Human Nutrition

• Vitamins


  • Complex organic compounds
  • Needed in small amount
  • Keep body healthy
  • Prevent deficiency diseases
• Fat soluble vitamins


  Can be stored in fats of body<|>Vitamin A,D,E,K
• Water soluble vitamins


  Cannot be stored in body<|>Have to be supplied in daily diet<|>Vitamin B,C
• Vitamin C (ascorbic acid)

  • Main source: citrus fruits (oranges, lemons), green vegetables, papaya, guava
  • Function: Formation of intercellular substances, Healthy epithelial tissues, Wound healing
  • Deficiency: scurvy - bleeding of gums, bruised skin, slow wound healing
• Vitamin D (calciferol)


  • Main source: fish liver oil, egg yolk, butter, fish, milk, sunlight
  • Function: Regulates absorption of calcium & phosphorous, for bone & teeth formation
  • Deficiency: Rickets - soft & fragile bones, deformities, bowed legs, poor teeth & bone formation
• Mineral Salts


  • Inorganic chemical
  • Required in small amounts
  • Help to build body tissues (bones)
  • To regulate metabolic activities (in form of enzymes or hormones)
• Mineral: Calcium

  • Main sources: Milk, cheese, cereals, dark green vegetables
  • Requirements: children about 1 g/day, more in pregnant & breast feeding women
  • Functions: building of teeth & bones, normal muscle functioning, blood clotting
  • Deficiency: Rickets
• Mineral: Iron

  • Main sources: Liver, meat, green leafy vegetables
  • Requirements: very little, 0.02 g/day, more in pregnant women
  • Functions: formation of haemoglobin in red blood cell
  • Deficiency: Anaemia - tiredness, weakness, breathlessness, ↓ of Hb level, red blood cell become smaller
• Dietary fibre (roughage)


  Indigestible fibrous material<|>Provides bulk to intestinal contents & helps peristalsis<|>If peristalsis does not occur properly: undigested matter takes time to pass through large intestine, ↑↑ H2 O absorped, hard & dry faeces, difficult removal of faeces through anus (constipation)
• Prevention of constipation

  Intake of enough fibre & drinking sufficient water<|>Regular exercise helps promote peristalsis
• Sources of dietary fibre

  • Fruits, vegetables
  • Cereals, bread
  • Nuts
• Water


  As main component of protoplasm, blood & tissue fluid<|>As a medium for all chemical reactions<|>As a reagent to hydrolase food by enzymes<|>As a cooling agent during sweating<|>Water is lost during urination, sweating & when we breathe out<|>Dehydration will occur if the water lost is not replaced
• Balanced Diet


  Contains the right amount of carbohydrates, fats, proteins, vitamin, minerals, water & roughage to meet the daily requirements
• Basal metabolism


  The amount of energy needed to carry on vital life processes of the body when it is in complete rest
• Examples of basal metabolism


  • Beating of the heart
  • Movement of muscles
  • Repair of worn out tissues
  • Maintaining body temperature
• BMR


  Measure of how fast chemical reactions are occurring when a person is completely at rest<|>Measure of the amount of energy required for vital activities
• Factors affecting BMR


  • Age
  • Sex
  • Body size
  • Health
  • Occupation (work)
  • Climate
• Malnutrition


  Feeding of unbalanced diet with either too much or too little of the right classes of food
• Effects of malnutrition


  • Eating excess of energy: obesity
  • Eating excess of saturated fats & cholesterol: ↑ risk of having coronary heart diseases
  • A diet deficient in fibre: constipation
• Starvation


  A shortage or complete lack of food for so long period of time
• Problems contributing to famine

  • Overpopulation
  • Unequal distribution of food
  • Natural calamities
• Stages of the human digestive system

  • Ingestion
  • Digestion
  • Absorption
  • Assimilation
  • Egestion
• Physical digestion


  Breakdown of food into smaller pieces without any chemical change to the molecules<|>In the mouth by chewing, by contraction of stomach wall (churning) & by action of bile (emulsification)<|>Increases surface area of food for the action of enzymes in chemical digestion
• Chemical digestion


  Breakdown of large food molecules into smaller ones<|>Occurs by digestive enzymes contained in saliva, gastric juice, pancreatic juice & intestinal juice<|>The chemical bonds in large complex food molecules are broken down in presence of water by process of hydrolysis<|>The small soluble food molecules formed can be easily absorbed into the bloodstream
• Digestive processes in the mouth


  • Food is broken physically into smaller pieces by teeth (chewing or mastication)
  • Salivary glands produce saliva that have water, mucus & enzymes salivary amylase
  • Water & mucus moisten and lubricate the food making it easier to swallow
  • Salivary amylase hydrolyses starch into maltose
  • The food is made into a round ball called bolus which is then swallowed down the oesophagus
• Oesophagus


  A muscular tube which leads form pharynx down to stomach<|>Its wall are made up of circular muscles & longitudinal muscles<|>These 2 muscles work antagonistically to move food along the oesophagus by peristalsis
• Digestive processes in the stomach

  • A muscular bag that churns the food for up to 4 hours
  • Gastric glands secrete gastric juice containing: Hydrochloric acid - provides acidic pH, stops action of salivary amylase, kills harmful bacteria
  • Pepsin (protease) - breaks down proteins into shorter polypeptide chain
  • Mucus - protects the stomach wall from being damaged by action of acid & protease enzyme
  • The stomach breaks down the food into a semi-liquid form called chyme
  • Little by little of it then released into the duodenum
• Digestive processes in the duodenum & ileum

  • Food mixes with 3 digestive juices: Bile - contains salts, bile pigments & sodium hydrogen carbonate to neutralize acidic chyme and provide alkaline pH, emulsify fats
  • Pancreatic juice - contains enzymes to further digest food
  • Intestinal juice - contains enzymes to further digest food
• Stomach acid


  • Kills harmful bacteria that may be present in the food
  • Featured in acidic pH
• Pepsin


  Protease that breaks down proteins into shorter polypeptide chains by hydrolysis
• Mucus


  Protects the stomach wall from being damaged by action of acid & protease enzyme
• Stomach digestion


  1. Breaks down food into a semi-liquid form called chyme

  2. Releases chyme little by little into the duodenum
• Bile


  Greenish-yellow liquid produced in liver<|>Stored in gall bladder and passes down bile duct to duodenum<|>Contains salts, bile pigments & sodium hydrogen carbonate
• Sodium hydrogen carbonate in bile

  Neutralizes acidic chyme from stomach<|>Provides an alkaline pH (7-8) for enzymes to work best in duodenum
• Bile salts


  Emulsify fats, breaking large fat molecules into smaller ones<|>Increases surface area for enzymes to act easier on them<|>Provides an alkaline medium & neutralize the acidity of the chyme
• Pancreatic juice


  Produced by pancreas and passes down the pancreatic duct to the duodenum<|>Contains NaHCO3 to neutralize the acidic chyme from stomach<|>Provides alkaline pH (7-8) for enzymes to work best<|>Contains amylase, trypsin, and lipase
• Intestinal juice


  Produced by intestinal glands in wall of small intestine<|>Contains maltase, invertase, lactase, and erepsin
• Final products of digestion

  • Glucose (from starch)
  • Amino acids (from proteins)
  • Fatty acids & glycerol (from fats & oils)
• Ileum


  • Surface area is increased by being long & coiled
  • Walls have tiny structures called villi
  • Villi contain many micro villi, increasing the surface area
• Villus


  • Finger-like shape provides large surface area for absorption
  • Cell wall is very thin (one cell thick) for rapid diffusion of food
  • Contains a network of blood capillary & lacteal vessels to carry away absorbed food