(34) Lipids Fats Part 1

Overview of Lipids

• Definition: Lipids are a broad category of compounds that include fats and oils.

  • Not synonymous with fats, although commonly used that way.

  • Fats are solid at room temperature, while oils are liquid.

Key Components of Lipids

• Composition: Made up of carbon, hydrogen, and oxygen, similar to carbohydrates.

• Triglycerides:

  • Constitute about 95% of the lipids found in food and the human body.

  • Structure consists of three fatty acid molecules bound to a glycerol backbone.

  • Various types of triglycerides depend on the nature of fatty acids (saturated vs. unsaturated).

Fatty Acids

• Types:

  • Saturated Fatty Acids: Filled with hydrogen; e.g., stearic acid (18 carbon atoms).

  • All carbon atoms are saturated with hydrogen.

  • Unsaturated Fatty Acids: Do not contain the maximum amount of hydrogen.

    • Monounsaturated Fat: Contains one double bond (e.g., oleic acid).

    • Polyunsaturated Fat: Contains two or more double bonds (e.g., omega-3, omega-6).

    • Essential Fatty Acids: Omega-3 and omega-6 are essential, meaning they must be obtained through diet.

Types of Fats in Foods

• Comparison of Oils and Fats:

  • Coconut Oil: High in saturated fats but has some monounsaturated fats and omega-6.

  • Soybean Oil: Primarily polyunsaturated omega-6 with less saturated fat.

  • Important to recognize distribution when discussing the health impacts of these oils.

Phospholipids

• Role: Component of all cell membranes; act as emulsifiers.

  • Structure includes hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

  • Essential for transport across cell membranes.

• Common Examples: Lecithin found in egg yolks, liver, wheat germ, peanuts, soy, milk.

• Less common than triglycerides in foods but present in various dietary sources.

Sterols

• Cholesterol: The most well-known sterol found in animal foods.

  • Not essential in the diet since the body can produce it.

  • Functions include being a component of cell membranes and aiding fat digestion.

• Plant Sterols:

  • Found in plant foods; can help lower cholesterol levels.

  • Examples include sterols from nuts and seeds.

Fat Digestion Process

• Mouth: Begins with lingual lipase, especially active in infants.

• Stomach: Mechanical breakdown occurs, and gastric lipase plays a minor role in digestion.

• Small Intestine:

  • Fat enters, and CCK hormone triggers bile release from the gallbladder.

  • Bile emulsifies fats allowing for better enzyme action.

  • Pancreatic Lipase: Works with intestinal lipase to break triglycerides into fatty acids and glycerol.

  • Hydrolysis is the process that breaks down triglycerides and phospholipids.

Role of Bile in Digestion

• Production: Made in the liver and stored in the gallbladder, aiding in fat digestion.

  • Removal of the gallbladder necessitates diet adjustments as less bile is available for emulsification.

• Function: Breaks down fat globules, facilitating enzyme action for digestion; vital for nutrient absorption.

Summary of Emulsification Process

• Emulsification allows fats to mix with digestive enzymes in a watery environment, enhancing fat absorption.

• Bile is key in this process, ensuring fats are adequately processed for absorption in the small intestine.