Food Classification and Functions for Primary 4

Food Classification and Functions

Performance Objectives

By the end of the lesson, students should be able to:

1. explain the meaning of food;
2. classify sources of food;
3. identify food nutrients;
4. discuss the functions of food nutrients;
5. explain what constitute an adequate diet;
6. identify the deficiency disease and symptoms of each nutrient.

Meaning of Food

Food is any substance eaten to provide energy, promote growth, and repair the body.

People eat food every day to stay alive and healthy. Food gives the body the strength to play, learn, and work.

Sources of Food

Food comes from different places. The two main sources of food are plants and animals.

Plant Sources of Food

Many foods eaten daily come from plants. These include fruits, vegetables, grains, and roots.

Examples of food from plants include:

1. Rice
2. Beans
3. Yam
4. Cassava
5. Maize
6. Plantain
7. Oranges
8. Mangoes
9. Spinach
10. Okra

Animal Sources of Food

Some foods come from animals. These foods often provide protein and other important nutrients.

Examples of food from animals include:

1. Beef (from cow)
2. Chicken
3. Fish
4. Eggs (from chicken)
5. Milk (from cow or goat)
6. Goat meat
7. Pork (from pig)

Classes of Food Nutrients and Their Functions

Food contains different substances called nutrients. These nutrients are important for the body to grow, stay healthy, and have energy. There are six main classes of food nutrients:

1. Carbohydrates
2. Proteins
3. Fats and Oils
4. Vitamins
5. Minerals
6. Water

Carbohydrates

Carbohydrates are the body’s main source of energy.

They give the body the power to do activities like running, playing, and thinking. Foods rich in carbohydrates are often called “energy-giving foods.”

Examples of carbohydrate-rich foods include:

1. Yam
2. Rice
3. Garri
4. Bread
5. Potatoes
6. Plantain
7. Maize
8. Sugar

Proteins

Proteins are essential for growth and repair of body tissues.

They help to build muscles, skin, and hair. Proteins also help the body to heal when injured. Foods rich in protein are often called “body-building foods.”

Examples of protein-rich foods include:

1. Beans
2. Meat (beef, chicken, goat meat)
3. Fish
4. Eggs
5. Milk
6. Groundnuts
7. Soya beans

Fats and Oils

Fats and oils provide a lot of energy and help the body absorb some vitamins.

They also help to keep the body warm. While important, fats and oils should be eaten in small amounts. They are also energy-giving foods.

Examples of foods rich in fats and oils include:

1. Palm oil
2. Groundnut oil
3. Butter
4. Margarine
5. Avocado
6. Nuts (like groundnuts and cashew nuts)

Vitamins

Vitamins help the body to stay healthy and fight diseases.

They are needed in small amounts but are very important for good eyesight, healthy skin, and strong bones. Foods rich in vitamins are often called “protective foods.”

Examples of vitamin-rich foods include:

1. Fruits (oranges, mangoes, pawpaw)
2. Vegetables (spinach, carrots, tomatoes)
3. Liver
4. Eggs
5. Milk

Minerals

Minerals help to build strong bones and teeth, and they help the blood to carry oxygen.

Like vitamins, minerals are also protective foods and are needed in small amounts for the body to function properly.

Examples of mineral-rich foods include:

1. Milk
2. Green leafy vegetables (like spinach, ugu)
3. Fish
4. Salt
5. Beans
6. Meat

Water

Water is very important for all body functions.

It helps to transport nutrients, regulate body temperature, and remove waste products from the body. A person should drink plenty of clean water every day.

Adequate Diet

An adequate diet, also known as a balanced diet, is a meal that contains all the classes of food nutrients in the right amounts.

Eating a balanced diet means eating a variety of foods from all the nutrient classes. This ensures the body gets all the energy, growth, and protection it needs to stay healthy and strong. Eating too much of one type of food and not enough of others can lead to health problems.

Deficiency Diseases and Their Symptoms

When the body does not get enough of a particular food nutrient, it can lead to a health problem called a deficiency disease. Each nutrient has specific diseases associated with its lack.

Carbohydrate Deficiency

Lack of enough carbohydrates can lead to a condition where the body does not have enough energy.

Symptoms include:

1. Feeling weak and tired
2. Lack of energy for daily activities
3. Weight loss

Protein Deficiency (Kwashiorkor)

Kwashiorkor is a severe disease caused by not eating enough protein, especially in children.

Symptoms include:

1. Swelling of the stomach and legs
2. Thinning hair that changes colour
3. Skin rashes
4. Failure to grow properly

Fat and Oil Deficiency

Not getting enough fats and oils can affect the body’s energy levels and ability to absorb certain vitamins.

Symptoms include:

1. Dry skin
2. Feeling cold easily
3. Lack of energy
4. Difficulty absorbing some vitamins

Vitamin Deficiency

Different vitamins prevent different diseases. Lack of specific vitamins can cause various problems.

Examples of vitamin deficiency diseases and their symptoms include:

1. Night Blindness (Vitamin A deficiency): Difficulty seeing in dim light or at night.
2. Beriberi (Vitamin B1 deficiency): Weakness, nerve problems, and heart issues.
3. Scurvy (Vitamin C deficiency): Bleeding gums, tiredness, and slow healing of wounds.
4. Rickets (Vitamin D deficiency): Soft and weak bones, leading to bowed legs in children.

Mineral Deficiency

Lack of important minerals can also lead to specific health problems.

Examples of mineral deficiency diseases and their symptoms include:

1. Anaemia (Iron deficiency): Feeling tired, weak, and looking pale due to lack of red blood cells.
2. Goitre (Iodine deficiency): Swelling in the neck area due to an enlarged thyroid gland.
3. Osteoporosis (Calcium deficiency): Weak and brittle bones that can break easily (more common in older people, but starts with poor calcium intake in youth).