Nutrition, Lipids Lecture #5

Macronutrients Lipids

• Lipids include triglycerides, phospholipids, and sterols.
• Triglycerides are the major lipid form (95%) in the body and food.
• Triglycerides are composed of three fatty acids attached to a glycerol backbone.
• Fatty acids vary in length and saturation.
• Saturated fatty acids are filled to capacity with hydrogen atoms.
• Unsaturated fatty acids have "empty spots" where hydrogen is missing.
• Monounsaturated fats have one point of unsaturation.
• Polyunsaturated fats have two or more points of unsaturation.
• Softer fats tend to have shorter-chain and more unsaturated fatty acids.
• Harder fats tend to have longer-chain and more saturated fatty acids.

Types of Lipids

• Triglycerides are the main type of lipid in the body.
• Phospholipids are important components of cell membranes.
• Sterols, like cholesterol, are essential for various bodily functions.

Role of Lipids in the Body

• Lipids provide energy storage.
• Lipids are crucial for cell structure, particularly in cell membrane composition.
• Lipids play important roles in hormone production.

Digestion and Absorption of Lipids

• Digestion of lipids begins in the small intestine.
• Bile emulsifies fats, making them accessible to enzymes.
• Enzymes break down triglycerides into smaller components (monoglycerides, free fatty acids, glycerol).
• Glycerol and short-chain fatty acids enter the bloodstream directly.
• Larger fragments (monoglycerides and long-chain fatty acids) are converted back into triglycerides and combined with protein to form chylomicrons.
• Chylomicrons travel through the lymphatic system to the bloodstream.
• A small amount of cholesterol passes through the large intestine with fiber.

Health Implications of Lipids

• High levels of LDL cholesterol are associated with increased risk of heart disease.
• High levels of HDL cholesterol may offer some protection against heart disease.
• Trans fats are associated with negative effects on heart health.
• Omega-3 fatty acids may have positive effects on heart health.

Hydrogenation and Dietary Recommendations

• Hydrogenation is a process used to solidify unsaturated fats.
• Hydrogenation can create trans fats.
• Limiting saturated and trans fats, and increasing unsaturated fats, is often recommended for health.

Essential Fatty Acids

• Linoleic acid and Linolenic acid are essential fatty acids.
• The body cannot produce essential fatty acids; they must be obtained from the diet.
• They play important roles in eicosanoid production.
• Eicosanoids are hormone-like substances that regulate various body functions.

Omega-3 and Omega-6 Fatty Acids

• Omega-3 and Omega-6 fatty acids are important polyunsaturated fats.
• Omega-3 fatty acids are often associated with positive health effects.
• Sources of Omega-3 fatty acids include fatty fish, flaxseed oil, and algae oils.
• Omega-6 fatty acids may have a variety of roles in the body, but a balanced diet is necessary to maintain omega-3/6 balance in the body.

Storage of Lipids

• Triglycerides, fats from food, are transported to fat deposits in muscle, breasts, and under the skin.
• Fat cells are active and secrete hormones that regulate appetite.
• The number of fat cells is usually set during adolescence, but then expands or shrinks.

Lipid Intake Targets

• The Acceptable Macronutrient Distribution Range (AMDR) for fat is 20-35% of total calories.
• Saturated fat intake should be less than 10% of total calories.
• Trans fat intake should be as low as possible (less than 1%).
• Consuming foods high in monounsaturated and polyunsaturated fatty acids is recommended.

Definitions

• Saturated Fats: Triglycerides where most fatty acids are saturated.
• Monounsaturated Fats: Triglycerides where most fatty acids have one point of unsaturation.
• Polyunsaturated Fats: Triglycerides where most fatty acids have two or more points of unsaturation.
• Essential Fatty Acids (EFAs): Fatty acids the body needs but cannot produce, thus must be consumed in the diet.
• Trans Fats: Unique fatty acid structure created through processing, not found in nature in large amounts.
• Monoglyceride: lipid breakdown product made of glycerol and one fatty acid.
• Short Chain Fatty Acids (SCFAs): less than 6 carbons, produced during gut bacteria's breakdown of fiber.
• Long Chain Fatty Acids (LSCFAs): 12 or more carbon atoms.
• Medium Chain Fatty Acids (MCFAs): 6-12 carbon atoms.
• Micelles: lipid spheres, important for nutrient absorption in the small intestine via assistance of bile.
• Fats: solid at room temperature
• Oils: liquid at room temperature

Notable Information

• Medium-chain triglycerides are highly soluble in water and require no bile for absorption.
• Short-chain fatty acids are metabolic products related to gut health, and are a fuel source for intestinal cells.

Lipids and Human Health

• Fats are a crucial energy source.
• Lipids are vital components of cell membranes.
• Essential fatty acids are important for several hormone and cell functions.
• Fats are involved in brain function and cognitive processes.
• Lipids aid in vitamin absorption, including fat-soluble vitamins A, D, E, and K.
• Fats contribute to satiety.

Fat in the Diet

• Controlling portion sizes of fatty foods helps manage calorie intake and maintain a healthy weight.
• Diets lower in saturated and trans fats can reduce heart disease and some types of cancer.
• Replace saturated fats with unsaturated fats where possible to lower heart disease risk.
• Incorporate a wider variety of healthy food choices, including fresh fruits, vegetables, whole grains, and lean proteins.

Recommendations for Omega-3 Fatty Acids

• Incorporating fatty fish into the diet 2 to 3 times per week promotes heart health.
• Grilling, baking, or broiling fish enhances its health benefits.
• Considering flaxseed and flaxseed oil as potential sources of Omega-3 fats.

Potential Health Benefits of Fish Oil

• Research supports the involvement of fish oil in reducing the risk of heart disease, promoting mental health, potential role in battling cancer, and may reduce risk of dementia
• Further research is important in these areas.

Food Sources of Omega-3 and Omega-6

• Various nuts, seeds, and oils contain Omega-3 and Omega-6 fatty acids.
• Fish and seafood are significant sources of Omega-3 fatty acids.

Phospholipids

• Phospholipids have a phosphate "head" and fatty acid "tails."
• These molecules act as emulsifiers, mixing fats and water.
• Phospholipids are major parts of cell membranes.

Sterols

• Sterols such as cholesterol, vitamin D, sex hormones, and stress hormones, are important components of various biological systems.
• Cholesterol plays a role in the synthesis of bile.
• Cholesterol is a vital part of cell membrane structure.

Trans Fats and Hydrogenation

• Trans fats are created during the hydrogenation process.
• Hydrogenation is used to solidify fats.
• Trans fats are associated with negative effects on health.
• Not all trans fats are created equal, nor do they all have the same health effects.

Effects of Processing on Unsaturated Fats

• Hydrogenation of unsaturated fats creates saturated fats and trans fats.
• Creates a spreadable fat (commonly in margarine).
• Result in a product that's more oxidation resistant and better suited for frying.

Trans Fats

• These are not naturally made by the body.
• Naturally found in dairy and beef in small amounts.
• Trans fats increase heart health risks, including raising LDL cholesterol and lowering HDL cholesterol.
• Trans fats contribute to inflammation throughout the body.

Digestion and Absorption of Lipids (continued)

• Bile is transported to the small intestine where it assists in the digestion of fats by converting them into smaller droplets.
• Enzymes further break down the fats before absorption.
• Triglycerides are formed and packaged into chylomicrons.
• Chylomicrons move into the lymphatic system and then into the bloodstream.

Action of Bile in Fat Digestion

• Bile emulsifies fats, making them easier for enzymes to digest.
• Bile compounds act as an emulsifier, mixing fats into water.
• This process makes the fats accessible to enzymes for efficient digestion.

Storage of Lipids (continued)

• Fat cells are active in hormone secretion and regulation.
• The number of fat cells stabilizes during adolescence, but then can expand or shrink.

Dietary Recommendations (continued)

• Limiting portion sizes of fatty foods is helpful for calorie control.
• Diets low in saturated and trans fats can reduce heart disease and some types of cancer.
• In general, increasing the amount of unsaturated fats in your diet may contribute to heart health.
• Consume more foods that are rich in monounsaturated or polyunsaturated fats in place of saturated fats.