UNIT 3: NUTRITION

• Our food is divided into seven main classes

  • carbohydrate
  • protein
  • fat
  • vitamin
  • mineral
  • fibre
  • water
• Carbohydrate

  • organic compound that contains carbon, hydrogen and oxygen
  • staple for humans because it supplies a lot of energy
  • examples are starch, glycogen and cellulose
  • starch - food stored in plants
  • glycogen - food stored in animals
  • cellulose - carbohydrate that forms the cell walls of plants
• Sources of carbohydrates

  • banana
  • rice
  • bread
  • potato
  • honey
  • sugar
• Protein

  • food substance that contains carbon, hydrogen, oxygen and nitrogen
  • protein is digested to the basic unit (amino acid)
  • required for growth
  • repair damaged tissues in the body
  • replace dead cells
  • synthesise enzymes, hormones and antibodies
• Fat

  • contains carbon, hydrogen and oxygen
  • formed from glycerol and fatty acid
  • high energy source and storage
  • each gramme of fat supplies two times the total energy supplied by carbohydrates
  • protects the organs of the body such as heart and kidneys
  • acts as a transporter for vitamin A, D, E, and K
  • excess fat in the body is stored under the skin as a heat insulator to regulate body temperature
• Vitamin

  • organic compound that does not supply energy
  • needed in small quantities to maintain good health
  • water soluble (Vitamin B and C)
  • fat soluble (Vitamin A, D, E and K)
• Vitamin A

  Sources: milk, egg yolk, fish oil

  Importance: helps with night vision, maintains skin health

  Effects of deficiency: night blindness, skin diseases
• Vitamin B

  Sources: yeast, liver, eggs

  Importance: maintains the function of the nervous system, formation of red blood cells

  Effects of deficiency: beri-beri, anaemia
• Vitamin C

  Sources: fruits, vegetables

  Importance: fight diseases, maintain the health of gums and mouth

  Effects of deficiency: scurvy (bleeding gums)
• Vitamin D

  Sources: butter, eggs, fish oil, also produced through sun exposure

  Importance: helps in the absorption of calcium, strengthens tooth enamel, maintains skin health

  Effects of deficiency: rickets, toothache, skin diseases
• Vitamin E

  Sources: grains, green vegetables

  Importance: maintains the function of reproductive system

  Effects of deficiency: sterility, foetus miscarriage
• Vitamin K

  Sources: milk, egg yolk, fish oil

  Importance: speeds up the blood-clotting process

  Effects of deficiency: prolonged bleeding
• Fibre

  • cannot be broken down by the digestive system
  • comprises of cellulose that is found in the cell wall of plants
  • stimulate peristalsis (movement caused by the constriction and relaxation of the muscles along the digestive tract)
  • easier for food to move along the digestive tract and prevent constipation
• Mineral

  • non-organic substance
  • do not supply energy
  • required in small quantities to regulate body processes to maintain health
• Calcium

  Source: milk, anchovies, prawns, green vegetables

  Importance: helps with blood-clotting, strengthens bones and teeth

  Effects of deficiency: rickets, osteoporosis
• Sodium

  Source: salt, meat, eggs

  Importance: maintains the functions of the nervous system

  Effects of deficiency: muscle cramps
• Iron

  Source: liver, meat

  Importance: builds haemoglobin in the blood

  Effects of deficiency: Anaemia
• Iodine

  Source: seafood, fruits

  Importance: Helps with the functions of the thyroid gland

  Effects of deficiency: Goiter
• Phosphorus

  Source: cheese, meat, eggs, vegetables

  Importance: strengthens bones and teeth, forms nucleic acid in DNA and RNA

  Effects of deficiency: rickets, brittle teeth, cannot build DNA and RNA
• Potassium

  Source: plants, animals

  Importance: helps with muscle contraction, maintains the function of the nervous system

  Effects of deficiency: muscle cramps, paralysis
• Water

  • compound (hydrogen + oxygen)
  • chemical solvent
  • transportation medium of nutrients and oxygen into the cells
  • transports waste materials such as urea and salt out of the cells
  • regulates body temperature through evaporation of sweat
• A balanced diet is a diet that contains all the food classes in the right quantities that are required by the body
• Factors that influence Calorific Requirement

  • Body size
  • Age
  • Work
  • Gender
  • State of health
  • Climate
• Body size

  • A person with a large body frame needs to take a bigger portion of food because he or she needs to have more energy compared to someone with a smaller frame
• Age

  • Children and teenagers require more carbohydrates for energy and protein for growth because they are growing and are more active compared to adults
• Work

  • Farmers, labourers and fishermen require more energy because they do heavy work. Therefore, their diet requirements are higher compared to people who work in an office.
• Gender

  • Generally, men are more muscular and they do more heavy activities. Therefore, they need bigger food portions than women
• State of health

  • People who are sick are weak. They require food suitable to their health condition
• Food digestion is the process of breaking down food that is compex and large into molecules that are small, simple and soluble so that they can be absorbed by the cells of the body
• Physical Digestion

  • the process of breaking down food into smaller particles in the mouth with the help of tongue, teeth and saliva
  • Involves peristalsis
• Chemical Digestion

  • The process of breaking down food from complex molecules into simple molecules with the help of enzymes
• 1. Mouth
  2. Oesophagus
  3. Stomach
  4. Duodenum
  5. Small intestine
  6. Large intestine
  7. Rectum
  8. Anus
• Similarities between Physical and Chemical Digestion

  • Break down of food occur
  • Happens in the digestive tract
• Mouth

  • Food is chewed by the teeth
  • Particles of food is softened by saliva
  • Salivary amylase in saliva breaks down starch into maltose
• Oesophagus

  • Food that enters the oesophagus is called bolus
  • The process of peristalsis at the wall of the oesophagus pushes the food into the stomach
• Stomach

  • Walls of the stomach secrete protease and hydrochloric acid. Hydrochoric acid activates the protease and kills bacteria in the food that enters the stomach
  • Protease breaks down protein into polypeptides
  • Food that is semi-liquid is called chyme
• Duodenum

  • Food enters the first part of the small intestine, that is the duodenum
  • The liver produces bile that is stored in the gall bladder
  • The bile emulsifies fat into small droplets and neutralises the acid in the chyme
  • The pancrease produces pancreatic juice which contain enzymes amylase, protease and lipase
  • Pancreatic amylase digests starch into maltose
  • Protease digests polypeptides into dipeptides
  • Lipase digests fat into fatty acids and glycerol
• Small intestine

  • The small intestine secretes enzymes maltase and protease
  • Maltase digests maltose into glucose
  • Protease digests dipeptides into amino acids
• Large intestine

  • Undigested food will enter the large intestine
  • the process of water reabsorption occurs
• Rectum

  • Food that is undigested, known as faeces, enters the rectum and is stored here