Chapter 5 The Lipids: Fats, Oils, Phospholipids, & Sterols

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Chapter 5The Lipids Fats, Oils, Phospholipids,
Sterols

• Basic Nutrition
• 10/1/07
• Dr. Fralinger

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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.

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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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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

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Usefulness of Fats in the Body

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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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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

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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

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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

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Phospholipids and sterols

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

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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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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

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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

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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

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How can I use my stored fat for energy?

• Fat depots-
• Muscles
• Breasts
• Insulating fat layer under the skin

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How can I use my stored fat for energy?

• When a persons body starts to run out of
  available fuel from food, begins to retrieve
  stored fat to use for energy
• Fat cells respond to the call for energy by
  dismantling stored fat molecules and releasing
  fat components into the blood

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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

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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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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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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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

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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

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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

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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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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

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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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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

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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

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Fat in the Diet

• Fat may be added to grains during manufacturing,
  processing, or cooking