Chapter
4 Carbohydrates
What Are Carbohydrates? • Organic compounds that contain carbon, hydrogen and oxygen (CH2O)
© Vinicius Tupinamba/ShutterStock, Inc.
© Mircea BEZERGHEANU/ShutterSto ck, Inc.
© Ayd/ShutterStock, Inc.
© Krunoslav Cestar/ShutterStock, Inc.
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 © Photodisc
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
© CSquared Studios/Photodisc
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 NonNutritive 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.
© Digital Stock