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Lipids

Lipids. Types of Lipids (fat). Triglycerides Fatty acids Phospholipids Sterols. Triglycerides. Most common lipid in food and body. Fatty Acids Are Carbon Chains of Varied Length. Long chain fatty acids 12 or more carbons Medium chain fatty acids 6-10 carbons Short chain fatty acids

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Lipids

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  1. Lipids

  2. Types of Lipids (fat) • Triglycerides • Fatty acids • Phospholipids • Sterols

  3. Triglycerides Most common lipid in food and body

  4. Fatty Acids Are Carbon Chains of Varied Length • Long chain fatty acids • 12 or more carbons • Medium chain fatty acids • 6-10 carbons • Short chain fatty acids • Less than 6 carbons

  5. Fatty Acids Vary in Saturation • Saturated fatty acids (SFA) • No double bonds • Monounsaturated fatty acids (MUFA) • One double bond • Polyunsaturated fatty acids (PUFA) • Many double bonds

  6. Saturation

  7. The Carbon Chain Shape Varies with Saturation • Unsaturated cis fatty acids • Bent (kinked) carbon chain • Trans and saturated fatty acids • Straight carbon chain • Hydrogenation • Adding hydrogen to make an unsaturated fat more saturated: results in trans fatty acids

  8. Food Sources of Triglycerides • Animal fats and vegetable oils • described by the predominate fatty acid • Dairy • Low-fat products are available • Grains • Naturally low in fat, except when fat is added (e.g. pastries, pancakes) • Fruits and Vegetables • Low in fat except avocados and coconuts

  9. Functions of Triglycerides • Provide Energy • Provide Compact Energy Storage • Insulate and Protect the Body • Aid Fat-Soluble Vitamin Absorption and Transport • Essential Fatty Acid Functions • Eicosanoids

  10. Phospholipids • Hydrophobic and Hydrophillic Ends • Functions • Components of cell membranes • Emulsifiers (e.g., bile) • Sources • Synthesized by the body • Food: egg yolks, wheat germ and peanuts

  11. Sterols • Carbons arranged in rings • Most well-known sterol is cholesterol • Functions • Steroid hormones, bile, cell membranes, lipoprotein shell (e.g., chylomicrons) • Sources • Synthesized by the body • Foods of animal origin (cholesterol) and plants (plant sterols such as sitostanol)

  12. Recommended Fat Intakes • No RDA • AMDR: 20-35% • Dietary Guidelines 2010: • Limit saturated and trans fat • AHA recommendations for those at risk for heart disease: • Limit saturated fats to 7% of total calories • Limit cholesterol intake to less than 200 mg

  13. Fat Intake • North American fat intake has doubled in the last century • Omega 6 intakes are plentiful • Omega 3 intakes are usually low • Food sources:cold-water fish, walnuts, flaxseeds, soybeans.

  14. Fat Digestion • Mouth • Lingual lipase • Stomach • Gastric lipase • Small Intestine • CCK triggers bile • Bile emulsifies fat  micelles are formed  acted upon by pancreatic lipase and colipase

  15. Fat Digestion in the Small Intestine • Triglycerides are broken down into monoglycerides and free fatty acids • Phospholipids are broken down into free fatty acids, glycerol and phosphoric acid • Cholesterol esters are broken down into cholesterol and free fatty acids

  16. Fat Absorption • Short- and medium-chain fatty acids are absorbed via the portal vein • Long chain fatty acids are re-esterified and enter the lymphatic system • Bile is recycled via enterohepatic circulation

  17. Cardiovascular Disease (CVD) • Major killer of North Americans • Development of CVD • Atherosclerotic plaque • Heart attack and stroke • Risk factors for CVD • age, gender, race and genetics (cannot change) • blood cholesterol and triglyceride levels, hypertension, smoking, physical inactivity, obesity, diabetes and other diseases (can change or prevent)

  18. 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 Include 2 grams plant stanols/sterols daily Soluble fiber intake of 20-30g Moderate sugar intake Keep body weight at a healthy level Increase physical activity Preventing CVD

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