Lipids
-
Upload
coby-riley -
Category
Documents
-
view
30 -
download
0
description
Transcript of Lipids
Lipids• Triglycerides
– Fats and oils
• Phospholipids– Lecithin
• Sterols– Cholesterol
Objectives
• After reading Chapter 4, class discussion and learning activities, you will be able to– Identify types (classification) of lipids – Describe the role of lipids in the body– Discuss lipid digestion, absorption
and transport– Calculate calories from fat
Objectives
• Identify food sources of fats• Discuss the health related effects
of lipids– Blood lipid profile– Omega fatty acids– Trans fatty acids– Hydrogenation
4
Triglycerides
p. 128
Fig 4-1
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
p. 129
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
p. 135-137 Fig 4-9
Phospholipids
Phospholipids• Phospholipids in
foods-Lecithin
• Roles of phospholipids– Plasma
membrane– Emulsifiers
Phospholipids
SterolsFound 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 200-400mg/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 DigestionOverview
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• Insure efficient use of protein and
carbohydrate
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
Sources 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
How Dietary FatAffects Blood Lipids
Type of Fatty Acid• Saturated
• Polyunsaturated
• Monounsaturated
• Omega-3
• Trans
Effects on Blood Lipids
- Total Cholesterol LDL Cholesterol - Total, LDL, HDL
Cholesterol - Total, LDL HDL Cholesterol- Triglycerides, Total
Cholesterol - Total, LDL HDL Cholesterol
Health Benefits of Lipids
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• Avoid ADDED
and Invisible Fat
• Avoid Tropical oils
– Coconut oil– Palm oil
Fat Distribution in Diet
Guidelines to Groceries
• Use whole, unprocessed vegetables, fruits, and grains without added fats
Guidelines to Groceries
• Use fat free milk and milk products
Guidelines to Groceries
• Use meat sparingly
• Use lean meats• Use meat
alternatives
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
Changing Guidelines for Fat Intake
Changing Guidelines• 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
Changing Guidelines• Limit hydrogenated fat foods
– Fried foods (fried in solid fats)– Fast foods (prepared in partially
hydrogenated oils/fats– Commercial baked goods– Snack foods
Replacing Saturated Fat with Unsaturated Fat
Objectives
• After reading Chapter 4, class discussion and learning activities, you will be able to– Identify types (classification) of lipids – Describe the role of lipids in the body– Discuss lipid digestion, absorption
and transport– Calculate calories from fat
Objectives
• Identify food sources of fats• Discuss the health related effects
of lipids– Blood lipid profile– Omega fatty acids– Trans fatty acids– Hydrogenation