WEEK 4 NOTES
WEEK 4 NOTES 2420-001
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This 6 page Class Notes was uploaded by Emma Trokel on Wednesday January 13, 2016. The Class Notes belongs to 2420-001 at University of Colorado at Boulder taught by S. Nelson in Spring 2016. Since its upload, it has received 14 views. For similar materials see Nutrition and Health Performance in Psychlogy at University of Colorado at Boulder.
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Date Created: 01/13/16
Week 4 Chapter 6 Lipids ● Lipids include ○ Fatty acid ○ Triglycerides ○ Phospholipids ○ Cholesterol ● Lipids are: ○ generally insoluble in water ○ less dense than water ○ fat and water do not mix very well ○ most of your blood is water ● The monomer of a lipid is fatty acid Lipid Consumption Patterns Do Americans eat more or less fat in 1988? 1987 to 1988 → approx. 54 lbs/year/person 2009 to 2010 → 62 lbs/year/person fat contributes ~33% of the average American’s daily caloric intake Major Function of Lipids Major function of lipids in foods: ● enhance the intestinal absorption of fatsoluble vitamins and phytochemicals ● contribute to rich flavor, smooth texture, and appetizing aroma of foods ● If there’s not enough fat, your body will not menstruate Triglycerides ● Composed of 3 fatty acids attached to a glycerol “backbone” ● ~95% of lipids in the body and foods is in the form of triglycerides ● “What’s the “Tri” in Triglycerides: fatty acids” Using Triglycerides for energy ● Adipose (Fat) cells can break down triglycerides into fatty acid and glycerol molecules before releasing them into bloodstream ● Liver can convert glycerol to glucose another energy source ● Triglycerides provide 9 kcal/g ○ carbohydrate and protein provide 4 kcal/g Sterols ● Sterols have carbons arranged in rings, which make them more chemically complex type of lipid than a triglyceride or phospholipid ● cholesterol is the most wellknown sterol Functions of Cholesterol The body uses cholesterol to make various substances, including: ● Vitamin D ● Steroid hormones ○ estrogen ○ testosterone ● Bile Trans fats What are trans fat? unsaturated fats with at least 1 trans double bond rather than the more common cis double bond Hydrogenation ● Process that adds hydrogen atoms to liquid vegetable oils ● humanmade process ● vegetable oil force extra hydrogen and turn it into a saturated fat Partial Hydrogenation: ● not all double bonds are hydrogenated ● natural cis double bonds convert to the unhealthy cis double bonds convert to the unhealthy trans form Trans Fats and Health Used in many processed foods: high amounts of trans fats in diet increase heart disease risk by raising blood cholesterol levels In 2013 the FDA announced a ban on the addition of trans fats to foods (there will be a gradual phase out of trans fats) Essential fatty acids ● essential fatty acids cannot be made in the body ● essential fatty acids are used to make several important compounds in the body ● The two essential fatty acids are: ○ Alphalinolenic acid ○ Linoleic acid ● Precursors of prostaglandins ○ Hormonelike substances formed from EPA, DHA, and arachidonic acid ● Effects of prostaglandins: ○ Stimulate uterine contractions ○ regulate blood pressure ○ promote immune system response Omega3 and Omega6 Fatty Acids ● Omega3 ○ Sources: fatty fish, canola oil, walnuts, and flaxseed ○ Actions: reduces inflammation, blood clotting and blood pressure ○ May reduce risk of heart disease ● Omega6 ○ Sources: animal fats and vegetable oils ○ Actions: increases inflammation and blood clotting ○ May also reduce risk of heart disease Phospholipids ● Chemically similar to a triglyceride; 1 fatty acid is replaced by a compound containing phosphorus and nitrogen groups ● Lecithin the main phospholipid in foods, such as egg yolks, liver, wheat germ, peanut butter, and soy ● help move lipids through blood Emulsifiers Phospholipids act as emulsifiers because they have hydrophobic and hydrophilic regions Hydrophobic region: Attracts lipids and avoids water Hydrophilic region: Attracts water and avoids lipids Lipoproteins and Atherosclerosis ● Lipoproteins: ○ transports lipids in blood ○ play major role in atherosclerosis development ○ Carry different types of lipids and can influence plaque formation differently High Density Lipoproteins (HDL) ● HDL is commonly called the “good” cholesterol ● Smallest and densest type of lipoprotein ● Transports cholesterol away from tissues and to the liver, where it can be eliminated Low Density Proteins ● LDL is commonly called the “bad” protein ● Conveys cholesterol to tissues ● May become oxidized LDL and contribute to atherosclerotic plaque ● you want low LDL levels because your capacity to move tissue to the heart is less Very Low Density Lipoproteins ● High levels may contribute to atherosclerosis ● VLDL primarily carries triglycerides ● Excessive alcohol and refined carbohydrate intakes stimulate VLDL production in the liver What Happens To Lipids In The Body? ● The duodenum, or upper small intestine, is the primary site of lipid digestion ● In the duodenum, pancreatic lipase digests triglycerides, forming primarily ○ Monoglycerides ○ Free fatty acids Bile ● Bile is made in the liver and stored in the gallbladder ● Bile contains bile salts that aid in lipid digestion ● Without bile, lipids clump together in large fat globules Journey into the general circulation Summary of Lipid Digestion and Absorption Stomach minor fat digestion occurs Liver produces bile that helps emulsify fat Pancreas secretes pancreatic lipase into small intestine Small Intestine main site for lipid digestion and absorption Anus less than 5% of undigested fat is excreted in feces Dietary Lipid Recommendations Acceptable Macronutrient Distribution Range → 20 to 35% of total calories US Dietary Guidelines, 2010 <10% of calories from saturated fats <300 mg cholesterol daily trans fatty acid intake as low as possible Lipids and Health: cardiovascular disease (CVD) CVD: diseases of the heart and blood vessels ● Most common forms of CVD are: ○ Heart disease (“Coronary artery disease”) ○ stroke ● 1 in 3 adult americans have some form of CVD ○ Responsible for ~28% of deaths in the US in 2011 Arteriosclerosis Condition that results from atherosclerosis Characterized by loss of arterial flexibility Commonly referred to as “hardening of the arteries” Contributes to hypertension What is hypertension? chronic condition characterized by abnormally high blood pressure levels May cause hardened arteries to tear or burst another way of saying high blood pressure because of those hardened arteries From Atherosclerosis to Cardiovascular Disease ● Atherosclerosis disease in which lipidcontaining plaques build up inside arteries ● Plaque forms in an artery when something irritates the lining of the artery wall. ○ Plaque narrows arteries, interfering with circulation. ○ Plaque may also result in the formation of a fixed clot a thrombus Embolus Formation A thrombus that breaks away and travels through the blood is an embolus if an embolus block lodges in a blood vessel of the heart, it can cause a heart attack If an embolus blocks a blood vessel in the brain and deprives brain cells of oxygen and nutrients, a stroke results Food Selection and Preparation Strategies to reduce dietary fat include: Reduce intake of fried foods Purchase lean cuts of meat and trim visible fat Replace some fatty foods with reduced fat or fat free alternatives Replace high fat sandwiches meats with nut butters choose low fat snack foods use less salad dressing on salads Fat Replacers Synthetic fat replacers were developed to meet consumer requests for lower fat foods Brands of fat replacers include: oatrim simplesse olean
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