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Chapter 5Lipidshttps://www.youtube.com/watch?v=QhUrc4BnPgg

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Lipids: Common Properties· Diverse group of chemical compounds· One common property, lipids do not readily dissolve in water· Should comprise 20% to 35% of an adult’s total calorie intake

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Types of Lipids and Fats· Types of lipids

· Triglycerides· Phospholipids· Sterols (Cholesterol)

· Fats (solid) and oils (liquid)· 9 kcal /gm

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Saturated Fatty Acid Structure

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Monounsaturated Fatty Acid Structure

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Polyunsaturated Fatty Acid Structure

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Fatty Acids and Triglycerides

· Found in our body and foods· In triglycerides, composed of three fatty acids bonded to glycerol, an

alcohol · Saturated fatty acids, higher in animal fats

· Solid form· Unsaturated fatty acids, higher in plant foods

· Liquid form· Cis and trans

· Fats are composed of both saturated and unsaturated

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Cis and Trans Fatty Acids

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Chemical Forms of Common Lipids

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Essential Fatty Acids

· Must be supplied by the diet to maintain health · Omega-3 fatty acid (alpha-linolenic acid)· Omega-6 fatty acid (linoleic acid)

· immune system function and vision· help form cell membranes· produce eicosanoids, which are involved in practically all important

functions in the body

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Omega-3 Fatty Acid

· Primarily from nuts, seeds, fish oil, flax seed oil

· Also found in canola, walnuts, mussels, crab, shrimp, and soybean oil

· Recommended intake of ~2 servings of fish per week

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Omega-3 Fatty Acid (alpha-linolenic acid)

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Omega-6 Fatty Acid

· Found in vegetable oils· Need is about 2-4 tablespoons a day

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Omega-6 Fatty Acid (linoleic acid)

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Essential Fatty Acids

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Health-Related Effects· Archidonic acid (Omega-6 )

· Increases blood clotting· Increases inflammatory responses

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Health-Related Effects

·DHA, EPA (Omega-3)· Decrease blood clotting· Reduce heart attack· Decrease inflammation · Excess may cause hemorrhagic stroke· Other possible uses: lower triglycerides,

rheumatoid arthritis, behavioral disorders

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Essential Fatty Acid Deficiency

· Flaky, itchy skin· Diarrhea· Increased risk of infection· Stunted growth and reduced wound healing

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Triglycerides

· Most common form of fats and oils· 3 fatty acids attached to a glycerol

· diglyceride breakdown product of triglyceride consisting of two fatty acids bonded to a glycerol backbone

· monoglyceride breakdown product of a triglyceride consisting of one fatty acid attached to a glycerol backbone

Glycerol + 3 FA’s Triglyceride + 3 H20

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Phospholipids

· Built on a glycerol backbone· Contains phosphorus compound(s)· Found in body· Synthesized by the body as needed· Component of cell membranes

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Sterols

· Multi-ringed structure· Do not have a glycerol backbone· Cholesterol is a sterol· Waxy substance· Do not readily dissolve in water· Found in animal foods

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Fats and Oils in FoodsSECTION 5.3

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Functions of Phospholipids

· Emulsifier· Bile acids· Lecithins· Improves food products

· Found in wheat germ, peanuts, yolks, soy beans, organ meat

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Emulsifiers

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Functions of Cholesterol

· Essential component of cell membrane· Produced by the liver· Found only in animal products· Forms important hormones

· estrogen· testosterone· vitamin D

· Precursor to bile acids

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Cholesterol Content of Foods

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Food Sources of Fat

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Fat Is Hidden in Some Foods

· Look on the Nutrition Facts labels· Look on the lists of ingredients· Control portion size

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Functions of Fat in Food

· Satiety· Flavor· Texture

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Low-Fat Diets

· Need time to adjust to taste of low-fat diet· flavorful fruits, vegetables

· Replace whole milk with 1% or skim· In time, whole milk will taste too creamy

· Weight control and reduced risk of chronic disease

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Fat-Replacement Strategies for Reduced-Fat Foods

· Fat commonly replaced with sugar· Keeps calories close to the same

· Water · Major component of margarine

· Z-trim® · Starch derivative that binds with water

· Fiber cellulose · Maltrin®, Stellar®, Oatrim

· Dairy-Lo® · Protein globules

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Fat Rancidity

· Contains products of decomposed oils· Breakdown of the C=C bonds by UV light, and/or O2

· Unpleasant odor and flavor· Polyunsaturated fatty acid more susceptible · Limited shelf life of food products

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Prevention of Rancidity

· Hydrogenation· Addition of antioxidants

· Vitamin E· Butylated hydroxyanisol (BHA)· Butylated hydroxytolune (BHT)

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Hydrogenation of Fatty Acids· Process used to solidify an oil· Addition of H to C=C double bonds· Increases shelf life of food product· Formation of trans fatty acid

· (similar to shape of saturated fatty acid)· Presents health risk like saturated fats

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Hydrogenation

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Excessive Trans Fatty Acid Intake

· Increases risk for cardiovascular disease· Required to be listed on food labels

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Minimize Intake of Trans Fat

· Limit use of hydrogenated fats· Limit deep-fried foods· Limit high-fat baked goods· Limit use of non-dairy

creamers

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Main Sources of Fatty Acids

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Making Lipids Available for Body Use

1. What enzyme is responsible for digestion of triglycerides?

2. What are the end products of fat digestion?3. What are the differences between the absorption of

long-versus short-chain fatty acids?

SECTION 5.4

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Lipase

· Salivary lipase· Gastric lipase· Pancreatic lipase

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Digestion of Fat in the Small Intestine

· Primary site of fat digestion· Hormone cholecystokinin (CCK)

· Stimulates release of pancreatic lipase· Bile acid released

· Emulsifies digested fat· Fat is broken down

· To monoglycerides and fatty acids in watery digestive juices

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Summary of Fat Digestion and Absorption

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Fat Digestion and Absorption

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Digestion of Phospholipids

· Enzymes released· From pancreas· From cells of the small intestine

· Broken down to · Glycerol· Fatty acids· Remaining parts

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Digestion of Cholesterol

· Enzymes released· From pancreas

· Cholesterol is absorbed

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Absorption

· 95% of dietary fat is absorbed· Diffused into the absorptive cells· Short- and medium-chain (<12 C) fatty acids

· Are water soluble· Enter the portal system

· Long-chain fatty acids re-form into triglycerides· Not water soluble· Enter the lymphatic system

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Carrying Lipids in the Bloodstream

1. How do lipids move through the bloodstream?2. How are dietary fats packaged in the small intestine

and transported?3. Where are VLDLs made and what do they contain?4. Where do the LDLs originate and what is their

destination?5. Why are HDLs considered “good” cholesterol?

SECTION 5.5

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Dietary Fats Are Carried by Chylomicrons· Fatty acids re-formed into triglycerides· Packaged into chylomicrons· Lipoprotein lipase

· Breaks down triglycerides in the chylomicrons· Chylomicron remnant

· Delivered to the liver

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Carrying Lipids in the Bloodstream

· Water and oil (fat) do not mix easily· Unique system of fat transportation is needed· Lipoprotein compound in bloodstream containing a core of lipids

with shell composed of protein, phospholipid, and cholesterol· Vehicle used for lipid transport

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Structure of a Lipoprotein

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Composition of Lipoproteins

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Major Lipoproteins in the Blood

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Lipoprotein Production and Function

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High-Density Lipoprotein (HDL)· Synthesized by liver and intestine· High proportion of protein · Picks up cholesterol from dying cells and other sources· Transfers cholesterol to other lipoproteins · Transfers cholesterol directly back to the liver

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Benefits of a High HDL level· Removes cholesterol from the bloodstream· HDL may block oxidation of LDL· Reduces risk of cardiovascular disease· Pre-menopausal women have higher HDL

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Scavenger Cells · Scavenger WBC removes (oxidized) LDL from circulation· Build-up of atherosclerosis plaque on walls of the blood vessels· Development of atherosclerosis· Increased vessel damage caused by

· Smoking, diabetes, hypertension, homocysteine, high LDL, infection

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Broader Roles for Lipids in the Body

1. What are functions of triglycerides in body?2. Where are phospholipids found in body?3. What are some compounds made from cholesterol

in body?

SECTION 5.6

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Functions of Fatty Acids

· Provide energy· Efficient storage of energy· Insulating and protecting body· Transport fat-soluble vitamins A, D, E,

and K· Phospholipids, become part of cell

membrane· Cholesterol, becomes part of hormones,

estrogen, testosterone, and precursor of active vitamin D hormone· Structural component in cells and

lipoproteins

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Phospholipids Form Cell Membranes

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Recommendations for Fat Intake1. How does percent of calories as fat in North

American diet compare to recommendations?2. What is limit for cholesterol intake?3. What are characteristics of Mediterranean diet?

SECTION 5.7

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Recommendations for Fat Intake· No RDA· AMDR: 20% to 35% of total kilocalories (44 to 78 g/d)· 2015 – 2020 Dietary Guidelines

· Limit saturated fats to <10% of total kcal· Shift from using solid fats to oils

· AHA Diet and Lifestyle Recommendations for Cardiovascular Disease Risk Reduction (2006)· Limit saturated fats to <7% of total kcal· Limit trans fats to <1% of total kcal· Limit cholesterol to <300 mg/d

· Average U.S. intake:· 33% of total kcal from fat· 13% of kcal from saturated fat· 180-320 mg cholesterol/day

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Other Recommendations

· Total fat intake may exceed 35% of total kcal as long as saturated and trans fat intakes are minimal

· Eat plenty of fruits and vegetables· Cut down on red meats· Cut down on simple sugars and refined carbohydrates· Promote healthy weight· Be active· https://www.youtube.com/watch?v=3Gqo3Y6WFYA

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Lipids Concept Map

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Nutrition and Your HealthLipids and Cardiovascular Disease

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Cardiovascular Disease

· Leading cause of death in North America· 600,000 people die each year· Annual cost is $108.9 billion each year

· Myocardial infarction· death of part of heart muscle· also termed a heart attack

· Cerebrovascular accident· death of part of brain tissue due typically to a blood clot· also termed a stroke

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Development of CVD

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Atherosclerotic Blood Vessel

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Risk Factors for CVD

· Total blood cholesterol > 200 mg/dl

· Smoking · Hypertension (> 139 / 89 mmHg)· Diabetes

· Low HDL (< 40 mg/dl)· Age· Family history· Blood triglycerides > 200 mg/dl· Obesity · Inactivity

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Signs of a Heart Attack

· Intense, prolong chest pain· Shortness of breath· Sweating· Nausea and vomiting· Dizziness· Weakness· Jaw, neck, shoulder pain· Irregular heartbeat

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Medications to Lower Blood Lipids

· Patient criteria· Previous heart attack· Existing CVD· Existing diabetes

· Heart Attack Risk Calculator· Medication to lower LDL

· Reduce cholesterol synthesis (Statins, “Lipitor”)· Binds to bile acids for elimination

· Medication to lower blood triglycerides · Reduce triglyceride synthesis

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Dietary Strategies to Lower LDL

· Reduce dietary saturated fat and cholesterol· Increase mono and polyunsaturated fats in diet· Increase dietary fiber (soluble)· Use products with plant sterols/stanols

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Plant Sterols/Stanols· 2 to 5 grams of plant sterols/stanols per day can reduce blood cholesterol

to similar extent as statin drugs· Decrease absorption of dietary cholesterol· Decrease reabsorption of cholesterol in bile (enterohepatic circulation)· Liver takes up cholesterol from blood to make more bile acids

· Added to food products· Margarine (e.g., SmartBalance®)· Orange juice (e.g., Minute Maid HeartWise®)

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Dietary Strategies to Lower Triglycerides

· Avoid overeating· Limit alcohol· Limit simple sugars· Small frequent meals· Include fish 2 times per week

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Diet and Lifestyle Strategies to Raise HDL

· Physical activity (≥45 min/day, 4 days/week)

· Don’t smoke· Eat regularly · Eat less total fat· Moderate alcohol

· 1 drink/day for women· 2 drinks/day for men

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Surgical Treatment for CVD

· Percutaneous transluminal coronary angioplasty (PTCA) - insertion of a balloon catheter into an artery, once advanced to area of lesion, balloon is expanded to crush lesion

· Coronary artery bypass graft (CABG) - removal and use of a saphenous vein (leg) or mammary artery, sewn into aorta, for bypass