Lecture on Lipids (Chapter 6)

Introduction to Lipids

• Definition: Lipids, commonly known as fats, are crucial for bodily functions but insoluble in water.
• Major Groups: Triglycerides, Phospholipids, Sterols.

Triglycerides

• Structure: Composed of one glycerol molecule and three fatty acids.
• Role:
  • Primary form of fat storage and energy source.
  • Insulation and protection for the body.
  • Aids in absorption of fat-soluble vitamins.
• Food Sources: Animal fats, vegetable oils, bakery items, dairy products.

Fatty Acids

• Chain Lengths: Short, medium, long; affect digestion speed.
• Types:
  • Saturated: No double bonds, solid at room temperature (e.g., butter, lard).
  • Unsaturated: One or more double bonds, liquid at room temperature (e.g., olive oil).
  • Trans Fat: Result from hydrogenation, solid at room temperature, linked to increased cardiovascular risk.

Phospholipids

• Function:
  • Main component of cell membranes.
  • Act as emulsifiers, aiding lipid transport in the bloodstream.
• Structure: Amphipathic with hydrophilic and hydrophobic parts.

Sterols

• Cholesterol: Essential for cell membranes, hormone production, vitamin D synthesis.
• Sources: Produced by the body and found in animal-based foods.

Essential Fatty Acids

• Types: Omega-6 (linoleic acid), Omega-3 (alpha-linolenic acid).
• Sources: Vegetable oils, nuts, fish, flax, walnuts.
• Importance: Reduce inflammation, regulate physiological functions.

Hydrogenation

• Purpose: Adds hydrogen to unsaturated fats, increases shelf life.
• Consequence: Creates trans fats, linked to increased cholesterol and cardiovascular risk.

Role of Lipids in the Body

• Energy: Provide 9 kcal per gram, fuel at rest and during exercise.
• Storage: Stored energy source.
• Hormones: Involved in hormone production and vitamin absorption.

Guidelines for Fat Intake

• AMDR: 20-35% of total daily energy; saturated fats should be 7-10%.
• Hidden Fats: Found in baked goods, fast food; read labels carefully.

Fat Replacers

• History: Developed to reduce fat content in foods.
• Issues: May cause digestive problems, not necessarily lower in calories.

Lipid Digestion and Absorption

• Process: Starts in the mouth, continues in the stomach and small intestine.
• Bile and Enzymes: Necessary for digestion and absorption.

Lipoproteins and Their Roles

• Types:
  • VLDLs: Transport triglycerides, levels affected by diet and exercise.
  • LDLs: Deliver cholesterol, high levels linked to heart disease.
  • HDLs: Good cholesterol, removes excess cholesterol, protective role.

Health Concerns

• Dietary Fat: Essential but high intake increases risk of cardiovascular disease, obesity, certain cancers.
• Cardiovascular Disease: Leading cause of death; linked to high fat intake, lifestyle factors.
• Prevention: Reduce saturated and trans fat intake, increase physical activity, fiber intake.

Conclusion

• Balance and moderation in diet are crucial.
• Understanding labels and dietary guidelines can help manage fat intake effectively.