Transcript Chapter04

Lipids
• Triglycerides
–Fats and oils
• Phospholipids
– Lecithin
• Sterols
– Cholesterol
Objectives
• After reading Chapter 4, class
discussion and case study work,
you will be able to
– Describe the role of lipids in the body
– Identify food sources of fats
– Discuss lipid digestion, absorption
and transport
– Calculate calories from fat
Objectives
• Identify types (classification) of
lipids
• Discuss the health related effects
of lipids
– Blood lipid profile
– Omega fatty acids
– Trans fatty acids
– Hydrogenation
Triglycerides
4
Triglycerides
• glycerol
Triglycerides
• glycerol + 3 fatty acids  triglyceride
Fatty Acids
• Length of fatty acid
– 18-24 carbons in length
• Degree of Saturation
–Saturated fatty-acid
–Monounsaturated fatty-acid
–Polyunsaturated fatty-acid
Fatty Acids
• Point of unsaturation
• Location of double bonds
–Omega number
•Omega-3 fatty acid
•Omega-6 fatty acid
Triglycerides
• Degree of saturation
determines:
–Firmness
–Stability
•Oxidation
–Antioxidants
Rancidity
• Definition: Deterioration of fat;
resulting in undesirable flavor/odor
– Flavor Reversion-soy oil; Cu, Fe
• Hydrolytic: Separation of glycerol
from fatty acids
– Short chain fatty acids
– Butyric fatty acid; butter
• Oxidative: Loss of hydrogen in
presence of air/heat
– Oxidation of double bonds
– Polyunsaturated fatty acids
Trans Fats
• Degree of unsaturation revisited
–Hydrogenation
–Cis vs. trans-fatty acids
•Trans fat occurs naturally in meat
and dairy foods
– Conjugated linoleic in milk
» Possibly positive for heart health
p. 108 NRAEF
Phospholipids
Phospholipids
• Phospholipids in
foods-Lecithin
• Roles of
phospholipids
–Plasma
membrane
–Emulsifiers
Phospholipids
Sterols
Found in plants
and animals
Cholesterol is
most abundant
Found in animals
only
Found in every cell
in man’s body
Body makes
~700mg/day
Dietary intake 200400mg/day
Dietary Cholesterol
Sterols
• Roles of sterols
–Manufacture bile acids
–Make hormones
•Estrogen and testosterone
–Make adrenal hormones
–Make Vitamin D
–Maintain cell membranes
Fat Digestion
• Hydrolysis
–Triglycerides  monoglycerides,
fatty acids, glycerol
Fat Digestion
• Mouth
– Melting
– Lingual Lipase
• Stomach
– Churning and mixing
– Gastric Lipase
Fat Digestion
• Small intestine
–Fat triggers the release of hormone
• Cholecystokinin (CCK)
–Gallbladder releases bile
–Bile emulsifies fat so it can be more
fully digested
• Pancreatic lipase
• Intestinal lipase
Fat Digestion
Fat Digestion
• Enterohepatic
circulation
• How bile travels
through the
body
Fat
Digestion
Overview
p.152
5-17
Lipid Transport
• Lipoproteins
–Chylomicrons
–VLDL = very-low-density
lipoproteins
–LDL = low-density lipoproteins
–HDL = high-density lipoproteins
Lipid Transport
Lipid Transport
• Lipoproteins and health
–LDL: carries cholesterol from
liver to the cells of the body
•High=Less healthy
–HDL: carries cholesterol from the
cells back to the liver
•High=More healthy
Roles of Triglycerides
• Fat stores
– Energy
– Protection
– Insulation
• Provide essential fatty acids
Essential Fatty Acids
• Linoleic acid and the omega-6 family
– Arachidonic acid
• Linolenic acid and the omega-3 family
– Alpha omega 3 fatty acids
– Marine omega 3 fatty acid
•EPA =eicosapentaenoic acid
•DHA = docosahexaenoic acid
Essential Fatty Acids
Health Effects of Lipids
• Blood lipid profile
– Cholesterol=<200mg/dL
– LDL=<100
– HDL=>60
– TG=<150
• Risks from saturated fats, trans
fats, cholesterol
• Benefits from polyunsaturated fats
monosaturated, omega-3
Health Effects of Lipids
• Risks from trans fats
– Alter blood cholesterol like saturated fats
– Raise LDL cholesterol
– Lower HDL cholesterol at high intakes
– Increase inflammation & insulin resistance
– AI = 5 gm/day
• Risks from cholesterol
– Not as implicated as saturated or trans fats
– Beware cholesterol sensitivity
• Limit intake <300 mg/day
Health Effects of Lipids
• Benefits from monounsaturated
fats and polyunsaturated fats
–Olive oil (monounsaturated)
•Lowers LDL and total cholesterol
•Lowers blood clotting factors
•Lowers blood pressure
•Provides phytochemicals which act
as antioxidants
Health Effects of Lipids
• Benefits from omega-3 fats
– Prevent arrhythmias
– Lower blood pressure
– Improve blood vessel function
– May ease inflammation
– Prevent repeat heart attack
•1 gm supplement daily for 3 years
• Balance omega-6 and omega-3
intakes
Recommended
Intakes of Fat
• DRI: 20-35% of energy intake
• Cholesterol: 200-300 mg/day
• Linoleic acid AI
–5% - 10% of energy intake
• Linolenic acid AI
–0.6 - 1.2% of energy intake
Guidelines to Groceries
• Limit whole milk and milk products
• Use vegetables, fruits, and grains
• Avoid invisible fat
• Avoid tropical
oils
• Use low fat
meats and
Alternatives
Fat Distribution in Diet
p. 162 Fig 5-23
Beware the Label
• “0 Trans Fat” – can still contain up
to 0.5 grams
• Look for “partially hydrogenated
vegetable oil” or “vegetable
shortening”
• IOM recommends trans fat intake
be “as low as possible”
Fat Substitutes
• “New” vegetable oils from “new” seed
– Soybean & other seeds with very low
levels of linolenic acid
• More stable but less omega-3 fatty acid
• Fat substitues
– Z-Trim made from corn, soy, oat fiber
– Oatrim made from whole oats
• Fat replacers
–Artificial fats
•Olestra
High-Fat Foods
• Changing guidelines for fat intake
High-Fat Foods
• Cook with olive oil or canola oil
• Monounsaturated fatty acids
• Nibble on nuts
• Omega-3 polyunsaturated fatty acids
• Feast on fish
• Marine omega-3 PUFA
• But beware of mercury
• Limit fatty meats, whole milk
products, and tropical oils
High-Fat Foods
• Limit hydrogenated fat foods
– Fried foods (fried in solid fats)
– Fast foods (prepared in partially
hydrogenated oils/fats
– Commercial baked goods
– Snack foods
Health Benefits of
Lipids
Objectives
• After reading Chapter 4, class
discussion and learning activities,
you will be able to
– Describe the role of lipids in the body
– Identify food sources of fats
– Discuss lipid digestion, absorption
and transport
– Calculate calories from fat
Objectives
• Identify types (classification) of
lipids
• Discuss the health related effects
of lipids
– Blood lipid profile
– Omega fatty acids
– Trans fatty acids
– Hydrogenation