Fats Flashcards
What are the 3 types of dietary fats?
Triglycerides (95% of fat)
Phospholipids
Sterols (5% of fats with phospho.)
What are the 3 fatty acid families
Saturated
MONO-unsaturated
POLY-unsaturated
Which fatty acid has double bonds?
unsaturated
Triglycerides
glycerol + 3 fatty acids
glycerol is the 3-carbon backbone of triglycerides that holds the fatty acids together
Phospholipids
Glycerol + 2 fatty acids + phosphorous
phosphorous makes the phospholipid water soluble, so they emulsify fat
responsible for cell membrane structure
Sterols
large complicated molecules, interconnected rings
form bile, vitamin d, steroid hormones, and cholesterol
Saturated fats
animal fats
exception: tropical plant fats (pam kernel oil, coconut oil)
Unsaturated fats
plants!
exception: Fish.
Where do we get the majority of our total saturated fat?
Animal sources, and junk food (ice cream, cakes, cookies)
Mouth’s role in digestion of lipid
TRIVIAL
Stomach role in lipid digestion
fat floats, which delays gastric emptying
Small Intestine role in lipid digestion
In the SI, fat is emulsified by BILE
Where is bile stored
GALLBLADDER
Where is bile made
LIVER
What happens to emulsified fats
Lipases from the pancreas break the fats into glycerol, individual fatty acids, and monoglycerides
Does anything break up triglycerides and phospholipids?
YES. Intestinal lipases similiar to pancreatic lipases.
How are small digested lipid products absorbed?
Small products can go directly into the blood stream and are taken to the liver
How are large digested lipid products absorbed?
Larger products are reformed into triglycerides, and incorporated into CHYLOMICRONS and go into the lymph system
Describe the structure of lipoproteins
Surface: Phospholipids with embedded proteins
Core: Cholesterol and Triglycerides.
What are the 4 types of lipoprotein?
- Chylomicron
- vLDL
- LDL
- HDL
Describe the relative composition difference between LDL and HDL
LDL: is low-density lipoprotein, and it has more lipid and less protein.
HDL: is high-density lipoprotein, and it has more protein and less lipid.
What is the absolute composition difference between LDL and HDL
HDL has less of everything per particle.
How long do chylomicrons spend circulating in the blood?
Minutes
Describe chylomicron process
Created in intestines, secreted into blood through subclavian vein, drops of triglycerides in adipose tissues, muscle. Eventually, chylomicron remnant with just dietary cholesterol goes back to liver.
What happens to chylomicron remnants in the liver?
It’s broken down.
vLDL circulation process
Same as chylomicron, but some gets cleared by the liver. Some that continues to lose TG and surface protein is then converted to LDL.
How long does vLDL circulation take
MINUTES.
Why do Chylomicron and vLDL get cleared so quickly from the blood? (within minutes)
They have a very effective protein on their surface (apolipoprotein E) that activates a receptor on cells.
When vLDL becomes an LDL, the effective protein (apo E) is lost which is why
LDL takes DAYS to circulate in the blood.
only apolipoprotein B is still with LDL and it only weakly activates cell receptors.
Where does a lot of the LDL go?
to the liver! receptors for LDL work slowly on LDL.
What happens when LDL particles work their way into the lining of blood vessels
Cholesterol contributes to PLAQUES in the arteries that create blockages, and eventually lead to heart disease
Try to describe how HDL particle gets formed
Gets protein from the liver, and cholesterol from cells all over the body.
What does HDL do? Describe reverse cholesterol transport
HDL particle delivers cholesterol FROM the cells of the body TO the liver.
Then it goes back for more.
Do we know how HDL is cleared from circulation?
Nope not yet, it’s unclear.
Why doesn’t dietary cholesterol contribute substantially to cholesterol in the blood?
The liver makes ~1000mg/day, and only about ~50% of cholesterol in the diet is absorbed, dietary/absorbed cholesterol is delivered to the liver, when the liver receives no dietary cholesterol it makes ~1000mg/day, so when the liver gets some dietary cholesterol it makes that much less total for a day.
For a lot of people, dietary cholesterol makes no difference unless its
OVER 2000 mg/day.
How does dietary saturated fat impact blood cholesterol?
High dietary saturated fat DOWNREGULATES the LDL receptor in the tissues that take it up.
This makes it even harder to clear LDL from the blood, making the LDL cholesterol levels in the blood rise.
What happens when we replaced saturated fat in the diet with unsaturated fat?
LDL receptors are UPREGULATED, and blood cholesterol levels decrease.
What’s the moot point?
Most sources of saturated fat are also sources of cholesterol, except for eggs (high C, low SF), shell fish (high C, low SF), and butter (low C, high SF)
What does the liver do
Makes bile
What does bile do
Emulsifies fat
What does the gall bladder do
It stores bile until needed
What does the bile duct do
Takes bile to the small intestine
Reaven Study
Intervention study, dietary cholesterol had no detectable change in LDL cholesterol, foods & chronic disease risk factors.
Fat Cells
Membrane can enlarge substantially to accommodate more fat storage
Function of Fat
- Main storage form of energy
- Secrete hormones and produce enzymes
- Shock absorbers
- Insulation
- Cell Membranes
- Poly-unsats have role in metabolic regulation
- Cholesterol is converted to bile acids, sex hormones, vitamin D, and cell membranes
How are fatty acids made from carbohydrates
Glucose is broken down, and the fragments can provide energy for tissues if needed, but if not needed the fragments can be reassembled into fatty acid chains.
Recommendations for fat
Under 30% of calories from total fat.
Recommendations for saturared fat
Under 10% of calories from saturated fat.
Theres no dietary requirement for saturated fat, body makes it on a daily basis.
What are some strategies for lowering LDL cholesterol
Increase Fiber
Decrease Sat. Fat and cholesterol
Plant sterols
Weight loss
Recommendation for cholesterol
Under 300mg/day, liver can accommodate much more than in regulating cholesterol balance
What are the essential polyunsaturated fatty acids
Linoleic Acid
Linolenic Acid
Omega-3 fats are always
polyunsaturated!
What’s the difference between omega-3 and omega-6
Position of the last double bond.
Omega-6 double bond is 6 carbons back from end carbon. Same with omega-3, 3 carbons back.
What’s the majority of polyunsaturated fat in our diets
Omega-6
Linoleic Acid
Omega-6, from plant based foods
Most vegetable/plant sources of fat (safflower, sunflower oil, walnuts, etc)
Linolenic Acid
Omega-3, from plant based foods
Few vegetable/plant sources of fat (flax is the single best sources, walnuts and soy yes but more omega-6)
What’s the DRI for the ratio of omega-6 to omega-3?
It’s controversial, but the DRI says a 10:1 ratio
EPA and DHA have no specific recommendation.
What’s the difference in structure between HDL and LDL
None!!!
It’s not the cholesterol, it’s the particle that carries it.
Is there a recommended amount of fish oil?
No DRIs, so it’s okay for landlocked people!
Can our bodies change fatty acids?
YES.
We can make them longer and also add double bonds.
Can our bodies turn omega 3 into omega 6?
No, once an omega 6, always an omega 6.
What are eicosanoids?
Hormone-like molecules used by the body to regulate metabolism?
4 families
Conversion of omega-3s.
Phospholipids
Found in the cell membrane of various cells.
Phospholipids are preferably
long chain, unsaturated fatty acid Arachidonic acid, EPA, and DHA (made by the body)
Why is omega-3 fatty acid potentially healthy
due to their hormone-like effects
What is linoleic acid converted into
arachidonic acid
What is linolenic acid converted into
EPA (inefficiently) and some EPA can be converted into DHA (inefficiently)
Since conversion of EPA and DHA is inefficient, the benefit of them is realized if
they are consumed in the diet!
For people with elevated triglycerides
3-4 grams/day of fish oil can substantially lower triglycerides
GISSI study in italy on fish intake
10% reduction in heart disease for fish lovers, barely statistically significant, fell into nutrient and chronic disease category, INTERVENTION.
Meta-analysis for omega-3
Nutrients & Chronic Disease; Interventions; Insufficient evidence of a secondary prevention effect among patients with a history of cardiovascular disease
Hydrogenated Vegetable Oil
Start with plant oil (unsaturated) and add H+ atoms making the fat saturated.
Fat becomes more solid, used for frying, spreading, and longer shelf life.
EX: Frosting, Butter.
Trans Fatty Acids
Found naturally in small amounts in dairy and meat.
Main dietary source is byproduct of hydrogenation process, unsaturated fatty acids change their shape. Makes a previously non-linear fatty acid STRAIGHT.
Worse for us than saturated fats. Primarily found in junk foods.
Fat Replacers
Unhealthy bc if your body can’t absorb it, you’ll probably poop it out!
EX: Olestra.
What are strategies for raising HDL cholesterol
- Weight-loss/exercise
- Decrease elevated triglycerides; decreased carb intake (junk-food carbs)
- Moderate alcohol intake
- Oral contraceptives or hormone replacement therapy
What fatty acids do we not get much of in our diet?
We get very little arachidonic acid in our diet, so body makes it from linoleic acid.
What are the symptoms of essential polyunsaturated fatty acids deficiencies
Reproductive Failure
Skin Abnormalities
Kidney/Liver Disorders
Retarded growth in infants and children
How can you differentiate between animal and plant saturated fats?
Animal fats are predominantly C16 & C18, where as plants are C12 & C14.
How does plant based saturated fat impact LDL and HDL
It causes both of them to raise
How do animal based saturated fats impact LDL and HDL
Lowers HDL and raises LDL
Which fatty acids are we recommended to get from our diet?
We inefficiently make EPA and DHA so we should consume it.
What are the benefits of omega-3s?
Increased blood thinning, increased vasodilation, decreased triglyceride, and decreased inflammation
