Lipids/FatsLipids/Fats

By Jennifer Turley and Joan ThompsonBy Jennifer Turley and Joan Thompson

© 2013 Cengage© 2013 Cengage

OverviewCategories, Chemistry, Functions & Foods of:

• Fat/Lipid• Triglycerides• Fatty Acids• Phospholipids• Sterols

Composition: Fats contain Carbon, Hydrogen, Oxygen

• Lipids are organic compounds • Lipids are soluble in fatCategories of Lipids:

1. Triglycerides2. Phospholipids3. Sterols

Lipids - Fats

Triglycerides “Fats”

• Energy Yield: Fats provide 9 Calories/gram. – Fats are the only type of lipid that

the body can convert to ATP or produce energy from.

– Fats are the most Calorically Dense energy producing nutrient.

Triglycerides “Fats”• Caloric density: Refers to the

Calories yielded per weight of the substance. – Triglycerides (dietary fats) provide 9

Calories per gram while protein and carbohydrate provide 4 Calories per gram and alcohol provides 7 Calories per gram.

Triglyceride ModelGlycerol+

3 Fatty Acids = A Triglyceride

3 units of water are released

Actual Triglyceride

Fatty Acids: CategoriesDietary fats are defined by the composition of the

fatty acids in the triglyceride.1. Saturated fat food sources are comprised of

mostly saturated fatty acids (SFAs). 2. Monounsaturated fat food sources are

comprised mostly of monounsaturated fatty acids (MUFAs).

3. Polyunsaturated fat food sources are comprised mostly of polyunsaturated fatty acids (PUFAs).

Fatty Acid: Examples

Stearic Acid

Oleic Acid

Alpha-linolenic acid

Saturated Fatty Acids

• Have 0 double bonds between the carbons.• Are found in animal products, hydrogenated

vegetable fats, & tropical oils (palm & coconut oil).

• Are solid at room temperature & unhealthy.

Chemistry ofStearic Acid,

a SFA

Monounsaturated fatty acids

Chemistry ofOleic Acid,a MUFA

• Have 1 double bond in the carbon chain

• Are healthy • High levels are in olive oil, canola oil, almonds, & avocado• Become semisolid when refrigerated • Are liquid at room temperature

Polyunsaturated fatty acidsChemistry of

Alpha-Linolenic Acid,a PUFA

• Have >1 double bond in the carbon chain. • Some are essential for the body. • Are found in plant oils like corn,

cottonseed, safflower, and sunflower oil.• Are liquid at room temperature.• Too much can promote cancer.

Fat Food Sources• Oils, butter, cream, lard, margarine,

dressings, cream cheese, olives, nuts & seeds are all examples of foods high in dietary fat.

• Try to chose healthy fats from plant sources, like those shown on the right.

Fatty Acid Composition of Common Fats

Essential Fatty Acids

• The body cannot make the essential fatty acids (EFAs).

• Linoleic Acid & Alpha-Linolenic Acid.• These EFAs are found in plant oils &

plant foods. • Deficiency characteristics develop

when they are lacking in the diet.

Essential Fatty Acids

• The AMDR level for adults that will optimize health are:– 5-10% of Calories from Linoleic Acid – 0.6-1.2% of Calories from Alpha-linolenic Acid

• Linoleic Acid is an omega 6 fatty acid.• Alpha-linolenic Acid is an omega 3 fatty acid.

Alpha-Linolenic Acid

COOHCH3

12

3

Linoleic Acid3 COOH

CH31

2 45

6

Essential Fatty Acids

Trans Fatty AcidsCreated in food processing when PUFAs or MUFAs are partially hydrogenated.

Functions of Fat• Increases satiety value of a meal.• Improves texture, flavor & aroma of food.• Required for fat soluble vitamin absorption.• Provides the body’s major energy stores.• Cushions vital organs.• Is an essential structural component of cell

membranes.• Provides insulation.

Fat: Dietary Recommendations• 20-35% of total dietary Calories should

come from fat. This is the AMDR.<7% should come from SFA. Limit trans fatty

acids.

• All excess Calories consumed whether from carbohydrates, proteins, or fats are converted to fat & stored in fat cells.

• Fat is the storage form of energy in mammals.

Phospholipids (lecithin)

• Non-Energy Yield: 0 Calories per gram. Phospholipids are non-caloric lipid substances.

• Sources: Lecithin is found in egg yolk and soy products and is the most common phospholipid consumed in the diet.

Phospholipids (lecithin)

Functions: 1. Phospholipids like lecithin

are emulsifiers that allow water soluble & fat soluble substances to mix (like oil & vinegar).

2. Lecithin provides choline which is a component of the neurochemical acetylcholine.

3. Phospholipids are used to make cell membranes.

Lecithin: A Phospholipid

Actual Structure of

Lecithin

Cell Membrane

Includes phospholipids, cholesterol, proteins.

Sterols Cholesterol is the most popular dietary sterol

Non-Energy Yield: Noncaloric, 0 Calories/gram

Sources of Cholesterol: 1. Exogenous: From outside the body.

Cholesterol is made by animals. It is only found in animal foods & byproducts.

2. Endogenous: Made inside the human body.

Exogenous Sources

• Egg yolk provides ~275 mg each.• Organ meats & crustaceans such as

crab, shrimp & lobster provide ~190 mg per 3 ounces.

• Much smaller amounts are in the fat portions of animal meats & products like milk.

Endogenous Sources

• Cholesterol is a very important molecule in the body.

• Cholesterol is made inside the human body, primarily in the liver, from SFA.

• Usually about 1 gram (1,000 milligrams) of cholesterol per day is produced in the body.

• It is a very waxy substance.

Cholesterol is used to make …

Cholesterol is used to make …

• Myelin sheath that covers nerve cells.

• Cell membranes.

Cholesterol Recommendation

• Cholesterol can be deposited in the artery walls leading to plaque buildup & heart disease.

• To maintain heart health, the dietary recommendation is to limit intake to < 300 mg/day.

• To improve heart health, limit intake to < 200mg/day.

Summary• Fat/Lipid is an organic compound.• Fat/Lipid is categorized as triglycerides,

phospholipids, and sterols. • Triglycerides provide 9 Calories per gram.• Triglycerides contains fatty acids that are categorized

as SFA, MUFA, & PUFA.• There are 2 EFAs that are PUFAs.• Triglycerides have many important functions.

Summary

• Consume 20-35% of Calories from fat & limit SFA to <7% of Calories.

• Phospholipids like lecithin, emulsify and help make up cell membranes and acetylcholine.

• Cholesterol is found in animal foods. It is not essential and can be made in the liver. It has many important functions in the body but intake should be limited to less than 300 mg/day.

References for this presentation are the same as those for this topic found in module 1 of the textbook