1.4_Lipids

Overview of Lipids

• Lipids are diverse biological molecules which play critical roles in nutrition.

Types of Lipids

• Triglycerides: Composed of glycerol and three fatty acid chains.

• Sterols: A type of lipid including cholesterol, which is transported in the bloodstream by lipoproteins.

Functional Roles of Triglycerides

• Provide energy (37.7 kJ/g).

• Store fat-soluble vitamins (A, D, E, K) and essential fatty acids.

• Contribute to cell membrane structure through phospholipids.

• Control metabolism and transport cholesterol.

• Enhance food palatability and provide satiety.

• Protect vital organs, known as visceral fat around organs.

• Help maintain core body temperature (adipose tissue).

Fatty Acids

• Classification:

  • Saturated Fatty Acids: No double bonds, solid at room temperature, found in animal fats.

  • Unsaturated Fatty Acids: One or more double bonds; includes:

    • Monounsaturated: One double bond (e.g., olive oil, avocados).

    • Polyunsaturated: Multiple double bonds (includes omega-3 and omega-6).

  • Trans Fatty Acids: Typically found in processed foods, formed by hydrogenation.

Comparison of Fatty Acids

• Saturated Fatty Acids:

  • Sources: Meat, butter, cheese.

  • Effects: Raise LDL (bad cholesterol) levels.

  • Recommendation: Limit to less than 10% of total energy intake.

  • Saturated fatty acids melt last

• Monounsaturated Fatty Acids:

  • Sources: Olive oil, avocados.

  • Effects: Lower LDL cholesterol levels.

  • Monounsaturated Fatty Acid melts second

• Polyunsaturated Fatty Acids:

  • Sources: Fatty fish (omega-3), safflower oil (omega-6).

  • Effects: Lower LDL, increase HDL (good cholesterol).

  • Polyunsaturated fats melt first (most double bonds= most kinked structure), having a kinked structure makes it hard to have a stabilized structure meaning it is the easiest to break.

• Trans Fatty Acids:

  • Sources: Typically found in processed foods, formed by hydrogenation.

  • Properties:

    • Trans fats have similar properties as unsaturated fats due to the fact that they have one or more double carbon bonds.

    • While unsaturated fats have a kinked structure due to double bonds, making them more fluid, trans fats are more linear and can pack tightly together, similar to saturated fats.

  • Effects: Adversely affect cholesterol levels by increasing LDL (bad cholesterol) and decreasing HDL (good cholesterol).

Essential Fatty Acids

Essential fatty acids (EFAs) are fatty acids that the body cannot synthesize on its own and therefore must be obtained through diet.

• Omega-3:

  • Found in: Fatty fish, walnuts, flaxseeds.

  • Health benefits: Vital for cell membranes, heart health, reduces inflammation.

• Omega-6:

  • Found in: Oils, seeds, grains.

  • Functions: Stimulates growth, maintains healthy skin, potentially lowers blood pressure.

  • Recommended Ratio: Ideal is 1:1 (omega-6 to omega-3).

Cholesterol

• Cholesterol Sources:

  • Animal products like meat, butter, eggs.

Types of Lipoproteins

• Low-Density Lipoproteins (LDL): Known as 'bad' cholesterol, linked to plaque formation in arteries.

• High-Density Lipoproteins (HDL): Known as 'good' cholesterol, helps transport waste to the liver.

Effects of Dietary and Lifestyle Factors

• Saturated Fatty Acids: Increase LDL cholesterol.

• Unsaturated Fatty Acids: Decrease LDL cholesterol.

• Trans Fatty Acids: Adversely affect cholesterol levels.

• Exercise: Increases HDL and helps maintain LDL levels.

• Fibre: Reduces cholesterol absorption, beneficial for heart health.

Conclusion: Importance of Fats in Diet

• Essential for various body functions, protecting organs, storing energy, and maintaining health overall.