1 Chapter 4 Carbohydrates: Sugars, Starches, and Fiber4-2

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4 Learning Objectives Discuss the difference between refined and unrefined carbohydrates. Compare the structure of simple and complex carbohydrates. Distinguish between soluble and insoluble fiber and name food sources of each. Define lactose intolerance and explain its cause. 4-3

5 Learning Objectives Discuss the effects of dietary fiber on gastrointestinal function and health. Describe the steps involved in metabolizing glucose to produce energy. Explain how the hormones insulin and glucagon are involved in regulating blood glucose levels. 4-4

6 Learning Objectives Compare the causes and consequences of type 1 and type 2 diabetes. Discuss the health risks and benefits associated with carbohydrates. Discuss artificial sweeteners. 4-5

7 What do you know already?

8 Macronutrients: Our Main QuestionsWhat are they? What do they do in us? Where do they come from? Structure Digestion Metabolism and Storage Recommended Allowances Consequences of too much Consequences of too little Other Issues (substitutes, etc.)

9 Sugars: What They Are? White sugar (sucrose)High-fructose corn syrup or corn syrup Sorbitol Brown sugar Molasses Honey Powdered sugar Raw sugar Fiber

10 Sugars: What They Do In Us.Carbohydrates meet your body’s energy needs Feed your brain and nervous system Keep your digestive system fit Within calorie limits, help keep your body lean Together with fats and protein, digestible carbohydrates add bulk to foods Indigestible carbohydrates yield little or no energy but provide other benefits DNA backbone

11 Carbohydrates: Where do they come from?Carbohydrate-rich foods come almost exclusively from plants Milk is the only animal-derived food that contains significant amounts of carbohydrate

12 Carbohydrates: Where do they come from? Synthesis of Glucose and Starch4-16

13 Carbohydrates (CH2O)n Simple carbohydrates (sugars) MonosaccharidesDisaccharides Complex carbohydrates (polysaccharides) Glycogen Starch Fiber

14 Simple Carbohydrates Monosaccharides C6H12O6 Glucose FructoseGalactose

15 Simple Carbohydrates: The MonosaccharidesGlucose C6H12O6 The essential energy source for all body functions. Other names: Dextrose and Blood Sugar. A component of each disaccharide. The body’s main source of energy. The main function of glucose is to supply the body with energy. Certain tissues, such as red blood cells and most parts of the brain derive almost ALL their energy from glucose. The brain and nervous system use almost all glucose for fuel . Glucose is the principal monosacharide in the body and exists in the ring form. Glucose, a six-carbon monosaccharide is called a “hexose” meaning 6, for 6 carbons.

16 Simple Carbohydrates: The MonosaccharidesFructose: The sweetest of all sugars (1.5 X sweeter than sucrose) Occurs naturally in fruits and honey “the fruit sugar” The chemical formula is the same as glucose, but the structure differs. This change in structure allows the fructose molecules to appear sweeter to our taste buds. Once fructose is absprbed nby the small intestine and transported to the lived, is is almost all metabolized as glucose. Fructose was discovered in the 1960’s, and the production of HFCS shortly followed. Heard of high fructose corn syrup? This is actually corn syrup that has been manufactured to contain between 46% and 60% fructose, making it much sweeter. The HFCS is actually a combination of dextrose.. Found in corn and fructose. It is a common sweetener in soft drinks, candy, etc. Is fructose, the “fruit sugar” any more nutritious to humans than plain sucrose, or table sugar? NO All sugars nourish your body in the same way. Fructose and sucrose are just different sugars, both simple sugars. SO what would be the advantage of using fructose as a sweetener? Since it is almost 1.5x sweeter than sucrose, it can be used in smaller amounts. Thus, products sweetened with fructose may be lower in calories when compared to their sucrose alternatives. The average American consumes approx. 47g fructose per day or about 8% of his or her total energy intake.

17 Simple Carbohydrates: The MonosaccharidesGalactose Seldom occurs freely in nature Binds with glucose to form sugar in milk: lactose. Once absorbed by the body, galactose is converted to glucose to provide energy. Galactose is the third major monosaccharide of nutritional importance. Again, comparison of the structure of a glycogen and glucose molecule would show that they are identical except for minor structural placement of molecules. Now is a good time to emphasize the key concept of nutrition: eth difference between INTAKE of a substance and the body’s USE of a substance. The body does not always use nutrients just as they are. Some substances are broken down and later reassembled into the same or a different substance when and where necessary. Ex: Galactose in the diet is metabolized to glucose or glycogen. When later required as in the mammary gland of a lactating female, galactose is resynthesized, using a variety of carbon atom sources.

18 Monosaccharides to PolysaccharidesMonosaccharides can be joined to make disaccharides and polysaccharides. Via condensation reactions Polysaccharides can be broken down to monosaccharides. Via hydrolysis reactions

19 Condensation Think of clay, if you take water out, it becomes hard

20 Hydrolysis If you put water into something, it breaks it apart

21 Disaccharides Maltose Sucrose Lactose

22 Simple Carbohydrates: The DisaccharidesMaltose Maltose = Glucose + Glucose Produced when starch breaks down. Used naturally in fermentation reactions of alcohol and beer manufacturing. Aromatic in baking Maltose results when 2 glucose molecules are bound together by a glycosidic bond as the result of a condensation reaction. Maltose is of nutritional interest primarily because it is a chemical intermediate in alcohol production in the beer and liquor industry. Maltose is one end result of the breakdown of starch molecules in grain. The maltose is used in the fermentation process. ````````````````````````````````````````````````````````

23 Simple Carbohydrates: The DisaccharidesSucrose Sucrose = Glucose + Fructose *Table sugar *Found naturally in plants: sugar cane, sugar beets, honey, maple syrup *Sucrose may be purified from plant sources into Brown, White and Powdered Sugars.

24 Simple Carbohydrates: The DisaccharidesLactose Lactose = Glucose + Galactose The primary sugar in milk and milk products. Many people have problems digesting large amounts of lactose (lactose intolerance) Because the lactose is formed with a beta bond, that causes complications in digestion.

25 Carbohydrates (CH2O)n Simple carbohydrates (sugars) MonosaccharidesDisaccharides Complex carbohydrates (polysaccharides) Glycogen Starch Fiber

26 The Complex Carbohydrates:Polysaccharides: containing 2 or more monosaccharides attached together Three types are important in nutrition: 1. Glycogen- digestible 2. Starch- digestible 3. Fiber- indigestible Oligosaccharides and polysaccharides are classified as complex carbohydrates. Polysacchariees conatin many monosaccharide units, up to 3000 or more. Most poly’s are synthesized from glucose, as when vegetables turn starch to glucose during maturation.

27 The Complex Carbohydrates:Glycogen The storage form of glucose in the body. Stored in the liver and muscles. Found in tiny amounts in meat sources. Not found in plants. Not a significant food source of carbohydrate. Glycogen is quickly broken down by the body for energy. Used when the body needs an immediated source of blood glucose. Highly branched chains allow quick release. Glycogen in the liver is broken down to blood glucose. Glycogen in the muscles is used for quick burst of energy during high-intensity and endurance physical activity. When blood glucose falls, glycogen is dismantled in the liver and released into the bloodstream as energy. Glycogen is bound with water, so as the glycogen is released so is water. The body only has enough glycogen to provide energy to the body for a few hours. For long-term energy needs in the deprovation of glucose, the body turns to fat as an energy source.

28 The Complex Carbohydrates:Starch The major digestible polysaccharide in our diet. Sources: Wheat, rice, corn, rye, barley, potatoes, tubers, yams, etc. Two types of plant starch: 1. Amylose 2. Amylopectin When you consume starch, your body hydrolizes the starch molecules, breaking them down into energy… glucose that your body can use. Grains are the richest food sources of starch, providing energy for people all over the world. Both types of starch are energy sources in plants, yielding 4kcal/g. Both are chains of glucose linked together by glycosidic bonds. The difference is that amylopectin is made of branched chains, while amylose is a straight chain of glucose molecules.

29 The Complex CarbohydratesFiber Indigestible polysaccharides Types of fiber: Soluble (dissolve in water)- gums, pectins, mucilages, some hemicellulose 2. Insoluble (do not dissolve in water)- cellulose, lignin, many hemicelluloses Fiber is the structural part of plants. The structure that holds together fiber is indigestible by the human digestive system. The bonds between the monosaccharides cannot be broken down by human enzymes. Pectins, gums and mucilages can be found inside and around plant cells. They help “glue” the plant together. These fibers either dissolve or swell when put into water and are thus SOLUBLE FIBERS. Cellulose: the primary structure of the plant cell walls Gums and mucilages, act as food stabilizers Insoluble fibers: generally do not dissolve in water.

30 Food Sources of Fiber Soluble fiber Insoluble fiber Fruits LegumesOats, barley, and rye Also seeds and vegetables Insoluble fiber Wheat bran, brown rice, whole grains Vegetables (cabbage, carrots) Fruits Legumes

31 Food Sources of Fiber Soluble fiber Insoluble fiber Fruits LegumesOats, barley, and rye Also seeds and vegetables Insoluble fiber Wheat bran, brown rice, whole grains Vegetables (cabbage, carrots) Fruits Legumes

32 Health Effects of FiberSoluble, viscous fiber Lowers risk of heart disease & stroke by: Binding bile Lowers risk of diabetes and controls diabetes by: Slowing glucose absorption Also holds moisture in stools, softening them Insoluble, nonviscous fiber Alleviates constipation and lowers risk of hemorrhoids and diverticulosis by: Increasing fecal weight and speeding fecal passage through the colon May help with weight management

33 Carbohydrate Digestion in the GI TractSimple Starch Fiber

34 Simple sugars: MonosaccharidesSimple sugars are simply absorbed without digestion

35 Carbohydrates in the Digestive TractDisaccharides and complex carbohydrates must be digested for mono-saccharides to be absorbed. Digestible vs. Indigestible carbohydrates 4-19

36 Lactose Intolerance Not enough enzyme lactase in the small intestine to digest the milk sugar lactose Symptoms: intestinal gas and bloating, diarrhea More common in Asian, Native American, and Mediterranean populations What are alternative means to meet calcium needs for lactose-tolerant populations? 4-20

37 Starch

38 Fiber

39 Indigestible CarbohydratesFiber, some oligosaccharides, and resistant starch Health implications Stimulate GI motility Promote a healthy microflora Slow nutrient absorption Increase intestinal gas 4-21

40 Soluble Fiber—Healthy HeartDissolves in water or absorbs water Can be broken down by the intestinal microflora Includes: pectins, gums, semicelluloses Food sources: oats, apples, beans, seaweeds Health benefits: lower blood cholesterol 4-34

41 Insoluble Fiber—Happy GI TractDoes not dissolve in water Cannot be broken down by bacteria in the large intestine Includes: cellulose, hemicellulose, and lignin Food sources: wheat bran, rye bran, and vegetables Health benefits: soften stools and decrease transit time 4-35

42 Indigestible Carbohydrates and the Risk of Colon CancerEpidemiologic studies: the incidence of colon cancer is lower in populations consuming diets high in fiber Recent intervention studies: not supportive of the epidemiologic observations The scientific consensus: enough evidence that diets high in fiber protect against colon cancer 4-36

43 Carbohydrate MetabolismStoring glucose as glycogen Using glucose for energy

44 How Glucose is Stored/Used: Getting Glucose Into Cells.

45 Constancy of Blood GlucoseDiabetes Type 1 diabetes Failure of insulin production Type 2 diabetes Obesity

46 Abnormal Blood Glucose Levels in Diabetes Mellitus4-28

47 Diabetes Mellitus: SymptomsImmediate Symptoms Excessive thirst, frequent urination, blurred vision, and weight loss Long-term complications Damage to the heart, blood vessels, kidneys, eyes, and nerves 4-29

48 Diabetes Mellitus: TreatmentDiet Carbohydrate intake should be distributed through the day to control blood glucose levels, Exchanging lists or other carbohydrate-counting tools is useful Exercise Increase sensitivities of body cells to insulin Medication Insulin injection for Type 1 Insulin can help for some Type 2 patients 4-30

49 Carbohydrate MetabolismMaking glucose from protein Gluconeogenesis Protein-sparing action of carbohydrates

50 Carbohydrate MetabolismMaking glucose from protein Gluconeogenesis Protein-sparing action of carbohydrates

51 Carbohydrate Metabolism

52 Carbohydrate MetabolismConverting glucose to fat Energetically expensive The conversion of excess glucose to fat requires many steps and costs a great deal of energy When presented with both glucose and fat, the body prefers to store the fat and use the glucose to meet immediate energy needs This maximizes energy storage

53 Carbohydrate MetabolismWhen presented with both glucose and fat, the body prefers to store the fat and use the glucose to meet immediate energy needs Use the glucose and store the fat

54 Gluconeogenesis Making glucose from protein 4-23

55 Carbohydrates are Needed to Break Down Fat4-24

56 Constancy of Blood GlucoseHypoglycemia Rare in healthy people

57 Hypoglycemia: Low Blood GlucoseCan occur in people with diabetes as a result of over-medication or imbalance between insulin level and carbohydrate intake Can result from abnormalities in the production or response to insulin or other hormones involved in blood sugar regulation Reactive and fasting 4-31

58 Constancy of Blood GlucoseGlycemic response Glycemic index A measure of how fast sugar is digested https://www.diabetesnet.com/diabetes_food_diet/glycemic_index.php

59 Glycemic Response The rate, magnitude, and duration of the rise in blood glucose that occurs after a food or meal is consumed. Glycemic index: a ranking of how a food affects blood glucose compared to the response of a reference food Glycemic load: an index of glycemic response 4-25

60 Accusations Against SugarsSugar causes obesity Sugar causes heart disease

61 Accusations Against SugarsSugar causes misbehavior in children and criminal behavior in adults

62 Accusations Against SugarsSugar causes cravings and addictions serotonin

63 Carbohydrate RecommendationsThe RDA: Minimum amount required to provide adequate glucose for the brain Set at 130 g/day (~ 420 kcalories) The Range of Healthy Intakes: Set at 45% to 65% of energy No more than 25% of energy should come from added refined sugars An AI for Fiber: Set at 38g/day for young adult men and 25g/day for young adult women 4-37

64 Carbohydrate Content of Selections from Each Food Group of MyPyramid4-38

65 Calculating Percentage Energy from Carbohydrate4-39

66 Carbohydrates on Food LabelsGrams of total carbohydrate, fiber, and sugars listed Amounts of soluble and insoluble fiber not required Total carbohydrate and fiber also listed as a percent of the Daily Value 4-41

67 Looking for Sugars and Fibers on the Food Labels4-42

68 Looking for Sugars and Fibers on the Food Labels4-43

69 Translating Recommendations into Healthy Diets4-44

70 Alternatives to Sugar Artificial sweeteners vs. sugar replacers (nutritive sweeteners) In the first enzymatic reaction, methanol is broken down into formaldehyde. If you've ever dissected a frog in biology class, you may have witnessed one of the many uses of this chemical. Formaldehyde reacts with the amino acids in proteins. Proteins are chains of amino acids that fold to form very unique structures. The way these chains fold gives proteins the proper shape and the flexibility to interact with other molecules. Formaldehyde diffuses into tissues and cells where it forms crosslinks between different amino acids. The protein is stuck rigidly in whatever conformation it was in and is no longer able to carry out any reactions! This property makes formaldehyde useful for a number of chemical processes that fix things in a particular state. Some examples are: embalming leather tanning corrosion prevention wood finishing Formaldehyde may also cause cancer in humans, but this requires long-term exposure. Formaldehyde doesn't stick around long in your body because it is so rapidly metabolized to formic acid by the second enzyme in this metabolic pathway. Formic acid is also extremely toxic to humans. It disrupts the function of a cell's mitochondria. Mitochondria normally serve as the "powerhouse of the cell" (for more information on mitochondria, see How Cells Work) and disrupting their function is like abruptly shutting down a nuclear reactor. Not only do all the cellular processes stop for lack of energy, but the cells themselves are blown apart by a massive accumulation of different molecules involved in energy production. The cells that make up the optic nerve are exquisitely sensitive to formic acid, which is why blindness is so closely associated with methanol poisoning. Does aspartame produce enough methanol to harm people? The short answer is, "there is a lot of controversy around this question," as you will see in several of the links below. Most people regularly consume up to 10 mg of methanol per day as part of their normal diet. One 12-ounce can of aspartame-sweetened soda contains about 200 milligrams of aspartame [reference]. You'd add a tenth of this amount to your diet as methanol following digestion (20 mg).

71 Alternative SweetenersAcceptable Daily Intakes (ADIs) set by FDA Cut down on kcalories in, but do not add whole grains, fruits, and vegetables to the diet Have been shown to reduce the incidence of dental caries Usefulness for weight loss controversial 4-45

72 Types of Alternative SweetenersSaccharin 200–700 times sweeter than sugar No warning labels required since May 2000 Aspartame Made of aspartic acid and phenylalanine Can be dangerous to people with phenylketonuria (PKU) Sucralose (Trichlorogalactosucrose) Sold under the name “Splenda” Derived from sugar 4-46

73 Types of Alternative SweetenersAcesulfame K 200 times as sweet as sugar Heat stable Neotame Similar to aspartame, with stronger chemical bond (cannot be broken down easily) 7000–13,000 times sweeter than sugar! Sugar alcohols Chemical derivatives of sugar Low-calorie: 0.2–3 kcalories/gram Can be described as “sugar free” on food labels 4-47

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75 Alternatives to Sugar Saccharine and cancer Aspartame and PKU

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77 Metabolism of Aspartame

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79 Sugar Alternatives on Food Labels

80 High Fructose Corn SyrupUnlike carbohydrates made up of glucose, fructose does not stimulate the pancreas into producing insulin. Nor does it promote the production of leptin, a hormone made by fat cells. Under normal conditions, the amount of insulin and leptin in the body signal to the brain that you’ve had enough to eat

81 Simple Carbohydrates: The DisaccharidesSucrose Sucrose = Glucose + Fructose *Table sugar *Found naturally in plants: sugar cane, sugar beets, honey, maple syrup *Sucrose may be purified from plant sources into Brown, White and Powdered Sugars.

82 High Fructose Corn SyrupIt could be like paying with pennies vs. paying with nickels. The whole thing could be like a wooden nickel or a trick.

83 Simple Carbohydrates: The MonosaccharidesGlucose C6H12O6 The essential energy source for all body functions. Other names: Dextrose and Blood Sugar. A component of each disaccharide. The body’s main source of energy. The main function of glucose is to supply the body with energy. Certain tissues, such as red blood cells and most parts of the brain derive almost ALL their energy from glucose. The brain and nervous system use almost all glucose for fuel . Glucose is the principal monosacharide in the body and exists in the ring form. Glucose, a six-carbon monosaccharide is called a “hexose” meaning 6, for 6 carbons.

84 Simple Carbohydrates: The MonosaccharidesFructose: The sweetest of all sugars (1.5 X sweeter than sucrose) Occurs naturally in fruits and honey “the fruit sugar” The chemical formula is the same as glucose, but the structure differs. This change in structure allows the fructose molecules to appear sweeter to our taste buds. Once fructose is absprbed nby the small intestine and transported to the lived, is is almost all metabolized as glucose. Fructose was discovered in the 1960’s, and the production of HFCS shortly followed. Heard of high fructose corn syrup? This is actually corn syrup that has been manufactured to contain between 46% and 60% fructose, making it much sweeter. The HFCS is actually a combination of dextrose.. Found in corn and fructose. It is a common sweetener in soft drinks, candy, etc. Is fructose, the “fruit sugar” any more nutritious to humans than plain sucrose, or table sugar? NO All sugars nourish your body in the same way. Fructose and sucrose are just different sugars, both simple sugars. SO what would be the advantage of using fructose as a sweetener? Since it is almost 1.5x sweeter than sucrose, it can be used in smaller amounts. Thus, products sweetened with fructose may be lower in calories when compared to their sucrose alternatives. The average American consumes approx. 47g fructose per day or about 8% of his or her total energy intake.

85 Table 4.1 More and Less Refined ChoicesRecommendations: Choose more foods with less refined carbohydrates Choose fewer foods with refined carbohydrates and added sugars 4-7

86 The Whole Grain Story A whole grain is the entire kernel of grain including: The bran: dietary fiber and vitamins The germ: vitamin E, protein, fibers, riboflavin, thiamin, and B6 The endosperm: starch, protein, some vitamins and minerals 4-8

87 Choosing Whole Grains 4-9

88 Choosing Whole Grains 4-10

89 More on Carbohydrates and HealthDiets high in sugars and refined starches increase the demand for insulin and may increase the risk for developing diabetes. Diets high in whole grains and other unrefined carbohydrates may reduce the risk of heart disease. Diets high in indigestible carbohydrates can relieve or prevent certain disorders that are caused by pressure in the lumen of the colon. 4-33