Dietary fibre and water (Extension)

Learning objectives To know the functions and sources of dietary fibre. To understand the health benefits of dietary fibre. To know the functions and sources of water. To understand the principles of fluid balance.

Dietary fibre Dietary fibre is a diverse group of carbohydrate found almost exclusively in plants Unlike other types of carbohydrate, these are not absorbed in the small intestine to provide energy, although it is broken down in the large bowel by bacteria.

Sources of dietary fibre Components of dietary fibre are found in different proportions in food, therefore it is important to eat a variety of fibre-containing foods.  Dietary fibre is found in: wholegrain cereals and cereal products; beans; lentils; fruit and vegetables; nuts and seeds.

Fibre in the diet Different types of dietary fibre have different functions in the body: some help prevent constipation (water intake must also be increased) to reduce the risk of diverticulitis and bowel cancer; some help maintain normal blood cholesterol levels; some help reduce the rise of blood glucose after a meal; some are associated with feelings of fullness to help control food intake, because foods high in fibre are often low in energy density. 

How much fibre do we need? Most people do not eat enough dietary fibre. The recommended average intake for dietary fibre is 18g per day for adults. Children need proportionately less. Young children are advised against consuming too much dietary fibre as it can make it too bulky. This may make them become full before they have eaten enough food to give them the vitamins, minerals and energy they need.

Fibre on food labels European regulations on nutrition and health claims state that a product claiming to be a ‘source of’ fibre should contain at least 3g of dietary fibre per 100g, and for a product which contains at least 6g of dietary fibre per 100g, this can be labelled as ‘high in’ fibre.

Can you think of ways to increase fibre in your diet? Here are some ideas. Have a bowl of wholegrain breakfast cereals, served with a handful of dried fruit. Switch from white to wholemeal or granary bread. Add oats to fruit or vegetable crumble toppings. Serve a side salad with a sandwich or pasta dish. Add beans and pulses to casseroles and soups.

Your Turn! I want you to research online and create the perfect healthiest breakfast. What makes it healthy?

Water Water is essential for life. It is the major component of body fluids and helps to maintain normal physical and cognitive functions, as well as the normal regulation of the body’s temperature. Water also helps to get rid of waste substances in the body. The body is nearly two-thirds water, so it is important to consume enough fluid to stay hydrated. If we do not consume enough water, we become dehydrated.

Water Our bodies lose water all the time, when we go to the toilet, from sweat and also through respiration. We need to replace this water by drinking regularly to prevent dehydration. Even mild dehydration can lead to headaches, irritability and loss of concentration. Did you know? Humans can survive for a few weeks without food, but they cannot go without fluids for more than two to three days.

Sources of water Water is provided by food such as soups, yogurts, fruit and vegetables (around 20% of our total fluid intake), as well as drinks such as milk and juice (around 80% of our total fluid intake). Water is a good choice of drink because it hydrates without the provision of energy.

How much water do we need? The amount of water and other fluids that we need to drink each day varies from person to person. The recommendation is to drink about 6 to 8 glasses of fluids a day to prevent dehydration. This is in addition to the fluid we get from food. We need to drink more when the weather is hot or when we are active.

What is thirst? The body’s first response when dehydration is detected is to signal the kidneys to conserve water. The thirst response is initiated when 1-2% of body mass is lost due to dehydration so it is important to drink if we are thirsty. The easiest way to spot that you might not be getting enough water is if your urine is a dark yellow colour during the day. If you are getting enough water your urine should be a pale straw colour.  Headache and tiredness are also symptoms.

What happens if we drink too much water? It can lead to ‘water intoxication’ with potentially life threatening hyponatraemia. This is caused when the concentration of sodium in the blood gets too low.

Question True or false? All types of dietary fibre have the same functions. True False

False. Different types of dietary fibre have different functions in the body – some help prevent constipation, some help maintain normal blood cholesterol levels. Next question

Question On average, how much dietary fibre should adults eat each day? 10g/ day 14g/ day 18g/ day 22g/ day

Wrong answer. Try again Next question

Correct answer. Next question

Question True or false? The easiest way to check for dehydration is by looking at urine colour. True False

True. If you are dehydrated, your urine is a dark yellow colour; if you are getting enough water your urine should be a pale straw colour.  Next question

Question What proportion of the body is water? About one-third About one-half About two-thirds

Wrong answer. Try again Next question

Correct answer. Next question

Question Which of the following is/are symptom(s) of mild dehydration? a) Headaches b) Irritability c) Thirst d) Loss of concentration e) All of the above a) b) c) d) e)

Wrong answer. Try again The end

Correct answer. The end