Lecture 6- Lipids(fats) Flashcards
Functions of lipids
- 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
Lipid molecule
- structure C, H, O
- does not dissolve in water
- 3 type of lipids in food:
• triglycerides (TG)
• phospholipids
• sterols
Triglycerides
- three fatty acid molecules • carboxylic acid, COOH, alpha end • methyl, CH3, omega end - one glycerol molecule • glycerol is an alcohol (COH)
Fatty acids facts
- 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
Fatty acids: Chain length
- 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
Fatty acids: degree of saturation
- saturated: no double bond
- monounsaturated: one double bind
- polyunsaturated: 2 or more double bond
- mono an poly= UFA (unsaturated fatty acids)
Fatty acids: structure of C bonding
Double vond can be found in:
- cis: kink
• H on same side
- trans: linear
• H on opposite side
- impacts shape and fluidityPartially hydrogenated fatty acids (trans fat)
What:
- H added under pressure= H opposite side C chain
Why:
- pack= more solid - less prone to become oxidized (rancid)
Essential fatty acids
- 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
Essential fatty acids metabolize to….
- 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
Saturated fats
- 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
Trans fatty acids
- extremely bad
- raise LDL cholesterol, and lowers the the HDL cholesterol
- margarine, crackers, cookies, fried-foods
Monounsaturated
- good
- reduces LDL cholesterol, and POSSIBLELY raises HDL cholesterol
- olive oil, canola oil, peanut oil, cashew nuts
Polyunsaturated
- good (some better than others)
- vegetable oils, fish oils, canola, cottonseed
Saturated Fat Needs
- AMDR: 20-35% Kcals
- general recommendations:
• saturate fat:
~ dietary guidelines: <7%
~ 20 g saturated fat (AHA: 15g)
Trans fat needs
- as low as possible, <2g on a 2000 kcal diet)
• current intake ~ 3% kcals
Adequate intake for EFA
- linoleic: most meet with no problem
- alpha-linolenic acid: less often met
• men (19-50yrs): 1.6g/d
• women (19-50yrs): 1.1g/d
Phospholipids structure
- glycerol
- 2 fatty acids
- phosphate containing molecule
Phospholipids
- properties: hydrophobic and hydrophilic ends
- liver makes phospholipids (not essential)
- foods: animal cell membranes, egg yolks, soybeans
Function of phospholipids
- 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)
Lipids digestion, absorption, and transport
- 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
Phospholipids shell of lipoproteins
- transports lipids and chilesterol in the blood
- phospholipids shell
- protein
- TG and chol rich interior
Sterols
- 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
Cholesterol functions
- base structure of
• bile salt precursor; bile salts make bile
• vitamin D
• hormones: testosterone, estrogen
- cell membrane structureCholesterol (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
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
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
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)
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
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
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
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
Intermediate density lipoprotein (IDL)
Delivery of dietary and other fatty acids
- loss of fatty acids
Low density lipoprotein (LDL)
Delivery of cholesterol to body cells
High density lipoprotein (HDL)
Picking up (scavenging) excess cholesterol from cells for delivery back to the liver
Energy from triglycerides
- fatty and glycerol release into curculation
- glycerol –> pyruvate –> acetyl CoA –> TCA
- FFA –> beta oxidation –> acetyl CoA –> TCA
- electrons carried to ETC
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
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
Ketone bodies
- made when there is excess acetyl CoA
• used for energy
• accumulte in blood
• excreted in urine
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
Cardiovascular disease
Abnormal condition of the heart and blood vessels
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
Coronary heart disease (CHD)
Heart not receiving enough blood
Stroke
Brain not receiving enough blood
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
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
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
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
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
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
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
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
Omega 3s are rich in whih foods?
- fish
- canola
- walnuts
- flax
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
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
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
Vegetarian diets
- have reduced CVD, regression of atherosclerosis, reduced mortality
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
Benefits of a vegetarian diet
- nutritents
- cost
- environment
- health
- Lower body weight (usually)
- Heart disease
- Blood pressure
- Digestion, constipation
- Cancer: prostate and colorectal
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
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
Vegetarian Diet is high in….
- Complext carbs
- Fiber
- Vitamins E and C and folic acids
- Carotenoids
- Phytochemicals
vegetarian diet is low in (usually)…
- Calories
- Saturated fat
- Cholesterol
