FNN100 Module 3: Carbohydrates (PDF)

Module 3: Carbohydrates FNN100 – WEEK 3 STEPH AN I E N I SH I PH D , R D In this Module… Part 1: Carbohydrates in the Canadian Diet Part 2: The Chemistry of Carbohydrates Part 3: Carbohydrates in the Body Part 4: Carbohydrates and Health Part 1: Carbohydrates in the Canadian Diet...

Module 3: Carbohydrates FNN100 – WEEK 3 STEPH AN I E N I SH I PH D , R D In this Module… Part 1: Carbohydrates in the Canadian Diet Part 2: The Chemistry of Carbohydrates Part 3: Carbohydrates in the Body Part 4: Carbohydrates and Health Part 1: Carbohydrates in the Canadian Diet Carbohydrates in the Canadian Diet Different types of carbohydrates in the Canadian diet Form the basis of most modern diets Carbohydrates in “whole foods,” such as fresh fruit, dairy, or whole grains, are in their natural state. Refining carbohydrates separates the carbohydrates from their vitamins, minerals, and fibre. Carbohydrate Processing: Unrefined and refined Whole grain products: Include the entire kernel of the grain: the germ, the bran and the endosperm. Refined grain products: Often have the bran and germ removed and just consist of the endosperm. Whole (Unrefined) Grain vs. Refined Grain Bran = Fibre Endosperm = Vitamins Germ = Vitamins Carbohydrates in the Canadian Diet Dietary Reference Intakes (DRI) for carbohydrate: AI – for infants only EAR, RDA – for children, adults and during pregnancy and lactation EAR for adults 19+ (men/women) – 100 g/day RDA for adults 19+ (men/women) – 130 g/day Fiber Recommendations DRI recommends that individuals ages 19 – 50 consume: Women: 25 g/day Men: 38 g/day Most people get only half of the fibre they need everyday. Carbohydrates in the Canadian Diet AMDR for carbohydrate 45-65% of total daily energy intake Emphasis is on grains, fruit and vegetables Added sugars ≤ 25% of total daily energy intake white sugar, brown sugar, corn syrup, malt, dextrose, etc. sugar-sweetened beverages (juices, pop, specialty coffees), cake, donuts, cookies, candy, etc. Carbohydrates are needed as part of healthy, balanced diet Part 2: The Chemistry of Carbohydrates What are carbohydrates? ▪ Carbohydrates are the sugars, starches and fibres found in fruits, grains, vegetables and milk products. ▪ They are the body’s preferred source of energy. Carbohydrates come mostly from foods that are plant based. Plants use energy from the sun (photosynthesis) to convert water and carbon dioxide in the air into glucose which can then be converted into starch. ▪ A chemical compound consisting of carbon, hydrogen, and oxygen. ▪ Arranged as monosaccharides, disaccharides, and polysaccharides. Types of Carbohydrates Carbohydrates Complex Simple Carbohydrates Carbohydrates (Oligo. & “sugars” Polysaccharides) Disaccharides: Starch: amylose, Monosaccharides: maltose, sucrose, Glycogen amylopectin lactose Hexoses: glucose, Pentoses: ribose, fructose, xylose…(later Dextrin Fibres galactose… courses) Other trioses, tetroses, heptoses Soluble Fibre Insoluble Fibre + more Carbohydrate structure Monosaccharides are made up of 1 sugar unit (single sugars) Simple Disaccharides are made up of 2 sugar carbohydrates units (double sugars) Polysaccharides are made up of more Complex than 2 sugar units carbohydrates Simple carbohydrates - Quick energy source. Digested quickly. Made up of one or two sugar molecules Types of Carbohydrates: Simple Simple carbohydrates or “sugars”: monosaccharides, disaccharides Monosaccharides: Hexoses (6 carbon sugars) – all C6H12O6 glucose, fructose, galactose differences between compounds based on location of ‘OH’ (hydroxyl group) account for differences in sweetness: fructose > glucose > galactose found in fruits, vegetables, milk (~10% of the carbohydrate we consume) highest amount of glucose then fructose then galactose (less common in food) Pentoses (5 carbon sugars) – C5H10O5 Found in riboflavin (vitamin B1) and in ribonucleic acid (RNA) Xylose (sugar alcohol); and others (more in future courses) Types of Carbohydrates: Simple (cont.) 1. Glucose: Primary component of polysaccharides; primary form of carbohydrate in body cells and blood Major product of photosynthesis Plants join glucose molecules into long chains (“starches”) Plants have different monosaccharide, disaccharide, and starch composition Contributes to differences in sweetness (taste) e.g., sugar cane, fruit = sweet; potatoes = less sweet, more “starchy” Common food sources: fruit, vegetables, honey, sugar, candy, juice…etc. Types of Carbohydrates: Simple (cont.) Glucose and Glucose Regulation (overview) Blood glucose level in the body is regulated by hormonal secretions Key hormones include: insulin and glucagon Blood glucose raises postprandially (following a meal) Blood glucose falls as glucose is taken up into the cells Types of Carbohydrates: Simple (cont.) 2. Fructose: Other names: “fruit sugar” (sweetest of all simple sugars) Found commonly in fruits, honey, also high fructose corn syrup (HFCS) Does not require insulin to enter body cells Less cariogenic than glucose (“cario”, like dental caries) 3. Galactose: Seldom found free in nature Usually bound with glucose in lactose (milk sugar); only monosaccharide obtained primarily from animal sources Types of Carbohydrates: Simple (cont.) Disaccharides: Pairs of monosaccharides joined through condensation reactions 2 reactants combine to form a larger product Broken down by hydrolysis Major reactant split into 2 products through addition of H20 Hydrogen (H) atom added to one reactant, hydroxyl group (OH) added to the other All disaccharides contain at least 1 glucose molecule maltose (glucose + glucose) sucrose (glucose + fructose) lactose (glucose + galactose) Types of Carbohydrates: Simple (cont.) Disaccharide: Maltose Sucrose Lactose glucose + glucose glucose + fructose glucose + galactose How produced? From break down of starch: From the refinement of 1) carbohydrate digestion in sugar cane and sugar humans; 2) fermentation beets process of starch to produce (degree of refinement alcohol determines colour and consistency (e.g., brown, white, powdered) Foods? In a limited number of foods “table sugar”; brown “milk sugar” (lactose in (e.g., germinating seeds of sugar (97% sucrose); milk products enhances cereal grains) white & powdered are intestinal calcium 100% sucrose absorption) (argument for dairy products versus supplements) Types of Carbohydrates Carbohydrates Complex Simple Carbohydrates Carbohydrates (Oligo. & “sugars” Polysaccharides) Disaccharides: Starch: amylose, Monosaccharides: maltose, sucrose, Glycogen amylopectin lactose Hexoses: glucose, Pentoses: ribose, fructose, xylose…(later Dextrin Fibres galactose… courses) Other trioses, tetroses, heptoses Soluble Fibre Insoluble Fibre + more Types of Carbohydrates: Complex Complex carbohydrates: Known as oligosaccharides and polysaccharides Oligosaccharides = 3-10 monosaccharides Polysaccharides > 10 monosaccharides Straight or branched chains of monosaccharides Not sugars but comprised of many sugar molecules joined through condensation reactions (e.g., starch, glycogen) Types of Carbohydrates: Complex (cont.) 1. Starch: Amylose and amylopectin are produced in varying amounts in starch Amylose: continuous single chains of glucose molecules joined in alpha (1-4) links Amylopectin: branched chains of glucose molecules joined in alpha (1-4) links with branches joined by alpha (1-6) links Many types of amyloses and amylopectins: produce different characteristics (flavour, solubility, thickening power)… food science! From a nutrition perspective, starches are all the same (all broken down to glucose) Types of Carbohydrates: Complex (cont.) 2. Glycogen: Storage form of carbohydrate (energy) in humans/animals Highly branched chains of glucose (10-18 chains) Highly branched = holds water (can store a limited amount of H20) Fast hydrolysis (release a very quick supply of energy) Body stores of glycogen last ~ 12-18 hours Types of Carbohydrates: Complex (cont.) 2. Glycogen (cont.): Can be relied upon for short term energy needs Long term energy needs rely on fat in adipocytes (adipose tissue) which is not as bulky and has no H20 Body requires glucose to function… Thus, liver glycogen converted to glucose and released to blood (muscle glycogen remains in muscles for use) When liver glycogen is depleted, body produces glucose via gluconeogenesis Types of Carbohydrates: Complex (cont.) 3. Dextrin Straight chain polysaccharide produced by the digestion of starch with acid or heat to form shorter chains Salivary and pancreatic enzymes produce dextrin Applying dry heat to starch produces dextrin Tastes sweeter than starch (its precursor) Types of Carbohydrates: Complex (cont.) 4. Fibre From plant sources only; not considered a nutrient Long chains of glucose molecules joined by beta (1-4) links Also known as “non-starch polysaccharides” E.g., cellulose has beta (1-4) links Humans do not produce enzymes capable of breaking beta bonds Some microorganisms in our GI tract can break some of the fibres down to some extent This process produces short chain fatty acids Types of Carbohydrates: Complex (cont.) 4. Fibre (cont.) Endogenous components of plant material in the diet which are resistant to digestion by secretions produced by humans Includes cellulose, pectins, hemicelluloses, mucilages, lignans, cutins, and tannins Also consists of substances such as phytates Different types of fibre are comprised of chains of monosaccharides, with different structures, and different properties Offer different health effects (growing area of research) Types of Carbohydrates: Complex (cont.) 4. Fibre (cont.) Total fibre = dietary fibre + functional fibre Dietary fibre: edible, non-digestible, from plants Functional fibre: isolated, extracted & added to food/pills for health benefits Can be described by these features: Solubility: the extent to which a solute (substance) can be dissolved (dispersed) in aqueous solution (e.g., water) Digestibility: the extent to which a substance can be digested (broken down into its component parts) by enzymatic action within the digestive tract Two types of fibre: Soluble (viscous) fibre Insoluble (non-viscous) fibre Two Types of Fibre Dissolves and swells up in water. Forms a gel that increases the transit time (i.e., takes Soluble longer) or slows the passage of food =Delays gastric emptying Helps lower cholesterol. Does not dissolve in water. Provides roughage/bulk and helps keep you regular. Insoluble Helps prevent constipation. Fibre in foods Soluble Fibre: Insoluble Fibre: Fruits (pectins) skins of fruits and vegetables Some legumes broccoli, celery Oats, Flaxseed blackberries, raspberries Barley whole wheat pasta Rye brown rice Guar gum from guar trees nuts and seeds Acacia gum from acacia trees Carrageenan from seaweed Psyllium Some hemicelluloses Fiber-containing foods usually have a combination of both soluble and insoluble fiber. Ways to Increase Dietary Fibre Intake: Add fibre slowly Drink lots of water Physical activity Consider nutrient content claims on food packages: Very high source of fibre ≥ 6 g fibre per serving High source of fibre ≥ 4 g fibre per serving Source of fibre ≥ 2 g fibre per serving Carbohydrate: Digestion Refer to physiology course for greater detail The process by which food is broken down into component parts (absorbable units) (digest = take apart) Highlights: [Mouth]: salivary amylase hydrolyses amylose into dextrins, maltotriose & maltose [Small intestine]: carbohydrases (e.g., pancreatic amylase) hydrolyses starch into dextrins, maltotriose & maltose Products of carbohydrate digestion: glucose, galactose, fructose Break 10 minutes 3 2 Part 3: Carbohydrates in the Body Carbohydrate: Absorption Refer to physiology course for greater detail The uptake of nutrients by the cells of the gastrointestinal (GI) tract for transport into either the blood or the lymph (and then on to body cells) Highlights: Active transport of monosaccharides (glucose, galactose, fructose) Absorbed via intestinal microvilli into the capillaries where they travel via the portal vein to the liver In the liver, galactose and fructose are converted to glucose (digestion) Glucose is transported via blood to all body cells Carbohydrates: Highlights of Digestion & Absorption Main product: glucose Primary energy source for nervous tissue Brain uses > 70% of glucose required by the body; red blood cells (RBC) use approx. 30% Carbohydrate (Glucose) Metabolism Recall: to generate energy, glucose is metabolized through cellular respiration (also called aerobic metabolism) Recall: cellular respiration produces ATP, a form of energy This metabolic pathway uses: 6 molecules of oxygen to convert 1 molecule of glucose into 6 molecules of CO2 , 6 molecules of H20 and ~38 molecules of ATP Recall: 3 potential fates of glucose: 1. Used to produce fuel for body cells 2. Single molecules of glucose stored as glycogen (liver and muscle) 3. Excess glucose stored as fat Fate 1: Fuel Production for Body Cells Oxidation of glucose > C02 + H20 occurs via 3 complex processes: 1. glycolysis 2. citric acid cycle/Kreb’s cycle/TCA 3. oxidative phosphorylation C6H12O6 + 6O2 > 6 CO2 + 6H20 + 38 ATP *ATP: adenosine triphosphate (main short term energy storage and transfer molecule of living organisms) Glycolysis: metabolic pathway in the cytoplasm of all cells; a 6-carbon molecule of glucose is broken down into 2 molecules of pyruvic acid (3C each) in the absence of oxygen (anaerobic) Some energy is released during glycolysis (exergonic); produces 2 ATP (~30 kcal dissipated as heat from ATP for each mole of glucose that is metabolized) Glycolysis: Summary 3 8 Glycolysis (Fate 1 of Glucose/Fuel for Body Cells) In muscle cells: When O2 is lacking (anaerobic conditions, i.e., when exertion exceeds cardiac capacity to deliver O2 and remove C02 from muscles), pyruvate is converted to lactate (lactic acid), released to blood, resulting in “oxygen debt” Associated with muscle pain during exertion (due to a change in pH caused by glycolytically generated acid, not lactic acid) Lactic acid in blood is converted to glucose in the liver (liver coordinates glycolysis, gluconeogenesis and lipogenesis) To reduce muscle fatigue, pause to relax muscles frequently and increase blood flow (allows O2 delivery and CO2 removal) 4 0 Oxidative Phosphorylation (Electron Transport Chain) 3 ATP are produced per NADH oxidized 2 ATP are produced per FADH2 oxidized GTP does not enter oxidative phosphorylation (O/P) but rather is directly phosphorylated to yield 1 ATP per GTP 4 1 Overall Energy Balance for Glucose Metabolism From glycolysis: 2 ATP (net) 2 ATP Anaerobic No additional E*produced Aerobic 2 NADH + 2H+ 4-6 ATP* 2 NADH + 2H+ 6 ATP** From CAC/TCA/Kreb’s: 6 NADH + 6H+ 18 ATP 2 FADH2 4 ATP From direct phosphorylation: 2 GTP 2 ATP TOTAL 36-38 ATP *depends on which pathway is used to move these NADH into mitochondria ** these are from the conversion of pyruvate to Acetyl CoA Fate 2: Excess Glucose stored as Glycogen When the cells’ energy need are met, excess glucose is used to saturate liver and muscle glycogen stores In the liver, excess glucose is converted to glycogen through the enzymatic actions of glycogen synthase Fate 3: Excess Glucose stored as Fat When cells’ energy needs are met, and glycogen stores are saturated, excess glucose is stored as fat (in adipocytes in adipose tissue) In liver, excess glucose is broken down and used to form fat Insufficient Glucose in the Body What happens when there is not enough (insufficient) glucose? The body produces glucose from various 3C substrates (including protein and pyruvate) Gluconeogenesis: the making of glucose from a non-carbohydrate source (gluco = glucose; neo = new; genesis = making) Which problems create insufficient dietary carbohydrate? ketosis (from inefficient breakdown of fatty acids) when the body uses its own protein to produce glucose (e.g., starvation, insufficient dietary carbohydrate, etc. ) ***Adults need a minimum of 100 g/day (to supply sufficient glucose for bodily functions and requirements) Insufficient Glucose in the Body (cont.) Using Protein to Produce Glucose: When there is insufficient carbohydrate available to the body, muscles deplete glycogen stores When glycogen stores are depleted, the body breaks down body protein to produce glucose Body protein (e.g., muscle cells) is broken down and cannot perform functions that only protein can perform E.g., growth and maintenance of body cells; transport of nutrients, hormones, etc.; production of enzymes and hormones; immune system regulation Diet and Insufficient Glucose in the Body Diets providing enough carbohydrate “spares” protein (preserves the body’s use of protein for its intended and essential functions) Referred to as the “protein sparing action” of carbohydrates Part 4: Carbohydrates and Health Health Effects of Carbohydrates Blood Glucose Regulation Diabetes mellitus: a disease caused by either insufficient insulin production or decreased sensitivity of cells to insulin; results in elevated blood glucose levels Hypoglycemia: a low blood-glucose level, usually below 2.2 to 2.8 mmol/L of blood plasma Blood-glucose response curve: a curve that illustrates the change in blood glucose that occurs after consuming food Health Effects of Carbohydrates (cont.) Blood Glucose Regulation (cont.) In order to provide a steady supply of glucose to the cells, the concentration of glucose in the blood is regulated by the liver and by hormones secreted from the pancreas Insulin: a hormone secreted by the pancreas in response to a rise in blood glucose levels Glucagon: a hormone secreted by the pancreas in response to a decline in blood glucose levels Glycemic response: how quickly and how high blood glucose rises after carbohydrates are consumed Glycemic index: a ranking of how a food affects the glycemic response Health Effects of Carbohydrates (cont.) Blood Glucose Regulation (cont.) Immediately after a meal, the blood glucose level rises. Insulin is released from the pancreas and stimulates the taking up of glucose into the cells, and the storage of glucose as glycogen in the liver and muscles. Several hours after a meal, the blood glucose levels fall. Glucagon is released from the pancreas and stimulates glycogen breakdown and the making of glucose (gluconeogenesis). A soluble fibre-rich meal slows down the rise in blood glucose (large spike with simple carbohydrate, no fibre, no protein) Low-glycemic index foods slow down the rise in blood glucose (i.e., they do not cause a large spike in blood glucose) Health Effects of Carbohydrates (cont.) Dental Caries: Bacteria living in the mouth form colonies on the teeth (“plaque”) If plaque is not removed, bacteria metabolize sugar (carbohydrate) and create acid on teeth/gums Acid dissolves tooth enamel and the underlying structures of the teeth and gums Increased risk of dental caries the longer the sugar and acid are in the mouth Stickier sugars are more cariogenic (versus soda which is less cariogenic) Health Effects of Carbohydrates (cont.) Sugar Considered “empty kilocalories” Low nutrient density Displaces other nutrients (consume high sugar foods instead of healthier, more nutrient-dense foods) – possible contribution to deficiencies? E.g., regular (not diet) soft drinks; chewy and hard candy, honey, sugar, HFCS, etc. Sugar Alcohols Sugar alcohols, like sorbitol, are added to foods to give them a sweet taste as an alternative to regular sugar. E.g. Erythritol, mannitol Health Effects of Carbohydrates (cont.) Carbohydrates and Heart Disease (Cardiovascular Disease) Diets high in sugar or refined carbohydrates have been shown to raise blood lipid levels (triglycerides); can lead to an increase in heart disease Diets high in whole grains have been found to reduce the risk of heart disease High carbohydrate diets increase levels of triglycerides & high density lipoproteins (HDL) cholesterol (the “good” cholesterol) High serum triglycerides are more extreme if the primary carbohydrate in diet is monosaccharides (simple sugars), especially fructose Soluble fibre in foods can bind to dietary cholesterol in the gut and is excreted via waste (without soluble fibre, cholesterol goes to liver) Health Effects of Carbohydrates (cont.) Indigestible Carbohydrates and Bowel Disorders Diets high in fibre or indigestible carbohydrates can relieve or prevent certain bowel disorders: hemorrhoids; diverticulosis; diverticulitis*; constipation Epidemiological studies have shown that the incidence of colon cancer is lower in populations that consume diets high in fibre Higher levels of fibre intake may be associated with lower risk of certain cancers but need to use caution: fibre vs. dietary pattern Fibre lowers serum estrogen/protective effect No evidence of effect for fibre supplements; more research needed *intestinal mucosa protrudes through muscular intestinal wall trapping feces in pouches; untreated becomes inflamed and painful Health Effects of Carbohydrates (cont.) Indigestible Carbohydrates and Other Conditions Viscous fibres increase insulin tissue response and protect against diabetes Unclear influence of dietary fibre on obesity Some fibre is fermented by gut bacteria, producing short-chain fatty acids (SCFA) which cannot be absorbed (yield energy: 1.5 -2.5 kcal/g) Some fibre lowers blood cholesterol levels (e.g. soluble fibres) Other Effects of Fibre (Indigestible Carbohydrate) At very high intakes (above AI), some types of fibre may lower nutrient availability by: Inhibiting digestive enzymes Creating a physical barrier Containing phytic acid which binds Ca (calcium), Fe (iron), Mg (magnesium), Zn (zinc) and decreases their absorption Anti-nutrient effects of high fibre diets may be addressed by physiological adaptations in absorption of affected nutrients Before Next Class Next Week Finish reading (Module 3 content): (Module 4) - Lipids WileyPLUS: Chapter 4 DRI: Carbohydrate: sugars and starches (pgs. 103-122) Start reading (Module 4 content): WileyPLUS: Chapter 4 DRI: Dietary fat: total fat and fatty acids (pgs. 123-143) Think about this for next class… What is the role of lipids in our body? https://cheeseontop.wordpress.com/category/random-posts/