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Lecture 3

NUTR1010 Week 3

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Department
Nutrition
Course
NUTR 1010
Professor
Laura E Forbes
Semester
Fall

Description
WEEK 3 Nutrition Carbohydrates are.. • One of the macronutrients • --> gives us energy! (4kcal/g) • Translates to "hydrated carbon" • --> consist of carbon, hydrogen, and oxygen • --> to nutrition experts, CHO means carbohydrate Extra Facts on Carbohydrates... • Found in all plant foods and milk • CHO in many foods are not a part of food guide • Meat, fish, poultry, and fats have no carbohydrates • Eggs and cheese have very little carbohydrates Another way to think about carbohydrates • Unrefined, refined, and added sugars • Unrefined = straight from the source • Refining carbohydrates removes fibre, vitamins, and minerals from the carbohydrate • Added sugars are the most refined carbohydrates The Chemistry of Carbohydrates 1. All carbohydrates are made up of sugar molecules (C6H12O6) Types of Carbohydrates • Simple Carbohydrates (sugars) • --> one (monosaccharide) or two (disaccharide) sugar molecules • Complex Carbohydrates • --> many sugar molecules strung together (starch, fibre) (polysaccharides) Sugar Terminology 2. Suffix -OSE means sugar 3. --> glucose, fructose, dextrose 4. Saccharide: sugar molecule The Monosaccharides • Glucose, Galactose, Fructose • Have differences in structure/orientation of elements • Free glucose and fructose found naturally • Galactose found only in disaccharides or polysaccharides • Monosaccharides are often added to processed foods Disaccharides 3. Sucrose: table sugar 4. Ingredient "sugar": sucrose 5. Maltose is naturally found in fermented food and is used as a food additive (helps preserve food) (glucose and glucose) 6. Lactose (glucose and galactose) is milk sugar 7. Lactose is less sweet than sucrose Starches • Storage form of carbohydrates for plants • Long strings of glucose • Straight - amylose • Branched - amylopectin • Lots of starch in grains, potatoes, and legumes Grain Structure Information • Bran layers: vitamins • Germ: protein and fat • Endosperm: starch Fibre • Provide structure to the leaves, stems, and seeds of plants • Can't be digested by humans • Can be digested by bacteria in the gut • Often made of glucose but can be other monosaccharides Types of Fibre Soluble Fibre • Absorb water • Often used as gelling agents or thickeners • Pectins, gums, mucilages • High in oatmeal, prunes, oat bran, barley, apples, legumes Insoluble fibre • Don't absorb water • Give stiff structure to plants • Cellulose, hemicellulose, lignin • Found in whole grains, vegetables, fruit skins and seeds Carbohydrate Digestion • Starts in the mouth (salivary amylase) • --> salivary amylase breaks starch into glucose and smaller polysaccharides • No carbohydrate digestion happens in the stomach Small Intestine Digestion of Carbohydrates • Pancreatic amylase • --> starch to glucose and maltose • Sucrase: sucrose to glucose and fructose • Maltase: maltose to 2 glucose molecules • Lactase: lactose to glucose and galactose CarbohydrateAbsorption • Monosaccharides -> intestinal cells -> blood • Blood delivers them to the liver • --> all monosaccharides to glucose • Glucose can be burned for energy or stored as glycogen Glycogen • Animals store glucose as glycogen • Found in liver and muscles • Liver: keeps blood glucose levels stable • Muscles: fast energy for exercise • NOT a dietary source of carbohydrate Indigestible Carbohydrate • Fibre, resistant starches and oligosaccharides go into the large intestine • Prevent constipation • Promote healthy gut bacteria • Causes gas september 25th, 2013 What does Carbohydrate do? *Provide the quickest source of fuel • Every cell can use glucose for energy • Red blood cells, brain and nerve cells rely on glucose • The body regulates blood glucose levels closely to make sure we have enough • --> regulated by insulin and glucagon What does CHO do? • Glucose and glycogen provide energy for exercise • "Hitting the wall" What does CHO do? *Spare protein • If your body is low on glucose, protein can be turned into glucose via gluconeogenesis • Your body needs protein to make organs, muscle, skin, enzymes, hormones, blood • Your body will steal protein from blood, organs, and muscle to make glucose What does CHO do? *Prevent Ketoacidosis • If you eat too little CHO, your brain starts to starve • You start making ketone bodies out of fat • Your brain can burn these for energy • BUT ketones are acids so they raise blood acidity • Too much acid in your blood can kill you Diabetes History • Too much glucose in the blood • First described in 1500BC • --> In egypt: great emptying of urine • --> In india: Sweet urine that attracts ants • - In 250BC the Greeks described it as the "the mending down of flesh and limbs into urine" History continued • Discoveries in the late 1700's to 1800's • --> doets fo meat or starvation diets with strenuous activity kept people with diabetes from dying • --> removing the pancreas of dogs caused diabetes • 1921: Banting and Best discovered Insulin • --> a "cure" for diabetes, a Canadian discovery What is insulin? • Ahormone secreted into the blood by the pancreas (in the Islets of Langerhans) • Works with glucagon to control blood glucose • When insulin is released, levels of glucose in the blood goes down What is Glucagon? • Another hormone secreted by the pancreas • When glucagon is released, glycogen gets broken down and released into the bloodstream to be used for energy • glucagon is released when glucose is goNE
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