LIPIDS C H A P T E R 6 1
LEARNING OUTCOMES Explain the basic chemical structure of fatty acids and how they are named Describe the functions of triglycerides, fatty acids, phospholipids and sterols in the body Classify and evaluate the different fatty acids based on their health benefits or consequences Identify food sources of triglycerides, fatty acids, phospholipids and sterols 2
LEARNING OUTCOMES Describe the recommended intake of lipids Identify strategies for modifying total fat, saturated fat, and trans fatty acids intake Explain the digestion, absorption, and transport of lipids in the body Discuss health concerns related to dietary fat intake Describe dietary measures to reduce the risk of developing cardiovascular disease 3
TRIGLYCERIDES Most common lipid in food and the body and in the foods we eat. 4
FUNCTIONS OF TRIGLYCERIDES Provide Compact Energy Source Insulate and Protect the Body Aid Fat Soluble Vitamin Absorption and Transport Essential Fatty Acid Functions 5
FOOD SOURCES OF TRIGLYCERIDES Fruits and Vegetables Low-fat except avocados and coconuts Dairy Low-fat products are available Grains Low-fat except when fat is added e.g. pastries, pancakes Fats Usually a combination of many fats together and described by the predominate fat. 6
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STRUCTURE Esterification Joining 3 fatty acids to a glycerol unit De-esterification Release of fatty acids-results in free fatty acids Diglyceride Loss of one fatty acid Monoglyceride Loss of two fatty acids Re-esterification Reattaching a fatty acid to a glycerol that has lost a fatty acid 8
CARBON CHAIN LENGTH Long chain fatty acids 12 or more carbons (e.g. Beef, lamb, plant oils) Medium chain fatty acids 6-10 carbons (e.g. coconut and palm oils) Short chain fatty acids Fewer than 6 carbons (e.g. dairy products) 9
SATURATION Saturated fatty acids No double bonds Increase blood levels of cholesterol Example: red meat, high-fat dairy, coconut and palm oil 10
Regal Theatres Small is 11 cups Popped in coconut oil 670 kcal, 36 grams saturated fat, 550 mg sodium Cinemark Theatres Small is 6 cups Popped in nonhydrogenated canola oil 420 kcal, 2 grams saturated fat, 620 mg sodium Want more butter? Each tbs. is 130kcal and has 2g saturated fat. 11
SATURATION Monounsaturated fatty acids One double bond Decrease blood levels of cholesterol Example: olive oil, canola oil, peanut oil 12
SATURATION Polyunsaturated fatty acids Many double bonds Decrease blood levels of cholesterol Example: Vegetable oils and fish oil 13
SHAPE CIS VS. TRANS 14
SHAPE CIS VS. TRANS Cis fatty acids Bent carbon chain Trans fatty acids Straight carbon chain Hydrogenation: Adding hydrogen to make an unsaturated fat more saturated-yields: trans fatty acids Solidifies the lipid, increases shelf life of product (tub margarine, baked goods) Increases cholesterol even more than saturated fat 15
SHOULD TRANS FATS BE LEGAL? Illegal Denmark, 2003 Banned in almost all foods Heart disease has fallen by 20% between 2001 (before the ban) and 2006 (two years after the ban) NY City, 2006 Restaurants/food service establishments Switzerland, 2008 Banned in almost all foods Legal or limited Some restrict the amount of trans fat in foods (Canada, Boston) Others mandate labeling Others have no laws concerning trans fat 16
NAMING FATTY ACIDS Omega System 1. Starting on the omega (methyl) end work your way across until you get to the first double bond. This will indicate whether a fatty acid is an omega three or six 2. Then count how many carbons are in the chain 3. Then count how many double bonds there are (including the first one) Omega-3 fatty acid is 18:3 ω3 Omega-6 is 18:2 ω6 There is another nomenclature system called delta (we will not study that method) 17
ESSENTIAL FATTY ACIDS 18
ESSENTIAL FATTY ACID NEEDS Body unable to synthesize so Adequate Intake has been established Approximately 2-4 tablespoons daily Omega-6 intake usually high, Omega-3 intake usually too low-this in balance has health consequences Deficiency Unlikely Could result in slowed growth, flaky and dry skin, delayed wound healing Toxicity No upper level set 19
TWO ESSENTIAL FATTY ACIDS Linoleic (omega-6) Beef, poultry, safflower oil, sunflower oil, corn oil, mayonnaise Regulates blood pressure, can increase blood clotting and inflammation Alpha-linolenic (omega-3) Cold water fish (salmon, tuna, sardines), walnuts, flax, canola oil Reduces inflammation, thins blood, and reduces plasma triglycerides 20
ESSENTIAL FATTY ACID SOURCES AHA advises 1000mg of DHA + EPA which is 2 servings of fish/week 500 mg as ALA 32 mg DHA 3000 mg of DHA+EPA in 6oz 3 soft gels=900mg of DHA + EPA 21
FOOD SOURCES OF FATTY ACIDS 22
FATTY ACID INTAKE RECOMMENDATIONS (IOM) 23
AMERICAN HEART ASSOCIATION RECOMMENDATIONS Limit saturated fats to 7% of total calories Minimize trans fat intake Limit cholesterol intake to less than 200 mg Eat at least two servings of fatty fish/week (tuna, salmon, mackerel, lake trout, herring, and sardines) 24
FAT INTAKE North American fat intake has doubled in the last century Too high Saturated fat, trans fat, Omega 6 Too low Omega 3 25
MEDITERRANEAN DIET Up to 40% fats consumed is from monounsaturated fatty acids Diet is high in Olive oil, fruits, vegetables, whole grains, beans, nuts, and seeds Small to moderate amounts of cheese, yogurt and fish Limits eggs and red meat Includes exercise 26
MEDITERRANEAN DIET Breakfast: Greek yogurt topped with berries and walnuts; Coffee or tea Lunch: Lentil soup with swish chard topped with taziki sauce; Hummus and pita Snack: Whole grain crackers and cheese Dinner: Roasted cod paired with a wheat berry salad consisting of olive oil vinaigrette, feta, parsley, and tomatoes and a glass of red wine Dessert: Fresh fruit drizzled with honey 27
FAT REPLACEMENTS Water, Protein, Air (soft serve ice cream) Carbohydrates Fiber (Ztrim) Corn syrups, syrup solids, and high-fructose corn syrups are used as fat replacers in many fat-free and reduced-fat cookies Engineered fats Olestra (Lays's Light, Ruffles Light, Doritos Light, and Tostitos Light) 28
OLESTRA Olestra is synthesized from sucrose, it can bond with six, seven, or eight fatty acids, making it too large and irregular to move through the intestinal wall and be absorbed. Because olestra is undigested, it inhibits absorption of fat soluble vitamins (fun side effects of this!) FDA requires manufacturers to add vitamins A, D, E and K to products made with olestra to counter that effect. 29
PHOSPHOLIPIDS Hydrophobic and Hydrophillic Ends Functions Component of cell membranes Emulsifier Sources Synthesized by the body Food: lecithin in egg yolks, wheat germ and peanuts 30
PHOSPHOLIPIDS EMULSIFY AND BILAYER 31
STEROLS Ring structure, most well known is cholesterol Functions Steroid hormones, bile, cell membranes, chylomicrons Sources Synthesized by the body(we make all the cholesterol we need) Food: animal origin (meat, fish, eggs, dairy)= Cholesterol Plant sterols block cholesterol absorption sites in the human intestine, thus helping to reduce cholesterol in humans, but there is some concern that they may block absorption of other important nutrients as well Food additive: Benecol and Take Control 32
STEROLS 33
FAT DIGESTION Stomach Gastric lipase Triglycerides are broken down into monoglycerides and free fatty acids Liver-makes bile Gall bladder CCK triggers bile release from gall bladder Pancreas Pancreatic lipase, phospholipase, cholesterol lipase into common bile duct, which empties to SI 34
FAT DIGESTION Small Intestine Bile emulsifies fat to form micelles (acted upon by pancreatic lipase) Phospholipids are broken down into free fatty acids, glycerol and phosphoric acid by enzymes from the SI and pancreas Cholesterol esters are broken down into cholesterol and free fatty acids by enzymes from SI and pancreas Most digestion in duodenum and ileum 35
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FAT ABSORPTION The lipid portion of micelles is absorbed by the brush border of the absorptive cells in the duodenum and jejunum Short and medium chain fatty acids are absorbed via the portal vein Long chain fatty acids are reesterified and enter the lymphatic system Bile is recycled via enterohepatic circulation 37
TRANSPORTING FAT Transporting fat through water-based blood and lymphatic system is a challenge Short and medium chain fatty acids travel via cardiovascular system to liver Long chain fa enter lymph system Fat is transported lipoproteins Lipid core Shell composed of protein, phospholipid and cholesterol that allow transportation 38
TYPES OF LIPOPROTEINS Chylomicrons Transport of dietary triglycerides from small intestine to cells VLDL Carries mainly triglycerides from liver to cells LDL Made mostly of cholesterol, carries cholesterol to cells HDL Made mostly of protein, pick up and recycle or dispose of cholesterol 39
LIPOPROTEINS 40
PATHWAYS FOR CHOLESTEROL UPTAKE High Density Lipoproteins (HDL or good cholesterol) How does it get its name? Picks up cholesterol throughout the body-eventually this leads to excretion of LDL Blocks oxidation of LDL Scavenger Pathway scavenger WBC embed in blood vessels and engulf and digest LDL Can build up over time-plague develops (what is this called?) 41
PLAQUE What can you do to prevent plaque buildup? What do cholesterol lowering medications do? How can you remove an existing plaque to prevent heart attack and stroke? 42
CARDIOVASCULAR DISEASE (CVD) Development of CVD Atherosclerotic plaque forms Result: Heart attack and stroke Risk factors Cannot change age, gender, race and genetics Can change blood triglyceride and cholesterol levels, hypertension, smoking, physical inactivity, obesity, diabetes and other diseases 43
KNOW YOUR NUMBERS 44
PREVENTING CVD (LIMIT) Total fat 20-35% total calories Saturated fat < 7 % total calories Trans fat low Polyunsaturated < 10% total calories Monounsaturated < 20% total calories Cholesterol < 200 mg daily 45
PREVENTING CVD (EMPHASIZE) Include 2 grams plant stanols/sterols Soluble fiber 20-30 g Eat fatty fish 2x/week Keep body weight at a healthy level Increase physical activity Do things to increase your HDL (exercise) 46
HEALTH CONCERNS Dangers of low fat diet? High polyunsaturated fat intake Excessive omega 3 fat intake Imbalances in omega 3 and omega 6 fats Diets high in trans fats Diets high in total fat 47
MAKING RECOMMENDATIONS Breakfast: Everything Bagel w/cream cheese, coffee w/cream and sugar Lunch: 12 inch Italian sub, Diet Coke, Baked Lays Snack: Quaker Granola bar Dinner: Easy Mac w/hotdogs Snack: Ice cream Changes if you were normal weight but have high cholesterol Changes if you were interested in Mediterranea n diet 48