Sources of lipids in our food

 

 

Discuss sources of lipids in our food. Be sure to address each of the following: saturated vs unsaturated, and types of lipids (triglycerides, fatty acids, phospholipids, and sterols). (USLO 5.1)
Outline process of lipid digestion, absorption, and transportation in the body. (USLO 5.2)
Differentiate LDL and HDL cholesterol and their roles in the body. Elaborate on their relationship to health and disease. (USLOs 5.2, 5.4)
Discuss the functions of lipids in the body as it relates to essential fatty acids (omega-6 and omega-3), and fats as an energy source. (USLO 5.3)
Discuss the RDA values for lipids for you and your immediate family members. How did you do in meeting those RDA values based on your nutrient intake report? Discuss ways in which you can improve. (USLO 5.5)

 

Small Intestine (Major Site):

Bile: Released from the gallbladder, bile emulsifies large fat droplets into smaller particles, increasing the surface area.

Pancreatic Lipase: The primary fat-digesting enzyme, it breaks down triglycerides into monoglycerides and free fatty acids.

Phospholipids are broken down by phospholipase, and sterols are mostly undigested.

 

2. Absorption

 

Micelles: Monoglycerides, free fatty acids, and cholesterol are packaged with bile salts into tiny transport structures called micelles.

Intestinal Cells: Micelles transport lipids to the surface of the intestinal absorptive cells (enterocytes) where the lipids diffuse across the membrane.

Short/Medium-Chain Fatty Acids are small enough to pass directly into the portal vein and travel to the liver.

Long-Chain Fatty Acids, Monoglycerides, and Cholesterol are reassembled into new triglycerides within the enterocytes.

 

3. Transportation

 

Chylomicrons: The newly formed triglycerides, cholesterol, and phospholipids are packaged with a protein coat to form chylomicrons—a type of lipoprotein.

Lymphatic System: Chylomicrons are too large to enter the capillaries directly, so they enter the lymphatic system first.

Sample Answer

 

 

 

 

 

 

 

Sources and Types of Lipids in Food

 

Dietary lipids (fats) come from a variety of sources and are categorized based on their chemical structure, particularly their saturation.1

 

 

Sources of Lipids

 

Lipid TypeSaturated vs. UnsaturatedPrimary Food Sources
Triglycerides (Most abundant dietary lipid)Can be bothSaturated: Animal fats (meat, whole milk, butter), coconut oil, palm oil. Unsaturated: Vegetable oils (olive, canola, peanut), nuts, seeds, avocados, fatty fish.
Fatty Acids (Building blocks of triglycerides)Saturated: No double bonds; solid at room temp. Unsaturated: Have one or more double bonds; liquid at room temp.Directly consumed in trace amounts, but mainly derived from the breakdown of dietary triglycerides.
PhospholipidsBoth, but primarily determined by their fatty acid chainsEgg yolks, liver, peanuts, soybeans, and as food emulsifiers (e.g., lecithin).
SterolsNot applicable; cholesterol is a complex structureCholesterol: Only found in animal products (meat, poultry, eggs, dairy). Plant sterols/stanols: Naturally in fortified foods (margarines, juices).

Saturated Fats: Found mainly in animal products (meat, butter, high-fat dairy) and some tropical oils (coconut, palm).2 They lack double bonds and are solid at room temperature.

 

Unsaturated Fats: Found in plant sources (vegetable oils, nuts, seeds, avocados) and fatty fish.3 They contain one (monounsaturated) or more (polyunsaturated) double bonds and are liquid at room temperature.