as wholemeal bread, fruit, and vegetables.
- Our bodies cannot digest fibre. However, it still helps the food move along the digestive system.
- As food moves through the large intestine, bacteria feed on the fibre and add bulk to the food.
- This bulk helps the muscles of the large intestine push the food along.
- Fibre acts like a sponge and soaks up the undigested wastes, which then form faeces.
- This makes it easy for waste to be removed from the body.
- If a person’s diet lacks fibre, they might experience problems such as constipation.
Vitamins
- Vitamins are needed by the body in very small amounts.
- When vitamins were first discovered, they were named with letters of the alphabet. Later, they were given chemical names as scientists learned more about them.
- Each vitamin has one or more uses inside the body.
- For example, Vitamin A helps the eyes see in dim light. It also helps to make a mucus lining for the respiratory, digestive, and excretory systems. This lining protects against infection from microorganisms.
- A lack of Vitamin C can cause the disease called scurvy.
- The symptoms of scurvy include bleeding gums and bleeding under the skin and into the joints. If left untreated, this can cause massive internal bleeding and death.
- Vitamin D helps the body take up calcium from food. This is important for making strong bones and teeth.
- Children who do not get enough vitamin D in their diet may develop the deficiency disease called rickets.
- In a person with rickets, their bones do not develop to their full strength. This can cause the leg bones to bend.
Minerals and Water
Minerals
- The human body needs about 20 different minerals to stay healthy.
- Two important minerals are calcium and iron.
- Calcium is needed to build strong bones and teeth.
- Iron is needed by the red blood cells. It helps them take oxygen from the lungs and carry it to all the cells in the body.
- If a person’s diet does not have enough iron, their red blood cells will carry less oxygen. This can make the person feel tired and weak.
- This condition is called anemia.
- Anemia can be treated by eating more foods that contain iron.
Did You Know?
- Each mineral can have more than one use in the body.
- For example, calcium is also used to help your muscles work.
- It also helps your blood to clot when you get a cut.
Water
- About 70% of the human body is made of water.
- A person can only live for a few days without drinking water.
- All the substances that the body needs to live dissolve in water.
- Water is found in all the cells of the body.
- All the chemical reactions that keep us alive happen in water.
- The blood is mostly made of water. It is the liquid that transports all the other blood components around the body.
- Water is also used to cool down the body when sweat evaporates from the skin.
The Nutrients and Energy in Food
Nutrients in Food
- The amounts of different nutrients found in food are determined through experiments and calculations.
- These amounts are usually listed for a food sample weighing 100 grams.
- The information is then presented in tables that show the nutrients in various common foods.
Energy in Food
- A piece of equipment called a bomb calorimeter is used to measure the amount of energy in food.
- To use a bomb calorimeter, a food item is placed inside, and oxygen is pumped in.
- The food is then set on fire.
- The device measures all the heat that is produced.
- Finally, the energy in 100 grams of the food is calculated in kilojoules (kJ).
- The results are used to create tables that show the energy content of different foods.
Keeping a Balance
- To be healthy, a diet must be balanced with the body’s needs.
- A balanced diet is one that has all the necessary nutrients in the correct amounts.
- To check if your diet is balanced, you can look at a chart that divides food into groups.
- The chart shows the main nutrients in each food group.
- You should try to eat at least one portion from each food group every day. You should also eat more from the groups that lack fat.
- Remember to include fibre in your diet, even though it is not digested.
- Fibre is essential for food to move through the large intestine efficiently.
- Foods with fibre include cereals, vegetables, and pulses such as peas and beans.
A Healthy Diet
- The body needs a range of nutrients to stay healthy. This can be achieved by eating a balanced diet.
- Diets can easily become unbalanced if you regularly eat high-energy snacks like sweets, chocolate, crisps, and ice cream between meals.
- These habits can lead to unhealthy conditions like obesity and tooth decay.
- There are alternatives to high-energy snacks that have less energy and more vitamins and minerals.
- Examples of these healthy alternatives are fruits and raw vegetables like celery, tomatoes, and carrots.
- To understand a balanced diet, you can look at a food pyramid.
- The food pyramid shows that you should eat large amounts of the foods at the bottom of the pyramid.
- You should eat smaller amounts of the foods in the middle sections.
- You should eat only very small amounts of the foods at the top of the pyramid.
Did You Know?
- Cooking helps us digest food and absorb more nutrients.
- However, some cooking methods can cause nutrients to be released from the food.
- For example, steaming or stir-frying can help release more nutrients than other methods, such as boiling.
QUESTIONS AND ANSWERS
In a patient with rickets, why do the leg bones bend more than the arm bones?
The text states that rickets is a disease where bones do not develop to their full strength. Leg bones bend more than arm bones because they have to carry the entire weight of the body. Since they are weak due to a lack of vitamin D, the pressure from standing and walking causes them to bend over time.
A meal contains carbohydrate, fat, protein, vitamin D, calcium and iron. What happens to each of these substances in the body?
- Carbohydrates: They are used as a source of energy for the body’s cells. Glucose, a simple form of carbohydrate, travels in the blood to the cells.
- Fats: They are used as a store of energy, which contains more energy than carbohydrates. They also provide insulation under the skin to help keep the body warm.
- Proteins: They are the building blocks for the body. They are used for growth and for repairing any damage to structures like muscles and bones.
- Vitamin D: It helps the body absorb calcium from food to make bones and teeth strong.
- Calcium: It is used to make bones and teeth strong. It also helps with muscle function and blood clotting.
- Iron: It is needed by red blood cells to help them carry oxygen from the lungs to the rest of the body.
What does the body need the following for?
- a) glucose: Glucose is needed for respiration, a process that releases energy to keep the body’s cells alive.
- b) fats: The body needs fats as a store of energy and for insulation beneath the skin to keep mammals warm.
- c) proteins: Proteins are needed for growth and to repair damage caused by illness or accidents. They are also the materials that make up structures like muscle and bone.
Why does the body need:
- a) calcium: The body needs calcium to make strong bones and teeth.
- b) iron: The body needs iron to help red blood cells carry oxygen from the lungs to the rest of the body.
What foods can people eat to prevent them from getting scurvy?
Foods people can eat to prevent scurvy include blackcurrant, orange, lemon, papaya, and guava.
What foods should people eat to prevent them from getting rickets?
The text provides a table that lists good sources of Vitamin D. To prevent rickets, people should eat foods like egg yolk, butter, cod-liver oil, pilchard, and herring. The text also mentions that sunlight is a source of Vitamin D.
Imagine you knew of someone who ate a lot of high-energy snacks.
- a) What could happen to them if they continued with this habit? Regularly eating high-energy snacks can lead to obesity and tooth decay.
- b) What advice would you give them to keep them healthy? You should advise them to eat a balanced diet. There are alternatives to high-energy snacks that have less energy but more vitamins and minerals, such as fruits and raw vegetables like celery, tomatoes, and carrots.
6. What is a balanced diet?
- a) What is a balanced diet? A balanced diet is one in which all the necessary nutrients are present in the correct amounts to keep the body healthy.
- b) Give examples of the quantities of different foods you would eat to keep your diet balanced. The text doesn’t provide specific quantities. However, it says that you should eat at least one portion from each food group every day, and more from the groups that lack fat. It also mentions that you should include fiber, which is found in foods like cereals, vegetables, and pulses.