Lipids Triglycerides Fats and oils Phospholipids Lecithin Sterols

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 üFound in plants and animals üCholesterol is most abundant üFound in animals only üFound in every cell in man’s body üBody makes ~700 mg/day üDietary intake 200400 mg/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=<200 mg/d. L – 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