Chapter 5 Lipids: Triglycerides, Phospholipids, and Cholesterol Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Lipids Lipid is the chemical term for fat Lipids contribute texture, flavor and aroma to foods The typical American diet contains about 34% of its energy from fat Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 2

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Sources of Fat Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Hidden Fat Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Triglycerides Major form of lipid in food and in the body Consist of three fatty acids attached to a glycerol molecule If only one fatty acid is attached to the glycerol, it is called a monoglyceride If two fatty acids are attached to the glycerol, it is called a diglyceride Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 5

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Fatty Acids The carbon chains of fatty acids vary in length from a few to 20 or more carbons Short-chain fatty acids have fewer than 6 carbons and remain liquid at colder temperatures Milk Medium-chain fatty acids range from 6 to12 carbons and solidify when chilled but are liquid at room temperature Coconut oil Long-chain fatty acids, containing between 14 to 22 carbons, are usually solid at room temperature Beef fat Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 6

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Saturated Fatty Acids Contain carbons in a chain that are bound to two hydrogens Most animal fats and tropical oils contain saturated fatty acids When fats are exposed to oxygen, the damage is called rancidity Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Unsaturated Fatty Acids Contain some carbons that are not saturated with hydrogen The essential fatty acids omega-3 and omega-6 are unsaturated fatty acids Monounsaturated and polyunsaturated fatty acids are unsaturated fatty acids Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Fatty Acids in Food Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 10

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Phospholipids Phospholipids are lipids attached to a phosphate group Phosphoglycerides, such as lecithin, are the major class of phospholipids Act as emulsifiers Phosphoglycerides form a lipid bilayer in cell membranes, helping to regulate what can pass into and out of a cell Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 11

Phosphoglycerides as Emulsifiers Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 12

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Sterols Found in plants and animals Do not dissolve well in water Cholesterol is a type of sterol found only in animals More than 90% of cholesterol in the body is found in cell membranes Diets high in cholesterol (from animals) can increase the risk of heart disease Plant sterols can help reduce cholesterol in the body Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 13

Food Sources of Cholesterol Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Lipid Transport and Delivery Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Lipoprotein Composition Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Low-Density Lipoproteins The liver is the major lipid-producing organ in the body Triglycerides produced in the liver are incorporated into entities called very-low-density lipoproteins (VLDLs) Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 17

Low-Density Lipoproteins Approximately ⅔ of IDLs return to the liver; the remainder are transformed in the blood into low-density lipoproteins (LDLs) If the amount of LDL cholesterol in the blood exceeds the amount that can be used by the cells, the result is a high level of LDLs High levels of LDLs in the blood have been associated with an increased risk for heart disease Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 18

High-Density Lipoproteins Most cells cannot break down cholesterol Cholesterol is returned to the liver to be eliminated from the body High levels of HDL in the blood help to prevent cholesterol from depositing in the artery walls Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 19

Lipid Functions in the Body Most lipids in the body are triglycerides stored in adipose tissue Deposits of adipose tissue help to: Define body shape Provide stored energy Insulate the body from temperature changes Protect internal organs against physical shock Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 20

Lipid Functions in the Body Lipids in the body are important for lubricating body surfaces, such as the mucous membranes of the eyes Cholesterol is used to make several hormones, including sex hormones and cortisol Polyunsaturated fatty acids help to regulate blood pressure and blood clotting Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 21

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Essential Fatty Acids Essential fatty acids are important for growth, skin integrity, fertility, and the structure and function of cell membranes Eicosanoids are made from omega-3 and omega-6 fatty acids Help regulate blood clotting, blood pressure and immune function Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 22

Essential Fatty Acid Deficiency If adequate amounts of essential fatty acids are not consumed, a deficiency can result Symptoms include dry and scaly skin, liver abnormalities, poor wound healing, growth failure in infants, and impaired hearing and vision Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 23

Eicosanoid Synthesis and Function Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Lipids and Cardiovascular Disease Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 25

Lipids and Cardiovascular Disease Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 26

Risk Factors for Heart Disease Age Gender High blood pressure Obesity Blood lipid levels Tobacco use Physical activity Diet Genetic background Diabetes Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 27

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Blood Lipid Levels Type of Lipid (mg/100 mL) Low Risk/Optimal Near Optimal Borderline High High Risk Total Cholesterol <200 200-239 ≥240 LDL <100 <70 in high risk individuals 100-129 130-159 ≥160 HDL ≥ 60 <40 Triglycerides <150 Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Dietary Factors to Reduce Risk Focus on whole foods Polyunsaturated and monounsaturated fats Plant foods B vitamins Antioxidants Moderate alcohol consumption Fiber Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 29

Mediterranean Diet Pyramid Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Dietary Fat and Cancer Populations who consume diets high in fat (animal fat) tend to have a higher incidence of cancer Consuming a diet high in fruits and vegetables may lower cancer risk Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Recommendations for Fat Intake Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Translating Recommendations into Healthy Diets Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. How To Use Food Labels Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Choosing Lean Meat Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. What about Eggs? One large egg contains 6 g of protein, and is good source of zinc, B vitamins, vitamin A, iron, and phytochemicals. Unlike many other sources of cholesterol, eggs are low in cholesterol-raising saturated fat. Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. More about Labels Copyright © 2016 John Wiley & Sons, Inc. All rights reserved.

Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. Reduced-Fat Foods Copyright © 2016 John Wiley & Sons, Inc. All rights reserved. 38