Overview
This lecture explains the structure, types, digestion, and health impacts of dietary fats, emphasizing the importance of fat variety and intake recommendations.
Structure and Types of Fats
- Fats are composed of a glycerol backbone and fatty acid chains.
- Fatty acids are chains of carbon and hydrogen atoms.
- When glycerol binds with one, two, or three fatty acids, it forms mono-, di-, and triglycerides.
- Fatty acids are categorized by chain length: short (2–5C), medium (6–12C), or long (13+C).
- Saturated fatty acids have only single bonds, pack tightly, and are solid at room temperature.
- Unsaturated fatty acids have one or more double bonds, are kinked, and are liquid at room temperature.
- Monounsaturated fats have one double bond; polyunsaturated fats have two or more.
- The position of double bonds classifies fatty acids as omega-3, -6, or -9.
Sources and Examples of Fatty Acids
- Omega-3s (ALA, EPA, DHA) come from flaxseed, walnuts, canola oil (ALA), and fish (EPA, DHA).
- Omega-6s (linoleic, arachidonic acids) are found in plant oils and animal products.
- ALA and linoleic acid are essential fatty acids (must be obtained from diet).
- Omega-9s (oleic acid) are found in canola and olive oils, and can be synthesized by the body.
Fat Configurations and Processing
- Cis configuration: functional groups on same side of double bond, causing kinks and fluidity.
- Trans configuration: functional groups on opposite sides, making fats straighter and solid.
- Trans fats are formed naturally in animals or artificially by partial hydrogenation of oils.
- Trans fats are linked to heart disease and have been removed from many foods.
Digestion and Absorption of Fats
- Triglycerides are hydrophobic and form fat globules.
- Lipases break triglycerides into free fatty acids and monoglycerides.
- Bile salts emulsify fats for better enzyme action.
- Fatty acids and monoglycerides form micelles, which transport them to intestinal cells.
- Inside enterocytes, they reassemble into triglycerides and pack into chylomicrons.
- Chylomicrons enter lymph, then blood, delivering fats to tissues and eventually the liver.
Health Effects of Dietary Fats
- Polyunsaturated fats (especially omega-3s) support heart health by lowering cholesterol and blood pressure.
- DHA is crucial for infant eye and brain development.
- Different saturated fats have varying health impacts; replacing saturated with polyunsaturated fats is beneficial.
- Health guidelines recommend 20-35% of daily calories from fats, with less than 10% from saturated fats, and minimal trans fat intake.
Key Terms & Definitions
- Glycerol — a three-carbon backbone in fats.
- Triglyceride — a fat molecule with three fatty acids attached to glycerol.
- Saturated fatty acid — no double bonds, solid at room temperature.
- Unsaturated fatty acid — one or more double bonds, liquid at room temperature.
- Essential fatty acid — fatty acid required from diet (e.g., ALA, linoleic acid).
- Chylomicron — a lipoprotein that transports fat from intestine into the body.
- Cis/Trans configuration — orientation of hydrogen atoms at double bonds.
Action Items / Next Steps
- Review dietary guidelines for recommended fat intake.
- Identify food sources of healthy fats for your diet.