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