Why does the body need nutrients?

The human body needs nutrients in order to function properly.

● respiration

● movement

● tissue growth and repair

● good health.

The nutrients eaten in a healthy diet include: carbohydrates, fats, protein, vitamins, minerals, fibre and water.

The body needs different nutrients for:

How much does the body need?

Dieticians and nutritionists plan balanced diets for patients because too little or too much of any nutrient can cause health problems. It is important to eat the right amount of nutrients.

Carbohydrates, proteins and fats are important for energy and are needed in large amounts.

The body only needs small quantities of vitamins and minerals.

Some minerals, like zinc, are only needed in minute quantities. These are trace elements.

Why do we need water?

About 70% of a person’s body weight comes from water. Humans can survive without food for a few weeks, but would die after a few days with no water.

The body needs water:

● in its cells, because chemical reactions take place in water

● to transport waste chemicals, like urea, out of the body

● to transport substances, like glucose, dissolved in blood

● to cool the body by evaporating as sweat.

What are carbohydrates?

Carbohydrates are the fuels that provide the body with energy.

Carbohydrates are compounds that contain the elements carbon, hydrogen and oxygen.

There are two types of carbohydrate: simple and complex.

● Simple carbohydrates are sugars. They are small molecules that are easily used by the body, like glucose and fructose.

● Complex carbohydrates are much larger molecules, like starch, that are used as an energy store.

What is fibre?

Fibre is a type of complex carbohydrate that the human body cannot digest. It is made of cellulose, which is found in the walls of plant cells.

Humans do not have the enzymes to digest cellulose.

If the body does not get enough fibre, the contents of the intestines stop moving. This can cause constipation.

Fibre passes through the gut, giving the muscles something to push against.

What are the functions of fats?

Fats are another source of energy for the body. They contain twice as much energy per gram as carbohydrates.

Fats are stored in a layer under the skin. It is broken down when the body needs energy.

Fat is a good insulator and reduces heat loss from the body. A layer of fat surrounds most organs to protect them.

Fats are also a good source of fat soluble vitamins A, D, E and K.

Why does the body need protein?

Protein is found in every cell in the body.

Proteins are found in lots of foods because they are present in all cells. They are found at their highest levels in meat, fish, milk and dairy foods, eggs, beans, lentils and nuts.

All enzymes are made of protein. Everyday processes, such as respiration, all use enzymes, so protein is vitally important for the body.

It is needed to grow new cells and replace old and damaged cells.

What are vitamins?

The body needs vitamins in small amounts. They are compounds that the body cannot make itself. There are two types of vitamins: water soluble and fat soluble.

Water soluble vitamins, like vitamin C and the vitamin B complex, are found in fruit and vegetables.

Fat soluble vitamins, like vitamins A, D, E and K, are found in animal and vegetable fats.

They cannot be stored in the body and must be eaten every day.

They can be stored in body fat.

What are minerals?

Minerals are elements, other than carbon, hydrogen, oxygen and nitrogen, that are vital for a healthy body.

They are only needed in small quantities but they are essential for several processes in the body, like transporting oxygen.

There are two groups of minerals. Some, like calcium, are needed in relatively large quantities.

Trace elements are only needed in very small amounts. They are often linked to correct enzyme function.

What is a healthy diet?

Dieticians and nutritionists provide advice about maintaining a healthy diet. They know that a healthy diet contains all the nutrients that the body needs to complete its life processes.

A healthy diet contains different types of nutrients:

● carbohydrates

● proteins

● fats

● vitamins and minerals

● fibre.

Can you think of examples of foods that contain these nutrients?

How much food do you need?

Dieticians give advice about the amount of food a person should eat. The food eaten in one day should provide the same amount of energy that a person needs to get through that day.

The amount of food that a person needs depends on how much energy they use. This is affected by:

● body size

● how active they are

● how fast they are growing.

Can you think of people who might need more or less food?

How much energy is in food?

Energy is normally measured in joules. However, energy in food is more often measured in calories.

1 calorie = 4.2 joules

Energy in food comes from carbohydrates, fats and proteins. The amount a person eats gives them energy for their activities.

How many slices of cake would a 24 year old man have to eat to get all of the energy he needs for a day?

This slice of chocolate cake contains 275 kilocalories (kcal).

Balancing energy intake

A person’s energy intake from food should be balanced with the amount of energy that they use.

A person who takes in too little energy will lose weight. Losing too much weight is dangerous and can be a sign of anorexia.

If a person takes in more energy than they use they will become overweight. Too much weight gain can cause obesity.

Obesity has been linked to an increased risk of getting heart disease or diabetes.

The risks of an unbalanced diet

If a person’s diet does not contain the right amount of nutrients, they risk becoming malnourished.

A diet that does not have enough vitamins or minerals could lead to a deficiency disease.

However, having a diet that contains too much of some nutrients, like sugar, fat or salt, will also cause health problems.

Do you know of any diseases caused by an unbalanced diet?

Dieticians and nutritionists can recognize the symptoms of an unbalanced diet and are able to suggest a suitable treatment.

What is a deficiency disease?

Vitamins and minerals are part of a balanced diet. They have many roles in the body and help it to stay healthy.

Deficiency diseases can be cured by eating the right food.

Each deficiency disease has characteristic symptoms. Nutritionists, dieticians and doctors need to be able to recognize these symptoms in order to diagnose the disease and cure the patient.

Vitamins and minerals cannot be made by the body. So, when they are absent from a diet, a person may suffer from a deficiency disease.

Vitamin A deficiency

Vitamin A is needed to form a pigment in the retina of the eye. This pigment is needed for night vision.

Vitamin A also helps to maintain healthy skin and mucus linings by preventing infections.

A person with a vitamin A deficiency would find it hard to see at night. They would also have dry skin and mucus linings.

What foods would you recommend a person ate to cure a vitamin A deficiency?

Vitamin B deficiency

The complex of B vitamins has many different functions in the body. Deficiencies of each vitamin cause different symptoms.

Vitamin B1 deficiency causes nerve cells to degenerate. This disease is also known as beriberi.

Vitamin B2 and vitamin B3 deficiencies cause dry and red skin and mouth sores. Vitamin B3 deficiency is also called pellagra.

Deficiency of vitamin B12 causes anaemia because the body cannot make enough red blood cells.

Vitamin C deficiency

The symptoms of scurvy are:

Vitamin C is important for health as it helps maintain the body’s immune system. It is also important for keeping skin and digestive linings healthy and absorbing iron from the gut.

If a person is deficient in vitamin C they could get scurvy.

● bleeding gums

● poor healing of wounds

● bruising from weakened blood vessels.

Vitamin D deficiency

Vitamin D helps the body to absorb calcium and phosphorous. A small amount can be made by cells in sunlight.

If a person doesn’t get enough vitamin D in their diet when they are young their bones don’t form properly.

This deficiency disease is called rickets. Rickets can also develop if a person’s diet does not have enough calcium.

The bones are weak and bend under the weight of the body.

Iron deficiency

Iron is used to make haemoglobin. Haemoglobin is used in red blood cells to transport oxygen.

If a person does not have enough iron in their diet they will get anaemia. A lack of iron in the blood means not enough oxygen can be carried to respiring cells. Sufferers of anaemia often feel tired.

If a person does not have enough iron in their diet, blood cells cannot form properly.

What can people with anaemia eat to add iron to their diet?

Calcium and phosphorus deficiency

Calcium and phosphorus are both needed for healthy teeth and bones.

When a person’s diet doesn’t contain enough calcium or phosphorus the bones and teeth are brittle and will break easily.

Osteoporosis is a disease that people get later in life if they do not eat enough calcium. Their bones become brittle and fragile.

Calcium and phosphorus are the minerals that give bones strength.

Eating too much

Dieticians recognize the importance of having a diet that includes all types of nutrient.

If a person takes in too much energy then the body will store it.

Regularly eating too much food causes people to gain weight. Excessive weight gain leads to obesity. A person is classed as obese when their body mass index is over 30.

Obesity is linked to a large number of health problems, including heart disease, diabetes and high blood pressure.

But, they are also aware of the health implications of eating too much of any type of nutrient.

Too much fat

Obesity is often associated with eating too much fat.

Fat is an important part of a healthy diet. It is used by the body for energy, insulation and to protect organs.

Eating the wrong type of fat is unhealthy. There are three types of fat: saturated, monounsaturated and polyunsaturated fat.

Eating too much saturated fat causes a rise in the level of cholesterol in the blood. This is linked to heart disease.

This is because, gram for gram, fat contains the highest calorific value of all the food groups. As a result, excess energy is stored as fat.

What is cholesterol?

Cholesterol is a lipid that is needed to make cell membranes. It is transported in the blood by molecules called lipoproteins.

● High-density lipoprotein (HDL) is called good cholesterol. It returns cholesterol lipids to the liver to be metabolized.

● Low-density lipoprotein (LDL) is also known as bad cholesterol. The molecules collect cholesterol and then stick it to the wall of arteries, forming plaques.

Eating too much saturated fat will increase the blood level of LDLs.

Clots can get big enough to block the artery. If a clot blocks a coronary artery then it causes heart disease.

What is heart disease?

Plaques of LDL and cholesterol on arterial walls narrow blood vessels and reduce blood flow. This increases blood pressure.

Over time, platelets and blood cells accumulate round the plaque and form a blood clot.

Heart muscle cells are starved of oxygen and die. When a lot of cells have been affected the person will have a heart attack.

Too much salt

Eating a diet that contains too much salt causes health problems later in life.

High blood pressure damages the cells in blood vessel walls.

The blood vessels in the eyes and the kidneys are also very sensitive to increases in blood pressure.

Salt causes blood pressure to rise.

Continued high blood pressure will cause the weakened blood vessels to rupture. If arteries supplying the brain or heart burst, they could cause a stroke or a heart attack.

Too much sugar

Eating a diet that is high in sugar for a long time can cause type 2 diabetes. People with type 2 diabetes have become resistant to the effects of insulin.

Insulin is a hormone made in the pancreas that controls levels of glucose in the blood and cells.

Glucose remains in the blood instead of being stored in the liver or used for respiration.

If left untreated, type 2 diabetes can lead to blindness, kidney failure and heart failure.

What is wrong with fast food?

People’s lifestyles affect their diet and health.

Some people eat a lot of fast food because it is quick and easy. But fast food and takeaways, like burgers and pizzas, contain lots of saturated fat, sugar and salt.

People who are very busy or have a stressful job often don’t have time to exercise. They eat more energy than they use and develop health problems.

The type of food people eat and the amount of exercise that they do will affect their health.

Why test food?

Most foods are complex mixtures of nutrients. Food labels have nutritional information to show the contents of that food.

Food analysts test the composition of foods to ensure that the nutritional information on food labels is accurate.

Food analysts use chemical and instrumental techniques to check the composition of food samples.

Why do food analysts need to check the accuracy of nutritional information?

Food analysts use tests to discover the nutritional value of food. There are two types of test: qualitative and quantitative.

Qualitative tests find out which substances are present in a sample. They provide descriptive information.

Quantitative tests find out how much of a substance is present. They provide numerical information.

Can you think of examples of qualitative and quantitative data?

Qualitative and quantitative tests

What are additives?Additives are natural or artificial chemicals that are added to food to make it more palatable.

● to improve taste

● to improve appearance

● to increase shelf-life.

There are three main reasons that additives are added to foods today:

In the past, herbs and spices were used as flavourings and salt, vinegar or lemon juice were added as preservatives.

What are E numbers?All food additives, excluding some flavourings, have been issued with identifying numbers.

E numbers are chemical identifiers that have been given to additives by the European Union (EU).

If an additive has been given an E number, it shows that it has met the safety requirements of the EU. Flavourings do not have E numbers because they are controlled by different regulations.

Additives must be listed by name or E number on food labels. Even natural additives, like ascorbic acid, have E numbers.

Types of additivesHistorically, natural ingredients were added to food to make it taste better and last longer. Now a large range of natural and artificial additives are used, including the following:

● antioxidants

● colourings

● flavourings and flavour enhancers

● preservatives

● sweeteners

● thickeners.

● emulsifiers and stabilizers

Using additives

Additives are found in almost all processed foods. They are used to improve the taste and appearance of food and to increase its shelf-life.

However, with the increase in popularity of organic food there has also been a gradual increase in the demand for foods that are completely free from additives.

Food manufacturers use additives to increase the saleability of food.

Why do you think food additives have become less popular?

Disadvantages of using additives

The use of additives has significantly improved the appeal and the shelf-life of modern food products.

But, there are also disadvantages to using so many food additives.

Several additives have been linked to serious health risks. Some preservatives, like sodium nitrite, may be carcinogens, also benzoic acid and tartrazine can cause allergic reactions.

Many artificial colourings, for example, tartrazine, have been blamed for causing hyperactivity in young children.

Why is food labelled?All food carries a label on its packaging. A label gives the customer important information about a food product.

Most information found on a label is required to be there by law.

European regulations exist to ensure a customer can make an informed choice about food. A label must list the ingredients, including additives, and give advice about storage and use.

What other types of information should be put on a food label?

What information is found on a label?A food label will contain detailed information about the food in

order to inform the customer about the product they are buying.

● Ingredients are listed in order of mass.

● All foods have a date mark. Best before dates are found on preserved food. Use by dates are found on perishable food.

● Storage instructions tell a customer the best way to store the food.

● Nutritional information shows the energy value of the nutrients in the food.

● All foods must have an overall mass or volume on their packaging.

Nutritional informationThere is no legal requirement for manufacturers to include nutritional information on food labels, unless they have made a specific nutritional claim, but many include it anyway.

This information gives the energy value of the food, as well as the quantities of major nutrients.

People use the nutritional information on food packaging as a guideline for eating a healthy diet.

What is the nutritional information for your favourite food?

Traffic light systemIt is useful for consumers to know the nutritional information of the food they are eating. It helps people maintain a healthy diet.

It can be difficult to interpret nutritional information tables. So a labelling system was set up to make it quick and easy to find out if a food contained a healthy level of nutrients.The traffic light labelling system uses a colour coded symbol to show whether a food contains a healthy amount of a nutrient.

Micro-organisms are living creatures that are too small to be seen with the naked eye. Examples of micro-organisms include bacteria and fungi.

Micro-organisms can be both harmful and useful to humans.

What type of micro-organisms are these?

fungus yeast (a fungus) bacterium

Some micro-organisms are used to produce useful substances like bread, yoghurt, beer, wine and cheese.

Others produce harmful substances called toxins that can damage health.

What are micro-organisms?

In the laboratory, micro-organisms can be grown in a liquid broth or on solid agar.

Micro-organisms grow best when they have:

food

warmth

moisture

optimum pH (specific to the micro-organism, but often around pH 7)

oxygen (for most micro-organisms, though not all need oxygen)

What do micro-organisms need to grow?

The fermentation mixture is kept at about 30oC. The wine is left in barrels for a few months to mature before bottling.

In wine-making, natural sugars in the grapes are used as an energy source by the yeast.

The grapes are first crushed, then enzymes in the yeast convert sugars in the grapes to ethanol.

glucose ethanol + carbon dioxide

How is yeast used to make wine?

Food poisoning is caused by either harmful micro-organisms, or by the toxins (poisons) they produce.

These micro-organisms contaminate food and multiply.

stomach pains

vomiting

diarrhoea

fever

headaches.

Eating them may produce any or all of the following symptoms:

What causes food poisoning?

Bacteria Ways infection can occur

Campylobacter

E. coli (most strains are harmless)

Salmonella

undercooked meat, especially poultry unpasteurized milk

undercooked minced beef

unpasteurized milk and eggs

untreated water

contact with animal faeces

contact with infected animals or people

unpasteurized milk

contact with infected people

undercooked meat and poultry

raw egg products

Which bacteria cause food poisoning?

In January 2009 in the USA, there was a food scare caused by contamination of peanuts with salmonella.

Foods that had been made with peanuts, peanut butter or peanut paste from contaminated sources were recalled. Peanuts are a common ingredient so a very wide range of foods were affected, including cookies, crackers, cereal, sweets, ice cream and pet treats.

The UK Food Standards Agency issued warnings to consumers not to eat certain peanut products from the USA. In the end, no-one in the UK was affected. However, food scares can affect several countries due to the volume of imported food.

Food contamination issues

There are micro-organisms on and all around you. Most are harmless, but some can cause food poisoning if they contaminate food. Food hygiene is about reducing the number of harmful micro-organisms that can get into food.

Food hygiene includes personal hygiene, cleaning techniques, waste disposal and pest control.

Public health inspectors monitor food hygiene in public places such as restaurants, but people should also be careful in their own homes.

What is food hygiene?

Bacteria need food, warmth, moisture, their optimum pH and (usually) oxygen to grow best.

Living on your food they have both food and moisture and probably a suitable pH (depending on the food).

Sealing containers can reduce the amount of oxygen that bacteria have.

The factors that can easily be controlled are warmth and oxygen.

They also prevent new bacteria from landing on the food.

How do conditions affect bacteria?

There are simple things that can be done to control the growth of bacteria using temperature. Heat the food to a temperature where

bacteria cannot survive. Most common bacteria that cause food poisoning are killed at around 70°C, so cook at a higher temperature than this. Water boils at 100°C, killing almost all bacteria.

Alternatively, cool the food to a temperature where bacteria cannot grow and multiply. Below 5°C most bacteria are inactive. Keep fridges below this temperature.

How does temperature affect bacteria?

Some simple rules for personal hygiene in food preparation are:

always wash your hands using soap or antiseptic wipes to remove most bacteria before handling food

don’t cough or sneeze over food

cover any cuts with a clean plaster

tie back hair

wear a clean apron.

Personal hygiene

There are several general measures that can be taken against all pests:

keep pests out of the kitchen by putting up mesh curtains and screens

keep food covered to prevent any insects from landing on it

do not store food on or near the floor

store food in sealed metal or plastic containers to stop mice, rats and insects from getting in.

What else can be done about pests?

Waste should be disposed of carefully to prevent contamination of food.

1) Try to reduce the presence of pests and micro-organisms around waste by ensuring that:

2) Prevent the waste from coming into contact with food, clean utensils and your hands by:

waste bins have lids

bins are emptied regularly.

washing your hands after touching waste or a bin.

Dealing with waste

Food preservation aims to slow down or stop the growth of micro-organisms.

This can be done by altering the conditions the micro-organisms are trying to live and multiply in.

Thinking about the conditions micro-organisms favour, can you:

Preserving food

think of any methods that might preserve food for longer?

give reasons as to why would they be effective?

Farming is the practice of cultivating the land or raising livestock to produce food and clothing materials.

Some farmers plough fields in order to grow crops. They are known as arable farmers.

Plant crops can also be used to make clothing, like cotton, or to feed livestock, like hay.

Pastoral farmers raise livestock until the farmer decides to sell the animals for food and clothing or decides to sell their produce, e.g. eggs and milk.

Can you think of a nearby farm? What do they produce?

What is farming?

Intensive farming has arisen out of the need to supply the food demands of a large population. It is governed by regulations controlling how crops are grown and animals are raised.

Intensive farming is the most efficient way of producing a large amount of food. Farmers aim to maximize production and profit.

Farmers use technology and chemicals to reduce losses and to maximize their yields.

The crop and livestock yields from intensive farms are very high.

What problems do you think intensive farming might cause?

Intensive farming

Organic farmers are governed by regulations that control the conditions under which they grow crops and raise animals.

artificial chemicals should be avoided

livestock must have freedom to roam

Organic farms aim to sustain the health of soil, ecosystems and people by imitating natural systems of production.

livestock are not routinely given antibiotics

genetically modified crops cannot be grown.

These regulations include:

Organic farming

Current methods of organic farming would not be able to support the needs of the Earth’s population, but it is becoming a popular way of farming.

● The environment benefits from a more sustainable method of farming.

● Farmers benefit from a higher profit.

Buying organic produce is a lifestyle choice. Some people are willing to pay extra for food that has been grown more naturally.

● Customers benefit as they believe organic food is more healthy.

Is there a benefit to buying organic food?

Why is organic farming popular?

Plants need suitable conditions and sufficient nutrients to grow.

In order to grow plants need:

● light

● water

● carbon dioxide

● minerals

● warmth.

Why do you think a plant needs these things to grow?

What do plants need to grow?

Plants make their own food by photosynthesis. This is a chemical reaction that uses energy from light to make glucose.

light energy

chlorophyll

carbon dioxide water oxygenglucose+ +

A plant needs carbon dioxide from the air and water from the soil to make glucose. Glucose is used and stored for energy.

Green chlorophyll pigments in leaf cells absorb light from the sun and use it to react water and carbon dioxide together.

What other nutrients do plants need?

Photosynthesis

All organisms need nutrients to grow and function properly.

The nutrients that plants need are minerals, like potassium or nitrogen, and are found as salts in the soil.

The salts dissolve in water that plants absorb for photosynthesis so the minerals are taken up as well.

Plants make their own glucose for energy but they need other nutrients to complete their life processes.

Nutrients from the soil

If a plant does not get enough of the minerals it needs it will develop a mineral deficiency and will not grow properly. Many mineral deficiencies have recognizable symptoms.

Why do mineral deficiencies cause these symptoms?

nitrogen deficiency

phosphorus deficiency

potassium deficiency

magnesium deficiency

Mineral deficiencies

Plants need nutrients from the soil to grow. But as they grow they remove minerals from the soil which need to be replaced.

Normally, when a plant dies and rots, nutrients return to the soil. But if crops are harvested this does not happen.

Farmers must replace the nutrients that have been lost from the soil in order to grow a fresh crop successfully.

Farmers use fertilizers to replenish the soil with nutrients. Fertilizers contain nitrogen, phosphorus and potassium.

Replacing nutrients in the soil

Livestock farmers raise animals for meat, eggs, milk or wool. To make the most profit they must increase production for a small increase in cost.

Farmers can make more money from animals by:

producing more animals

making animals grow quicker.

rearing higher quality animals

How do you think intensive and organic farmers increase production and profit?

Increasing livestock production

Intensive farming methods increase the amount of meat that is produced by controlling the environment an animal lives in. These methods cause animals to grow faster by:

limiting their movement

keeping them warm

using antibiotics.

feeding them a diet of concentrates with additives

How do these methods increase an animal’s growth rate?

Intensive farming

Animals are also more likely to catch diseases if they are living in an enclosed environment.

Animals are often kept in confined conditions so that the environment that they grow in can be controlled. But, cramped conditions can cause problems for an animal’s development.

Animals can develop abnormal behaviours, for example, chickens will pluck out each others feathers.

The EU has set up regulations to stop these problems but some people do not think they are strict enough.

The problems with intensive farming

Organic farmers believe that animals benefit from living in more natural conditions.

Produce from organic farms has been exposed to fewer chemicals and some people say this improves its quality.

Organic farms have a lower yield of meat and eggs because the animal’s energy is used for processes other than growing.

Animals are allowed to roam freely and use more energy moving and staying warm.

Natural conditions