Lipids

Lipids Overview

• Learning Objectives:

  • Understand the types and composition of lipids

  • Familiarize with the sources of lipids

  • Comprehend the transport mechanisms of lipids

  • Grasp the implications of lipids in atherosclerosis

Types of Lipid Molecules

• Main Types:

  • Triglycerides

  • Phospholipids

  • Sterols

• Fatty Acids:

  • Saturated fatty acids

  • Monounsaturated fatty acids

  • Polyunsaturated fatty acids (PUFA)

• Examples:

  • Cholesterol

  • Lecithin

Triglycerides

• Components:

  • Glycerol: forms the triglyceride backbone

  • Three fatty acids: can vary in length and saturation

• Types of Triglycerides:

  • Monoglyceride: One fatty acid on glycerol

  • Diglyceride: Two fatty acids on glycerol

• Role: Major form of lipid in food and body

Fatty Acids

• Structure:

  • Hydrophilic carboxyl head (acid group)

  • Hydrophobic carbon tail

  • Methyl end (CH3)

• Categories Based on Length:

  • SCFA (2-4 carbons)

  • MCFA (6-10 carbons)

  • LCFA (>12 carbons)

• Bonds:

  • Saturated: All carbons have hydrogens

  • Unsaturated: Not all carbons have hydrogens

    • Monounsaturated (MUFA)

    • Polyunsaturated (PUFA)

    • Omega fatty acids (Omega-3, Omega-6)

Polyunsaturated Fatty Acids (PUFA)

Omega-6 (n-6)

• Example: Linoleic acid (18:2n-6)

• Sources: Sunflower, corn, soybean oils

• Functionality: Essential for cell membranes, growth, skin health, reproductive health, blood pressure, and clotting

Omega-3 (n-3)

• Sources:

  • ALA (Alpha-Linolenic Acid, 18:3n-3) - essential

• Functions:

  • Structural component of cell membranes, notably brain and nervous system

  • Regulates blood pressure and clotting

• Other Types:

  • Eicosapentaenoic acid (EPA, 20:5n-3)

  • Docosahexaenoic acid (DHA, 22:6n-3) - important for fetal development

Eicosanoids

• Definition: Derived from omega-3 and omega-6 fatty acids

• Functions:

  • Omega-3 eicosanoids - anti-inflammatory

  • Omega-6 eicosanoids - promote inflammation

• Health Implications: Regular EPA and DHA consumption reduces heart attack and stroke risks

• Optimal Ratio: Canadian diets exhibit an imbalance favoring omega-6 over omega-3

Fat Modifications

Hydrogenation

• Process: Adding hydrogen to liquid unsaturated fats

• Effects: Improves shelf life, taste, but alters unsaturated fatty acids, increasing saturated fat

Trans Fats

• Found in: Margarines, baked goods, snacks, and fried foods

• Health Effects: Raise LDL and lower HDL cholesterol levels, increasing CVD risk

Phospholipids

• Definition: Lipids attached to a phosphate group

• Structure: Glycerol, two fatty acids, and phosphate

• Function: Form lipid bilayers in membranes, regulating passage into/out of cells

• Sources: Egg yolks, soybeans, and peanuts

Sterols

• Definition: Lipids found in plants and animals; cholesterol is a key sterol

• Structure: Ringed molecular structure, does not contain fatty acids

• Role in Body: Synthesized by the liver, aids in synthesizing Vitamin D, bile acids, and hormones

Lipid Transport

• Lipoproteins: Particles composed of lipids, phospholipids, and proteins for lipid transport

• Types of Lipoproteins:

  • Chylomicrons

  • VLDL

  • IDL

  • LDL

  • HDL

Cardiovascular Disease (CVD)

• Statistics: Leading cause of death in Canada

• Risk Factors: Diet and lifestyle impact heart disease risk, with 40% of Canadians having elevated cholesterol

Pathogenesis of Atherosclerosis

• LDL Cholesterol: Forms when cholesterol oxidizes; binds to macrophages via scavenger receptors

• Atherosclerotic Plaque: Composed of cholesterol, smooth muscle cells, fibrous tissue, and calcium deposits

Dietary Impact on Heart Disease

• Target Blood Lipids Values:

  • Total Cholesterol: < 5.2 mmol/L

  • HDL: > (M); > (F)

  • LDL: < 3.5 mmol/L

  • Triglycerides: <

  • Total Cholesterol/HDL Ratio: < 5.0

• Strategies to Reduce Heart Disease Risk:

  • Omega-3 and omega-6 intake

  • Monounsaturated fats and plant foods consumption

  • Adequate B vitamins and moderate alcohol

Dietary Reference Intake (DRI) for Fat

• Recommendations:

  • Total calories from fat: 20-35%

  • Omega-6: 5-10%

  • Omega-3: 0.6-1.2%

  • Minimize saturated fat while maintaining adequacy

  • Avoid trans fats

Saturated Fat Debate

• Key Finding: Replacing saturated fats with polyunsaturated fats leads to reduced CVD risk

• Advice: Shift dietary patterns towards unsaturated fats, incorporating healthful diets (DASH or Mediterranean diet)

Conclusion

• Overall Theme: Dietary fats play a crucial role in health, particularly in cardiovascular disease management and prevention.