Basic 8 · Career Technology · Food Commodities
The Functions of Food in the Body
In this topic you will explore the nutrients found in food, explain the function of each nutrient in the body, and identify Ghanaian foods that are good sources of each nutrient.
By the end of these notes you should be able to:
- Explain the meaning of food, nutrients and nutrition
- Describe the functions of carbohydrates, proteins and fats
- Describe the functions of vitamins, minerals, water and dietary fibre
What you already know
- Food commodities and their sources (Basic 7)
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
Lesson 1
- Strand
- Materials For Production
- Sub-strand
- Food Commodities
- Indicator
- B8.2.4.1.1 – Explore the functions of food to the body
Introduction
Why does a learner who skips breakfast feel weak by mid-morning? Why do growing children need eggs, beans and fish? The answers lie in the nutrients in food and the jobs they do in the body.
1. Food, Nutrients and Nutrition
Nutrients: Chemical substances in food that the body needs for energy, growth, repair and protection.
Nutrition: The process by which the body takes in and uses food.
There are six main classes of nutrients: carbohydrates, proteins, fats and oils, vitamins, minerals and water. Dietary fibre is also important, although it is not digested. Each nutrient has special functions, and no single food contains all of them in the right amounts.
2. Carbohydrates
Carbohydrates are the body's main source of energy. They include starches and sugars. Energy from carbohydrates allows us to walk, play, think and keep the heart beating. Good Ghanaian sources include maize (used in kenkey and banku), rice, millet, sorghum, yam, cassava (fufu, gari), cocoyam, plantain and sweet potato. Too much sugar, however, can cause tooth decay and weight gain.
3. Proteins
Proteins build and repair the body. They are needed to grow muscles, skin, hair and blood, to heal wounds and to make substances that fight infection. Children, pregnant women and sick people need extra protein. Animal sources include fish, meat, eggs, milk and snails; plant sources include cowpea, groundnuts, soya beans and bambara beans. Combining a cereal with a legume, as in waakye, gives good-quality protein.
4. Fats and Oils
Fats and oils give concentrated energy, keep the body warm, protect organs such as the kidneys, and carry vitamins A, D, E and K. Sources include palm oil, groundnut oil, shea butter, coconut oil, avocado, groundnut paste and the fat in meat and fish. Red palm oil is also rich in vitamin A. Too much fat, especially from fried foods, can lead to obesity and heart disease, so fats should be eaten in moderation.
| Nutrient | Main function | Ghanaian sources |
|---|---|---|
| carbohydrates | energy | maize, rice, yam, cassava, plantain |
| proteins | growth and repair | fish, eggs, meat, beans, groundnuts |
| fats and oils | concentrated energy, warmth, protection | palm oil, groundnut oil, avocado, shea butter |
New words
- nutrient
- A substance in food needed by the body.
- carbohydrate
- A nutrient that gives energy.
- protein
- A nutrient for growth and repair.
- moderation
- Eating something in reasonable amounts.
Summary
- Nutrients are substances in food needed for energy, growth, repair and protection.
- Carbohydrates give energy; proteins build and repair; fats give concentrated energy and warmth.
- Ghana has many good sources of each, and fats and sugars should be eaten in moderation.
Class activity: Nutrient Sorting
- Examine a maize cob, cowpea seeds and garden eggs.
- Sort pictures of Ghanaian foods into carbohydrate, protein and fat sources.
- Explain one function of each nutrient.
You need: Maize cob, Cowpea seeds, Garden egg
Exercises
Answer in your exercise book first, then check your answers.
1. The main function of carbohydrates is to…
- A. give energy
- B. build muscles
- C. heal wounds
- D. carry oxygen
Show answer
Answer: give energyEnergy foods.2. Which food is a plant source of protein?
- A. cowpea
- B. cassava
- C. rice
- D. sugarcane
Show answer
Answer: cowpeaLegume.3. Fats help to keep the body warm.
- A. True
- B. False
Show answer
Answer: TrueInsulation.4. A nutrient that builds and repairs the body is ______.
Show answer
Answer: proteinBody building.5. Name two sources each of carbohydrates and proteins.
Show answer
Answer: Carbohydrates: yam, rice; proteins: fish, beans.Any correct.6. Why do children and pregnant women need extra protein?
Show answer
Answer: Their bodies are growing and building new tissues rapidly.Growth.
Lesson 2
- Strand
- Materials For Production
- Sub-strand
- Food Commodities
- Indicator
- B8.2.4.1.1 – Explore the functions of food to the body
Introduction
Vitamins and minerals are needed only in small amounts, but without them the body cannot work properly. Water and fibre are also essential for good health.
1. Vitamins
| Vitamin | Function | Sources |
|---|---|---|
| vitamin A | healthy eyes and skin; fights infection | red palm oil, carrots, mango, pawpaw, dark green leaves, eggs |
| B vitamins | release energy from food; healthy nerves | whole grains, beans, groundnuts, meat, eggs |
| vitamin C | healthy gums and skin; heals wounds; helps absorb iron | oranges, pineapples, pawpaw, guava, tomatoes, peppers |
| vitamin D | strong bones and teeth | sunlight on the skin, fish, eggs |
| vitamin K | helps blood to clot | green leafy vegetables |
2. Minerals
| Mineral | Function | Sources |
|---|---|---|
| calcium | strong bones and teeth | milk, small fish with bones (such as anchovies), dark green leaves |
| iron | forms haemoglobin to carry oxygen in blood | kontomire, beans, liver, red meat, fish |
| iodine | healthy thyroid gland and brain development | iodised salt, seafood |
| zinc | growth and fighting infection | meat, fish, beans, nuts |
| sodium and potassium | fluid balance, nerves and muscles | salt, bananas, plantain, oranges |
3. Water
Water makes up about 60 percent of the body. It carries nutrients and oxygen in the blood, removes wastes in urine and sweat, keeps body temperature steady, aids digestion and lubricates joints. In Ghana's hot climate, young people should drink about six to eight glasses of clean water a day, more when exercising. Thirst, dark urine and headaches can be signs of dehydration.
4. Dietary Fibre
Dietary fibre (roughage) comes from plant foods such as vegetables, fruits, whole grains, beans and the skins of fruits. It is not digested, but it adds bulk to food, helps food move through the intestines and prevents constipation. Fibre also helps control blood sugar and keeps us feeling full. Diets high in refined foods and low in fruit and vegetables lack fibre.
5. Nutrients Working Together
Nutrients work together. Vitamin C helps the body absorb iron from beans and kontomire; vitamin D helps the body use calcium; fats carry vitamins A, D, E and K. This is why a varied diet, with foods from all groups, is better than eating large amounts of one food.
New words
- vitamin
- A nutrient needed in small amounts for health.
- mineral
- An inorganic nutrient such as iron or calcium.
- dehydration
- Lack of enough water in the body.
- dietary fibre
- Plant material that helps digestion.
Summary
- Vitamins such as A, B, C, D and K protect health and help body processes.
- Minerals such as calcium, iron and iodine build bones, blood and support growth.
- Water and dietary fibre are essential, and nutrients work best together in a varied diet.
Class activity: Protective Foods Display
- Collect pictures or samples of fruits and vegetables.
- Label each with the vitamins or minerals it provides.
- Make a class display on protective foods.
You need: Maize cob, Cowpea seeds, Garden egg
Exercises
Answer in your exercise book first, then check your answers.
1. Which vitamin helps heal wounds and is found in oranges?
- A. vitamin C
- B. vitamin A
- C. vitamin D
- D. vitamin K
Show answer
Answer: vitamin CCitrus.2. Iodine is mainly obtained from…
- A. iodised salt
- B. sugar
- C. rice
- D. cassava
Show answer
Answer: iodised saltThyroid.3. Dietary fibre helps prevent constipation.
- A. True
- B. False
Show answer
Answer: TrueRoughage.4. Lack of enough water in the body is ______.
Show answer
Answer: dehydrationWater loss.5. State three functions of water in the body.
Show answer
Answer: Carries nutrients, removes wastes, controls body temperature (or aids digestion).Any three.6. Explain how vitamin C helps the body use iron.
Show answer
Answer: Vitamin C helps the body absorb iron from plant foods, so eating oranges with beans improves iron intake.Absorption.
Homework
- List everything you ate yesterday and write the main nutrient in each food.