1. Carbohydrates: Plant-Derived Energy Nutrients4
Carbohydrates: Plant-Derived Energy Nutrients

2. What Are Carbohydrates?
One of the three macronutrients
Important source of energy for all cells
Preferred energy source for nerve cells
Composed of carbon, hydrogen, oxygen
Good sources: fruits, vegetables, grains

3. What Are Carbohydrates?
Glucose
The most abundant carbohydrate
Produced by plants through photosynthesis

5. What Are Carbohydrates?
Simple carbohydrates
Contain one or two molecules
Commonly referred to as sugars
Monosaccharides contain one molecule
Glucose, fructose, and galactose
Disaccharides contain two molecules
Lactose, maltose, and sucrose

8. What Are Carbohydrates?
Complex carbohydrates
Oligosaccharides contain 3 to 10 monosaccharides
Most polysaccharides consist of hundreds to thousands of glucose molecules
Starch, glycogen, most fibers

10. Complex Carbohydrates
Starch
Plants store carbohydrates as starch
Amylose—straight chain of glucose
Amylopectin—branched chain of glucose
Resistant starch (fiber)—glucose molecules linked by beta bonds are largely indigestible
Sources: grains, legumes, fruits, vegetables

11. Complex Carbohydrates
Glycogen
Storage form of glucose for animals (humans)
Not found in food and therefore not a source of dietary carbohydrate
Stored in the liver and muscles

12. Complex Carbohydrates
Fiber
Composed of long polysaccharide chains
Dietary fibers are non-digestible parts of plants
Functional fibers are non-digestible forms of carbohydrates extracted from plants or manufactured in a laboratory and have known health benefits
Total fiber = Dietary fiber + Functional fiber

13. Complex Carbohydrates
Soluble fibers
Dissolve in water; viscous and gel-forming
Fermentable, digested by intestinal bacteria
Associated with risk reduction of cardiovascular disease and type 2 diabetes
Examples: pectin, gum, mucilage
Found in citrus fruits, berries, oats, beans

14. Complex Carbohydrates
Insoluble fibers
Do not dissolve in water, nonviscous
Cannot be fermented by bacteria in the colon
Promote regular bowel movements, alleviate constipation, and reduce diverticulosis
Examples: lignins, cellulose, hemicelluloses
Good sources: whole grains, seeds, legumes, fruits, and vegetables
ABC Video Whole Grains

15. Carbohydrate Digestion
Salivary amylase
Enzyme that begins carbohydrate digestion in the mouth
Breaks carbohydrates down to maltose
Carbohydrate digestion does not occur in the stomach
Stomach acids inactivate salivary amylase
Carbohydrate Digestion

16. Carbohydrate Digestion
Most chemical digestion of carbohydrates occurs in the small intestine
Pancreatic amylase
Enzyme produced in the pancreas and secreted into the small intestine
Digests carbohydrates to maltose

17. Carbohydrate Digestion
Additional enzymes in the microvilli digest disaccharides to monosaccharides
Maltase
Sucrase
Lactase
Monosaccharides are absorbed into the cells lining the small intestine and then enter the bloodstream

19. Carbohydrate Digestion
All monosaccharides are converted to glucose by the liver
Glucose circulating in the blood is our primary energy source
Excess glucose is stored as glycogen in the liver and muscles

21. Carbohydrate Digestion
We do not have the enzymes necessary to digest fiber
Bacteria in the large intestine can break down some fiber
Most fiber remains undigested and is excreted in the feces
Carbohydrate Absorption

22. Blood Glucose Regulation
Blood glucose must be closely regulated
Hormones control blood glucose levels:
Insulin
Glucagon
Epinephrine
Norepinephrine
Cortisol
Growth hormone
Hormonal Control of Blood Glucose

23. Blood Glucose Regulation: Insulin
Secreted by beta cells of the pancreas
Stimulates glucose transporters (carrier proteins) to help take glucose from the blood across the cell membrane
Stimulates the liver to take up glucose and convert it to glycogen

25. Blood Glucose Regulation: Glucagon
Secreted by alpha cells of the pancreas
Stimulates the liver to convert glycogen to glucose
Stimulates gluconeogenesis, the production of glucose from amino acids

27. Blood Glucose Regulation: Epinephrine and Norepinephrine
Secreted by the adrenal glands and nerve endings when blood glucose is low
Increase glycogen breakdown in the liver, releasing glucose into the blood
Responsible for our “fight-or-flight” reactions to danger

28. Blood Glucose Regulation: Cortisol and Growth Hormone
Secreted by the adrenal glands to act on the liver, muscle, and adipose tissue
Cortisol increases gluconeogenesis and decreases muscle glucose use
Growth hormone decreases muscle glucose uptake, increases fatty acid mobilization and use, and increases liver glucose output

29. Blood Glucose Regulation: Glycemic Index
A food’s potential to raise blood glucose
Foods with a high glycemic index cause a sudden surge in blood glucose, triggering a large increase in insulin, which may be followed by a dramatic fall in blood glucose
Foods with a low glycemic index cause low to moderate fluctuations in blood glucose

30. Blood Glucose Regulation: Glycemic Index
Not always easy to predict
Food’s absorption rate varies with type of carbohydrate, preparation methods, and its fat and fiber content
Most foods are eaten in combination in a meal

31. Blood Glucose Regulation: Glycemic Load
Used to determine the effect of a food on a person’s glucose response
Grams of carbohydrates in a food are multiplied by the glycemic index
Glycemic index and glycemic load remain controversial
Evidence of health benefits is weak

32. Blood Glucose Regulation: Value of Lower Glycemic Index
Less fluctuations in blood glucose
Risk reduction for heart disease and colon cancer
High fiber intake helps to improve fat levels in the blood (higher HDL and lower LDL)
Foods with lower glycemic index:
Beans, fresh vegetables, whole wheat

34. The Role of Carbohydrates
Energy
Each gram of carbohydrate: 4 kcal
Red blood cells use only glucose for energy
Both carbohydrates and fats supply energy for daily activities
Glucose is especially important for energy during exercise

36. The Role of Carbohydrates
Ketosis
Fat breakdown during fasting forms ketones
Excess ketones increase blood acidity and cause ketoacidosis
Sufficient energy from carbohydrates prevents ketone production as alternate energy source
Fad Diets

37. Carbohydrates Spare Protein
Gluconeogenesis occurs when a diet is deficient in carbohydrate
The body will make its own glucose from protein
Amino acids from these proteins cannot be used to make new cells, repair tissue damage, support the immune system, or perform any of their other functions

38. Complex Carbohydrates Have Health Benefits
Fiber
May reduce the risk of colon cancer
Helps prevent hemorrhoids, constipation, and other intestinal problems
May reduce the risk of diverticulosis
May reduce the risk of heart disease
May enhance weight loss
May lower the risk of type 2 diabetes
Diverticulosis and Fiber

41. How Much Carbohydrate?
Recommended Dietary Allowance (RDA) is 130 grams/day to supply adequate glucose to the brain
Acceptable Macronutrient Distribution Range (AMDR) is 45% to 65% of daily calories
Focus on fiber-rich carbohydrate foods

43. Simple Carbohydrates Diets high in simple sugars:
Can cause tooth decay
May increase “bad cholesterol”
May decrease “good cholesterol”
May contribute to obesity
ABC Video Sugar and Processed Food

45. Complex Carbohydrates
Most Americans eat too little complex carbohydrates
Enriched foods are foods in which nutrients that were lost during processing have been added back so the food meets a specified standard
Fortified foods have nutrients added that did not originally exist in the food (or existed in insignificant amounts)

47. Complex Carbohydrates
Adequate Intake (AI) for fiber
25 g per day for women
38 g per day for men, or
14 g of fiber for every 1,000 kcal per day
It is best to get fiber from food (also a source of vitamins and minerals)
An adequate fluid intake (at least 8 oz/day) with high-fiber diets is recommended

51. Alternative Sweeteners
Nutritive sweeteners
Sucrose, fructose, honey, and brown sugar contain 4 kcal energy per gram
Slow-absorbing sugar alcohols: 2−3 kcal/gm
Non-nutritive (alternative) sweeteners
Provide little or no energy
Safe for adults, children, people with diabetes

53. Alternative Sweeteners
Saccharin
Acesulfame-K
Aspartame
Sucralose
Truvia and PureVia (stevia plant)

55. Diabetes Inability to regulate blood glucose levels Type 1 diabetes
Gestational diabetes
Uncontrolled diabetes can cause nerve damage, kidney damage, blindness, and can be fatal

56. Diabetes—Type 1 Accounts for 10% of all cases
Body does not produce enough insulin
Causes hyperglycemia (high blood glucose)
Requires insulin injections
May be an autoimmune disease

57. Diabetes—Type 2
Insulin insensitivity (insulin resistance): cells become less responsive to insulin
Metabolic syndrome: a cluster of risk factors that increase the risk for type 2 diabetes
Once known as adult-onset diabetes
Increasing in children and adolescents

58. Diabetes—Type 2
Cause is unclear, but genetics, obesity, and physical inactivity play a role
Treat with weight loss, healthy eating, regular exercise, and, if necessary, medications
Healthy lifestyle choices may prevent or delay the onset of type 2 diabetes

62. Hypoglycemia
Low blood glucose may cause shakiness, sweating, anxiety, weakness
Reactive hypoglycemia: pancreas secretes too much insulin after a high-carbohydrate meal
Fasting hypoglycemia: pancreas produces too much insulin, even when someone has not eaten

64. Lactose Intolerance
Insufficient enzyme lactase to digest the lactose-containing foods
GI symptoms: gas, cramping, diarrhea
Variations in extent of intolerance
Not to be confused with milk allergy
Need alternate sources of calcium