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Title: Chapter 5 The Lipids: Fats, Oils, Phospholipids,


1
Chapter 5 The Lipids Fats, Oils, Phospholipids,
Sterols
  • Basic Nutrition
  • 10/1/07
  • Dr. Fralinger

2
Introduction
  • Lipids
  • Family of organic compounds soluble in organic
    solvents but not in water
  • Include triglycerides, phospholipids, and sterols
  • Cholesterol
  • Member of sterols
  • Soft, waxy substance made in the body
  • Fats
  • Lipids solid at room temp.
  • Oils
  • Lipids liquid at room temp.

3
Introduction
  • CVD
  • Disease of the heart and blood vessels
  • Triglycerides
  • Chief form of fat in foods and the human body
  • Phospholipids
  • Similar to triglycerides, except have a
    phosphorous containing acid
  • Present in all cell membranes

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5
Introduction
  • Lecithin
  • Phospholipid manufactured by the liver and found
    in many foods
  • Major constituent of cell membranes
  • Sterols
  • One of the 3 classes of dietary lipids
  • Structure similar to cholesterol

6
Usefulness of Fats in the Body
  • Fat is the bodys chief storage form for the
    energy from food eaten in excess of need

Fats in the body Fats in food
Energy stores Nutrient
Muscle fuel Energy
Emergency reserve Transport
Padding Raw materials
Insulation Sensory appeal
Cell membranes Appetite
Raw materials Satiety
Texture

7
Usefulness of Fats in the Body
  • Fat vs. Glucose
  • Glucose stored as glycogen
  • Glycogen holds lots of water, so its bulky and
    heavy ? body cant store enough to provide energy
    for very long
  • Fats pack tightly w/o water and can store much
    more energy in a small space
  • Fats provide more than twice the energy of carbs,
    so efficient storage form of energy

8
Usefulness of Fats in the Body
  • Essential fatty acids
  • Fatty acids that the body needs but cannot make
    in amounts sufficient to meet physiological needs
  • Serve as raw materials for body to make molecules
    required

9
Usefulness of Fats in the Body
  • Lipids not only serve as energy reserves but also
  • cushion vital organs
  • protect body from temp. extremes
  • carry fat-soluble nutrients phytochemicals
  • serve as raw materials
  • provide major component of cell membranes

10
Usefulness of Fats in the Body
  • Lipids
  • provide more energy per gram than carbohydrate
    and protein
  • enhance the aromas and flavors of foods
  • contribute to satiety after a meal

11
Triglycerides Fatty Acids Glycerol
  • Fatty acids
  • Organic acids composed of carbon chains of
    various lengths
  • Glycerol
  • Organic compound three carbons long
  • Serves as the backbone for triglycerides
  • Body combines 3 fatty acids w/ one glycerol to
    make a triglyceride, the storage form of fat

12
Saturated vs. Unsaturated Fatty Acids
  • Saturated fatty acid
  • Carries max possible of hydrogen atoms (no
    points of unsaturation)
  • Point of unsaturation
  • Site in a molecule where the bonding is such that
    additional hydrogen atoms can easily be attached

13
Saturated vs. Unsaturated Fatty Acids
  • Unsaturated fatty acid
  • Lacks some hydrogen atoms and has one or more
    pts. of unsaturation
  • Monounsaturated fatty acid
  • Contains one point of unsaturation
  • Polyunsaturated fatty acid
  • Has two or more pts. of unsaturation

14
Saturated vs. Unsaturated Fatty Acids
  • Saturated fats
  • Triglycerides where most fatty acids are
    saturated
  • Trans fats
  • Contain unusual fatty acids (trans f.a.) formed
    during processing

15
Saturated vs. Unsaturated Fatty Acids
  • Monounsaturated fats
  • Triglycerides where most of the fatty acids have
    one pt. of unsaturation
  • Polyunsaturated fats
  • Triglycerides where most of the fatty acids have
    two or more pts. of unsaturation

16
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17
Saturated vs. Unsaturated Fatty Acids
  • Therefore, fatty acids are energy-rich carbon
    chains that can be
  • saturated (filled with hydrogens)
  • monounsaturated (w/ one pt. of unsaturation)
  • polyunsaturated (w/ more than one pt. of
    unsaturation)
  • Degree of saturation of the fatty acids in a fat
    determines the fats softness or hardness

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19
Phospholipids and sterols
  • Phospholipids
  • Soluble in water and fat
  • Can serve as an emulsifier
  • substance that mixes w/ fat and water
  • permanently disperses fat in water, forming an
    emulsion

20
Phospholipids and sterols
  • Emulsification
  • Process of mixing lipid with water by adding an
    emulsifier
  • Phospholipids help fats travel back and forth
    across the lipid-containing membranes of cells
    into the watery fluids on both sides

21
Phospholipids and sterols
  • Sterols
  • Cholesterol is an example
  • Serves as the raw material for making bile
  • Bile
  • Another emulsifier important to digestion
  • Made by the liver from cholesterol and stored in
    the gallbladder
  • allows enzymes to split fatty acids from glycerol
    for absorption

22
Phospholipids and sterols
  • Sterols play roles as part of bile, vitamin D,
    the sex hormones, and other important compounds

23
Digestion and Absorption of Fats
  • In the stomach, fats separate from other food
    components
  • In the small intestine, bile emulsifies the fats,
    enzymes digest them, and the intestinal cells
    absorb them
  • Monoglycerides
  • Products of the digestion of lipids
  • Consist of glycerol molecules with one fatty acid
    attached

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25
Transport of Fats
  • Glycerol and shorter-chain fatty acids pass
    directly through the cells of the intestinal
    lining into the bloodstream where they travel
    unassisted to the liver
  • Large lipids are incorporated into chylomicrons
    for transport in the lymph and blood
  • Blood and other body fluids are watery, so fats
    need lipoproteins to carry them in these fluids

26
Transport of Fats
  • Lipoproteins
  • Clusters of lipids associated with protein
  • Serve as transport vehicles for lipids in blood
    and lymph
  • Major classes are the chylomicrons, the VLDL, the
    LDL, and the HDL

27
Transport of Fats
  • Chylomicrons
  • Clusters formed when lipids from a meal are
    combined with carrier proteins in the cells of
    the intestinal lining
  • Transport food fats through the watery body
    fluids to the liver and other tissues

28
How can I use my stored fat for energy?
  • Fat depots-
  • Muscles
  • Breasts
  • Insulating fat layer under the skin

29
How can I use my stored fat for energy?
  1. When a persons body starts to run out of
    available fuel from food, begins to retrieve
    stored fat to use for energy
  2. Fat cells respond to the call for energy by
    dismantling stored fat molecules and releasing
    fat components into the blood

30
How can I use my stored fat for energy?
  • 3. Cells break them down further into small
  • fragments
  • 4. Each fat fragment is combined with a
  • fragment derived from glucose
  • 5. Energy-releasing process continues,
  • liberating energy, CO2, and water

31
How can I use my stored fat for energy?
  • Therefore, to use the energy stored as fat, must
    create a greater demand for it in the tissues by
    decreasing intake of food energy, increasing the
    bodys expenditure of energy, or both
  • When low on fuel, the body draws on its stored
    fat for energy carbs are necessary for the
    complete breakdown of fat

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33
Dietary Fat, Cholesterol, and Health
  • Choosing a diet too high in saturated fats or
    trans fats invites the risk of heart and artery
    disease (CVD)
  • Cancer
  • Obesity

34
Lipoproteins and Heart Disease Risk
  • The chief lipoproteins are chylomicrons, VLDL,
    LDL, and HDL
  • Blood LDL and HDL concentrations are among the
    major risk factors for heart disease

35
Lipoproteins and Heart Disease Risk
  • VLDL
  • Carry triglycerides and other lipids made in the
    liver to the body cells for their use
  • LDL
  • Transport cholesterol and other lipids to the
    tissues
  • Made from VLDL after they have donated many of
    their triglycerides to body cells
  • HDL
  • Critical in the process of carrying cholesterol
    away from body cells to the liver for disposal

36
Lipoproteins and Heart Disease Risk
  • The more of the following factors present, the
    more urgent the need for changes in diet, etc. to
    reduce heart disease risk
  • High blood LDL cholesterol
  • Low blood HDL cholesterol
  • High blood pressure (hypertension)
  • Diabetes (insulin resistance)
  • Obesity
  • Physical inactivity
  • Cigarette smoking
  • An atherogenic diet
  • High in sat. fats, including trans fats
  • Low in veggies, legumes, fruit, and whole grains

37
What does food cholesterol have to do with blood
cholesterol?
  • Most saturated food fats raise blood cholesterol
    more than food cholesterol does
  • High blood cholesterol is an indicator of risk
    for CVD
  • Main dietary factors associated with elevated
    blood cholesterol are high saturated fat and
    trans fat intakes

38
What does food cholesterol have to do with blood
cholesterol?
  • LDL cholesterol indicates a risk of heart disease
    because the LDL are carrying cholesterol, made
    mostly from saturated fat in the diet, to the
    body tissues to be deposited there

39
What does food cholesterol have to do with blood
cholesterol?
  • Dietary cholesterol makes a smaller but still
    significant contribution to elevated blood
    cholesterol
  • Five food that contribute about 70 of the food
    cholesterol in the US diet
  • Eggs, 30
  • Beef, 16
  • Poultry, 12
  • Cheese, 6
  • Milk, 5

40
What does food cholesterol have to do with blood
cholesterol?
  • Genetic inheritance modifies everyones ability
    to handle dietary cholesterol somewhat
  • Many people exhibit little increase in their
    blood cholesterol even with a high dietary intake

41
Lowering LDL Cholesterol
  • Trimming fat from food trims calories and, often,
    saturated fat and trans fat as well
  • Oxidation
  • Interaction of a compound with oxygen
  • LDL is susceptible to damage by oxidation,
    thereby making it dangerous to the arteries of
    the heart

42
Lowering LDL Cholesterol
  • Dietary antioxidant
  • Substance in food that significantly decreases
    the damaging effects of reactive compounds
  • Adequate intakes of these, such as vitamin C,
    vitamin E, selenium, and antioxidant
    phytochemicals, may slow LDL oxidation

43
Recommendations Applied
  • Dietary measures to lower LDL in the blood
    involve reducing saturated fat and trans fat and
    substituting monounsaturated and polyunsaturated
    fats
  • Cholesterol-containing foods are nutritious and
    are best used in moderation by most people

44
Essential Polyunsaturated Fatty Acids
  • Linoleic and linolenic acid
  • Essential body does not make them on its own
  • Serve as raw materials from which eicosanoids are
    made
  • Eicosanoids
  • Biologically active compounds that regulate body
    functions

45
Essential Polyunsaturated Fatty Acids
  • Eicosanoids
  • Act somewhat like hormones, affecting
  • muscle relaxation and contraction
  • blood vessel dilation and constriction
  • blood clot formation
  • blood lipid regulation
  • immune response to injury and infection including
    fever, inflammation and pain

46
Deficiencies of Essential Fatty Acids
  • Leads to observable changes in cells
  • When diet is deficient in all of the
    polyunsaturated fatty acids
  • Reproductive failure
  • Skin abnormalities
  • Kidney and liver disorders
  • Infants
  • Growth hindered and vision impaired

47
Omega-6 and Omega-3 Fatty Acid Families
  • Omega-6
  • Linoleic acid
  • Endmost double bond six carbons from the end of
    the carbon chain
  • Arachidonic acid
  • Omega-6 derived from linoleic acid
  • Omega-3
  • Linolenic acid, EPA, DHA (fish oils)
  • Endmost double bond three carbons from the end of
    the carbon chain

48
Omega-6 and Omega-3 Fatty Acid Families
  • A diet that includes two meals of fatty fish each
    week can reduce deaths and illness from heart
    disease, especially in those who have already
    suffered a heart attack
  • Fish is more beneficial than supplements of fish
    oil
  • Evidence that omega-3 may support immunity and
    inhibit development of certain cancers

49
Omega-6 and Omega-3 Fatty Acid Families
  • For healthy people a normal diet to prevent
    deficiencies must have
  • Grains
  • Seeds
  • Nuts
  • Leafy veggies
  • Oils
  • Fish

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51
Fish oil supplements
  • FDA does not permit labels to claim that they can
    prevent or cure diseases
  • May raise LDL cholesterol
  • Excessive amounts can interfere with normal
    functions
  • Made from fish skins and livers, which may have
    toxic concentrations of pesticides, mercury, etc

52
Fish oil supplements
  • Species most heavily contaminated with mercury
  • Shark
  • Swordfish
  • King mackerel
  • Fresh tuna steaks
  • tilefish
  • Lower in mercury
  • Shrimp
  • Canned light tuna
  • Salmon
  • Pollock
  • catfish

53
Effects of Processing of Unsaturated Fats
  • Vegetable oils make up most of the added fat in
    the US diet because fast-food chains use them for
    frying, food manufacturers add them to processed
    foods, and consumers tend to choose margarine
    over butter

54
Hydrogenated Vegetable Oil
  • Hydrogenation
  • Process of adding hydrogen to unsaturated fatty
    acids to make fat more solid and resistant to the
    chemical change of oxidation
  • Makes fats stay fresher longer and also chages
    physical properties
  • Points of unsaturation are weak spots that are
    vulnerable to attack by oxygen
  • When unsat. pts. In the oils of food are
    oxidized, the oils become rancid and the food
    tastes off
  • Cooking oils should be stored in tightly covered
    containers that exclude air

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56
Hydrogenated Vegetable Oil
  • Vegetable oils become more saturated when they
    are hydrogenated
  • Hydrogenated fats resist rancidity better, are
    firmer textured than unsaturated oils, but they
    also lose the health benefits of unsaturated oils

57
Trans fatty acids
  • Fatty acids with unusual shapes that can arise
    when polyunsaturated oils are hydrogenated
  • Consuming these poses a risk to the health of the
    heart and arteries by raising LDL and lowering HDL

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59
Fat in the Diet
  • Fats added to foods during preparation or at the
    table are a major source of fat in the diet
  • Majority of added fats in the diet are invisible
  • They are the hidden fats of fried foods and baked
    goods, sauces and mixed dishes, and dips and
    spreads

60
Fat in the Diet
  • Meats account for a large proportion of the
    hidden fat and saturated fat in many peoples
    diets
  • Most people consume meat in larger amts. Than
    recommended
  • The choice between whole and fat-free mild
    products can make a large difference to the fat
    and saturated fat content of a diet
  • Cheeses are a major contributor of saturated fat

61
Fat in the Diet
  • Fat may be added to grains during manufacturing,
    processing, or cooking
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