LIPIDS Lipids: Definition A family of compounds soluble in organic compounds but not in water. 3...
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Transcript of LIPIDS Lipids: Definition A family of compounds soluble in organic compounds but not in water. 3...
LIPIDS
Lipids: Definition
A family of compounds soluble in organic compounds but not in water.
3 classes of lipids: Triglycerides: 95 % of lipids in foods Phospholipids: e.g..: lecithin Sterols: e.g..: cholesterol
Lipids: Fats and Oils
Fats: those lipids that are solid at room temperature(70 degrees F) beef fat, pork fat, etc...
Oils: those lipids that are liquid at room temperature(70 degrees F) vegetable oils
Lipids: Functions
Provide Calories: 9 Cal/ gram Lipids carry fat soluble vitamins in
food and in body Vitamins A, D, E, K
Provide building material for body adipose tissue, components of cell
membranes, many hormones, nerve coverings
Lipids: Functions (cont.)
Thermal insulation 1/2 of fat is subcutaneous
Protection for organs the rest of fat surrounds organs and
protects them Essential Fatty Acids: Linoleic and
Linolenic Acids abundant in plant oils and fish oils
Triglycerides: Glycerol + 3 Fatty Acids Glycerol: similar to sugar 3 carbons long Fatty Acids: Can differ in two ways
Degree of saturation Saturated: 0 double bonds Monounsaturated: 1 double bonds Polyunsaturated: 2 or more double bonds
Chain length: how many carbons long it is 4-6 Carbons: short chain 8-12 Carbons: medium chain 14+ Carbons: long chain
Saturated Fatty AcidsRaises blood cholesterolSolid at room temperatureHigh in animal fatsTropical plant fats
coconut oil, palm oil, cocoa oil
Mono Unsaturated Fats Lowers blood cholesterol Lowers LDL - cholesterol No effect on HDL - cholesterol Liquid at room temperature Olive oil, canola oil, peanut oil
Polyunsaturated FatsLowers LDL-cholesterolLowers HDL-cholesterolVegetable oilsFish oils
Essential Fatty Acids
PUFA’s required in diet Omega-6 PUFA’s - Linoleic acid
Omega-3 PUFA’s - Linolenic acid
3-6 g/day (1 tsp veg. oil)
Essential Fatty AcidsDeficiency SyndromeRare fat malabsorption in infants
Dermatitis, hair loss, poor wound healing
Essential Fatty Acids Functions
Component of phospholipids in cell membranes
Synthesis of Eicosanoids Prostaglandins Leukotrienes
Potent hormone-like chemicals
Eicosanoid FunctionsRegulate smooth muscle contractions
Regulate blood pressure
Regulate blood clotting
Dietary Effects on EicosanoidsOmega-6 PUFA (Veg Oils)
increase blood clotting increase blood pressure increases risk of heart disease
Dietary Effects on Eicosanoids Omega -3 PUFA’s (fish oils,
canola) decreases blood clotting decreases blood pressure decreases blood viscosity decreases risk of heart
disease
Omega-3 fatty acids & heart disease Prevent cardiac arrhythmias Act as antithrombotic agents Inhibit growth of atherosclerotic
plaques Act as antiinflammatory agent Lower VLDL and increase HDL Omega 3s could cut risk of second
heart attack
% Total polyunsaturated fat
0 50 100 150
Canola oil
Avocado
Peanuts
Walnuts
Beef
Trout
Salmon
Omega 3
Omega 6
Omega 3 Animal Sources Shellfish, sardines, albacore
tuna, salmon, mullet, herring, trout, mackerel and anchovies
Omega 3 Plant Sources Canola oil, soybeans, flaxseed,
walnuts, wheat germ
Hydrogenation of Fatty Acids Polyunsaturated fatty acids subject to
oxidative rancidity PUFAs are also liquid at room temperature Hydrogenation makes them more saturated
This makes them resistant to oxidative rancidity This makes them solid at room temperature this also increases the amount of Trans-fatty
acids
Hydrogenation: trans-fatty acids Trans-fatty acids are mistakes
that happen with hydrogenation Increase risk of heart disease Elevate LDL-cholesterol and may lower
HDL-cholesterol What is better, butter or margarine? MedlinePlus
: Trans fat alternative may have its own problems
CIS – TRANS Configuration
Top Ten “Trans Fat” Foods Spreads Packaged foods Soups Fast Food Frozen Food Baked Goods Chips and Crackers Breakfast Food Cookies and Candy Toppings and DipsNo trans fat in new Crisco formula - Diet & Nutrition -
MSNBC.com
Which of the following statements regarding hydrogenation is FALSE?1. It creates trans
fats2. It is the process
of adding hydrogen bonds
3. It creates a heart healthy product
81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
101 102 103 104 105 106 107 108 109 110
Triglycerides: Fatty Acids
Rule of thumb: the more saturated, the more solid it is at room temperature Also the longer the Fatty Acid, the
more solid at room temperature Safflower oil is mostly (74%) PUFA:
liquid at room temperature Beef fat is mostly (48%) Saturated:
solid at room temperature
Digestion of Fats As fat enters the small intestine
Bile is secreted from the gall bladder into the small intestine
Bile is produced by the liver and stored in the gall bladder
Bile disperses fat into smaller fat droplets Pancreatic enzymes break fat into 2
separate fatty acids and a monoglyceride
Digestion of Fats Fatty acids are arranged as
lipoproteins for absorption and transport.
Chylomicron: A lipoprotein produced by cells lining the small intestine. Composed of fatty acids surrounded by
phospholipids and proteins Soluble in water
Digestion of Fats Chylomicrons are absorbed by
cells of the small intestine, then Travel through the lymphatic system Transferred to the bloodstream
Short- and medium-chain fatty acids are absorbed more quickly since they are not arranged into chylomicrons.
Digestion of Fats Triglycerides in the chylomicrons must
be disassembled by lipoprotein lipase before they can enter body cells.
After entering body cells, triglycerides can be Used immediately for energy Used to make lipid-containing compounds Stored in liver and muscle cells
Phospholipids:
Similar to triglycerides Glycerol + 2 fatty acids and 1 phosphate
containing group. e.g..: lecithin in egg yolks: emulsifies fat with
water(vinegar) in a permanent emulsion in mayonnaise
Not an essential nutrient. Can be made in the body.
http://telstar.ote.cmu.edu/Hughes/tutorial/cellmembranes/
Phospholipid Structure
Sterols
Cholesterol: most recognized sterol not an essential nutrient: can be made in
the body from fats Many hormones are also sterols
e.g..: estrogen: a predominantly female hormone is similar to cholesterol
Vitamin D is a sterol is made from dehydro-cholesterol in skin
with sun exposure
Cholesterol absorption
Serum cholesterol: Lipid Profile Total serum cholesterol =
cholesterol found in several particles in the blood. Particles are called lipoproteins
chylomicrons: fat and cholesterol from digestion
very low density lipoproteins: VLDL; fat and cholesterol assembled in liver and sent into blood
Serum cholesterol: Lipid Profile
low density lipoproteins: LDL; fat and cholesterol left over as VLDL drops off triglycerides to cells
Carries cholesterol towards tissues such as heart arteries
high levels increases risk of atherosclerosis
© 2004, 2002 Elsevier Inc. All rights reserved.
Natural Progression of AtherosclerosisNatural Progression of Atherosclerosis
(From Harkreader H. Fundamentals. Philadelphia: W.B. Saunders, 2000)
Coronary Artery Disease
Lipid Profile
Types of lipoproteins: high density lipoproteins (HDL):
made in liver but function is to carry cholesterol back from tissues such as heart to the liver where liver can repackage or use for other purposes
low HDL-cholesterol: increases risk of heart disease
high HDL-cholesterol is protective against heart disease: taking away substances that can block heart arteries
Serum LevelsOptimal High Very high
Total <200 200-239 >240
LDL <100 130-159 >190
HDL >60
Triglycerides
<100 150-199 >500
Recommendations Total fat intake 20-35% of energy Decrease saturated fat to less than
7% of calories Keep trans fats low Fish twice/week Dietary cholesterol under 200 mg
Recommendations Dietary fiber 20-30 grams/day
10-20 grams soluble fiber Maintain normal blood glucose Eat throughout the day Maintain a healthy body weight Maintain an active lifestyle
Fat Sources Visible fat
Butter, margarine, shortening, cooking oils, etc
Cream cheese, sour cream, salad dressings
Hidden fat Biscuits, peanuts, animal products Cooking methods
Fat Replacers Simplesse: milk and egg protein
based FDA approved for ice cream desserts
and dairy products Not heat stable, can’t be used in
heated products 1 to 2 Cal/gram vs 9 Cal/gram in fat
So a saving of Calories occurs
Fat Replacers Olestra (Olean, sucrose polyester)
Fatty acids attached to sucrose with ester bonds
0 Calories Heat stable; foods requiring cooking can use
this product Fat free French fries, potato chips
FDA approved but problems may exist fat soluble vitamins lost
Attach to olestra and end up in feces
Olestra
Olestra Problems Digestive problems
may cause diarrhea, cramping, gas probably not health problems but
unpleasant Other losses
Fat Soluble Vitamins Phytochemicals in foods
lycopene, a relative of vitamin A may be lost lycopene related to eye health and reduced risk of
degeneration of eyesight
Fat Replacers: Caprenin Approved for use in candies triglyceride with glycerol and 3 fatty
acids fatty acids are unusual
capric (C8:0) caprylic(C10:0) behenic(C22:0)
Not as well absorbed; only 5 Cal/gram vs 9
Fat Replacers: Caprenin Calorie savings
Old Milky Way Light: 190 Cal and 45 Cal from fat
Regular Milky Way 280 Cal and 95 Cal from fat