Lipids Essential nutrients Provide energy Help transport fat- soluble nutrients Contribute to flavor and texture of food Photo © PhotoDisc

Lipids What are lipids? –Triglycerides Stored in adipose tissue Fats and oils in food –Phospholipids Plant and animal origin Body can make them Soluble in fat and water –Sterols Cholesterol

Fatty Acids Are Key Building Blocks Fatty acid –Determines solid or liquid at room temp –Basic structure: (-COOH); (-CH 3 ) Chain length –4 to 24 carbon length

Fatty Acids Are Key Building Blocks Saturation –Saturated fatty acid All single bonds –Unsaturated fatty acid One or more double bond –Monounsaturated fatty acid One double bond –Polyunsaturated fatty acid More than one double bond

Fatty Acids Are Key Building Blocks Cis vs. trans –Cis fatty acids Occur naturally Chain is bent –Trans fatty acids Produced by hydrogenation Chain is straighter

Fatty Acids Are Key Building Blocks Nonessential and essential fatty acids –Nonessential fatty acids Can be made in the body

Fatty Acids Are Key Building Blocks Nonessential and essential fatty acids –Essential fatty acids Can’t be made in body Must come from food Omega-3 (alpha-linolenic acid) and omega-6 (linoleic acid) Used to make eicosanoids

Triglycerides Structure –Glycerol + three fatty acids Functions –Energy source 9 kcal/g –Energy reserve Form of stored energy in adipose tissue –Insulation and protection Visceral fat –Carrier of fat-soluble vitamins –Sensory qualities in food

Triglycerides in Food Sources of omega-3 fatty acids –Soybean, canola, walnut, flaxseed oils –Salmon, tuna, mackerel, fish oil supplements Sources of omega-6 fatty acids –Seeds, nuts, vegetable oils –Meat, poultry, eggs Commercial processing –Oxidation Photos © PhotoDisc

A healthy diet contains a balance of omega-3 and omega-6 fatty acids. Omega-3 help reduce inflammation. Some omega-6 tend to promote inflammation. The typical American diet contains times more omega-6 than omega-3. The ratio should be in the range of 2:1 - 4:1, omega-6 to omega-3.

Phospholipids –Glycerol + two fatty acids + phosphate group Phospholipid functions –Emulsifiers Keeps fat suspended in water Keep oil and water mixed –Cell membranes

Phospholipids Cell membrane –Double layer of phospholipids –Important role in nerve cells

Phospholipids Lipid transport –Stomach Break fats into tiny particles for digestion –Intestine Continue emulsifying fat –Blood Surface of lipoproteins that carry lipid particles in the body

Phospholipids Emulsifiers (lecithin) –In body Phospholipid with choline –In food Used as emulsifiers

Sterols Cholesterol functions –In cell membranes –Precursor: Vitamin D Sterol hormones Bile salts Cholesterol synthesis in liver –Found only in animal foods

Lipid Digestion and Absorption –Mouth Chewing + lingual lipase –Stomach Triglycerides to diglycerides and free fatty acids (FFA) –Small intestine Emulsified by Bile Digested by pancreatic lipase

Lipid absorption –Micelles Carry monoglycerides and fatty acids to microvilli Bile salts absorbed = enterohepatic circulation Lipoprotein Cylomicron –Deliver dietary lipids from intestines to cells and liver

Digestion and absorption of sterols –50% of dietary cholesterol is absorbed Fat increases absorption Plant sterols and dietary fiber decrease absorption

Lipids in the Body –Very-low-density lipoproteins (VLDL) Deliver triglycerides to cells –Intermediate-density lipoproteins Converted to LDL –Low-density lipoproteins (LDL) Deliver cholesterol –High-density lipoproteins (HDL) Pick up cholesterol for removal

Lipids in the Diet 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 Photos © PhotoDisc

Lipids in the Diet Role of fat replacers –Olestra Sucrose + fatty acids Indigestible— provides no calories Reduces absorption of fat-soluble vitamins

Lipids and Health Obesity –High-fat diets promote wt gain Heart disease –Major risk factors High blood cholesterol –High LDL and low HDL Smoking High blood pressure

Lipids and Health Atherosclerosis –Slow, progressive hardening and narrowing of arteries –Promoted by high blood cholesterol –Lipoprotein a [Lp(a)] Inflammation and atherosclerosis –C-reactive protein

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 products

Lipids and Health Reduce 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 Limit your intake of saturated and trans fat and cholesterol

Lipids and Health Cancer –Stages of development Initiation Promotion Progression –Role of nutrition and diet Factors that promote or protect

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 If you drink alcohol, limit consumption