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Topic 5 -Lipids

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University of Waterloo
KIN 346
Rhonna Hanning

Topic 5: Lipids Fats/Lipids – Triglycerides – Fatty acids ○ Saturated fatty acids (SFA) ○ Monounsurated fatty acids (MUFA) ○ Polyunsaturated fatty acids (PUFA) – Phospholipids – Cholesterol – Plant sterols Roles of Fats in the Body 1) Cell structure –cell membranes 2) Fuel and energy storage –9kcal/g, long term storage 3) Hormones –steroids, testosterone 4) Protection –cushions internal organs 5) Thermoregulation –provides heat 6) Transportation –lipoproteins, fat soluble vitamins Structure of Lipids – Fatty acids – Glycerol – Triglycerides – O-3 and O-6 fats – Hydrogenation – Methyl group – Carboxyl group – Essential fatty acid – 18 carbons – 2 C=C bonds – Omega-6 n-6 – Polyunsaturated – Linoleic acid 1 – Glycerol backbone – Mixed triacylglycerol – 3 fatty acids – SFA – MUFA – PUFA Essential Fatty Acids (EFA) – Alpha linolenic (APA) and linolenic (LA) acids are essential fatty acids – ALA (18:3 omega-3) serves as a precursor for eicoapentaenoic acid (EPA – 20:5, n-3) and docosahexaenoic acid (DHA – 22:6, n-3) – HUFAs (highly unsaturated fatty acids) – LA (18:2 omega-6) undergoes elongation and desaturation to form arachidonic acid (20:4, n-6) The Pathway From One Omega-6 Fatty Acid to Another 2 Hydrogenation – What is hydrogenation? ○ Adding H to UFA  More solid  Less susceptible to oxidation – What does it produce? ○ Cis fatty acid ○ Trans fatty acid 3 Dietary Fat – DRI Acceptable Macronutrient Distribution Range (AMDR): ○ 20-35% of energy  30-40% 1-3yr  15-35% 4-18yr ADA/DC 2007 ○ 5-10% of energy from n-6 PUFA ○ 0.6-1.2% of energy from n-3 PUFA  Now ~ 5% and 0.5% in Canada ○ Essential Fatty Acids  Lionleic Acid Al 17g males, 12g females  α Linoleic AcidAl 1.6g males, 1.1g females – Average North American diet provides ~31-35% of energy as fat – CCHS 2.2 (2004) – Males 19-30 mean 32%, 10.4% SFA ○ 9-10%>35% – Females 19-30 mean 32.5%, 10.5% SFA ○ 20%>35% -though only 7% in Ontario What About Saturated Fats and Trans Fats? – DRI “keep low” or “low as possible” –  risk for CHD – No upper limit – Impossible to eliminate from diet entirely – CDA –SFA <10% of energy – “It is the position of the ADA and DC that dietary fat for the adult population should…emphasize a reduction in SFA and trans fatty acids and an increase in n-3 PUFAs” Sources of Fatty Acids Saturated Fatty Acids – Meat –e.g., fat from red meats, processed meats – Added fats and oils –e.g., lard, butter, tropical oils (coconut oil, palm oil) – Milk –e.g., from milk, yogurt, cheese – Poultry, eggs, nuts Trans Fatty Acids – Commercial baked goods – Commercial fried chicken and fish – Some margarines – Fried potatoes – Snack foods Monosaturated Fatty Acids – Vegetable oils –e.g., olive oil, canola oil, peanut oil – Nuts –e.g., almonds, sesame seeds – Avocado Poly Unsaturated Fatty Acids – Vegetable oils –e.g., sunflower oil, corn oil – Nuts –e.g., walnuts – Mayonnaise – Salad dressings 4 Linoleic Acid – Leafy vegetables – Seeds – Nuts – Oils – Poultry Alpha Linoleic Acid – Walnuts – Flax Eicosapentaenoic Acid (EPA) – 20C –e.g. omega-3 enriched eggs Docosahexaenoic Acid (DHA) – 22C –e.g., salmon – 2 servings of fatty fish/week provide ~450-500mg EPA and DHA/d What Was Done? – On June 20, 2007, Health Canada adopted the recommendation of the Trans Fat Task Force to (achieve in 2 years) – Limit trans fat content of vegetable oils and soft margarines to 2% of total fat – Limit trans fat content for all other foods to 5% of total fat content, including ingredients sold to restaurants Congugated Linoleic Acids (CLA) – PUFA 18:2 double bonds on adjacent carbons ○ Cis-9, trans-11; trans-11, cis-12 ○ E.g., butter 4.7mg CLA/g fat; rib roast 2.9mg CLA/g fat – Small amounts of naturally occurring trans fats in milk and meat of ruminants – 70% of dietary CLA from milk products – No evidence in tha CHD (coronary heart disease) – Not considered trans fats on food labels in Canada Phospholipids – Functions – Emulsification – Membrane components ○ Allows fat, hormones to travel across ○ Enables dispersion of fat in fluids 5 Sterols – Contain a 4C ring – Variety of side chains – Functions: ○ Bile acids ○ Sex hormones ○ Adrenal hormones ○ Vitamin D ○ Cholesterol Top Dietary Sources of Cholesterol – Dietary is found only in foods of animal origin –True – Top sources in the North American diet: ○ Eggs, beef, poultry, cheese, milk ○ Other high sources ○ Shellfish, liver Cardiovascular Disease – CVD –leading cause of death in Canada – In 2006, CVD accounted for 30% of all deaths in Canada (more than 72 000) – Although rates have been steadily declining over 40 years, with aging population, # of people with CVD is expected to increase – R
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