NUT 1004 Lecture 7 Fats PDF

1 Fats and Other Lipids Kemar Bundy MSc, MPH, PhD (C) NUT 1004 University of Technology, Jamaica  Learning Outcomes Identify the major kinds of lipids, including triglycerides and cholesterol. List functions of lipids in the body and in foods....

1 Fats and Other Lipids Kemar Bundy MSc, MPH, PhD (C) NUT 1004 University of Technology, Jamaica  Learning Outcomes Identify the major kinds of lipids, including triglycerides and cholesterol. List functions of lipids in the body and in foods. Explain the differences in chemical structures of saturated, monounsaturated, polyunsaturated, and trans fatty acids. Identify major food sources of each kind of lipid, including the essential fatty acids, phospholipids, and cholesterol. Discuss the roles of essential fatty acids, phospholipids, and cholesterol in the body. Discuss the digestion, absorption, and transport of lipids in the body.  Lipids Overview Lipids include: Fatty acids Triglycerides Phospholipids Cholesterol generally insoluble Lipids are in water less dense than water ©McGraw-Hill Education  4 Types of Lipids Triglycerides Most common lipid in food & body ___ fatty acids + ___ glycerol Phospholipids Cell membranes Emulsifiers Sterols Cholesterol Hormones All Lipids Contain carbon, hydrogen, and oxygen Do not dissolve in water ©McGraw-Hill Education  Major lipid functions in the body ©McGraw-Hill Education 5  Lipids in Foods Major Functions of Lipids in Foods: Enhance the intestinal absorption of fat-soluble vitamins and phytochemicals Contribute to rich flavor, smooth texture, and appetizing aroma of foods ©McGraw-Hill Education  Fatty Acids 1 Fatty acids contain a hydrocarbon chain (carbon and hydrogen atoms) with a methyl group (CH3) at one end and an acid group (COOH) at the other. Fatty acids vary in their number of carbons: Short-chain fatty acids — 2 to 4 carbons Medium-chain fatty acids — 6 to 12 carbons Long-chain fatty acids — 14 to 24 carbons ©McGraw-Hill Education  Fatty Acids 2 Saturated fatty acid- Each carbon atom within the chain holds 2 hydrogen atoms. Unsaturated fatty acid - Fatty acid that is missing hydrogen atoms, and as a result, the molecule has 1 or more double bonds in the carbon chain. Monounsaturated fatty acid (MUFA) Polyunsaturated fatty acid (PUFA) ©McGraw-Hill Education Fatty Acids 3 Fatty Acids and Their Structures ©McGraw-Hill Education Saturation (Number of Double Bond Saturated fatty acid: All bonds between the carbons are single C-C bonds: Every carbon has formed the maximum bonds with hydrogen Solid at Room Temp Monounsaturated fatty acid: One double bond found in the chain: Missing 2 hydrogens in the chain Liquid at Room Temp Saturation (Number of Double Bond Polyunsaturated fatty acid: 2 or more double bonds in the chain: Hydrogens missing at these double bonds Liquid at Room Temp Trans fatty acids are created via hydrogenation: Add hydrogen to carbon chain of unsaturated fats Chain becomes more: Saturated Straight Fat becomes more solid  Essential Fatty Acids Essential fatty acids cannot be made in the body. Must be supplied by the diet The 2 essential fatty acids are: Alpha-linolenic acid (ALA), an omega-3 fatty acid. Linoleic acid (LA), an omega-6 fatty acid. The body uses the essential fatty acids to make: DHA EPA AA Infants require DHA and EPA for proper growth and nervous system development. Deficiency signs: scaly skin, hair loss, poor wound healing ©McGraw-Hill Education The essential fatty acids and the substanc derived from them (ALA) (LA) Omega-3 Fatty Acids ©McGraw-Hill Education  What are Trans Fats? Unsaturated fats with at least 1 trans double bond rather than the more common cis double bond. Why trans fats as unsaturated fats is solid at room temperature? ©McGraw-Hill Education  Trans Fats and Health Partially hydrogenated oils (PHOs) are made by a manufacturing process that adds hydrogen atoms to unsaturated fatty acids. Converts natural cis fatty acids to trans fatty acids PHOs less likely to undergo oxidation than polyunsaturated fatty acids PHOs are unhealthy fats. ▪ FDA determined PHOs posed a health risk, and the agency banned their use in foods. ▪ Ban is supposed to go into effect in 2021. Trans Fatty Acids and Hydrogenation ©McGraw-Hill Education  Triglycerides Composed of 3 fatty acids attached to a glycerol “backbone” Approximately 95% of lipids in the body and in foods is in the form of triglycerides. The triglycerides in fats and oils are mixtures of saturated and unsaturated fatty acids. Lipid Overview ©McGraw-Hill Education  Comparing fatty acid contents of common eaten fats and oils ©McGraw-Hill Education 17  Phospholipids A phospholipid is chemically similar to a triglyceride. 1 fatty acid is replaced by a compound that contains phosphorus and, often, nitrogen. Hydrophilic and hydrophobic parts Function as emulsifiers because of hydrophilic and hydrophobic parts Emulsifiers keep oily and watery substances mixed together. Figure 6.5 Figure 6.6 ©McGraw-Hill Education  Phospholipids Structure similar to TAGs except: 1 fatty acid is replaced with 1 phosphate compound Phosphate head is hydrophilic - Allows phospholipid to function in watery solution Fatty acid tail is hydrophobic - phosphate head will face water (polar) fatty acid tail will face lipid (non-polar) Function as emulsifiers because of hydrophilic and hydrophobic parts Emulsifiers keep oily and watery substances mixed together.  Phospholipids 2 Phospholipids in food Lecithin: The main phospholipid in foods--rich sources are egg yolks, liver, wheat germ, peanut butter, and soy. Eggs are often used in cooking for their emulsifying ability. Phospholipids in human cell membranes ©McGraw-Hill Education  Sterols 1 Sterols have carbons arranged in rings. Cholesterol is the most well-known sterol. ©McGraw-Hill Education  Sterols Cholesterol: Only made by animals, including human liver The body uses cholesterol to make various substances, including: Vitamin D Steroid hormones Bile Plant Sterols and Stanols: Plants make small amounts of sterols (plant sterols and stanols). Plant sterols and stanols are not well absorbed by the human intestinal tract, but they compete with cholesterol for absorption. Plant sterols and stanols may reduce cholesterol absorption, which would be beneficial. ©McGraw-Hill Education Lipid Digestion and Absorption 1 The duodenum is the primary site of lipid digestion. Fatty chyme in the small intestine stimulates release of cholecystokinin (CCK). CCK stimulates pancreas to release lipases. Bile salts aid lipid digestion. ©McGraw-Hill Education  Lipid Digestion Step 4 Step 1: Mouth + lingual lipase Step 2: Bolus + lingual lipase enters stomach. Lingual lipase activates in acid. Step 3: Fatty chyme enters the duodenum. CCK is secreted: Pancreas → pancreatic lipase Gallbladder → releases bile Step 5 Step 4: Bile emulsifies lipids Step 5: Pancreatic lipase → free fatty acids + monoglycerides ©McGraw-Hill Education Lipid Digestion and Absorption 2 Cholesterol does not undergo digestion; absorbed intact. Micelles help transfer lipids to absorptive cells Chylomicron is a type of lipoprotein ©McGraw-Hill Education  Lipid Absorption Step 1: Micelles are formed. Transport lipids to absorptive cells. Step 2: Triglycerides reformed Step 3: Triglycerides + cholesterol + protein + phospholipids → chylomicron Step 4: Chylomicrons enter lacteals and bloodstream ©McGraw-Hill Education  Lipid Transport Chylomicrons-(type of lipoprotein) form in absorptive cell and enter lacteal of villus Lipoproteins help transport lipids in lymphatic/immune system and in the bloodstream. ©McGraw-Hill Education Summary of Lipid Digestion, Absorption, and Elimination Digestion, Absorption, and Emulsification of Bile ©McGraw-Hill Education  Recycling Bile Salts How foods rich in fiber can lower blood cholesterol levels? ©McGraw-Hill Education  Using Triglycerides for Energy Adipose cells remove free fatty acids and glycerol from blood and reform into triglycerides (fat) for storage. When the body’s cells need energy: Adipose cells break down stored triglycerides into fatty acid and glycerol molecules before releasing them into bloodstream. Cells remove fatty acids from the bloodstream and metabolize them for energy. Liver removes the glycerol molecules and converts them to glucose—another energy source. ©McGraw-Hill Education  Lipid Consumption On average, fat contributed about 38% of Jamaican’s daily caloric intake in 2017-2018. Acceptable macronutrients distribution range (AMDR) for fat is 20-35% of total calories In 2017-2018, average saturated fat intake was about 12% of total calories. Recommendation for saturated fat intake is