Lecture 9 Macronutrients FAT

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Lecture 9 Macronutrients FAT Guest lecturer
Dr Karen Murphy
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Overview of LecturesDietary Fat

• requirements
• energy value
• types
• digestion
• absorption

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Dietary Fat

• RDI
• lt 35 of Etotal general
• lt 30 of Etotal athletes
• Energy potential
• 37 kJ/g fat or (9 kcal/g fat)
• 50g packet of Smiths Crisps has 16g fat
• Energy per serve 1098kj
• Energy from fat 592kj (16g x37kj)

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Dietary Fat

• Typical intakes (g/d)

Source NNS 1995, 19yrs, Howe et al 2006
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Lipids

• Sterols
• cholesterol
• foods animal (cholesterol meat, dairy)
• foods plants (phytosterols, olive oil)
• hormones

• Phospholipids
• fat in cell walls
• foods emulsifiers,
• eggs, liver peanuts

• Triglycerides (fats/oils)
• storage fat
• foods 95 of foods

pg 145
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Phospholipids
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Phospholipids

• Roles
• Constituent of cell membranes
• Facilitate movement of lipids across membranes
• Enable fat soluble vitamins and hormones to pass
  in and out of cells
• emulsifier
• eg. lecithin

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Sterols
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Sterols

• Roles
• Present in animal (cholesterol) and plant foods
  (phytosterols)
• Bile acids, hormones, vitamin D etc
• Most common sterol is cholesterol
• Cholesterol is a structural component of cell
  membranes
• Cholesterol homeostasis

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Fats in Food

• Visible fat
• butter
• margarine
• vegetable oil
• lard (dripping)
• cream
• fat on meat

• Hidden fat
• chicken skin
• cakes
• biscuits
• fast-food
• sausages
• pizza

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Fatty Acids

• a hydrocarbon chain
• carboxyl group (COOH) at one end
• methyl group (CH3) at other end
• gt 40 fatty acids in food

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Structure of Fatty acid molecule

• H H H H H H H O
• H C C C C C C C C OH
• H H H H H H H
• Methyl end (CH3) Carboxyl or acid end
  
• (Omega end) (COOH) (Alpha end)

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Fatty Acids

• 2 - 24 carbons in length
• some very long chain fatty acids in algae ie. 28
  carbons in length
• simplest Acetic Acid (2 carbons)
• (Vinegar)

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Fatty Acids

• Acetic Acid is a two-carbon organic acid
• H O
• H C C OH
• H

Methyl end (CH3)
Carboxyl or acid end (COOH)
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Fatty Acids

• 3 types of fatty acids

• Saturated (SFA)
• no double bonds between carbon atoms
• animal fat
• palm oil
• coconut oil
• eg. 160, Palmitic acid

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Saturation

• H
• H C H
• H

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Saturated Fat In Selected Foods

• Food Saturated fat
  (g/100g)
• Coconut - fresh 24.2 (27)
• - desiccated 57.5 (65)
• Butter 54.0 (82)
• Potato chips, plain 14.1 (32)
• Hot chips, deep fried 8.1 (18)
• Avocado 4.9 (23)
• Beef steak (fillet, grilled, fat trimmed) 3.4 (8)
• Lamb chop 8.3 (16)
• Mars bar 10.1 (17)

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Fatty Acids

• Monounsaturated (MUFA)
• one double bond between carbon atoms
• olive oil
• peanut oil
• canola oil
• eg. 181n-9, Oleic acid

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Mono-unsaturation

• H O
• H C C C C OH
• H H H
• Only ONE double bond between carbon atoms

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Fatty Acids

• Polyunsaturated (PUFA)
• many double bonds between carbon atoms
• vegetable oils/margarines
• Sunflower, Canola
• fish
• Tuna, Salmon, Sardines
• eg. 182n-6, Linoleic acid

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Poly-unsaturation

• H H H H O
• H C C C C C C OH
• H
• more than ONE double bond between carbon atoms

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A Mixed Triglyceride

• Structure of a polyunsaturated fatty acid
• FIGURE 5.6 P160 Whitnry Rolfes

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FATTY ACIDS

• How do we measure fatty acids?
• In food?
• In blood?
• Fatty acids are measure based on their chain
  length, degree of unsaturation and molecular
  weight.

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FATTY ACIDS

• Fat extraction (organic solvents)
• Free form (TG free fatty acids)
• Convert to measurable form (FAME)
• Analysis (GC)
• Quantitate ( total fatty acids)

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Homogenise with solvent (CM)
Extract lipid
Add a methyl ester (FAME)
TAG glycerol and FFA
Extract FAME into solvent like ether
Report in total fatty acids based on peak areas
Peaks elute at different times based on chain
length and MW, SCFA first
Analysis by Gas Chromatography
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Fatty Acids

• Stability
• Degree of saturation affects stability
• Oxidation more double bonds
• Double bonds are unstable
• React with oxygen and oxidise
• Rancidity
• Antioxidants

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Fatty Acids

• HYDROGENATION
• adding of hydrogen atoms to a polyunsaturated or
  monounsaturated fat
• makes the fat more saturated
• makes the fat more solid
• protects against oxidation extends shelf life

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Hydrogenated Fatty Acid
H H
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Fatty Acids

• HYDROGENATION
• produces trans fatty acids
• relationship between cholesterol, heart disease
  trans fatty acids
• Authorities wanting to rid industry of trans fats
  (chemically produced not the rumen derived)
  voluntary stage

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Fatty Acids

• Trans spreads

• McDonalds, Hungry Jacks, KFC, Danisco etc
  attempting to look at new ways of substituting
  trans fats in their products
• A recent publication Trans Fat Reduction is
  currently selling for 30,000 euros published by
  LMC International Ltd.

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Recommended Reading

• Whitney Rolfes (2005)
• Understanding Nutrition 10th Ed.
• Chapter 5. The Lipids
• The Chemists view of Triglycerides Fatty Acids
• Wahlqvist (2002)
• Food Nutrition
• Chapter 13. Fats

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Trans Fatty Acids

• relationship between heart disease trans -
  fatty acids?
• Ascherio Willett, 1997. Health effects of trans
  Fatty acids, AJCN, 66 (suppl.), 1006S-1010S.
• trans either occur naturally in dairy (from
  rumen) but majority produced by hydrogenation.

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Cis and Trans Fatty Acids

• cis fatty acids are most natural occurring
  unsaturated fatty acid in diet.
• cis molecules fold back in a U shape.
• hydrogens are on same side of the double bond.
• trans fats has hydrogens on opposite sides of the
  double bond.

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Trans Fatty Acids
Food Examples

• Naturally occurring
• ie. trans-181
• Dairy products
• Milk
• butter

• Manufactured
• some margarines
• cakes biscuits
• potato crisps
• peanut butter
• fish chips
• fast food

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