What Are Carbohydrates? Chapter 4 Carbohydrates: Simple Sugars and Complex Chains. Monosaccharides. Simple Sugars 9/18/17 BIOL 103

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1 What Are Carbohydrates? Chapter 4 Carbohydrates: Simple Sugars and Complex Chains BIOL 103 Sugars, starches, and fibers Major food sources: Plants Produced during photosynthesis Two main carbohydrate types Simple Complex Monosaccharides Glucose Fructose Galactose Simple Sugars Monosaccharides Glucose/Dextrose Most simple sugar in nature Gives food a mildly sweet flavor Usually joined to another sugar in foods to form disaccharides, starch, dietary fiber Provides energy to body cells: Blood sugar levels Only fuel source used by brain 1

2 Fructose/Levulose Monosaccharides Tastes the of all the sugars Occurs naturally in fruits and vegetables Found in fruits, vegetables, honey, and corn syrup High Fructose Corn Syrup Why do we use it? Before 1970s à U.S. cane sugar à too expensive 1980s, food companies switched to cheaper corn Pepsi/Coke switched in 1984 High Fructose Corn Syrup How is it made? 1. Convert glucose à fructose, using isomerase 2. Add corn syrup, then a specific ra[o of glucose Why is High Fructose Corn Syrup associated with weight gain? 1. Cheap corn à supersize 2. Fructose does not release à less produc[on à eat more à fat produc[on Compared to glucose, fructose is preferen[ally metabolized to lipid in the liver. However, note that overconsump[on of ANY forms of sugar will contribute to weight gain. 2

3 Galactose Rarely occurs as a monosaccharide in food Usually bonds to glucose to form Monosaccharides Simple Sugars Disaccharides: Consist of two monosaccharides linked together Sucrose: glu + fru Lactose: glu + gal Maltose: glu + glu Linked by bonds Disaccharides Sucrose: glucose + fructose Made from sugar cane and sugar beets Listed as sugar on food labels Lactose: glucose + galactose Found in milk and milk products Lactose Intolerance Who has it? Anyone who does not have enough Why do you get it? Lactase nonpersistence (most common) Injury/infec[on to intes[ne usually during infancy Developmental lactase deficiency in premature infants Congenital lactase deficiency: rare gene[c disorder from birth 3

4 Disaccharides Maltose: glucose + glucose Seldom occurs naturally in foods Product of starch breakdown Found in germina[ng cereal grains Complex Carbohydrates Chains of three or more sugar molecules Oligosaccharides 3-10 sugar molecules Examples sources: dried beans, peas, and len[ls Polysaccharides Long chains of monosaccharides Structural differences affect how they behave in water and with hea[ng Diges[ble or non- diges[ble Complex Carbohydrates Starch Storage form of energy in Found in grains, legumes, and tubers Long chains of glucose units Amylose AmylopecCn Digested more rapidly than amylose Resistant starch: A starch that is not digested Complex Carbohydrates Glycogen Storage form of carbohydrates in Highly branched chains of glucose units Blood glucose Most stored in our and Carbohydrate loading 4

5 Complex Carbohydrates Fiber Non- diges[ble carbohydrates and lignins Dietary fiber: soluble + insoluble fiber Fruits, vegetables, legumes, and whole grains FuncConal fiber: Isolated and added to foods Total fiber: Sum of dietary fiber and func[onal fiber Types of Dietary Fiber Dietary Fiber Soluble Dissolves in water à gel- like à Insoluble Does not dissolve in water Fermentable Example: Fruits, vegetables, legumes, oats, oat bran, legumes (dried beans and peas) Fermentable vs. Non- fermentable Example: Bran por[on of whole grains, skins of fruits/ vegetables, cauliflower, potato skins 5

6 Review Ques[ons 1. What is the difference between starch and glycogen? 2. What is the difference between starch and fiber in terms of diges[on in the human body? 3. What is HFCS 65 made up of? 4. In your own words, why is consuming high fructose corn syrup associated with weight gain? 5. What are the health benefits of consuming soluble fiber? How about for insoluble fiber? Carbohydrate Diges[on Diges[on breaks down carbohydrates to single sugars Mouth Salivary amylase Stomach HCl s acidity stops the ac[on of salivary amylase à stops carbohydrate diges[on Diges[on Small intes[ne Carbohydrate Diges[on PancreaCc amylase con[nues starch diges[on Brush border enzymes digests disaccharides Other diges[ve enzymes: Maltase, sucrase, and lactase Carbohydrate Diges[on Diges[on Bonds that link glucose molecules Alpha bonds starch Beta bonds cellulose/fiber, resistant starch 6

7 Carbohydrate Absorp[on Absorp[on in the small intes[ne Glucose, galactose, fructose molecules travel to the liver through the portal vein Liver converts the absorbed monosaccharaides to glucose: Galactose à glucose Fructose à glucose Carbohydrates and Glucose in the Body Excess glucose is stored as Liver glycogen (~1/3) Muscle glycogen (~2/3) 7

8 Carbohydrates and Glucose in the Body Glucose is our primary fuel 1. To drive chemical processes 2. To maintain normal blood glucose levels Other sources of energy: What is the order of energy usage by body? Consequence of Low Blood Sugar Sparing body protein Adequate carbohydrates prevent body from making glucose from body proteins Preven[ng ketosis Ketone bodies à ketosis à dehydra[on Body needs a minimum of 50 to 100 grams of carbohydrate/day to prevent ketosis Carbohydrates and Glucose in the Body Regula[ng blood glucose Hyperglycemia vs. Hypoglycemia Carbohydrates and Glucose in the Body Regula[ng blood glucose Controlled by hormones: Insulin: Glucagon: Blood Glucose (FasCng) Blood glucose (2 hrs aoer meal) Normal mg/dl <140 mg/dl Hyperglycemia >126 mg/dl >200 mg/dl Hypoglycemia <72 mg/dl N/A Epinephrine (Adrenaline): Fight- or- flight hormone 8

9 Regula[ng Blood Glucose Glycemic Index measures effect of food on blood levels Different foods vary in their effect on blood glucose levels Foods with Glycemic Index cause faster and higher rise in blood glucose Glycemic Index High Blood Glucose: Diabetes Mellitus What is diabetes? A chronic disease in which the body s ability to produce or respond to insulin is impaired, resul[ng in prolonged high blood sugar Normally: Eat food with glucose à blood and cells If too much blood glucose à pancreas releases insulin à blood glucose decreases If you have diabetes: 9

10 High Blood Glucose: Diabetes Forms of diabetes mellitus: Diabetes Type I: Diabetes Type II: GestaConal diabetes: Postprandial (1-2 hrs aoer eacng) Blood Sugar Measurements Normal: postprandial blood glucose <140 mg/dl Diabe[cs: postprandial blood glucose is >200mg/dL Pre- diabe[c: postprandial blood glucose 140mg/dL- 200mg/dL Consequences of hypo/hyperglycemia Severe hypoglycemia Ketosis, ketoacidosis Coma, death Short- term hyperglycemia Ketosis, ketoacidosis (more common in type- I) Long- term hyperglycemia Diabetes complica[ons damages to nerves, blood vessels, and thus, result in impaired func[ons of our organs The Role of Carbohydrates in Our Diet Cons: excess simple sugar à weight gain, poor nutrient intake, tooth decay Pros: high intake of foods rich in dietary fiber offers many health benefits, including reduced risk of: Obesity Type 2 diabetes Cardiovascular disease Gastrointes[nal disorders Increase fiber intake gradually while drinking plenty of fluids 10

11 Carbohydrates and Health Fiber and obesity Possible role in weight control Fiber and type 2 diabetes Berer control of blood glucose Fiber and cardiovascular disease Can lower blood cholesterol levels Fiber and gastrointescnal disorders Healthier gastrointes[nal func[oning Carbohydrates and Health Nega[ve effects of excess fiber: If add supplemental fiber too quickly, may have side effects: abdominal bloa[ng, gas Can bind small amounts of minerals à prevent some mineral absorp[on Examples: Zinc, Calcium, Iron Fiber does not have UL: because ea[ng a lot of fiber (found naturally in foods) doesn t really affect overall health of healthy people. Carbohydrates and Health Modera[ng sugar intake Use less added sugar Limit sot drinks, sugary cereals, candy, ice cream, and sweet desserts Choose fresh fruits or those canned in water The Role of Carbohydrates in Our Diet Choosing Carbohydrates Wisely Increase fruit, vegetables, whole grains, low- fat milk Strategies Eat peel fruit/vegetables Eat legumes Choose brown rice Choose high- fiber cereal Drink plenty of water! 11

12 Carbohydrates and Health NutriCve sweeteners: Monosaccharides, disaccharides, and sugar alcohols Natural vs. refined Non- nutricve sweeteners: Saccharin Aspartame Acesulfame K Sucralose Nutri[ve Sweeteners NutriCve Sweeteners: 1. Natural: mono + di- saccharides e.g. honey, maple syrup 2. Refined: mono + di- saccharides extracted from plant food e.g. white sugar, fructose 3. Sugar Alcohol/Polyols: may be sugar/sucrose free, and low in calories. e.g. xylitol, mannitol, sorbitol Sugar- Free Candies Non- Nutri[ve Sweeteners MalCtol = sugar alcohol From plants Benefits: No tooth decay Nearly as sweet as sugar à I can eat more Laxa[ve effect: 15 gummy bears (40g) = 1 dose Non- nutricve sweeteners: ar[ficial sweeteners ; yields almost no energy Types: 1. Saccharin (1970s; bladder cancer) 2. Aspartame (phenylalanine + aspar[c acid; PKU) 3. Acesulfame K (stable under heat) 4. Sucralose (used in baked goods, beverages, gela[n, etc.) Saccharin: Sweet N Low Aspartame: NutraSweet, Equal Acesulfame K: Sweet One, Sunere Sucralose: Splenda 12