1. Chapter 5 Lipids: Triglycerides, Phospholipids, and Cholesterol
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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
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Sources of Fat
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Hidden Fat
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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
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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
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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
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9. 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
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Fatty Acids in Food
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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
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12. Phosphoglycerides as Emulsifiers
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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
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14. Food Sources of Cholesterol
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15. Lipid Transport and Delivery
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16. Lipoprotein Composition
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17. 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)
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18. 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
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19. 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
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20. 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
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21. 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
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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
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23. 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
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24. Eicosanoid Synthesis and Function
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25. Lipids and Cardiovascular Disease
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26. Lipids and Cardiovascular Disease
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27. Risk Factors for Heart Disease
Age
Gender
High blood pressure
Obesity
Blood lipid levels
Tobacco use
Physical activity
Diet
Genetic background
Diabetes
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Blood Lipid Levels
Type of Lipid (mg/100 mL)
Low Risk/Optimal
Near Optimal
Borderline High
High Risk
Total Cholesterol
<200
≥240
LDL
<100
<70 in high risk individuals
≥160
HDL
≥ 60
<40
Triglycerides
<150
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29. Dietary Factors to Reduce Risk
Focus on whole foods
Polyunsaturated and monounsaturated fats
Plant foods
B vitamins
Antioxidants
Moderate alcohol consumption
Fiber
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30. Mediterranean Diet Pyramid
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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
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32. Recommendations for Fat Intake
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33. Translating Recommendations into Healthy Diets
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How To Use Food Labels
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Choosing Lean Meat
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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.
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More about Labels
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Reduced-Fat Foods
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