Module 5

• Lipids


  The chemical term for fat, a group of organic molecules, most of which do not dissolve in water, hydrophobic
• Types of lipids


  • Triglycerides
  • Phospholipids
  • Sterols

  
• Lipid transport in the body

  Atherosclerosis
• Roles of lipids in the body

  • Texture
  • Taste
  • Flavor
  • Aroma
• Recommended dietary lipids


  • 20-35% of total daily kcal (19+y)
  • n-6: 12-17 g/day
  • n-3: 1.1-1.6 g/day
• The Canadian Community Health Survey (CCHS) (2004-2015) revealed: Fat in the Canadian diet declined from ~40% in 1978 to ~31% in 2004; in 2015 it remains at ~31%
• 50% of Canadians' fat intake comes from two of the [OLD Food Guide] food groups: meat & alternatives (31.6%) and milk & alternatives (17.9%)
• 25% of fat comes from fast foods and snack foods (baked goods)
• Intakes above the 35% of total daily intake highest in the 31-50 y age group
• Plant-based fat sources


  • Cottonseed
  • Linseed
  • Canola
  • Sunflower
  • Sesame
  • Olives
  • Coconut
  • Palm
  • Avocadoes
  • Nuts
  • Seeds
• Animal fat sources


  • Meat
  • Fish
  • Eggs
  • Poultry
  • Dairy
• Visible fat


  • Butter
  • Margarine
  • Oil
  • Salad dressing
  • Fat on meat
  • Chicken skin
  • Meat fibres
  • Milk
  • Dairy products
  • Whole grain cereals
  • Nuts
  • Baked goods
  • Eggs

  
• Invisible fat


  • Butter
  • Margarine
  • Oil
  • Salad dressing
  • Fat on meat
  • Chicken skin
  • Meat fibres
  • Milk
  • Dairy products
  • Whole grain cereals
  • Nuts
  • Baked goods
  • Eggs

  
• Triglycerides


  Major form of lipid in food and body, major form of stored energy

  
• Fatty acids


  Methyl end (CH3) and carboxyl end (COOH), water soluble carboxyl group, carbon chain not water soluble

  
• Triglyceride formation (condensation)


  1. Carboxyl group

  2. Hydroxyl group

  
• Types of fatty acids determined by

  • Length of carbon chain (4-26C)
  • Number of C=C (degree of saturation)
  • Location of double bonds

  
• Short chain fatty acid (SCFA)

  Less than 10 carbons, rare, anti-inflammatory properties
• Medium chain fatty acid (MCFA)

  10-15 carbons, 4-10% of fatty acids in food, more water soluble, readily absorbed

  
• Long chain fatty acid (LCFA)

  More than 16 carbons, most common chain length in food
• Saturated fatty acids


  Carry maximum number of hydrogen atoms, no C=C bonds, usually solid at room temp, very stable

  
• Unsaturated fatty acids


  Have at least one double (C=C) bond, creates "cis" kinks, lower melting point than saturated

  
• Monounsaturated fatty acid (MUFA)


  Only one C=C bond

  
• Polyunsaturated fatty acid (PUFA)


  Has two or more C=C bonds

  
• Omega-9 fatty acid


  Numbering starts from methyl end
• Essential fatty acids


  Fatty acids that are not made in sufficient amounts to meet physiological need, include omega-6 and omega-3

  
• Omega-6 PUFA


  Linoleic acid, converts to arachidonic acid
• Omega-3 PUFA


  Alpha-linolenic acid, converts to EPA and DHA
• Ideal ratio of omega-6 to omega-3 is between 1:1 to 5:1, Western diets provide ratios of between 10:1 and 30:1
• Soybean oil is currently the biggest sources of omega-6 fatty acids in North America because it is cheap and found in all sorts of processed foods
• Cis configuration of unsaturated fatty acids

  H atoms on same side of C=C, most common, forms "kink", lower melting point

  
• Trans configuration of unsaturated fatty acids

  H atoms on opposite sides of C=C, few in nature, higher melting point, most produced by partial or total hydrogenation

  
• Sources of processed seed and vegetable oils high in omega-6

  • Soy
  • Sunflower
  • Cottonseed
  • Corn oil
• Soybean oil is currently the biggest source of omega-6 fatty acids in North America because it is cheap and found in all sorts of processed foods
• Omega-3 DRI AI (14-50y)


  • Males: 1.6 g/day
  • Females: 1.1 g/day
• Triglycerides


  Unsaturated fatty acids in cis or trans configurations, determined by position of H atoms around C=C

  
• Cis configuration


  • H atoms on same side of C=C
  • Most common configuration of FA in nature
  • Forms "kink"
  • Lower melting point
• Trans configuration


  • H atoms on opposite sides of C=C
  • Few in nature
  • Higher melting point
• Trans fatty acids (TFA) in foods are mostly produced by partial or total hydrogenation

  
• Partial hydrogenation


  1. Break some C=C bonds and add H

  2. Changes configuration of H atoms at some C=C from cis to trans

  3. Results in trans fatty acid (more linear)