week 9

• Diet


  Our habitual intake of certain types of food & drink (not just one meal)
• Diet


  • Can be measured by frequency of intake of various classes of macronutrients, vitamins and minerals
  • Can be influenced by biological factors, energy expenditure, social factors, psychological factors, disease
• Macronutrients


  Carbohydrates, Fats, Proteins
• Micronutrients


  Vitamins, Minerals (metals & ions)
• Carbohydrates


  • A common source of energy in living organisms, but they are not essential nutrients
  • Can exist as monosaccharides, disaccharides or polysaccharides
• Monosaccharide


  • Glucose
• Disaccharide


  • Sucrose
• Polysaccharide


  • Amylose starch
• Sources of carbohydrates


  • Starch, sugar and fibre are the major carbohydrates in our diet
• Dietary fibre


  • Indigestible carbohydrates, such as cellulose, derived from plants
  • Reaches the large intestine where it is metabolised by our gut microbes to extract about 10% of our daily calories
  • Can delay gastric emptying, helping you feel fuller for longer
• Protein


  • Forms ~17% of the human body
  • Constantly turning over, and needs to be replaced
• Essential and non-essential amino acids

  • Of the 20 major amino acids, 9 cannot be synthesized by man, and must be supplied in the diet
  • These are called essential amino acids
• Essential amino acids


  • Phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine
• Fats


  • Triglycerides, which are esters of three fatty acid chains and the alcohol glycerol
  • Dietary oils are fats that are liquid at room temperature
• Saturated and unsaturated fats

  • Saturated fatty acids have no double bonds
  • Mono-unsaturated fatty acids have one double bond
  • Poly-unsaturated fatty acids (e.g. omega-3 and omega-6) have multiple double bonds
• Vitamins


  • Organic compounds and vital nutrients that an organism requires in limited amounts for health
  • Low levels can cause specific diseases
  • Often act as cofactors for enzymes
  • Classified as water-soluble or fat-soluble
• Cofactors and coenzymes


  • Cofactors are non-protein chemicals which are required for the biological activity of some enzymes
  • Cofactors are either inorganic ions or complex organic molecules called coenzymes
  • Coenzymes are mostly derived from vitamins
• Water soluble vitamins


  • All of the eight B-vitamins and vitamin C
• Vitamin B1 (thiamine)


  A coenzyme required for the catabolism of sugars and amino acids
• Vitamin B2 (riboflavin)


  A precursor of cofactors called FAD and FMN, which are needed for various enzyme reactions involved in cellular metabolism
• Vitamin B3 (niacin)


  A precursor of the coenzymes NAD and NADP, which are essential for many cellular metabolic processes
• Vitamin B9 (folic acid)


  • Involved in many critical cellular processes
  • Involved in the synthesis of DNA bases and carbon transfer between molecules
• Vitamin B12


  • Has a key role in the normal functioning of the brain and nervous system, and the formation of red blood cells
  • Supports the synthesis of DNA and neurotransmitters, and the metabolism of fatty acids and amino acids
• Vitamin C


  • Plays a key role in the synthesis of collagen
  • Supports wound-healing and helps prevent bleeding from capillaries
  • An anti-oxidant
• Fat soluble vitamins


  • Vitamins A, D, E & K
  • Absorbed with dietary fat via chylomicrons
• Vitamin A


  A group of unsaturated organic compounds that are required for growth and development, maintenance of the immune system and good vision
• Vitamin D


  • A group of fat-soluble vitamins which support intestinal absorption of calcium, iron, magnesium, phosphate, and zinc
  • Very few natural foods contain vitamin D, so they are fortified
• Vitamin E


  • A group of compounds that include both tocopherols and tocotrienols
  • A fat-soluble antioxidant that also regulates protein kinase C
• Vitamin K


  A group of structurally similar, fat-soluble vitamins that control blood clotting and the use of calcium in bones
• Dietary minerals


  The chemical elements required by living organisms, other than carbon, hydrogen, nitrogen, and oxygen
• Major dietary minerals


  • Na+, K+, Cl-, Ca2+, PO4 2-, Mg2+ & Fe2+
• Potassium


  • The main intracellular cation
  • Deficiency can lead to hypertension and abnormal heart rhythm (cardiac arrythmias)
• Calcium


  • Provides hardness for bones, and is essential for many signalling pathways
  • Required for muscle contraction
  • Lack of calcium causes weak bones and neuromuscular problems
• Iron


  • Required for the production of haemoglobin, which carries oxygen in the blood
  • Also involved in the electron transport chain
• Zinc


  • Required as a cofactor for the activity of many enzymes
  • Deficiency results in poor wound healing and diarrhoea
• Copper


  • A cofactor for many enzymes & proteins
  • Required for the crosslinking of collagen
  • Excess results in liver cirrhosis, deficiency is rare but can trigger anaemia
• Phytochemicals

  • Thousands of different compounds recently discovered in plant-derived foods
  • Likely contribute to the health benefits associated with a plant-rich diet
• A "good" diet requires an appropriate balance of macro- and micro-nutrients, which can only be achieved with a sufficiently varied diet, comprising foods which provide those nutrients
• Haemoglobin


  Carries oxygen in the blood
• Haemoglobin


  • It is also involved in the electron transport chain