Carbohydrates

Chapter

4

What Are Carbohydrates?

• Organic compounds that contain carbon, hydrogen and oxygen (CH2O)

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Single Sugars: Monosaccharides and Disaccharides

• Monosaccharides: The Single Sugars• Glucose

• Found in fruits, vegetables, honey• “Blood sugar”—used for energy

• Fructose• Found in fruits, honey, corn syrup• “Fruit sugar”

• Galactose• Found as part of lactose in milk

Other Monosaccharides and Derivative Sweeteners

• Pentoses• Single sugar molecules that contain five

carbons• Examples: RNA, DNA, part of the dietary

fiber component of food• Sugar alcohols

• Derivative of monosaccharides• Examples: used as nutritive sweeteners

Disaccharides: The Double Sugars

• Disaccharides—two linked sugar units• Sucrose: glucose + fructose

• “Table sugar”• Made from sugar cane and sugar beets

• Lactose: glucose + galactose• “Milk sugar”• Found in milk and dairy products

• Maltose: glucose + glucose• Found in germinating cereal grains• Product of starch breakdown

Joining and Cleaving Sugar Molecules

Complex Carbohydrates

• Oligosaccharides• Polysaccharides

• Starch• Long chains of glucose units• Found in grains, vegetables, legumes

• Glycogen• Highly branched chains of glucose units• Body’s storage form of carbohydrate

Complex Carbohydrates: Fiber• Dietary + Functional = Total Fiber• Indigestible chains of monosaccharides

• Nonstarch polysaccharides: long chains• Cellulose, hemicellulose, pectins, gums, mucilages• Lignins

• Found in fruits, vegetables, grains, and legumes

Complex Carbohydrates: Fiber

• Other fiber types• Cellulose• Hemicelluloses• Pectins• Gums and Mucilages• Lignins• B-Glucans• Chitin and Chitosan

Carbohydrate Digestion and Absorption

Carbohydrate Digestion and Absorption

• Mouth• Salivary amylase begins digestion of starch

• Small intestine• Pancreatic amylase completes starch digestion• Brush border enzymes digest disaccharides

• End products of carbohydrate digestion• Glucose, fructose, galactose• Absorbed into bloodstream

• Fibers are not digested but are excreted in feces

Carbohydrates in the Body

• Normal Use of Glucose• Using Glucose for Energy• Storing Glucose as Glycogen• Sparing Body Protein• Preventing Ketosis

Carbohydrates in the Body: Regulating Blood Glucose Levels

Regulating Blood Glucose Levels

• Insulin• Glucagon• Epinephrine• Glycemic Index

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Inadequate Regulation of Blood Glucose Levels: Diabetes Mellitus

• Diabetes mellitus• Body either does not produce enough

insulin or does not use insulin properly• Both genetics and environmental factors

seem to be involved• See Diet and Health chapter for more

information on DM

Carbohydrates in the Diet

• Recommended carbohydrate intake• AMDR = 45–65% of calories• Daily Value (for 2,000 kcal) = 300 grams• Dietary Guidelines

• “reduce intake of added sugars”• Choose and prepare foods and beverages with

little added sugar• Choose whole grains, vegetables and fruits

• Current consumption

Choosing Carbohydrates Wisely

• Strategies for Increasing Fiber Intake• Eat more whole-grains• Eat fruits and

vegetables with peel• Add legumes• Choose high-fiber

cereals

Carbohydrates in the Diet

• Moderating sugar intake• Use less added sugar (white

sugar, brown sugar, honey and syrups)

• Limit soft drinks, sugary cereals, and candy

• Choose fresh fruits or those canned in water or juice

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Carbohydrates in the Diet• Nutritive Sweeteners

• Natural v. refined• Sugar alcohols

• Non-nutritive Sweeteners• Saccharin• Aspartame• Acesulfame K• Sucralose • Other sweeteners

Carbohydrates and Health

•Sugar and Dental Caries•Fiber and Obesity•Fiber and Type 2 Diabetes•Fiber and Cardiovascular Disease•Fiber and Gastrointestinal Disorders•Negative Health Effects of Excess Fiber

An Apple a Day…• The old adage, “An apple

a day keeps the doctor away” has persisted over time due to actual health benefits from apples.

• Apples have a high pectin content, a soluble fiber known to be an effective GI regulator. © Photodisc

Cellulose

• Cellulose forms the nondigestible, fibrous component of plants.

• It is part of grasses, trees, fruits, and vegetables.

Increasing Fiber Intake

• To increase your fiber intake, eat more breads, cereals, pasta, rice, fruits, vegetables, and legumes.

• Eat fruits and vegetables with the peel, if possible, as this is high in fiber.

• Add fruit to muffins and pancakes.• Add legumes, such as lentils and pinto, navy,

kidney, and black beans to casseroles.

Position on Nutritive and Non-Nutritive Sweeteners

• It is the position of the Academy of Nutrition and Dietetics that consumers can safely enjoy a range of nutritive and non-nutritive sweeteners when consumed in a diet that is guided by current federal nutrition recommendations, such as the Dietary Guidelines for Americans, and the Dietary References Intakes, as well as individual health goals.

Dental Health• Good dental hygiene, adequate

fluoride, and proper nutrition help maintain healthy teeth.

• A well-balanced diet contains vitamins and minerals crucial for healthy bones and teeth.

• To help prevent dental caries, avoid continuous snacking on high-sugar foods.

Position on Health Implications of Dietary Fiber

• It is the position of the Academy of Nutrition and Dietetics that the public should consume adequate amounts of dietary fiber in the form of plant foods.

Effects of Excess Fiber

• With all of its health advantages, high fiber intake can cause problems, especially in those who drastically increase their fiber intake in a short period of time.

• A sudden increase in fiber can cause increased intestinal gas and bloating.

• If you increase your fiber intake, you should also increase your water intake to prevent constipation.

Total Fiber

• Dietary fiber consists of nondigestible carbohydrates and lignin that are intact and intrinsic in plants.

• Functional fiber refers to isolated, nondigestible carbohydrates that have beneficial physiological effects in humans.

• Total fiber is the sum of dietary fiber and functional fiber.

Babies and Honey• Because honey and Karo

syrup may contain spores of the bacterium Clostridium botulinum (botulism), they should never be fed to infants younger than one year of age.

• Infants do not produce as much stomach acid as older children and adults, which can allow the spores to germinate in the GI tract.

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