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The Lipids Triglycerides Phospholipids Sterols Lipids • Triglycerides (TG) –Fats and oils • Phospholipids • Sterols Fatty Acids (FA) & TG • glycerol-a sugar alcohol, backbone of a FA! • REM: they have carbon (C), so they are organic! FA & TG glycerol + 3 FA TG + H2O Condensation of Glycerol & Fatty Acids to Form a Triglyceride Fatty Acids –Length (size matters) –Saturated vs. unsaturated • Acetic Acid (most simple) Saturated Fatty Acids • How many carbons? Stearic acid – 18-carbon Simplified structure Fatty Acids • Point of saturation (where?) • Degree of saturation (how much?) –Saturated fatty acid •Monounsaturated •Polyunsaturated An impossible chemical structure: Why? Oleic acid – 18-carbon, monounsaturated Linoleic acid – 18-carbon, polyunsaturated OMEGA NUMBER: Ω-3 vs. Ω-6 Fatty Acids TG: Why Does Saturation Matter? • Unsaturation effects: –Firmness –Stability •Oxidation –Antioxidants Triglycerides:What about “hydrogenated oils?” –Hydrogenation-hydrogen added to mono- or polyunsaturated fats to make them solid by reducing the number of double bonds (C=C). –Cis vs. trans-fatty acids Hydrogenation Cis- and Trans-Fatty Acids Compared So what? It’s a nice picture. Trans fats are bad!!! • In the body trans fats behave like saturated fats! Why? • They contribute to higher LDL cholesterol and lower levels of "good" HDL cholesterol = heart disease. Phospholipids Phospholipids (PL) • Phospholipids in foods • Roles of PL –Plasma membrane –Emulsifiers (help oil and water exist together) Membrane Structure PL Hydrophobic tail vs. hydrophilic head: more on this later. Sterols Sterols • Roles of sterols: Good –Bile acids –Sex hormones –Adrenal hormones –Vitamin D • Roles of sterols: Bad -Atherosclerosis-hardening of arteries. Fat Digestion Yummy...or not. Fat Digestion • Hydrolysis –Triglycerides monoglycerides, fatty acids, glycerol Fat Digestion Fat Digestion • Mouth –Melting –Lingual lipase Fat Digestion • Stomach –Churning and mixing –Gastric lipase Fat Digestion • Small intestine –CCK-hormone which signals bile release! •Bile emulsifies fats. Fat Digestion Fat Digestion Fat Digestion • Small intestine –Pancreatic lipases –Intestinal lipases Fat Digestion Overview Fat Digestion • Enterohepatic circulation • Note how fiber helps remove excess cholesterol!! Lipoproteins and health Factors that lower LDL and raise HDL – Weight control – Replace saturated fat with monounsaturated fat and polyunsaturated fat in the diet – Soluble fibers – Phytochemicals – Moderate alcohol consumption – Physical activity (biggest helper) • Genes influence lipoprotein activity. Roles of Triglycerides • Fat stores –Energy –Protection –Insulation Essential Fatty Acids Fat Metabolism • Storage as fat –Adipose tissue –LPL = lipoprotein lipase...fat storage. Lipid Metabolism • Using fat for energy – Hormone-sensitive lipase...triglyceride release. – Provides very little glucose...problem during fasting? Health Effects of Lipids • Blood lipid profile • Heart disease • Risks from saturated fats Health Effects of Lipids:US Diet Dietary Cholesterol Health Effects of Lipids • Benefits:monounsaturated and polyunsaturated fats • Cancer • Obesity Health Effects and Recommended Intakes of Lipids • Recommended Intakes of Fat – DRI: 20-35% of energy intake (400-700 kcalories of a 2,000-kcal diet). – FDA recommends 10% of energy intake from s • Linoleic acid AI 5-10% of energy intake Linolenic acid AI 0.6-1.2% of energy intake – aturated, 30% of energy intake total fat Health Effects and Recommended Intakes of Lipids – Daily Values • 65 g fat based on 30% of 2000-kcal diet • 20 g sat. fat based on 10% of 2000-kcal diet • 300 mg cholesterol – USDA Food Guide considers saturated fats discretionary kcalories. – Too little fat can be detrimental to health. Health Effects and Recommended Intakes of Lipids • Health Effects of Lipids – Blood lipid profile • Reveals concentrations of lipids in the blood • Desirable levels – Total cholesterol < 200 mg/dL – LDL cholesterol < 100 mg/dL – HDL cholesterol ≥ 60 mg/dL – Triglycerides < 150 mg/dL Cutting Fat Cuts kCalories and Saturated Fat Guidelines to Groceries • Milk and milk products • Vegetables, fruits, and grains • Invisible fat High-Fat Foods • Changing guidelines for fat intake High-Fat Foods • Cook with olive oil • Nibble on nuts • Feast on fish –But beware of mercury? High-Fat Foods • Mediterranean diet?
