Lipids: Triglycerides and Fatty Acids

Triglycerides

• Comprise 95% of dietary fat.
• Composed of a glycerol backbone and three attached fatty acids.
  • The fatty acid chains are the main focus.

Fatty Acids: Fundamental Structure

• Made of a hydrocarbon chain with:
  • A methyl group at one end.
  • A carboxyl group at the other end.
• Composed of carbon, hydrogen, and oxygen (like carbohydrates).
• Linear structure (unlike the polygon shape of carbohydrates).

Differences Between Fatty Acid Chains

• Chain Length:
  • Refers to the number of carbons in the fatty acid chain.
  • Short-chain fatty acids: Less than 6 carbons.
  • Medium-chain fatty acids: 6 to 12 carbons.
  • Long-chain fatty acids: More than 12 carbon atoms.
  • Importance: Affects absorption and health impacts.
• Degree of Saturation:
  • Saturated Fats:
    • Completely hydrogenated (each carbon atom is bonded to the maximum number of hydrogen atoms).
    • Each carbon has four electrons in its outer shell, paired with hydrogen in single, nonpolar covalent bonds.
    • Nonpolarity affects solubility (e.g., oil doesn't mix with water).
    • Stable bonds are resistant to rancidity and spoilage.
    • Pack closely together, making them solid at room temperature.
    • Common dietary sources: animal products (meat, dairy) and tropical oils.
    • Health: While essential, excessive saturated fat increases cardiovascular disease risk.
  • Unsaturated Fats:
    • Have one or more points of unsaturation (missing hydrogens).
    • Double bonds form between carbon atoms at these points.
    • Monounsaturated Fats: One point of unsaturation.
    • Polyunsaturated Fats: Two or more points of unsaturation.
    • Less stable; vulnerable to oxidation and rancidity.
    • Double bonds introduce rigidity and create kinks in the chain, making them liquid at room temperature.
    • Generally considered the healthiest fats.
• Position of Double Bonds:
  • Polyunsaturated fats are categorized by the location of the first double bond from the omega carbon.
  • Omega-3 Fatty Acids:
    • Include EPA, DHA, and linolenic acid.
    • EPA and DHA are crucial for brain development and other bodily functions; primarily found in fish and breast milk.
    • Linolenic acid (from plant sources) can be converted to EPA and DHA, but conversion is limited, so fish consumption is recommended.
    • Benefits: Lower blood pressure, LDL cholesterol, and blood clotting; anti-inflammatory.

Triglyceride Composition

• Triglycerides are mixed, containing different chain lengths and levels of saturation.
• They do not consist of all saturated or all unsaturated fatty acids.
• $95\%$ of dietary fat is triglycerides, reflecting the varied composition of fats in foods.

Common Sources of Fat

• Foods contain different types of fats, but one type is usually predominant.
• Animal fats and tropical oils are high in saturated fats.
  • Animal-sourced saturated fats are mostly long-chain fatty acids.
  • Tropical oils are mostly medium-chain fatty acids.
  • These differences affect absorption and cholesterol levels.
• Olive and avocado oils are mostly monounsaturated fats.
• Corn and canola oils are highest in polyunsaturated fats.
• Fish oil is predominantly polyunsaturated, a prime source of DHA and EPA omega-3 fatty acids.

Health Implications

• Saturated vs. Unsaturated Fats:
  • Medium-chain saturated fats increase LDL cholesterol but may not be as detrimental as long-chain saturated fats.
    • Still considered on the "bad" list.
  • Trans fats are the worst type of fat.
  • Polyunsaturated omega-3 fatty acids (especially from seafood) are considered the healthiest for heart disease.
  • Followed by plant-based omega-3s, omega-6s, and monounsaturated fats.
• Recommendations:
  • Focus on replacing "red" fats with "green" fats.
  • Eliminate trans fats entirely.
  • Limit saturated fats to up to $10\%$ of the diet.
  • Prioritize medium-chain over long-chain saturated fats when choosing.
• Olive Oil:
  • Polyunsaturated fats are generally better for LDL cholesterol than monounsaturated fats.
  • Extra virgin olive oil (EVOO) has added benefits like polyphenols and antioxidants.
  • Grocery store olive oil may be lower quality due to processing, shipping, and storage, which can degrade beneficial compounds.
  • Local specialty stores may offer higher-quality, freshly cold-pressed oils with robust flavors and more health benefits; check the nutritional breakdown.

EVOO Label

• Consider pausing the video to examine the contents of an EVOO label provided.