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Chapter 4. The Carbohydrates: Sugar, Starch, and Fiber. The Body’s Need for Carbohydrates. The primary role of carbohydrates is to provide the body with energy (calories). Carbohydrates are the preferred fuel for the brain and nervous system.

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Chapter 4

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Chapter 4

The Carbohydrates: Sugar, Starch, and Fiber

 2010 Cengage-Wadsworth

The Body’s Need for Carbohydrates

The primary role of carbohydrates is to provide the body with energy (calories).

Carbohydrates are the preferred fuel for the brain and nervous system.

Carbohydrates are the ideal fuel compared to other alternatives:

Less expensive than protein.

High-fat diets are associated with chronic disease.

 2010 Cengage-Wadsworth

Carbohydrate Basics

Carbohydrates: compounds made of single sugars or multiples of them and composed of carbon, hydrogen, and oxygen atoms.

carbo = carbon (C)

hydrate = water (H2O)

Complex carbohydrates: long chains of sugars (glucose) arranged as starch or fiber. Also called polysaccharides.

poly = many

saccharides = sugar unit

Simple carbohydrates (sugars): the single sugars (monosaccharides) and the pairs of sugars (disaccharides) linked together.

 2010 Cengage-Wadsworth

Carbohydrate Basics

Carbohydrate-rich foods are obtained almost exclusively from plants.

Milk is the only animal-derived food that contains significant carbohydrate.

All carbohydrates are composed of single sugars, alone or in various combinations.

 2010 Cengage-Wadsworth

 2010 Cengage-Wadsworth

 2010 Cengage-Wadsworth

Simple Carbohydrates

Single Sugars - Monosaccharides:

Glucose: (GLOO-koce) the building block of carbohydrate; a single sugar used in both plant and animal tissues as quick energy. A single sugar is known as a monosaccharide.

mono = one

Fructose: (FROOK-toce) fruit sugar—the sweetest of the single sugars.

Galactose: (ga-LACK-toce) another single sugar that occurs bonded to glucose in the sugar of milk.

 2010 Cengage-Wadsworth

Simple Carbohydrates

Double Sugars - Disaccharides:

Sucrose: (SOO-crose) a double sugar composed of glucose and fructose. A double sugar is known as a disaccharide.

di = two

Maltose: a double sugar composed of two glucose units.

Lactose: a double sugar composed of glucose and galactose; commonly known as milk sugar.

 2010 Cengage-Wadsworth

Simple Carbohydrates

Added Sugars:

Sugar cane and sugar beets are purified to make sucrose.

Food examples include white (table) sugar, brown sugar, powdered sugar.

Sucrose is common in sweets.

A sampling of foods providing added sugars to the diet.

 2010 Cengage-Wadsworth

Simple Carbohydrates

Enzymes: protein catalysts. A catalyst facilitates a chemical reaction without itself being altered in the process.

(Proteins are discussed in Chapter 6.)

Lactose intolerance: inability to digest lactose as a result of a lack of the necessary enzyme lactase.

Symptoms include nausea, abdominal pain, diarrhea, or excessive gas that occurs anywhere from 15 minutes to a couple of hours after consuming milk or milk products.

 2010 Cengage-Wadsworth

 2010 Cengage-Wadsworth

 2010 Cengage-Wadsworth

Complex Carbohydrates: Starch

Complex carbohydrates include starch and fiber.All starchy foods are plant foods.

  • Starch: a plant polysaccharide composed of hundreds of glucose molecules, digestible by human beings.

  • Polysaccharide: a long chain of 10 or more glucose molecules linked together in straight or branched chains; another term for complex carbohydrates.

 2010 Cengage-Wadsworth

Complex Carbohydrates: Starch

Sources of starch include:

  • Seeds such as grains, peas and beans.

  • Legumes including dried beans, lentils and soybeans.

  • Root vegetables (yams) and tubers (potatoes).

 2010 Cengage-Wadsworth

Complex Carbohydrates: Starch

  • Most societies have a staple grain that provides most of the people’s food energy.

  • Staple grain:a grain used frequently or daily in the diet. Examples include:

    • Corn in Mexico

    • Rice in Asia

    • Wheat in Canada, Europe and USA

    • Millet, rye, barley, and oats

  •  2010 Cengage-Wadsworth

     2010 Cengage-Wadsworth

    Complex Carbohydrates: Starch

    Refined:refers to the process by which the coarse parts of food products are removed.

    Enriched: refers to a process by which the B vitamins thiamin, riboflavin, niacin, folic acid, and the mineral iron are added to refined grains and grain products at levels specified by law.

    Fortified foods: foods to which nutrients have been added. Typically, commonly eaten foods are chosen for fortification with added nutrients to help prevent a deficiency of a nutrient (iodized salt, milk with vitamin D) or to reduce the risk of chronic disease (juices with added calcium).

     2010 Cengage-Wadsworth

    Husk (chaff)






    A wheat


    p. 110

    Complex Carbohydrates: Fiber

    Fiber: the indigestible residues of food, composed mostly of polysaccharides. The best known fibers are cellulose, hemicellulose, pectin, and gums.

    Comes from the supporting structures of plants: leaves, stems and seeds.

    Cannot be broken down by human digestive enzymes although some may be broken down by bacteria residing in the digestive tract.

    Fiber has few if any calories because it is not digested.

     2010 Cengage-Wadsworth

    Complex Carbohydrates: Fiber

    Insoluble fiber includes the fiber types called cellulose, hemicellulose, and lignin.

    Insoluble fibers do not dissolve in water.

    Soluble fiber includes the fiber types called pectin, gums, mucilages, some hemicelluloses, and algal substances (for example, carageenan).

    Soluble fibers either dissolve or swell when placed in water.

     2010 Cengage-Wadsworth

    Foods rich in insoluble fiber:

    Foods rich in soluble fiber:


    Brown rice

    Green beans

    Green peas

    Many veggies





    Wheat bran

    Whole-grain products







    Oat bran




    Insoluble fiber:

    • Holds water in the colon and increases bulk to the stool.

    • Stimulates muscles and helps maintain health and tone.

     2010 Cengage-Wadsworth

    Soluble fiber:

    • Binds cholesterol compounds and may lower blood cholesterol.

    • Improves body’s handling of glucose.

     2010 Cengage-Wadsworth

    Diverticulosis: The outpocketings of intestinal linings that balloon through the weakened intestinal wall muscles are known as diverticula.

     2010 Cengage-Wadsworth

    Choosing Carbohydrates

     2010 Cengage-Wadsworth

    Choosing Carbohydrates

    Added Sugars: Use Discretion

    Choose and prepare foods with little added sugar (Dietary Guidelines).

    Added Sugar:sugars and other caloric sweeteners that are added to foods during processing or preparation. Added sugars do not include naturally occurring sugars that are found in milk and fruit.

     2010 Cengage-Wadsworth

    Choosing Carbohydrates

    Choose most often the naturally occurring sugars (DRI).

    For those who meet their nutrient needs, maintain a “healthy body weight” and still need additional calories--maximum intake = 25% or less for added sugars (DRI).

     2010 Cengage-Wadsworth

    Breakfast: Try a higher-fiber grain: oatmeal, whole-grain muffin, or whole-grain cereal

    Whole grains are low in fat and added sugars

    Baking recipes: Substitute whole-grain flour for 1/4 of all-purpose flour

    Make a fiber-rich snack mix from whole grain cereals, popcorn, and nuts

    Try whole-wheat pasta, rice, and breads

    Combine whole grains in mixed dishes

    Make Half Your Grains Whole

     2010 Cengage-Wadsworth

    How the Body Handles Carbohydrates

    If the blood delivers more glucose than the cells need, glycogen will be built.

    Glycogen (GLY-co-gen): a polysaccharide composed of chains of glucose, manufactured in the body and stored in liver and muscle.

    As a storage form of glucose, liver glycogen can be broken down by the liver to maintain a constant blood glucose level when carbohydrate intake is inadequate.

     2010 Cengage-Wadsworth

     2010 Cengage-Wadsworth

    is broken down in the body to:

    A. When a person overeats (feasting):

    Food component:

    and then stored as:

    Liver and

    muscle glycogen





    Body fat stores

    B. When a person draws on stores (fasting):

    and then used for:

    is broken down in the body to:

    Storage compound:

    Liver and

    muscle glycogen





    Fig. 4-4, p. 119

    When a person eats, blood glucose rises. High blood glucose stimulates the pancreas to release insulin. Insulin serves as a key for entrance of blood glucose into cells. Liver and muscle cells store the glucose as glycogen. Excess glucose can also be stored as fat.

     2010 Cengage-Wadsworth

    Later, when blood glucose is low, the pancreas releases glucagon, which serves as the key for the liver to break down stored glycogen into glucose and release it into the blood to raise blood glucose levels.

     2010 Cengage-Wadsworth

    How the Body Handles Carbohydrates

    Insulin: a hormone secreted by the pancreas in response to high blood glucose levels; it assists cells in drawing glucose from the blood.

    Glucagon (glue-cuh-gon): a hormone released by the pancreas that signals the liver to release glucose into the bloodstream.

     2010 Cengage-Wadsworth

    Carbohydrates--Friend or Foe?

    Glycemic index (GI): a scale that ranks carbohydrate-containing foods by how much they raise blood glucose levels compared to a standard food such as glucose or white bread. The glycemic load (GL) is a measure of the extent to which blood glucose is raised by a given amount of carbohydrate-containing food.

    Glycemic effect: the effect of food on a person’s blood glucose and insulin response – how fast and high the blood glucose rises and how quickly the body responds by normalizing.

     2010 Cengage-Wadsworth

    High glycemic index foods:

    French, white, other soft breads/bagels

    Rice (medium-grain)

    Certain cereals (Cheerios, Corn Flakes, Rice Krispies)


    Mashed potatoes

    Honey, regular soft drinks, jelly beans


    Intermediate glycemic index foods:


    Cream of Wheat, instant oatmeal, Shredded Wheat

    Sourdough & rye breads

    Banana, pineapple, orange juice

    Ice cream



    Low glycemic index foods:

    Whole-grain, heavy breads

    Rice (long-grain)

    Bran cereals, toasted Muesli cereal, whole oats

    Apples, oranges, peaches

    Baked beans, lentils, other legumes


    Milk, yogurt

    Sweet potatoes

    Tomato soup

     2010 Cengage-Wadsworth

    Hypoglycemia & Diabetes

    Hypoglycemia (HIGH-po-gligh-SEEM-eeuh): an abnormally low blood glucose concentration—below 60 to 70 mg/100 mL.

    Ketosis: abnormal amounts of ketone bodies in the blood and urine; ketone bodies are produced from the incomplete breakdown of fat when glucose is unavailable for the brain and nerve cells.

    Hyperglycemia: an abnormally high blood glucose concentration, often a symptom of diabetes.

     2010 Cengage-Wadsworth


    Diabetes (dye-uh-BEET-eez): a disorder (technically termed diabetes mellitus) characterized by insufficiency or relative ineffectiveness of insulin, which renders a person unable to regulate the blood glucose level normally.

    Type 1 diabetes

    Type 2 diabetes

    Gestational diabetes (see Chapter 11)

     2010 Cengage-Wadsworth

     2010 Cengage-Wadsworth

    Sugar and Health

    Research studies have not shown a direct link between sugar and obesity, diabetes, heart disease, hyperactivity in children or criminal behavior.

    Empty-calorie foods: a phrase used to indicate that a food supplies calories but negligible nutrients.

     2010 Cengage-Wadsworth

     2010 Cengage-Wadsworth

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