Lecture 6- Lipids(fats) Flashcards
0
Q
Functions of lipids
A
- provide energy: at rest, fasting and during moderate intensity excercise, prolonged excercise
- energy storage
- padding (protection) and insulation
- component of the cell membrane
- synthesizes compounds
- absorption and transport fat-soluble vitamins
- satiety
- flavor and mouthfeel (the texturethat the food has in your mouth
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Q
Lipid molecule
A
- structure C, H, O
- does not dissolve in water
- 3 type of lipids in food:
• triglycerides (TG)
• phospholipids
• sterols
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Q
Triglycerides
A
- three fatty acid molecules • carboxylic acid, COOH, alpha end • methyl, CH3, omega end - one glycerol molecule • glycerol is an alcohol (COH)
3
Q
Fatty acids facts
A
- fatty acids vary by: • chain length • degree of saturation • structure of carbon bonding • variation impact fatty acid properties - TG (and foods) are comprised of a mixture of fatty acids - some fatty acids are essential - some are better or us than others
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Q
Fatty acids: Chain length
A
- short chain FA: fewer than 6 carbons
- medium chain FA: 6-12 carbons
- long chain FA: 14 or more
- shirt and medium FA chains get directly absorbed into circulation, liquid at room temperature
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Q
Fatty acids: degree of saturation
A
- saturated: no double bond
- monounsaturated: one double bind
- polyunsaturated: 2 or more double bond
- mono an poly= UFA (unsaturated fatty acids)
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Q
Fatty acids: structure of C bonding
A
Double vond can be found in:
- cis: kink
• H on same side
- trans: linear
• H on opposite side
- impacts shape and fluidity
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Q
Partially hydrogenated fatty acids (trans fat)
A
What:
- H added under pressure= H opposite side C chain
Why:
- pack= more solid - less prone to become oxidized (rancid)
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Q
Essential fatty acids
A
- 18 C long omega 3&6 are essential
- linoleic acid: omega 6
• most vegetables oils, nut oils - alpha linolenic acid: omega 3
• canola and soybean oil, flaxseed oil, walnuts
• cold water fish oils are a source of EPA and DHA
• omega 3 associated with reduced heart disease
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Q
Essential fatty acids metabolize to….
A
- metabolize to longer FA
- precursors of Eicosanoids
• hormone like properties that regulate cellular functioning (prostaglandins, thromboxanes, leukotrienes)
• “local hormones”
• eisanoids from omega 3s reduce inflammation, blood clotting and acts as vasodialators (favorable, heart healthy) - blood clotting, vasoconstriction/ dilation, inflammation, immune function, and other body process
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Q
Saturated fats
A
- bad
- raises LDL cholesterol and HDL cholestetol
(LDL is really bad, risk factor for a lot of heart disease; HDL is a good thing) - coconut, palm, palm kernel oil, butter, cream, cheese, beef fat, whole milk
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Q
Trans fatty acids
A
- extremely bad
- raise LDL cholesterol, and lowers the the HDL cholesterol
- margarine, crackers, cookies, fried-foods
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Q
Monounsaturated
A
- good
- reduces LDL cholesterol, and POSSIBLELY raises HDL cholesterol
- olive oil, canola oil, peanut oil, cashew nuts
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Q
Polyunsaturated
A
- good (some better than others)
- vegetable oils, fish oils, canola, cottonseed
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Q
Saturated Fat Needs
A
- AMDR: 20-35% Kcals
- general recommendations:
• saturate fat:
~ dietary guidelines: <7%
~ 20 g saturated fat (AHA: 15g)
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Q
Trans fat needs
A
- as low as possible, <2g on a 2000 kcal diet)
• current intake ~ 3% kcals
16
Q
Adequate intake for EFA
A
- linoleic: most meet with no problem
- alpha-linolenic acid: less often met
• men (19-50yrs): 1.6g/d
• women (19-50yrs): 1.1g/d
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Q
Phospholipids structure
A
- glycerol
- 2 fatty acids
- phosphate containing molecule
18
Q
Phospholipids
A
- properties: hydrophobic and hydrophilic ends
- liver makes phospholipids (not essential)
- foods: animal cell membranes, egg yolks, soybeans
19
Q
Function of phospholipids
A
- emulsifier
- part of the cell membrane (phospholipid bilayer)
- helps with fat digestion/ absorption forming micelles (lecithin+ bile salts+ electrolytes= bile)
- helps transport dietary fats in circulation (phospholipid shell)
- in food: emulsifier (mayonnaise, salad dressing)
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Q
Lipids digestion, absorption, and transport
A
- TG are large: hard for lipase to reach
- bile: emulsifies fat, making smaller droplets called micelles
- micelles: water soluble and stay suspended in water based intestinal content
- lipase
- monoglycerides and FFA are absorbed
21
Q
Phospholipids shell of lipoproteins
A
- transports lipids and chilesterol in the blood
- phospholipids shell
- protein
- TG and chol rich interior
22
Q
Sterols
A
- rings of carbon
- found in food and made in body
- cholesterol is most common dietary sterol
• synthesized by animals amd humans, not plants - plants make differeny sterols: actually healthy and may reduce cholesterol
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Q
Cholesterol functions
A
- base structure of
• bile salt precursor; bile salts make bile
• vitamin D
• hormones: testosterone, estrogen
- cell membrane structure
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Cholesterol (a sterol)
- sources: produced by animals= animal product
- non essential: liver makes cholesterol
- health: raises LDL cholesterol
- dietary guidelines:
• <300 mg/d
3oz meat= 100mg
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Lipid digestion
- mouth: not much
- stomach: gastric lipase
- SI:
• CCK: stimulates gall bladder to release bile and pancreatic lipase
• brush border lipase
• bile emulsifies to form micelle
• liases hydrolyze TG into monoglycerides and two free fatty acids
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Lipids in the body: absoprtion and transport
- in the enterocyte
• short and medium chain FA enter capillary and circulation
• long chain FA reassemble into TG
~ combine with cholesterol, phospholipids and small protein
- you now have a lipoprotein called a chylomicron
- chylomicrons enter thr lymph then the blood stream
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4 differeny lipoprotein
- chylomicrons: the least dense b/c it had lots if triglycerides (85%)
- very low density lipoprotein (VLDL): 55% triglycerides
- low density lipoprotein (LDL)
- high density lipoprotein (HDL)
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Fat transport: chylomicrons
- chylomicrons carry dietary triglycerides and chilesterol to cells
- fatty acids and glycerol are taken up by cells
- fatty acids
• used as fuel: especiallyin muscle cells
• resynthesized to TG in adipose cells for storage
- remaining particle (chylomicron remnant) is full of cholesterol travels to the liver
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Fat transport: other players
- cholesterol and endogenous TG (lipogenesis) are packed up and carried by:
- VLDL: delivers TG from the liver to tissue cells
- LDL: delivers cholesterol to tissues
- HDL: removes chilesterol from cells and delivers to liver
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Fat transport: liver
Liver makes TG from excess CHO, alcohol and protein(lipogenesis)
- making fat from nonfat substances
- in liver cells
- far carried in VLDL protein
- glucose, alcohol, and protein all can be made to acetyl CoA to be made into fatty acids
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Very low density lipoprotein (VLDL)
Delivery of dietary an other fatty acids
- loss of fatty acids
- made in liver, carried endogenous TG and chilesterol to blood cells, TG rich
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Intermediate density lipoprotein (IDL)
Delivery of dietary and other fatty acids
| - loss of fatty acids
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Low density lipoprotein (LDL)
Delivery of cholesterol to body cells
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High density lipoprotein (HDL)
Picking up (scavenging) excess cholesterol from cells for delivery back to the liver
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Energy from triglycerides
- fatty and glycerol release into curculation
- glycerol --> pyruvate --> acetyl CoA --> TCA
- FFA --> beta oxidation --> acetyl CoA --> TCA
- electrons carried to ETC
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Beta oxidation
- works on fatty acids from triglycerides
- occurs in the mitochondria
- chopping off two carbons at a time and it connected to conenzyme and made into an acetyl CoA
- the total becomes 8 acetyl CoA
- glucose only makes 2 acetyl CoA
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Carbs assist in fat metabolism: acetyl CoA to the TCA cycle
- acetylc CoA combines with oxaloacetate at the first step in the TCA
- acetyl CoA concentration rise with FA metabolism
- oxaloacetate is maintained by pyruvate, primarily from CHO
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Ketone bodies
- made when there is excess acetyl CoA
• used for energy
• accumulte in blood
• excreted in urine
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Ketones are used for energy
- converted back to acetyl CoA and enter TCA cycle
| - oxaloacetate being formed from glycerol, protein (muscle and organs), CHO as they are available
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Cardiovascular disease
Abnormal condition of the heart and blood vessels
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Atherosclerosis
Narrowing and hardening of blood vessels that supply blood to the heart muscle, brain an other parts if thr body
- when plaque is being built up in your blood vessels
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Coronary heart disease (CHD)
Heart not receiving enough blood
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Stroke
Brain not receiving enough blood
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Dietary factors that promote heart disease
- dietary cholesterol: increase LDL cholesterol
- saturated fat: increase LDL cholesterol
- trans fatty acids: increase LDL C and decrease HDL C
- excess carbs: increase TG, decrease HDL C
- excess energy; increase body fat, increase risk of diabetes
Saturated fat will have a greater affect in thr LDL C than the dietary cholesterol
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Heart healthy diet
- low sat fat (25g daily (10-25g soluble for cholesterol lowering, optional)
- 2-3g of plant sterols, optional
- limit added sugars: <6 tsp for women, and 9 tsp for men
- omega 3 fatty acids
- excercise
- nuts, fruits, and vegetables, and whole grains
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Soluble fiber: health benefits
- lowers cholesterol
- soluble fiber binds with bile salts/acids
• decrease reabsorption of bile salts/acid
• increase hepatic conversion of cholesterol to bile acids
• decrease saturated fat/ cholesterol absorbed= decrease LDL-C
- AHA recommends 10-25g of soluble fiber daily to lower cholesterol
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Plant sterols: sitosterol
- found in plants
- blocks cholesterol absorption by competing with cholesterol space in te micelle
- 2-3g lowers cholesterol by 10%
- fortified margarines
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Olive oil
-reduced oxidation of LDL, inflammation, endothelial dysfunction, blood pressure, and blood clotting
- although probable benefits, potential concerns exist
• calories! (120/1 tbs)
• no independent effect on LDL-C lowering
• no RCTs of isolated MUFA or olive oil on morality or heart disease mortality
• olive oil can be processed an losed functionality
• data in monkeys shows similar extent of atherosclerosis in MUFA rich diet as compared to a diet high in saturated fat
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Foods contributing to the health benefits of a mediterranean diet
- olive oil
- alcohol
- nuts (1oz 5x/week)
- low meat: SF content
- beans and legunes: SF content, fiber, antioxidants, phytochemicals
- fruits and veg: fiber, antioxidants, phytochemicals
- omega 3 fatty acids (crete: purslane, snails, eggs, meat), supported by multiple randomized control trials
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Mega dose vitamins
- mega dose supplements have not shown to be beneficial
- recent studies have shown increase risk of death in high risk people with vit A, E, Bs, beta carotene
• vit E and beta carotene doses were much larger than a multi vit. Supplement
• vit A doses equivalent to multi vit supplement doses
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Should we supplement omega 3s?
- omega 3 fatty acids produce beneficial eicosanoids (reduce inflammation, blood clotting, and acts as vasodilators) and protect against heart disease
- fish consumption= decrease CVD in people without heart disease
- omega 3 capsules studies have decrease CVD in people with a heartattack
- omega 3 capsule have resulted harm in men taking nitrate medication with large fih oul consumption and recents studies hve found no benefit or harm
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Omega 3s are rich in whih foods?
- fish
- canola
- walnuts
- flax
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Should we supplement B vits?
- B6, B12, and folic acid lower homocysteine, a risk marker for heart disease
- supplements in doses higer than a multi-vit have shown to increase the risk of death in high risk people (2 studies)
- eat the food
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Mediterranean diet: how to do it
- eat lots of veg
- have smaller amounts if meat
- eat fish twice a week
- eat healthy fats: canila, walnut, and olive oil
- cook vegetarian meals one a week
- eat fruit for dessert
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The mediterrean diet
- observational data and radomized data show people that eat a mediterranean diet have lower rates of cardiovascular disease
- 28-30% reduced risk of CVD events
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Vegetarian diets
- have reduced CVD, regression of atherosclerosis, reduced mortality
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Types of vegeterian diets
- vegan:a person who eats only plant foods
- lacto-vegetarian: a person who consumes only plant products and dairy products (no eggs)
- ovo-vegetarian:a person who consumes only plant products and eggs
- lacto-ovo-vegetarian: a person who consumes plant products, dairy products and eggs
- pescetarian: a person who consumes plant products but excludes all animal flesh except for seafood products
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Benefits of a vegetarian diet
- nutritents
- cost
- environment
- health
* Lower body weight (usually)
* Heart disease
* Blood pressure
* Digestion, constipation
* Cancer: prostate and colorectal
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Concerns of a vegetarian diet
- B12:naturally found only in animal products
- iron and zinc: meat is a rich source, less bioavailable from plants
- calcium/vit D
- EPA/DHA
- protein
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How to plan for a vegetarian diet
- protein: legumes, soy, nuts, seeds, whole grain
* Complementary proteins: legume + grain/nut/seed
- iron: leafy greens, dried fruit, whole grains, lentils, fortified products
- zinc: whole grains, lentils, seeds
- B12: fortified cereal and soymilk, multivits
- omega 3 fatty acids: plant sources
- calcium: fortified tofu, soymilk, orange juice and cereal, broccoli
* Calcium needs to work with Vit D so that it can work
- Vit D: sun exposure or fortified soymilk amd cereal
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Vegetarian Diet is high in....
- Complext carbs
- Fiber
- Vitamins E and C and folic acids
- Carotenoids
- Phytochemicals
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vegetarian diet is low in (usually)...
- Calories
- Saturated fat
- Cholesterol
