1. Carbohydrates: Sugars, Starches, and Fiber
Chapter 4
Carbohydrates: Sugars, Starches, and Fiber

2. Objectives for Chapter 4
Compare and contrast the monosaccharides, disaccharides, and polysaccharides.
List the functions of carbohydrates in the body.
Explain the process of digesting and absorbing dietary carbohydrates.
Explain how the body uses, regulates and stores glucose and the hormones involved in the process.
Describe the guidelines for carbohydrate intake, including the AMDR for carbohydrates, the DRI for fiber, and the recommendation for consuming simple sugars.
Identify good food sources for each type of carbohydrate.
Describe the potential health implications of consuming too much or too little added sugar.
List alternative sweeteners used as sugar substitutes.
Importance of fiber

3. 1. What Are Carbohydrates and Why Do You Need Them?
Found primarily in plant-based foods:
Carbon, Hydrogen and Oxygen molecules made from plants converting CO2 and H20 into C6H12O6 and larger molecules.
Grains, vegetables, fruits, nuts, legumes
Range from simple to complex
Most desirable form of energy for body
Brain, muscles and red blood cells especially rely on glucose for fuel source

4. 1. Photosynthesis: How Glucose Is Made
Figure 4.1

5. 1. Where Do Carbohydrates Come From?
Plants use the energy of light to make the energetic monosaccharide glucose. This form of carbohydrate is the most abundant carbohydrate in nature. It is also:
combined with minerals from soil to make other compounds, such as protein and vitamins.
Glucose units linked together and stored in form of starch.

6. 1. What Are Simple and Complex Carbohydrates?
Simple carbohydrates: monosaccharides and disaccharides
Three monosaccharides: glucose, fructose, galactose
Disaccharides: two monosaccharides joined together
Maltose (beer) = glucose + glucose
Sucrose (table sugar) = glucose + fructose
Lactose (milk sugar) = glucose + galactose

7. 1. Simple Carbohydrates
Figure 4.2

8. 1. What Are Simple and Complex Carbohydrates?
Complex carbohydrates: polysaccharides
Long chains and branches of sugars linked together
Three forms of carbohydrates
Starch, Glycogen & Fiber
Starch is the storage form in plants.
Glycogen is the storage form in animals
Fiber is part of plant that we eat but can’t digest

9. 1. Complex Carbohydrates

10. 2. Functions of Carbohydrates a. Fiber
Fiber is part of plant that we eat but can’t digest yet is important to our health.
Examples: cellulose, hemicellulose, pectin
Humans lack digestive enzyme needed to break down fiber
Dietary fiber: naturally found in foods
Functional fiber: added to food for beneficial effect
Example: Psyllium added to cereals
Total fiber = dietary fiber + functional fiber

11. 2. Fiber – soluble and insoluble
Fiber is classified by its affinity for water
Soluble fiber: dissolves in water and is fermented by intestinal bacteria
Many are viscous, have thickening properties
Move more slowly through GI tract
Examples: Pectin in fruits and vegetables, beta-glucan in oats and barley, gums in legumes, psyllium
Insoluble fiber: cellulose, hemicellulose, lignins
Move more rapidly through GI tract, laxative effect
Examples: bran of whole grains, seeds, fruits, vegetables

12. 2. Most Plant Foods Contain Both Soluble and Insoluble Fibers
Figure 4.3

13. 2. Functions of Carbohydrates b. Glycogen
Glycogen is the storage form of glucose in animals.
Stored in liver and muscle cells
Only limited amounts
Important source of glucose for blood
Why don’t animal foods provide a good source of carbohydrates?
Answer: Glycogen gets converted to other forms once the animal dies.

14. 2. Functions of Carbohydrates c. Starch
Starch is the complex carbohydrate that is found ready in plants that are instantly ready to be used as energy
Three edible parts: bran, endosperm, germ

15. 2. From Wheat Kernel to Flour
Refined grains: milling removes bran and germ
Some B vitamins, iron, phytochemicals, and dietary fiber lost as a result
Examples: wheat or white bread, white rice
Enriched grains: folic acid, thiamin, niacin, riboflavin and iron added to restore some of the lost nutrition
Whole grain foods contain all three parts of kernel
Examples: brown rice, oatmeal, whole-wheat bread

16. 3. DIGESTION: From Carbohydrates to Glucose in Your Body
Figure 4.4

17. 3. Carbohydrate Digestion
Digesting a meal of pasta (starch), milk (lactose) and cherries (sucrose and fiber):
Carbohydrate digestion starts in your mouth with mechanical and chemical digestion. Saliva contains amylase enzyme (-ase = enzyme)
HCl in your stomach stops carb digestion but begins again in your small intestine.
All complex carbohydrates are now broken down into Monosaccharides.

18. 3. Some People Cannot Digest Milk Sugar
Lactose: Glucose and Galactose
principal carbohydrate found in dairy products
People with a deficiency of the enzyme lactase cannot digest lactose properly
Lactose maldigestion is natural part of aging
As soon as baby stops nursing, body makes less lactase
Lactose intolerance: when lactose maldigestion results in nausea, cramps, bloating, diarrhea, and flatulence

19. 3. Some People Cannot Digest Milk Sugar
Tips for tolerating lactose:
Gradually add dairy products to your diet
Eat smaller amounts throughout day rather than large amount at one time
Eat dairy foods with a meal or snack
Try reduced-lactose milk and diary products
Lactase pills can be consumed with lactose-laden meals or snacks

20. 3. Do you know how much lactose are in your food?
Table 4.1

21. 4. Uses of Carbohydrates
Your body only can use glucose as energy. Therefore:
monosaccharides (glucose) are either used immediately for energy in muscles, red blood cells or brian,
Excess monosaccharides (glucose, fructose & maltose) are stored in limited amounts in the liver
Excess monosaccharides (glucose, fructose & maltose) are stored in unlimited amounts as fat

22. 4. Uses of Carbohydrates
Glucose supplies energy for body, required for brain, nervous system, red blood cells
Fat can provide fuel for muscle, other tissues
Under starving conditions (18 hours or more) protein can be converted to glucose.
Hormones regulate amount of glucose in blood
Insulin is released by pancreas to convert excess glucose to glycogen (limited amount) or fat (unlimited amount) in response to high blood glucose levels after a carbohydrate-heavy meal.

23. 4. Carbohydrates Fuel Your Body Between Meals
When blood glucose begins to drop, pancreas releases the hormone glucagon to raise blood glucose levels
Directs release of glucose from stored glycogen in liver = glycogenolysis
Signals liver to start gluconeogenesis = making glucose from noncarbohydrate sources, mostly protein
Epinephrine (adrenaline) also stimulates glycogenolysis and increases blood glucose levels
“Fight or flight” hormone: stress, bleeding, low blood glucose levels trigger its release

24. 4. Carbohydrates Fuel Your Body During Fasting
Liver glycogen stores depleted after about 18 hours
Without glucose, fat can’t be broken down completely and ketone bodies are produced, which are acidic.
Ketosis: elevated blood levels after fasting about two days
Protein from muscle and organs broken down to make glucose
Brain switches to using ketone bodies for fuel to spare protein-rich tissues.
If fasting continues, protein reserves are depleted and death is inevitable.

25. 4. Hormones Help Maintain Healthy Blood Glucose Levels in Your Body
Figure 4.6

26. 4. Generating Energy from Glucose
Figure 4.5

27. 5. How Much Carbohydrate Do You Need and What Are the Best Food Sources?
Minimum amount of carbohydrates needed daily
DRI: 130 grams per day for brain function
Consume diet with low-to-moderate amounts of simple carbohydrates and higher amounts of fiber and other complex carbohydrates
Dairy, whole grains, whole fruits, vegetables, legumes, nuts, and seeds provide natural simple carbohydrates and/or complex carbohydrates

28. 5. Don’t forget about Fiber!
DRI: 14 grams of fiber per 1,000 calories to promote heart health
Most Americans fall short: about 15 grams per day
Gradually increasing fiber in your diet will minimize side effects, such as flatulence
As you add fiber to your diet, you should also drink more fluids
Table 4.2

29. 6. Food Sources of Carbohydrates
Figure 4.7

30. 6. Food Sources of Fiber
Figure 4.8

31. 7. What’s the Difference Between Natural and Added Sugars?
Naturally occurring sugars found in fruits and dairy
Usually more nutrient dense; provide more nutrition per bite
Added sugars are added by manufacturers and are often “empty calories” (provide little nutrition).
Examples: soda, candy
Taste buds can’t distinguish between naturally occurring and added sugars

32. 7. Slices of an Orange versus Orange Slices
Figure 4.9

33. 7. Processed Foods and Sweets Often Contain Added Sugars
Finding the added sugars in your foods:
Sugars on food labels appear under numerous different names
Honey and fructose are not nutritionally superior to sucrose
Naturally occurring sugars are not distinguished from added sugars on the Nutrition Facts panel

34. 7. Nutrition in the Real World: Avoiding a Trip to the Dentist
Carbohydrates play a role in dental caries
Fermentable sugars and starch feed bacteria coating teeth, producing acid to erode tooth enamel
To minimize tooth decay:
Eat three balanced meals daily
Keep snacking to a minimum, choosing whole fruits and raw vegetables
Include foods that fight dental caries: cheese, sugarless gum
Regular dental care and good dental hygiene

35. 7. Finding Added Sugars on the Label: The Many Aliases of Added Sugar
Figure 4.10

36. 7. Where Are All These Added Sugars Coming From?
Figure 4.11

37. 7. It is getting harder to stay healthy in modern times.
Table 4.3

38. 7. The Many Sizes of Soft Drinks
Figure 4.12

39. 7. What Is Diabetes Mellitus and Why Is It an Epidemic?
Diabetes mellitus: individual has high blood glucose levels due to insufficient insulin or insulin resistance
Glucose can’t enter cells, which burn fat for fuel
Without glucose, acidic ketone bodies build up, causing life-threatening diabetic ketoacidosis: untreated can result in coma, death
Type 1 diabetes: 5 to 10 percent of cases
Autoimmune disease: insulin-producing cells in pancreas destroyed—insulin injections required
Develops in childhood, early adult years

40. 7. What Is Diabetes Mellitus and Why Is It an Epidemic?
Type 2 diabetes: 90 to 95 percent of cases
Cells are resistant to insulin, eventually insulin-producing cells are exhausted, pancreas decreases and medication and/or insulin is required
People 45 and older or at risk for diabetes should be tested.
Prediabetes: impaired glucose tolerance
Blood glucose higher than normal but not yet high enough to be classified as diabetes
Damage to heart and circulatory system can occur.

41. 7. What Is Diabetes Mellitus and Why Is It an Epidemic?
Blood glucose control is key
Nutrition and lifestyle goals:
Physical exercise
Well-balanced diet containing:
High-fiber carbohydrates from whole grains, fruits, vegetables
Low-fat milk
Adequate lean protein sources
Unsaturated fats

42. 7. What Is Diabetes Mellitus and Why Is It an Epidemic?
Glycemic index (GI) and glycemic load (GL) classify effects of carbohydrate-containing foods on blood glucose
GI: ranks foods’ effects on blood glucose compared with equal amount of pure glucose
GL: adjusts GI to take into account the amount of carbohydrate consumed
Eating carbohydrate-heavy foods with protein, fat lowers GI

43. 7. Glycemic Index
Sugar is not prohibited; starch causes same rise in blood glucose levels
Figure 4.15

44. 7. What Is Diabetes Mellitus and Why Is It an Epidemic?
Cases of diabetes are on the rise
Sixth leading cause of death in the United States.
Over 200,000 Americans die from diabetic complications annually
Rapidly rising in children
Obesity, overweight, and physical inactivity increase risk
Preventing type 2 diabetes:
Losing excess weight, physical exercise, heart-healthy, plant-based diet

45. Table 4.7

46. 7. What Is Hypoglycemia?
Hypoglycemia:blood glucose level below 70 mg/dl
Symptoms: hunger, shakiness, dizziness, perspiration, light-headedness
May occur in people with diabetes when they don’t eat regularly to balance effects of insulin or blood glucose-lowering medication
Can cause fainting, coma

47. 7. Change in Blood Glucose After Eating a High-Carbohydrate Meal
Figure 4.16

48. 8. What Are Sugar Substitutes and What Forms Can They Take?
Calorie-Free Sweeteners:
Saccharin (Sweet’N Low): 200 to 700 percent sweeter than sucrose
Aspartame (Nutrasweet, Equal): 200 percent sweeter
People with PKU (disorder where you are unable to digest a certain amino acid) need to monitor all dietary sources of phenylalanine, including aspartame.
Acesulfame-K (Sunette): 200 percent sweeter
Sucralose (Splenda): 600 percent sweeter
Rebaudioside A (Truvia, PureVia): 200 percent sweeter
Neotame: 7,000 to 13,000 percent sweeter

49. 8. Growing Interest in Sugar-Free Foods and Beverages
Figure 4.13

50. 8. Listings of Sugar Substitutes
Table 4.4

51. 9. Why Is Fiber So Important?
Fiber is resistant to digestion but has many powerful health effects.
Fiber helps lower risk of developing:
Constipation
Diverticulosis, diverticulitis
Obesity: high-fiber foods add to satiation
Heart disease: soluble fibers lower elevated blood cholesterol levels
Colorectal cancer
Diabetes mellitus: slow digestion and absorption of glucose

52. 9
Table 4.5

53. Carbohydrate Assignment