Overview
This lecture covers the structure, types, digestion, health impacts, and dietary recommendations of fats and fatty acids in nutrition.
Structure and Types of Fats
- Fats are composed of glycerol (3-carbon backbone) and fatty acid chains.
- Fatty acids are chains of carbon and hydrogen; classified by chain length: short (2–5C), medium (6–12C), and long (13+C).
- The process linking glycerol and fatty acids releases water and forms mono-, di-, or triglycerides.
- Saturated fatty acids have only single carbon bonds, are straight, and usually solid at room temperature.
- Unsaturated fatty acids have one or more double bonds, causing kinks and are usually liquid at room temperature.
- Monounsaturated fatty acids have one double bond; polyunsaturated have two or more.
Classification by Double Bond Position
- The “omega” system numbers carbons from the methyl end to the first double bond (omega-3, omega-6, omega-9).
- Omega-3 fats include ALA (from plants), EPA, and DHA (from fish/marine sources).
- Omega-6 includes linoleic acid (plant oils) and arachidonic acid (animal sources).
- Omega-9 (oleic acid) is found in canola/olive oil, almonds, and can be made by the body.
Cis and Trans Fats
- Most natural unsaturated fats are in a cis configuration, causing bends and fluidity.
- Trans fats have straight chains due to the trans configuration, leading to solidity.
- Trans fats are produced by partial hydrogenation of oils and are associated with health risks.
Digestion and Absorption
- Triglycerides are hydrophobic and form fat globules.
- Lipases and bile salts help break fats into monoglycerides and free fatty acids.
- These form micelles, which enter intestinal cells, reform as triglycerides, and are packaged into chylomicrons.
- Chylomicrons enter the lymphatic system, then the blood, delivering fats to tissues.
Health Impacts & Recommendations
- Polyunsaturated fats are precursors to prostaglandins, help lower blood pressure, and improve cholesterol profiles.
- Long-chain omega-3 fatty acids lower plasma triglycerides and support infant brain and eye development.
- The effects of saturated fats vary; replacement with polyunsaturated fats is beneficial, but not so with refined carbs.
- Recommended fat intake is 20–35% of daily calories, with less than 10% from saturated fat and minimal trans fat.
Key Terms & Definitions
- Triglyceride — Fat molecule with three fatty acids linked to glycerol.
- Saturated Fat — Fatty acid with no double bonds, solid at room temperature.
- Unsaturated Fat — Fatty acid with one or more double bonds, liquid at room temperature.
- Monounsaturated Fatty Acid — Fatty acid with one double bond.
- Polyunsaturated Fatty Acid — Fatty acid with two or more double bonds.
- Cis/Trans Configuration — Arrangement of atoms around a double bond; cis causes bends, trans is straighter.
- Chylomicron — Lipoprotein particle that transports dietary fats from the intestine to the bloodstream.
Action Items / Next Steps
- Review recommended dietary fat intake and types of fats in your own diet.
- Read more about the health effects of different fatty acids, especially omega-3 and omega-6 sources.