After studying this chapter you will be able to understand: What are lipids? fatty acids are key building blocks, triglycerides, phospholipids, sterols, lipid digestion and absorption, transportation of lipids in the body, recommendations for fat intake, lipids and health.
Chapter Lipids: Not Just Fat What Are Lipids? • • Essential nutrients – Provide energy – Help transport fat-soluble nutrients throughout the body Contribute greatly to the flavor and texture of food Lipids Include… • • • Triglycerides (most abundant lipids) – In body: stored in adipose tissue – In food: “fats and oils” Phospholipids (~2% of dietary lipids) – Plant and animal origin – Body can make them – Soluble in fat and water Sterols (very, very small % of lipids) – Most well known: Cholesterol Fatty Acids Are Key Building Blocks • Fatty acid – Determines whether a fat is solid or liquid at room temperature – Basic structure: (-COOH); (-CH3) Fatty Acids Are Key Building Blocks • Chain length – Fatty acids differ in chain length – Lengths vary from to 24 carbons – Grouped as shortchain, mediumchain, and longchain Fatty Acids Are Key Building Blocks • Chain Length – Shorter fatty acids remain liquid at room temperature and even with refrigeration – Shorter fatty acids also are more water- Fatty Acids Are Key Building Blocks • Saturation – Saturated fatty acids • – Unsaturated fatty acids • – All single bonds between carbons One or more carbon bonds is a double bond Monounsaturated fatty acid (MUFA) Polyunsaturated fatty acid (PUFA) Fats with more double bonds are generally Fatty Acids Are Key Building Blocks • Cis vs trans – Unsaturated fatty acids can vary in shape – Cis fatty acids – • Chain is bent • Occur naturally Trans fatty acids • • Chain is straighter Transportation of Lipids in the Body • High-Density Lipoproteins (HDL) – Pick up cholesterol for removal or recycling Recommendations for Fat Intake • Recommended intake – Reduce saturated fat, trans fat, and cholesterol – Total fat: 20–35% of calories – Less than 10% of calories from saturated fat – Less than 300 mg per day of cholesterol Recommendations for Fat Intake • Essential fatty acid requirements – • Linoleic acid should provide about 2% of calories Omega-6 and omega-3 balance – Ratio of 6:1 omega-6 to omega-3 fatty acids • Seafood (fatty fish), canola or soybean oil Recommendations for Fat Intake • Current dietary intakes – Americans eat ~33% of total calories from fat – Average calorie intake has increased = Americans consuming more total grams of fat – Saturated fat intake ~11% • Cheese, pizza, grain-based desserts, chicken, sausage, etc Recommendations for Fat Intake • Role of fat replacers – Different types of composition – Olestra • Sucrose + fatty acids • Indigestible— provides no calories • Reduces absorption of fat-soluble vitamins Lipids and Health • Heart disease – Major risk factors • High blood cholesterol – High LDL and low HDL • Smoking • High blood pressure Lipids and Health • Reducing heart disease risk – AHA diet and lifestyle recommendations • Consume an overall healthy diet • Aim for a healthy body weight • Aim for a desirable lipid profile • Aim for normal blood pressure • Aim for normal blood glucose levels • Be physically active • Avoid use of and exposure to tobacco Lipids and Health • Reducing heart disease risk – AHA recommendations • • • • Balance calorie intake and physical activity to achieve or maintain a healthy body weight Consume a diet rich in fruits and vegetables Choose whole-grain, high-fiber foods Consume fish, especially oily fish, at least twice a week Lipids and Health • Reducing heart disease risk – AHA recommendations (cont.) • • • • Minimize your intake of beverages and foods with added sugars Choose and prepare foods with little of no salt If you consume alcohol, so in moderation Follow the AHA recommendations when eating outside of the home Lipids and Health • Obesity – High-fat diets promote weight gain – Significant within the U.S population • • 34.9% of American adults 17% of American children and adolescents Lipids and Health • Metabolic syndrome – Affects ¼ of American adults – Cluster of at least three symptoms • Excess abdominal fat • High blood glucose • High serum triglycerides • Low HDL cholesterol • High blood pressure Lipids and Health • Cancer – Results from complex mix of lifestyle, hereditary, and environmental factors – Role of nutrition and diet complex • • Evidence suggests 30-40% are due to poor food choices and physical inactivity Some dietary factors act as promoters, while others serve a protective role Lipids and Health • Cancer – Dietary and lifestyle factors for reducing cancer risk • Maintain a healthful weight • Adopt a physically active lifestyle • Consume a healthy diet • Limit alcohol consumption Lipids and Health • Putting It All Together – Healthy People 2020 objectives target reducing deaths from heart disease and stroke and reducing the number of adults with high blood cholesterol levels ... Nonessential Fatty Acids – Essential fatty acids • Must come from food • Cannot be made by the body • Two families: • – Omega-3 (alpha-linolenic acid) – Omega-6 (linoleic acid) Pre-cursors to... well known: Cholesterol Fatty Acids Are Key Building Blocks • Fatty acid – Determines whether a fat is solid or liquid at room temperature – Basic structure: (-COOH); (-CH3) Fatty Acids Are Key Building... adipose tissue Insulation and protection: Visceral fat Subcutaneous fat Carrier of fat- soluble nutrients Triglycerides • Functions – Carrier of Fat- Soluble Compounds • – Improves intestinal absorption