Lipids Types, Food Sources, Functions What Are Lipids? Lipids Diverse group of molecules that are insoluble in water Fats The lipid content of diets and foods 1
Lipids in Body Cells and Tissues Types of Lipids in body cells and tissues: Triacyglycerols or Triglycerides (or TGs) Glycerolphospholipids Sphingolipids Eicosanoids Cholesterol Functions of Lipids Stored in the Body TGs serve as fuels providing the body with energy Glycerolphospholipids and sphingolipids are found in membanes and in blood lipoproteins at the interfaces between the lipid components of these structures and surrounding water. These membrane lipids form hydrophobic barriers between subcellular compartments and between cellular constitutes and extracellular milieu Eikosanoids regulate many cellular processes, mainly inflammation 2
Triglycerides (or TGs) TGs contain: Three fatty acid molecules One glycerol molecule Triglycerides (or TGs) Fatty acids are determinant for classification of TGs Fatty acids are classified by: 1. Carbon chain length 2. Saturation level 3. Shape 3
Triglycerides: Saturation According to saturation, fatty acids can be divided into three categories: 1. Saturated fatty acids have hydrogen atoms surrounding every carbon in the chain 2. Monounsaturated fatty acids lack one hydrogen atom (one double bond) 3. Polyunsaturated fatty acids have more than one double bond 4
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Triglycerides Hydrogenation: hydrogen atoms are added to unsaturated fatty acids. As a result: oils become more solid and more saturated trans fatty acids are created risk of cardiovascular disease increases risk of cancer development may also increase 6
Hydrogenated fat-rich foods Essential Fatty Acids The Essential Fats are a group of fatty acids that are essential to human health. Omega-3 ( 3) Linolenic acid Omega-6 ( 6) Linoleic acid 7
Structure of EFAs LINOLEIC ACIDS (Omega 6) Eighteen-carbon essential fatty acids that contain two double bonds. 18:2 (9,12) LINOLENIC ACIDS (Omega 3) Eighteen-carbon essential fatty acids that contain three double bonds 18:3 (9,12,15) Function of EFAs Formation of healthy cell membranes Proper development and functioning of the brain and nervous system Production of the Eicosanoids Thromboxanes Leukotrienes Prostaglandins Responsible for regulating blood pressure, blood viscosity, vasoconstriction, immune and inflammatory responses. 8
Essential Fatty Acid Deficiency Side Effects hemorrhagic dermatitis skin atrophy dermatitis dry skin weakness impaired vision mood swings edema high blood pressure high triglycerides hemorrhagic folliculitis hemotologic disturbances (ex: sticky platelets) immune and mental deficiencies impaired growth Who are at risk for deficiency? Long-term TPN patients without adequate lipid Cystic Fibrosis Low Birth Weight Infants Premature infants Severely malnourished patients Patients on Long-term MCT as fat source Patients with fat malabsorption Hepatorenal Syndrome Sjogren-Larsson Syndrome Multisystem neuronal degradation Crohn s disease Cirrhosis and alcoholism Reye s Syndrome Short bowel syndrome 9
Triene:Tetraene Ratio T/T ratio is the marker used to diagnose essential fatty acid deficiency. Characterized by: A decrease of Arachidonic (20:4 6)acid An increase of Mead s acid (20:3 9). (This acid is produced in excess during EFAD) Triene:Tetraene ratio of >0.4 is considered EFAD Some studies suggest a lower threshold of 0.2 EFAD development: can be as early as 2 to 4 weeks on TPN without lipids Phospholipids Phospholipids contain Glycerol backbone, two fatty acids, phosphate Soluble in water Transport fat in the bloodstream Manufactured in our bodies (not required) 10
Sterols Sterols contain multiple rings of carbon atoms Plant sterols appear to block the absorption of dietary cholesterol Cholesterol is made in our bodies and therefore is not necessary in the diet Sex hormones, vitamin D, bile 11
Cholesterol The main sterol compound, essential to life 100g in human body, most in cell membranes, in myelin layers around neurons Cell membrane structure Human skin barrier (toxins, water loss) Precursor of steroid hormones (testosterone, estrogen, progesterone, cortisone) Precursor of bile acids Formation of vitamin D (with UVs) Dietary sources All foods containing animal fat contain cholesterol to varying extents Major dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry Human breast milk also contains significant quantities of cholesterol From a dietary perspective, cholesterol is not found in significant amounts in plant sources OPTIMAL CHOLESTEROL LEVELS (AHA) Total Cholesterol Less than 200 mg/dl Desirable level that puts you at lower risk for coronary heart disease 200 to 239 mg/dl Borderline high 240 mg/dl and above High blood cholesterol. Twice the risk of CAD as below 200 mg/dl 12
Estimates of the percentages of CVD attributable to some modifiable risk factors Risk factor Chol 200mg/dl or greater 43% Physical inactivity 35% BP 140/90 mmhg or greater 25% Cigarette smoking 22% Obesity 7% Diabetes 8% Estimate 25 Blood lipids include: Chylomicrons present only after a meal Very-low-density lipoproteins (VLDL) Low-density lipoproteins (LDL) High-density lipoproteins (HDL) 13
OPTIMAL CHOLESTEROL LEVELS (AHA) HDL Cholesterol Less than 40 mg/dl Low level. A major risk factor for CAD 40 to 59 mg/dl The higher the level the better 60 mg/dl and above High level. Considered protective against CAD LDL Cholesterol Less than 100 mg/dl Optimal 100 to 129 mg/dl Near or above optimal 130 to 159 mg/dl Borderline high 160 to 189 mg/dl High 190 mg/dl and above Very high 14
Chylomicron 15
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Plant sterols reduce serum cholesterol levels. Eur Heart J. 2009, 30(4): 404 409 Lipids Beta oxidation breaks down fatty acids to form acetyl Coenzyme A Lipids have more potential chemical energy and can be more fully oxidized as an energy fuel Therefore, we gain more energy, gram for gram, from fats than from carbohydrates 17
Lipids and Health The Roles of Fat 9 kcal per gram Major fuel at rest Fuel at exercise Stores energy Provides the body with essential fatty acids Essential for absorption of at-soluble vitamins Regulates cell function Maintains membrane stability Provides insulation Provides flavors and textures of foods Helps us feel satiated 18
How Much Fat? Acceptable Macronutrient Distribution Range (AMDR) for fat: 20 35% of calories Minimize saturated and trans fatty acid intake to lower risk of heart disease Active people may need more energy from carbohydrates and can reduce their fat intake to 20 25% of total calories 19
How Much Fat? Dietary Reference Intakes (DRIs) set for essential fatty acids Linoleic acid: 5-10% of total calories Alpha-linolenic acid: 0.2-1.2% of total calories A lower ratio of omega-6/omega-3 fatty acids is more desirable in reducing the risk of many of the chronic diseases of high prevalence in Western societies Saturated fat: less than 8% of energy Trans fats: reduced to the absolute minimum Food Sources of Fat Visible fats Fats we add to foods Butter, cream, mayonnaise, salad dressings Invisible fats Fats hidden within foods Occur naturally or added during processing Baked goods, dairy, meats, fast foods 20
Food Sources of Fat Beneficial fats Omega-3 fatty acids may be low in diets Fish, walnuts, canola are of high content in omega-3 fatty acids Switching to more healthful fats without increasing total fat intake Use olive in place of butter or margarine Select low-fat or nonfat dairy products 21
Food Sources of Fat Fat replacers Used to lower fat content of foods Found in chips, cakes, cookies May cause GI side effects in large amounts Example: olestra (Olean) Fats in Food 22
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Cardiovascular Disease Cardiovascular disease Dysfunction of the heart or blood vessels Can result in heart attack or stroke 25
Cardiovascular Disease Risk factors for cardiovascular disease: Being overweight Physical inactivity Smoking High blood pressure Diabetes mellitus Inflammation Cardiovascular Disease Dietary fats increase blood lipids Highly saturated and trans fat intakes increase blood cholesterol Omega-3 fatty acids reduce inflammation and blood triglycerides 26
Cardiovascular Disease Diets high in saturated fats Decrease the removal of LDLs from the blood Increase blood cholesterol levels Contribute to the formation of plaques that can block arteries 27
Cardiovascular Disease Diets high in trans fatty acids: Can raise blood levels of LDL-cholesterol as much as saturated fat Are abundant in hydrogenated vegetable oils (margarine, baked goods, fried foods) FDA requires that trans fatty acid content be listed on labels for conventional foods and some dietary supplements 28
Cardiovascular Disease Lifestyle changes can prevent or reduce cardiovascular heart disease Total fat intake: 20 35% total calories Saturated fat: less than 8% total calories Monounsaturated fat: more than 12% Polyunsaturated fat: more than 10% Cholesterol: less than 200 mg per day Trans fat: reduce to absolute minimum Increase omega-3 fatty acids Dietary fiber: 20 30 grams per day Cardiovascular Disease Lifestyle changes can prevent or reduce cardiovascular heart disease Maintain normal blood glucose level Eat throughout the day No more than 2 alcoholic beverages per day for men and 1 drink per day for women Maintain an active lifestyle Maintain a healthful body weight Decrease salt intake 29