Human nutrition

• Balanced diet


  A diet containing all 7 key nutrients, in correct amount and proportion.

  The nutrients are: carbohydrates, proteins, fats, vitamins, minerals, water and fibres
• Factors affecting a diet

  Age, as you age you need to eat less since metabolism slows down

  Gender, generally males need to eat more

  Activities, the more activities the more you need to eat
• Factors which may change woman's diet

  Pregnancy, may need to eat more calcium for the fetus's bones and teeth

  Breast-feeding, women may need to eat a little more
• Function of carbohydrates


  For energy, for growth, movement, cell division, tissue repair and protein synthesis
• Function of proteins


  For growth, bones and needed to make proteins, such as: haemoglobin, anti-bodies and hormones
• Function of fat


  Insulation

  Energy

  And to make cell membranes
• Function of vitamin C

  For making stretchy protein called collagen, which can be found in skin

  Keeps tissue in good repair
• Function of vitamin D

  Helps to absorb calcium

  For bones and teeth
• Function of calcium minerals

  For bones and teeth

  For blood clotting
• Function of iron minerals

  To produce haemoglobin, the red pigment in the blood which carries the oxygen
• Function of water


  For cytoplasm

  Blood

  Remove waste products from kidney (urea)
• Function of fibres


  Helps along the digestive tract

  Can retain water in the faeces to prevent constipation
• Causes of starvation


  Eating too little food
• Causes of constipation


  Not eating enough fibres

  Not drinking enough water
• Causes of coronary heart disease

  Obesity

  Diabetes

  Eating too much fats
• Causes of obesity


  Eating too much
• Causes of scurvy


  Not enough intake of vitamin C
• Malnutrition


  Not eating a balanced diet, may be because:

  1) Eating too much or too little

  2) Not eating nutrients in proportion

  3) May be lacking a key nutrient
• Deficiency of vitamin D

  Rickets, soft, deformed bones
• Deficiency of iron minerals

  Anaemia, not enough red blood cells, so not enough oxygen being supplied to tissues
• Causes and effects of kwashiorkor

  Eating too much carbohydrates and too little proteins.

  Symptoms: victim may look underweight but has bloated belly.
• Causes and effects of marsmus


  Shortage of energy in diet

  Victim looks underweight

  Dry skin

  Brittle hair
• Ingestion


  The taking in of substances, such as food and drinks, into the body through the mouth.
• Mechanical digestion


  The breakdown of food into smaller pieces without any chemical change to the food molecules.
• Chemical digestion


  The breakdown of larger insoluble molecules into smaller soluble molecules.
• Absorption


  The movement of small food molecules and ions in to the walls of the small intestine, into the blood
• Assimilation


  The movement of digested food molecules into the cells, where they are used and become part of the cell.
• Egestion


  The passing of food which had not been digested or absorbed, as faeces, through the anus
• Diarrhoea


  The loss of watery faeces.
• Rehydration therapy


  Treatment for cholera and diarrhoea.

  Fluids are added directly to the blood stream using a drip, instead of having to ingest all the fluids.
• How cholera happens


  1) Bacteria cholera is ingested

  2) Cholera bacteria multiply and stick to walls of alimentary canal

  3) The bacteria releases a toxin which causes release of chlorine ions from the blood, which cause water to diffuse into the lumen from the blood capillaries.

  4) Too much water in the lumen causes watery faeces, there is now too litte chlorine ions and water in the blood.
• Mouth


  Has tongue and teeth which breakdown food into smaller pieces.
• Salivary glands


  Secrete saliva

  Saliva moistens food so it can be easily swallowed

  Saliva has amylase which breaks down starch
• Oesophagus


  After the food is chewed and swallowed it passes from the moth to the stomach through the oesophagus, by waves of contracting muscles, called peristalsis
• Stomach


  Has acid and pepsin, which start breakdown of proteins

  Walls of stomach churn the food into a liquid
• Liver


  Produces bile

  Breaks down amino acids not used into urea, which is sent to the kidney to be excreted

  Also stores excess glucose from the blood as glycogen
• Gall bladder


  Stores bile

  Passes bile through bile duct into the duodenum, neutralising the acid from the stomach.
• Pancreas


  Secretes digestive enzymes in an alkaline fluid into the duodenum
• Small intestine (duodenum and ileum)

  Secretions from the gall bladder and pancreas complete digestion

  Digested molecules and water absorbed
• Large intestine (colon)


  Absorbs water from remaining material