Lipids/Fats By Jennifer Turley and Joan Thompson © 2013 Cengage

Overview Categories, 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 fat Categories of Lipids: 1. Triglycerides 2. Phospholipids 3. 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 Model Glycerol + 3 Fatty Acids = A Triglyceride 3 units of water are released

Actual Triglyceride

Fatty Acids: Categories Dietary 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 of Stearic Acid, a SFA

Monounsaturated fatty acids Chemistry of Oleic 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 acids Chemistry 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 – % 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 COOH CH Linoleic Acid 3 COOH CH

Essential Fatty Acids

Trans Fatty Acids Created 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 …

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