1. Carbohydrates: Facts to Know
Concept 7

2. Pop Quiz True or False? You don’t need to eat carbohydrates.
Plants are our only source of carbohydrates.
Popcorn is a whole grain.
People who are lactose intolerant need to avoid all dairy products.
Insulin is a type of sugar found in the blood.
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3. What Are Carbohydrates and Why Do You Need Them?
A diet staple found mainly in plant-based foods
Examples: grains, fruits, vegetables, nuts, and legumes
Also found in dairy foods
The primary sugar in high-carbohydrate foods is glucose.
Photosynthesis: the process by which green plants create carbohydrates using energy from the sun
Chlorophyll: the green pigment in plants that absorbs the energy from sunlight to start the process

4. Photosynthesis: How Glucose Is Made
Figure 7.1

5. What Are Carbohydrates and Why Do You Need Them?
Glucose is the most abundant carbohydrate in nature.
Plants use glucose as energy or combine it with minerals from soil to make protein or vitamins.
Plants link glucose units together and store them in the form of starch.

6. What Are Simple and Complex Carbohydrates?
Monosaccharides and Disaccharides Are Simple Carbohydrates
Polysaccharides Are Complex Carbohydrates
Starch Is Stored in Plants
Fiber Is Not Digestible, but Is Important
Grains, Glorious Whole Grains
Glycogen Is Stored in Animals

7. What Are Simple and Complex Carbohydrates?
Simple carbohydrates include:
Monosaccharides: one sugar unit
Disaccharides: two sugar units combined
Complex carbohydrates include:
Polysaccharides: many sugar units combined

8. Monosaccharides and Disaccharides Are Simple Carbohydrates
The monosaccharides:
Glucose: produced by plants
Fructose: found in fruit; sweetest of the simple sugars
Galactose: simple sugar found in dairy foods
The disaccharides are created by combining monosaccharides.
Glucose + fructose = sucrose (table sugar)
Glucose + glucose = maltose (sugar in grains)
Glucose + galactose = lactose (milk sugar)

9. Monosaccharides and Disaccharides
Figure 7.2 a,b

10. Polysaccharides Are Complex Carbohydrates
Polysaccharides are long chains of monosaccharides linked together.
Three groups:
Starch
Fiber
Glycogen

11. Polysaccharides
Polysaccharides are long chains of many glucose units joined together in a straight chain or with branches.
Figure 7.2c

12. Polysaccharides Are Complex Carbohydrates
Starch is stored in plants.
Consists of many glucose units strung in a chain
May be straight or branched chains
Found in pasta, rice, bread, and potatoes

13. Polysaccharides Are Complex Carbohydrates
Fiber is not digestible, but is important.
Dietary fiber: found naturally in foods
Functional fiber: added for a beneficial effect
Soluble fiber: dissolves in water, viscous
Found in fruits, vegetables, beans, and oats
Fermented by bacteria in large intestine
Moves slowly through intestinal tract; has laxative effect
Insoluble fiber: does not dissolve in water
Found in seeds, cereal fiber, whole-grain bran, and some fruits and vegetables
Moves more quickly through intestinal tract

14. Grains, Glorious Whole Grains
A whole grain is made up of three edible parts:
Bran: indigestible outer shell
Rich in fiber, B vitamins, phytochemicals, and minerals
Germ: the seed
Provides vitamin E, heart-healthy fats, phytochemicals, and B vitamins
Endosperm: the starchy part of the grain
Contains protein, B vitamins, and some fiber (in smaller amounts than the bran)

15. Grains, Glorious Whole Grains
Two categories of grain products:
Refined grains are grain kernels stripped of bran and germ, leaving only the endosperm.
Enrichment: attempts to restore some of the nutrients lost in refinement by adding back folic acid, thiamin, niacin, riboflavin, and iron
Whole grains include the entire edible grain kernel—the bran, the germ, and the endosperm.
Consumption of whole grains may reduce risk of heart disease, stroke, and diabetes.

16. Polysaccharides Are Complex Carbohydrates
Glycogen is stored in animals.
The form of glucose stored in the liver and muscle cells of humans and animals
Can be an important source of glucose for the cells of the body
Breaks down when the animal dies and is not available in meat or poultry consumed

17. Some People Cannot Digest Milk Sugar
Lactose Maldigestion Develops with Aging
Severe Lactase Deficiency Produces Lactose Intolerance

18. Lactose Maldigestion Develops with Aging
The inability to digest lactose in foods due to inadequate levels of the enzyme lactase
A natural part of the aging process
25 percent of Americans affected
75 percent of adults worldwide affected
People of some ethnic origins tolerate lactose better than others.
Despite lactose maldigestion, many people can still enjoy milk, yogurt, and cheese.

19. Severe Lactose Deficiency Produces Lactose Intolerance
Occurs when maldigestion of lactose results in nausea, cramps, bloating, flatulence, and diarrhea
Not the same as a milk allergy
Can be improved by:
Consuming smaller amounts of dairy at a time
Eating dairy foods with a meal or snack rather than by themselves
Choosing lactose-reduced dairy products or items with lower lactose levels
Taking lactase pills before lactose-containing meals

21. How Does Your Body Use Carbohydrates?
Insulin Regulates Glucose in Your Blood
Carbohydrates Fuel Your Body between Meals
During Fasting, Your Body Breaks Down Fat and Protein

22. Insulin Regulates Glucose in Your Blood
Hormones are chemical messengers that regulate important conditions in the body.
Insulin: a hormone released by the pancreas that helps move glucose into your cells and determines whether it will be used immediately as energy or stored for later
Carbohydrate-rich meals increase blood glucose.
Elevated blood glucose triggers release of insulin.
Glucose can be stored as glycogen in the liver and muscle cells or as fat.

23. Insulin Directs Excess Glucose into Storage
Figure 7.3a

24. Carbohydrates Fuel Your Body between Meals
When blood glucose levels drop, your body calls on its glycogen reserves.
Glucagon: a hormone released by the pancreas when blood glucose drops
Directs release of glucose from stored glycogen in the liver
Signals the liver to manufacture glucose from noncarbohydrate sources such as protein
Epinephrine (adrenaline): another hormone that can act on liver and muscle cells to stimulate breakdown of glucose
“Fight-or-flight” hormone

25. The Pancreas Releases Glucagon When Blood Glucose Is Low
Figure 7.3b

26. During Fasting, Your Body Breaks Down Fat and Protein
Fasting depletes glycogen stores, which forces the body to rely on breakdown of fat and protein for fuel.
Without glucose, fat breakdown is incomplete and creates by-products called ketone bodies.
Ketone bodies accumulate in the blood, causing it to be slightly acidic.
Leads to ketosis
Ketosis often occurs in individuals who are fasting or following strict low-carbohydrate diets.
Protein from muscles and organs is also broken down to make glucose during fasting.
If fasting continues, death is inevitable.

27. The Top Five Points to Remember
Glucose, fructose, and galactose are simple carbohydrates. Glucose is the preferred fuel for the brain and red blood cells.
Two monosaccharides are joined to form disaccharides. Sucrose (table sugar), lactose (milk sugar), and maltose are examples of disaccharides.
Many glucose units are joined together to form polysaccharides. Glycogen (found in animal tissue), starch (found in plants), and fiber are examples of polysaccharides.

28. The Top Five Points to Remember
Lactose maldigestion is the inability to properly absorb the milk sugar lactose because of a reduced amount of the enzyme lactase.
Blood glucose is maintained in a healthy range by hormones. Insulin directs glucose into your cells. Glucagon increases blood glucose. Ketone bodies are created when fat is incompletely broken down during fasting.

29. Answers to the Pop Quiz
FALSE. You need a minimum amount of carbohydrates daily to fuel your brain.
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30. Answers to the Pop Quiz
FALSE. Dairy products also contain carbohydrates in the form of a sugar called lactose.
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31. Answers to the Pop Quiz
TRUE. Popcorn, along with brown rice, bulgur, and oatmeal, is a whole grain.
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32. Answers to the Pop Quiz
FALSE. Many people who are lactose intolerant are still able to enjoy some dairy products, especially if eaten with meals.
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33. Answers to the Pop Quiz
FALSE. Insulin is a hormone produced by the pancreas. It helps regulate glucose levels in your blood.
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