Lipids Triglycerides –Fats and oils Phospholipids –Lecithin Sterols –Cholesterol.

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