2.25.08 Lipids

Lipids ch. 5

Lipids are organic compounds. They contain C, H, & O, but the difference between CHO and lipids is that lipids have many more C & H relative to O.

1. Triglycerides
2. Phospholipids
3. Sterols


Triglycerides

Commonly known as "fat"
95% of dietary lipids
Structure: Glycerol attached to three Fatty Acids (FA). Glycerol is treated like CHO in the liver.

There are three types of FA. The three FA attached to the glycerol can be any combination of the three. (Saturated, monounsaturated, polyunsaturated)


Glycerol: 3 carbon chain
All FA have an even # of Carbons.

Canola Oil
FA are monounsaturated usually and saturated FA are least common in canola oil

Saturated FA
Saturated with H
Sources: red meat, milk, butter, lard, coconut oil, palm oil (tropical oils)
usually solid at room temp
assoc w/ increased risk of CVD, Colon cancer, prostate cancer, breast cancer
assoc w/ inc. blood cholesterol
assoc w. inc. levels of LDL

NO reason to consume saturated FA

Monounsaturated FA
contain one double bond (lose 2 H)
Sources: avocado, olive oil, peanut oil, canola oil
fewer health risks
assoc w/ lower blood cholesterol
No effect on HDL

Polyunsaturated FA
Contains 2 or more double bonds
gets rid of 2 H per double bond
Sources: corn oil, safflower oil, soybean oil (not as easy to cook with)
Usually liquid at room temp.
assoc w/ decreased blood cholesterol
assoc w/ Inc. HDL
essential PUFA- Need from diet because we can't make it (polyunsat. FA)
1. Omega 3 FA
2. Omega 6 FA

Omega 6
Linoleic Acid
Sources: Corn oil, safflower oil, soybean oil, plant sources ONLY
maintains structure and function of cell membranes
symptoms of deficiency: skin lesions

Omega 3
Linolenic Acid
Canola and soybean oil, wheat germ, walnuts, plant sources ONLY
precursor found in fish-can be made into O3 by the body with the same benefits
active in eyes and brain function
Deficiencies: visual problems, subtle neurological problems, skin rash, liver and kidney problems
2% of total kcals for adequate intake of essential FA.

Phospolipids

Comprise 3% of dietary lipids
nonessential
emulsifiers- promotes mixing of 2 liquids that are not mutually soluble.
part of cell membrane structure.
Sources: eggs, liver, soybeans, wheat germ, peanuts
lecithin

Sterols
comprise 2% of dietary lipids
nonessential
vital to life: bile acids, sex hormones, vitamin D, majority of cell membrane
Forms deposits on artery walls
Sources: meat, egg yolks, fish, chicken, dairy, animal sources ONLY

Recommendations for decreasing Total Cholesterol and LDL
(in order of best to least affective)
1. Reduction of saturated fat
2. reduction of body fat
3. increase in dietary CHO and fiber (esp. fruit, veggies, beans, oat products)

Recommendations for Increasing HDL
In order
1. Aerobic exercise
2. Weight (fat) reduction
3. Smoking cessation
4. Moderate alcohol consumption

Fate of Dietary Triglycerides (fats)
When you eat fat, usage is prioritized by the body's needs
pkt. pg. 6

1. Used for energy
2. Used to produce: nonessential FA (regulates blood clotting, blood pressure, immune response), Cholesterol, phospholipids, Fat soluble vit. (ADEK, Reg 10 of total kcals in form of fat to ensure absorption of these).
3. Storage (as fat): Visceral (internal), muscle triglycerides, subcutaneous.

Digestion: During beta oxidation, the body breaks off the terminal two C molecules and attaces them to CoA and sends that through the Kreb's Cycle. As it needs more energy, it will repeat this cycle. This is why the C chains in FA are in even #s.

In a 15% body fat male:
Fat storage: adipose (100,000 kcals), muscle triglycerides (2800 kcals)

The place you store fat the easiest is the hardest to lose from. There is no spot usage of fat in visceral storage.

Three Stores:

1. In blood-FFA (Free Fatty Acids)
2. Viscerally/Internal/Subcutaneous
3. Muscle triglycerides

Blood FFA are limited so visceral fat breaks down to supply blood with more FFA.
Muscle triglycerides are site specific. They are predominently used during high I workouts. Less I to lose visceral fat.

Hydrogenation of Fats

At room temp:
1. Makes fats more solid
2. Increased shelf life (decreases rancidity)
3. Adding H to C=C
4. Increases saturation
5. Increases risk for CVD

Partially hydrogenated
- some C=C still remain but the configuration changes from CIS to TRANS isomers
Naturally, the H's are on the same side but trans isomers have their H's on opposite sides of the double bonded Carbons. These are foreign to the body so we are unable to metabolize them correctly.
Trans isomers are NOT found naturally
recent research indicates health risks assoc w/ trans isomers
at least 7% or less overall kcals should come from Trans fat

pg. 8 (Strategies for Lowering Fat Intake)-READ! There will be a test question from this page.