The Lipids: Triglycerides, Phospholipids, and Sterols

Lipids (what, include) 

Has carbon, hydrogen, and oxygen. 

Include: 

• Triglycerides (= 1glycerol + 3 fatty acid) 

• Saturated fatty acid 

• Unsaturated fatty acid (Monounsaturated and polyunsaturated) 

Fatty Acids

Chains of carbons + hydrogen attached

• Carboxylic acid (COOH) at one end

• Methyl (CH3) group at other end

Carbon chain length (examples)

• Very long chain (20-24C) (Fatty fish)

• Long chain (6-18C) (Meats, seafood, veg oils) (most common)

• Medium Chain (6-12C) (Mostly dairy)

• Short Chain (4C or fewer) (Mostly dairy)

Degree of unsaturation

Saturated Fatty acid

• NO double bonds

• Fully hydrogen loaded

Unsaturated Fatty acid

• Monounsaturated (1 double bond)

• Polyunsaturated (1+ double bond)

How to name Polyunsaturated

Differ by the location of the double bond. By the position of the double bond closest to the methyl group (omega #)

Naming Monounsaturated fatty acids

Mostly Omega 9 group

Triglycerides

3 fatty acid + glycerol molecule

• To form, there must be a condensation reaction. 

Firmness of Solid fats and oils 

• The more unsaturated the fatty acid, the more liquid it is at room temperature. 

• Shorter the carbon chain the softer at room temp.

Stability of solid fats and oils

Exposure to O2 spoils fats

• Double bond unstable, monounsaturated less susceptible, saturated fats more resistant to O2 

• Heat/light speed up rancidity 

Slow speed of rancidity (solid fat/oils)

• Storage system (fridge, sealed, away from light) 

• Addition of antioxidants 

• Hydrogenation 

Hydrogenation

Produce trans fatty acids

• Adds H’s to unsaturated fatty acid (reduce double bond) 

• Makes more liquid at room temp

• Increases shelf life. 

Trans fatty acid (do what to body)

Behave like saturated fats

• High blood cholesterol increases the risk of heart disease. 

Phospholipids

One glycerol, two of three attachments occupied by fatty acids and the third group attached to the phosphate group and molecule of choline.

Phospholipids (does)

• Phosphate and choline

• Soluble in water and fat

• Emulsifier used in food production

• found naturally in some food

• cell membranes

• Lecithin (supplement that has no benefits and may cause problems in large doses)

Digestion of fat (where and what)

It occurs in the small intestine (mostly)

Enzymes: 

• Pancreatic lipases 

• some intestinal lipases  (remove fatty acid individually) 

Route of fat once emulsified in small intestine

1) Most are reabsorbed from the small intestine into the blood/recycled back into the liver.

2) Reaches the large intestine, control bacteria growth, can be trapped in fiber (shit out) 

Lipid Absorption

Small molecules digest triglycerides and diffuse into intestinal cells.

Large molecules are emulsified into bile. 

Newly made lipids transported with protein and chylomicrons 

Released into lymphatic system precisely regulated (thoracic duct) 

Types of lipoproteins (largest/least dense - smallest/most dense)

1) Chylomicrons

2) VLDL (low-density lipoprotein)

3) LDL (Low-Density Lipoprotei-

4) HDL (High Density Lipoprotein)

Chylomicrons

Transport lipid intestinal cells to rest of body cells over body remove chylomicrons as they pass (b/c of specialized proteins (receptors)

VLDL (Low-Density Lipoprotein)

Formed by liver. Made to transport lipids to many tissue in body. Made mostly of triglycerides as travels through body becomes cholesterol. 

LDL (Low-Density Lipoprotein)

Becomes LDL made of cholesterol and moved throughout body. Cells use triglycerides, and phospholipids from LDL. Build new membrane, hormones, etc. 

HDL (High-density Lipoprotein)

Made by liver to remove cholesterol from cells + carry back to liver. Prevents plaque buildup and breakup due to anti-inflammatory.

Factors that lower LDL and/or raise HDL

• Healthy body weight

• Monounsaturated or polyunsaturated instead of saturated, fat in diet

• Phytochemicals

• Moderate (if any) alcohol consumption

• Physical activity

Sterols (structure)

Multiple ring structure

Sterol in what

Present in plants, animal food (only in animal food had cholesterol

Important body compounds

• Inhibit cholesterol absorption

Cholesterol 

• Forms plaque, which leads to atherosclerosis 

• Endogenous - Cholesterol made inside body. 

• Animals produce ONLY

• Makes bile acids, hormones, vitamin D 

• Structural component of cells 

Roles of Triglycerides

• Provide energy (9Kcal/g)

• Unlimited storage form energy (adipose tissue)

• Secrete hormone (ex; adipokines) 

• Other functions (Temp. insulation, shock absorption, cell signaling, structural material for cell membranes) 

Essential Fatty Acids

• Linoleic Acid (omega-6 fatty acid) 

• Linolenic Acid (omega-3 fatty acid) 

• Eicosanoids 

Linoleic Acid

• Component of membrane phospholipids

• Makes arachidonic acid 

Linolenic Acid 

• Component of membrane phospholipids 

• Makes EPA and DHA 

Eicosanoids

• Made from arachidonic acid and EPA

• Hormone like

• May oppose each other 

Recommended Intakes of Saturated Fats, trans Fats, and Cholesterol.

• NO RDA or UL for saturated fats or trans fat

• DRI (20-30% daily energy intake from fat) (<10% from saturated fat) (as little trans fat and cholesterol as possible) 

Heart disease

• Lower LDL cholesterol when replacing saturated fats

• Omega-3 fatty acids have several heart health benefits.

Cancer

• Possibly reduce oxidative stress and inflammation

• Reduce cancer-related deaths

Omega-3 supplements

Routine taking: not recommended

• Excessive intake may have negative effects 

• Limit: 3g/day without medical consultation. 

DRI (Linoleic and Linolenic acid)

• Linoleic Acid 5-10% (Omega 6)

• Linolenic Acid 0.6-1.2% (omega 3) 

• No set for EPA or DHA (omega 3, marine source). 

Heart Health

• Type of fat is more important then amount.

• Choose unsaturated (Plants, nuts, olive oil, fish) fat instead of saturated (Animals and tropical) 

Mediterranean Diet

Focused on plant based meals

DASH Diet

(Dietary Approaches to stop Hypertension)

• Based on increasing nutrients that lower BP (K, Mg, fibre, Ca) 

• Decrease harmful nutrients (Saturated fat, sodium, sugar) 

The Mind Diet

(Mediterranean - DASH Diet Intervention for Neurodegenerative Delay)

• Targets brain health, improving cognitive development, decreases Alzheimers risk, heart disease, diabeters and some cancers.