2. Nutrients and their Sources Study Session 2 Nutrients and their Sources 3



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2. Nutrients and their Sources

Study Session 2  Nutrients and their Sources 3

Introduction 3

Learning Outcomes for Study Session 2 3

2.1  Classification of essential nutrients 3

2.1.1  Macronutrients 3

2.1.2  Micronutrients 4

Box 2.1  Nutrient types and their names 4

Question 4

Answer 4

2.2  Macronutrients in detail 4

2.2.1  Carbohydrates 5

2.2.2  Classification of carbohydrates 5

Question 5

Answer 5


Question 5

Answer 6


2.3  Proteins 6

2.3.1  Sources of protein 6

Question 7

Answer 7


2.4  Fats and oils 7

2.4.1  Classification of fats 8

Question 8

Answer 8


2.5  Water 8

2.6  Fibre 9

2.6  Including fibre in the diet 9

2.7  Micronutrients in detail 9

2.7.1  Vitamins 9

2.7.2  Minerals 11

Question 12

Answer 12

2.8  A balanced diet 12

2.8.1  Helping families to have good balanced diet 13

2.8.2  The mixture of foods to use 14

2.8.3  Adding other foods to the staple food 14

Question 15

Answer 15

Summary of Study Session 2 15

Self-Assessment Questions (SAQs) for Study Session 2 16

SAQ 2.1 (tests Learning Outcomes 2.1, 2.2 and 2.3) 16

Answer 16

SAQ 2.2 (tests Learning Outcomes 2.3, 2.4 and 2.5) 16

Answer 17

SAQ 2.3 (tests Learning Outcome 2.6) 17

Answer 17


Study Session 2  Nutrients and their Sources

Introduction


In the previous session you learned about nutrition, nutrients, food and food choices. In this session, you will learn about each nutrient in more detail. You will learn about the major categories of nutrients, the main sources of these, their function, and how our body uses each of these nutrients for healthy growth and development.

There are seven main classes of nutrients that the body needs. These are carbohydrates, proteins, fats, vitamins, minerals, fibre and water. It is important that everyone consumes these seven nutrients on a daily basis to help them build their bodies and maintain their health. Deficiencies, excesses and imbalances in diet can produce negative impacts on health, which may lead to diseases.

This study session will help you to explain to families and individuals in your community the importance of consuming a healthy and balanced diet, and how to do this with the resources available to them.

Learning Outcomes for Study Session 2


When you have studied this session, you should be able to:

2.1  Define and use correctly all of the key words printed in bold. (SAQ 2.1)

2.2  Classify foods into groups according to their nutrients and differentiate between macronutrients and micronutrients. (SAQ 2.1)

2.3  List the sources and functions of the nutrients. (SAQs 2.1 and 2.3)

2.4  Describe vitamins and their classification. (SAQ 2.2)

2.5  Explain the functions of the common minerals that people require in their diet. (SAQ 2.2)

2.6  Describe a balanced diet for people in your community. (SAQ 2.3)

2.1  Classification of essential nutrients


Based on the amount of the nutrients that each person needs to consume on a daily basis, these nutrients are categorised into two groups. These are macronutrients, which should be consumed in fairly large amounts, and micronutrients, which are only required in small amounts.

2.1.1  Macronutrients


‘Macro’ means large; as their name suggests these are nutrients which people need to eat regularly and in a fairly large amount. They include carbohydrates, fats, proteins, fibre and water. These substances are needed for the supply of energy and growth, for metabolism and other body functions.

Metabolism means the process involved in the generation of energy and all the ‘building blocks’ required to maintain the body and its functions.

Macronutrients provide a lot of calories but the amount of calories provided varies, depending on the food source. For example, each gram of carbohydrate or protein provides four calories, while fat provides nine calories for each gram.

2.1.2  Micronutrients


As their name indicates (‘micro’ means small) micronutrients are substances which people need in their diet in only small amounts. These include minerals and vitamins.

Although most foods are mixtures of nutrients, many of them contain a lot of one nutrient and a little of the other nutrients. Foods are often grouped according to the nutrient that they contain in abundance (see Box 2.1).


Box 2.1  Nutrient types and their names


Foods that contain a lot of protein are called body-building foods or growing foods. Foods that contain a lot of fat or carbohydrates and perhaps only a little protein are called energy-giving foods.

Foods in which the most important nutrients are vitamins or minerals are called protective foods.


Question


What are some of the common foods consumed in your community? Make a list in your Study Diary.

Answer


You might have included some of the following in your list; ‘injera’, maize, ‘kocho’, bread, porridge (‘genfo’), egg, meat, butter, ‘shiro’, ‘kitta’, milk, cheese, yogurt, different types of fruits, sugar cane, cabbage, lettuce, lentils, nuts, beans, fish, chicken, fish, oils, and breastmilk.

End of answer

If people are to stay healthy they must eat a mixed diet of different foods which contain the right amount of nutrients.

2.2  Macronutrients in detail


You are now going to look at the different macronutrients in more detail.

2.2.1  Carbohydrates


Carbohydrates are referred to as energy-giving foods. They provide energy in the form of calories that the body needs to be able to work, and to support other functions.

Carbohydrates are needed in large amounts by the body. Indeed, up to 65% of our energy comes from carbohydrates. They are the body’s main source of fuel because they are easily converted into energy. This energy is usually in the form of glucose, which all tissues and cells in our bodies readily use.

For the brain, kidneys, central nervous system and muscles to function properly, they need carbohydrates. These carbohydrates are usually stored in the muscles and the liver, where they are later used for energy.

The main sources of carbohydrates are bread, wheat, potatoes of all kinds, maize, rice, cassava, ‘shiro’, pasta, macaroni, ‘kocho’, banana, sweets, sugar cane, sweet fruits, and honey. Other foods like vegetables, beans, nuts and seeds contain carbohydrates, but in lesser amounts.


2.2.2  Classification of carbohydrates


Based on the number of sugar units, carbohydrates are classified into three groups; these are monosaccharides, disaccharides and polysaccharides. You need to know the classes of carbohydrates to enable you to give relevant advice to patients with special needs like diabetes (when someone has problems regulating the amounts of glucose in their body).

Monosaccharides and disaccharides are referred to as simple sugars or simple carbohydrates that our body can easily utilise. For this reason, people with diabetes mellitus shouldn’t eat too many of these carbohydrates. Examples include sugar, honey, sweet fruits and sugar cane. Polysaccharides are called complex carbohydrates and they need to be broken down into simple sugars to be used by our body. They can be consumed by diabetic patients without restriction. Examples include starch and cellulose.


Question


Can you think of examples of foods that are sources of carbohydrate?

Answer


Bread, ‘teff’, maize, ‘kocho’, potatoes, sugar cane, honey, sweet fruits, pasta, macaroni and ‘shiro’ are good sources of carbohydrates.

End of answer


Question


Which of these foods are simple sugars and should not be eaten in large quantities by patients who have diabetes?

Answer


Sugar cane, honey, sweet fruits and biscuits are among the food groups that shouldn’t be consumed by patients with diabetes.

End of answer


2.3  Proteins


About 10–35% of calories should come from protein. Proteins are needed in our diets for growth (especially important for children, teens and pregnant women) and to improve immune functions. They also play an important role in making essential hormones and enzymes, in tissue repair, preserving lean muscle mass, and supplying energy in times when carbohydrates are not available.

Pregnant women need protein to build their bodies and that of the babies and placentas, to make extra blood and for fat storage. Breastfeeding mothers need protein to make breastmilk.


2.3.1  Sources of protein


The main sources of proteins are meats, chicken, eggs, breastmilk, beans, ground nuts, lentils, fish, cheese and milk.

All animal foods contain more protein than plants and are therefore usually better sources of body building foods. However, even though plant proteins (see Figure 2.1) are usually not as good for body-building as animal proteins, they can become more effective nutritionally when both are mixed with each other.



Figure 2.1  Meat is a good source of protein. (Photo: Dr Basiro Davey)


Question


Look again at the list of foods you wrote in Section 2.1.2. Which of these foods are sources of protein? Which of these food groups have good quality protein?

Answer


Beans, nuts, lentils, breastmilk, meat, egg, chicken, cheese and milk are sources of protein. Really good quality protein can be found in animal sources such as breastmilk, meat, eggs, chicken, cheese and milk.

End of answer



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