Lipids

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

4

Triglycerides

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

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

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