Topic 2.1: Nutrition (2.1 - 2.2)

2.1 Classes of Food
1. Seven classes of food:

      a) Carbohydrate
          - Made up of carbon, hydrogen and oxygen
          - Main sources of energy for human
          - Main sources: rice, bread, potatoes, cereals, etc
          - Basic unit for carbohydrates is glucose
          - Example: starch, cellulose, sugars and glycogen

      b) Proteins
          - Made up of carbon, hydrogen, oxygen, nitrogen and sulphur.
          - For growth and repair tissues        
          - Basic unit: amino acid
          - Main sources: meat, fish, milk, egg, chicken

      c) Fats
         - Made up of carbon, hydrogen and oxygen
         - For source of energy and keep our body warm
         - Basic units: fatty acids and glycerol
         - Main sources: vegetables oil, fish oil, animal fat, etc

      d) Minerals
          - Inorganic substances needed by body
          - Minerals are required in small amount and vital for good health

          - Sources: almost every type of food

      e) Vitamins
          - Vitamins are organic compound that are vital for healthy growth
          - Fat-soluble : A, D, E,K
          - Water-soluble: B, C

          - Main sources: liver, eggs, milk cereals, fruits, vegetables, etc

      f) Water
        - Important to body
        - Dissolve and transport digested food, gases, hormones and excretory products
        - Regulate body temperature
        - Main sources: fruits, vegetables and minerals water
      g) Fibre
          - Made up of cellulose from plant cell walls
          - Cannot be digested by human digestion system and helps to prevent constipation
          - Main sources: beans, cereals, brown rice, fruits and leafy vegetables

2. Food test
2.2 Importance of Balance Diet
1. A balanced diet consists of all classes of food in right amount to meet requirements of the body.
2. Balance diet provides energy, building materials (for cells and tissues), repair damaged tissues, maintaining body functions and helps fight diseases

3. Factors that determine balanced diet: age, sex, body size, occupation, state of health and climate.
4. Energy stored in food is referred to calorific value or energy value

5. Calorific value of food is defined as the amount of energy released from one gram of food.
6. Measured in calories (cal) or joules (J)
   1 cal = 4.2 J
7. Energy value of main food classes
8. Calculation of calorific value of some food taken:
      If a student has his meal by taking the food shown below:
      Rice 200g, fried egg 100g and banana 50g, calculate the calorific value he has taken:
      Rice                                             = 1200 x 2
                                                          = 2400 kJ
      Fried egg                                      = 800 x 1
                                                          = 800 kJ
      Banana                                         = 150 /2
                                                          = 75 kJ
      Total calorific value has taken       = 2400 + 800 + 75
                                                          = 3275 kJ


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