Recording-2025-03-18 Lipids Pt. 2

Overview of Lipids

• Lipids are crucial macromolecules, including triglycerides, phospholipids, and sterols (cholesterol).

Triglycerides

• Comprised of a glycerol backbone and three fatty acids.

• The variety and type of fatty acids determine the properties of the fat.

Phospholipids

• Amphipathic molecules: Have hydrophilic (water-attracting) and hydrophobic (fat-attracting) parts.

• Critical for cell membrane formation—every cell contains a bilipid layer mainly of phospholipids.

• Lecithin: Common phospholipid that acts as an emulsifier, crucial for bile production and food processing.

  • Emulsifies fats allowing them to mix with water in digestion.

  • Acts by forming a bridge between fat and water, preventing separation.

• Sources include egg yolks, peanuts, organ meats, and processed foods.

Cholesterol and Sterols

• Sterols, primarily cholesterol, serve various functions, with a complex multi-ring structure that makes them more solid than triglycerides or phospholipids.

• Cholesterol is essential in bile production and forms part of cell membranes; about 33% of the brain is cholesterol.

• Sources of cholesterol are exclusively from animal products; the body synthesizes cholesterol as needed.

  • The liver is responsible for cholesterol production.

  • Dietary cholesterol does not equate to blood cholesterol levels unless a person has pre-existing high cholesterol.

• Health concerns: High cholesterol levels can lead to vascular blockages.

Fat Digestion

• Begins in the mouth with insignificant lingual lipase; most fat digestion occurs in the small intestine.

• Cholecystokinin (CCK): Hormone released when fat enters the small intestine, stimulating gallbladder bile release and pancreatic lipase secretion.

• Bile emulsifies fats, increasing the surface area for lipases to act.

• Breakdown products of triglycerides include monoglycerides, free glycerol, and free fatty acids.

• Solubility traits: Short-chain fatty acids are water-soluble and enter the bloodstream; longer-chain fatty acids are reformed into triglycerides.

• Long-chain fatty acids are packed into chylomicrons (fat transporters) for lymphatic system transport before entering the bloodstream.

Lipoproteins

• Chylomicrons: Carry dietary fats from the intestine to tissues.

• VLDL (Very Low-Density Lipoprotein): Transports fats produced by the liver.

• LDL (Low-Density Lipoprotein): Carries cholesterol, often referred to as "bad cholesterol" due to its potential to clog arteries.

• HDL (High-Density Lipoprotein): Known as "good cholesterol"; helps remove cholesterol from arteries, returning it to the liver for excretion.

• Lipoproteins differ in composition, size, and function, with chylomicrons mainly carrying triglycerides.

Health Recommendations for Fats

• No established RDA for fat intake; 20-35% of total caloric intake from fats is recommended.

• Limit saturated and trans fats, especially for those at risk of heart disease; specific intake recommendations based on health risks.

• Essential fatty acids:

  • Omega-3 fatty acids: ~1 g/day recommended, known for anti-inflammatory properties.

  • Omega-6 fatty acids: higher intake is generally maintained through diet.

Health Concerns Related to Lipids

• Link between high sugar intake, refined carbohydrates, and heart disease; excessive sugar causes the liver to convert sugars into fat, potentially raising cholesterol levels (via VLDL to LDL transformation).

• Cardiovascular disease risks: Age, genetics, high blood cholesterol/triglycerides, hypertension, diabetes, and obesity contribute to increased risks of heart disease and strokes.

The Mediterranean Diet

• Promotes healthy fats, particularly monounsaturated fats, along with regular physical activity.

• Encourages fiber-rich foods and limited saturated fat intake.

• Western diets typically contain excessive sugars and omega-6 fatty acids while lacking sufficient omega-3s, suggesting the need for balanced dietary adjustments.