chapter 4

2010 Cengage-Wadsworth

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.

• Carbohydrates are the ideal fuel compared to other alternatives: Less expensive than protein. High-fat diets are associated with chronic disease.


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.


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.


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.


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.


Simple CarbohydratesAdded 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.


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.


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.



Sources of starch include:

• Seeds such as grains, peas and beans.

• Legumes including dried beans, lentils and soybeans.

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



• 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



• 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).

p. 110

A wheatkernel

Endosperm

Bran

Husk (chaff)

Germ

Branlayers


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.


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.


Insoluble fiber:• Holds water in the

colon and increases bulk to the stool.

• Stimulates muscles and helps maintain health and tone.

Soluble fiber:• Binds cholesterol

compounds and may lower blood cholesterol.

• Improves body’s handling of glucose.

Foods rich in insoluble fiber:Bran

Brown rice

Green beans

Green peas

Many veggies

Nuts

Rice

Seeds

Skins/peels

Wheat bran

Whole-grain products

Foods rich in soluble fiber:Barley

Broccoli

Carrots

Corn

Fruits

Legumes

Oat bran

Oats

Potatoes

Rye


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


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.



• 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).


• 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


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.

Glucose

Glucose

Fig. 4-4, p. 119

is broken down in the body to:

Storage compound:

and then stored as:

Liver andmuscle glycogenstores

Body fat stores

and then used for:

Energy

GlucoseCarbohydrate

A. When a person overeats (feasting):

GlucoseLiver and

muscle glycogenstores

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

Food component:

is broken down in the body to:


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.


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.


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.


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.


High glycemic index foods:

French, white, other soft breads/bagels

Rice (medium-grain)

Certain cereals (Cheerios, Corn Flakes, Rice Krispies)

Waffles

Mashed potatoes

Honey, regular soft drinks, jelly beans

Pretzels

Intermediate glycemic index foods:

Watermelon

Cream of Wheat, instant oatmeal, Shredded Wheat

Sourdough & rye breads

Banana, pineapple, orange juice

Ice cream

Popcorn

Raisins

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

Carrots

Milk, yogurt

Sweet potatoes

Tomato soup


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.


Diabetes

• 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)


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.

chapter 4

Documents

sugar of milk

milk sugar

brown sugar

powdered sugar

sugar cane

sugar beets

single sugars monosaccharides

white table sugar