Lipids

• Triglycerides

  Is composed of one molecule of glycerol and three fatty acid chains (chains of fatty acids)
• Sterols

  Another type of lipid, including cholesterol
• Types of fatty acids

  • Saturated
  • Unsaturated
  • Monounsaturated
  • Polyunsaturated
  • Trans fatty acids
• Saturated fatty acids


  • Fully loaded with hydrogen atoms, only contain single bonds, solid at room temperature, higher melting point
• Sources of saturated fats

  • Animal products - cream, cheese, butter, beef, sausages, pork
  • Non-animal products - coconut oil, palm oil, cocoa butter (chocolate)
• Monounsaturated fatty acids


  • Not fully loaded with hydrogen, contain one double bond between carbon atoms, liquid at room temperature, lower melting point
• Sources of monounsaturated fats


  • Avocados, nuts e.g. macadamias and almonds, cooking oils e.g. canola, peanut and olive oil
• Polyunsaturated fatty acids


  • Contain two or more double bonds between carbon atoms, liquid at room temperature, lower melting point
  • Polyunsaturated fatty acids are identified by position of the double bond in relation to the methyl group (CH3) end
  • Described by omega number
  • Omega 3 has 1st double bond three carbons away from methyl end
  • Omega 6 has first double bond six carbons away from the methyl end
• Sources of polyunsaturated fats

  • Omega-3 - oily fish e.g. salmon, sardines, walnuts, chia seeds, soybeans
  • Omega-6 - sunflower seeds, sesame seeds, pumpkin seeds, sunflower oil
• Naturally Occurring Unsaturated Fatty Acids

  Hydrogens attached to the carbon atoms are on the opposite side of the carbon chain
• Sources of trans fatty acids

  • Not found naturally in high quantities in any food, artificially produced trans fats used in commercially produced foods such as biscuits, cakes, pastries, hydrogenated vegetable fats for deep frying, Copha
• Cholesterol- Sterols


  • Most common is cholesterol and is also comprised of carbon, hydrogen and oxygen
  • Cholesterol features glycerol and fatty acid chains similar to triglycerides.
  • However, in cholesterol, fatty acid chains are fused as rings, giving it a steroid section and is classification of a sterol.
  • Excess can lead to some health concerns in relation to atherosclerosis and heart disease
• Sources of cholesterol

  • Most cholesterol is made in the liver, small amount comes from the diet (meat, fish, eggs, dairy)
• Types of lipoproteins


  • Chylomicrons
  • Very-low density lipoprotein (VLDL)
  • Low-density lipoprotein (LDL)
  • High-density lipoprotein (HDL)
  • Dependent on size and density
• Lipoproteins

  • Cholesterol is a waxy substance and only slightly soluble in water and blood (hydrophobic), therefore it requires transport with hydrophilic (mix and dissolve in water) proteins in molecules called lipoproteins
  • Consists of hydrophobic core (cholesterol & triglycerides)
  • Core is surrounded by hydrophilic membrane consisting of phospholipids, free cholesterol and protein
• LDL cholesterol


  • Smaller than VLDL
  • Derived from VLDL
  • Greater cholesterol and fewer triglycerides than a VLDL
  • LDL circulates throughout the body delivering cholesterol - lead to depositing LDL on artery walls and becoming trapped (forming plaque)
• HDL cholesterol


  • Smallest
  • Produced by the Liver
  • HDL removes excess cholesterol from the cells and carries it back to the liver for recycling and disposal
  • Lowest proportion of lipids and highest proportion of protein
• 30% of our daily energy should come from fats and oils, no more than 10% from saturated fat and no more than 1% from trans fats
• Source of Energy

  • Provide 37.7kJ per 1g, energy storage (adipose tissue under skin and around organs)
  • When energy is required, triglycerides are broken down into glycerol and fatty acid chains from fat cells in adipose tissue and used to create energy in the form of ATP
  • 30% of our daily energy should come from fats and oils
  • No more than 10% from saturated fats
  • No more than 1% from trans fat
  • Fat keeps the feeling of satiety and regulate appetite
• Functions of essential fatty acids (omega-3 and omega-6)

  • The body cannot synthesise these and therefore they must be consumed from the diet
  • Overall support functioning of the circulatory and immune systems
  • Omega 3: keeps the heart beating regularly reducing the risk of abnormal heartbeat (arrhythmia) thinning the blood and therefore reducing the risk of clotting and supporting the immune system
  • Omega 6: also assists in blood clotting processes

  *both essential fatty acids are useful in fetal/ infant brain development and in the reduction of low-density lipoproteins
• Functions of Cholesterol

  • Cholesterol is needed by cells for its structural role in the cell membrane as it creates stability
  • Cholesterol is also required for the synthesis of body compounds including bile, hormones and Vitamin D
  • Cholesterol is a waxy substance that requires a transport molecule to move around the bloodstream (same as triglycerides)
• Limit saturated fats, choose lean meats, remove skin & fat from meats, choose low-fat/reduced dairy, choose unsaturated fats where possible (nuts, veg oils, fish, avocado), choose cooking methods that use less addition of fats
• Lipids

  • The lipid family includes triglycerides (fats & oils) and phospholipids and sterols
  • 95% of the foods we eat include triglycerides
  • 5% of lipids are phospholipids and sterols
  • Triglycerides are composed of carbon, hydrogen, and oxygen and supply the body with energy
  • Come in two main forms
  • Fats that are solid at room temperature - higher melting points
  • Oils that are liquid at room temperature - lower melting point
  • a food is classified by the type of fat that is more predominant in the food source
• Structure and Classification of Lipids

  • All fatty acids have the same basic structure - a chain of carbon and hydrogen atoms with an acid group (COOH) at one end and methyl group (CH3) at the other end. 
  • They differ from one another by the length of carbon chains and in the number and location of their double bonds. 

  Most naturally occurring have an even number of carbon chains (4-24)

  • 12-24 for meat fish vegetable oils
  • 10 dairy products
• Unsaturated Fatty Acids

  • Monounsaturated Fatty Acids
  • Polyunsaturated Fatty Acids
• Bonds

  • oxygen can only form two bonds, hydrogen can only form one bond, and carbon can only bond four bonds
• Naturally Occurring Unsaturated Fatty Acids

  • have double bonds known as cis, meaning the hydrogen atoms are attached to the carbon atoms with a double bond on the same side as the carbon chain
• Hydrogenation

  • Trans-fatty acids are mainly made through a process called hydrogenation – trans fats are known as hydrogenated fats
  • Hydrogenation is a process by which vegetable oils are converted to solid fats simply by adding hydrogen atoms.
  • During hydrogenation, the double bonds break and a hydrogen atom is added, creating a trans-fatty acid – becomes saturated 
  • This process converts unsaturated fatty acids to saturated acids 

  Trans-fats form when manufacturers turn liquid oils into solid fats.
• Why Manufactures Prefer Trans Fatty Acids

  • Longer shelf life
  • Improves texture - makes them more solid
  • Reduce Rancidity - change in colour, smell, and taste
• Sources of Trans Fatty Acids

  • Not found naturally in high quantities in any food 
  • Artificially produced trans fats used in commercially produced foods such as biscuits, cakes, pastries
  • Hydrogenated vegetable fats for deep frying
  • Copha
• Process of Fatty Acids

  • Fatty acids rarely occur free in food or in the body and are most often attached to a glycerol molecule via their acid end, making a triglyceride.
  • To make a triglyceride, a series of condensation reactions combine a hydrogen atom from the glycerol and a hydroxyl group (OH) from a fatty acid, forming a molecule of water. A triglyceride may be composed of a mixture of more than one type of fatty acid
• Chylomicron

  • Largest
  • Least dense
  • They transport lipids (triglycerides and cholesterol) to cells all over the body and become smaller as their contents gets depleted
• Very Low Density Lipoproteins

  • Smaller than chylomicrons
  • Produced by the liver and are triglyceride rich
  • Transport triglycerides from the liver to body cells (muscle, adipose tissue) - as they deplete in triglycerides, they shrink in size shifting to an LDL
• Transportation of Storage and Fat Soluble Vitamins

  Fat soluble vitamins: A, D, E, K

  • These congregate with triglycerides during digestion and move into the bloodstream and travel to adipose tissue where they are stored until needed. 
  • Therefore, triglycerides are also considered to provide storage for fat-soluble vitamins. 

  *lipoproteins are required to transport fat soluble molecules as they are hydrophobic 
• Cushioning and Insulation of Vital Organs

  • Triglycerides are stored in fat cells found around internal organs (visceral fat) and under the skin. 
  • This adipose tissue provides protective cushioning and thermoregulation, specifically insulation as adipose tissue generates heat.
• Lipids


  Important in the diet as they are an energy source, protect organs, carry/store fat-soluble vitamins, synthesis of Vit D, bile & hormones, cell membrane structure
• 30% of our daily energy should come from fats and oils
• No more than 10% from saturated fat
• No more than 1% from trans fats
• Limit saturated fats

  1. Choose lean meats

  2. Remove skin & fat from meats

  3. Choose low-fat/reduced diary