Chapter 4 Carbohydrates Sugars Starches and Fiber 2010

What Are Carbohydrates? Ø Produced by plants during photosynthesis Ø After eating plant foods, humans convert the carbohydrates into glucose Ø Glucose • Most abundant carbohydrate • Preferred source of energy for the blood, brain, and nervous system Ø Carbohydrate-rich plant foods make up the foundation of diets all over the world © 2010 Pearson Education, Inc.

Classification of Carbohydrates Ø Simple carbohydrates • Monosaccharide • Disaccharide • Perceived as sweeter than complex carbohydrates - Mixes with saliva and reacts with taste buds Ø Oligosaccharides Ø Complex carbohydrates • Polysaccharides © 2010 Pearson Education, Inc.

Monosaccharides Ø Three nutritionally important monosaccharides • Glucose • Fructose • Galactose © 2010

Monosaccharides Ø Glucose • Blood glucose and blood sugar in the body • Most abundant monosaccharide in the body - Is the preferred and main source of energy for the brain and red blood cells • Part of every disaccharide • Only monosaccharide in starches © 2010 Pearson Education, Inc.

Monosaccharides Ø Fructose • Sweetest of natural sugars • Found abundantly in fruits • Part of high-fructose corn syrup Ø Galactose • Commonly occurs as part of dissaccharide lactose © 2010 Pearson Education, Inc.

The Structural Differences between Glucose, Galactose, and Fructose Figure 4. 2

Disaccharides Ø Three Disaccharides • Sucrose - Most common • Lactose • Maltose -

Monosaccharides Link to Form Disaccharides Figure 4. 3

Polysaccharides Ø Starch • Plants store glucose in chains of starch - Amylose - Straight chain - More resistant to digestion - Resistant starch ü May improve health of digestive tract ü May improve glucose tolerance ü May stimulate growth of beneficial intestinal bacteria - Amylopectin - Branched chains - Easier to digest © 2010 Pearson Education, Inc.

Polysaccharides Ø Fiber • Nondigestible polysaccharides • Provides no energy • Classification - Soluble - Pectins, beta-glucan, some gums, mucilage - Easily fermented by intestinal bacteria • Carbon dioxide, methane, some fatty acids - Insoluble - Cellulose, lignin, some hemicelluloses - Not easily fermented © 2010 Pearson Education, Inc.

Fiber Health Benefits Ø Soluble fibers • Slow gastric emptying and may delay absorption of some nutrients - Helps reduce serum cholesterol - Improve appetite control - Normalize blood glucose levels • May help protect against colon cancer Ø Insoluble fibers • Relieves constipation Ø Most plant foods contain both soluble and insoluble fibers © 2010 Pearson Education, Inc.

Polysaccharides Ø Glycogen • Storage form of glucose in animals • Long, branched chains of glucose • Stored in liver and muscle • Liver glycogen response to blood glucose (BG) levels BG glycogen breakdown BG • Muscle glycogen can be broken down for energy for the muscle © 2010 Pearson Education, Inc.

The Comparison of Starch and Glycogen Molecules Figure 4. 4

Oligosaccharides Ø Similar in length to simple carbohydrates Ø Similar in makeup to polysaccharides Ø Humans lack the enzymes necessary to digest them Ø Intestinal microflora digest and ferment them • Cause bloating, discomfort, and flatulence Ø Food sources • Legumes, beans, cabbage, brussels sprouts, broccoli © 2010 Pearson Education, Inc.

The Structure of an Oligosaccharide Figure 4. 7

Quick Review Ø Ø Complex carbohydrates • Polysaccharides: starch, fiber, glycogen • Fiber - Soluble – fermented by intestinal bacteria; moves slowly - Insoluble – moves quickly through and reduces constipation - Functional – added to foods Oligosaccharides • Contain three to ten units • Part of cellulose in cell walls © 2010 Pearson Education, Inc.

Carbohydrate Digestion and Absorption Ø Disaccharides and starches are digested to monosaccharides Ø Monosaccharides are easily absorbed Ø Fiber passes through the GI tract undigested © 2010 Pearson Education, Inc.

Figure 4. 8 a

Figure 4. 8 b

Figure 4. 8 c

Figure 4. 8 d

Absorption of Carbohydrates Ø Once digested to monosaccharides • Absorbed through the intestinal cell mucosa • Transported to the liver via the portal vein • Metabolic needs direct fate of the monosaccharides - Galactose and fructose • Used by the liver for energy • Converted to glucose - Glucose • Used for energy • Converted to glycogen through glycogenesis • Converted to glycerol and fatty acids for storage in addipocytes © 2010 Pearson Education, Inc.

Glucose Is Stored in the Liver and Muscle Cells as Glycogen Figure 4. 9

Quick Review Ø Ø Ø Digestion of carbohydrates begins in the mouth Most carbohydrate digestion takes place in the small intestine Carbohydrates are broken down to monosaccharides for absorption Monosaccharides are converted to glucose in the liver and • Used as energy • Stored as glycogen in the liver and muscle cells • Stored as glycerol and fatty acids in the adipocytes Fiber travels to the colon undigested and most is eliminated from the body © 2010 Pearson Education, Inc.

Lactose Intolerance Ø Deficiency of lactase, the enzyme that digest lactose • Maldigestion – inability to digest lactose due to low levels of the enzyme • Intolerance - Maldigestion resulting in nausea, cramps, bloating, flatulence, and diarrhea © 2010 Pearson Education, Inc.

Functions of Carbohydrate Ø Provide energy • 4 kilocalories per gram Ø Maintain blood glucose • Carbohydrate intake • Glycogenolysis > 4 hours after a meal Ø Spare protein • Prevents the need for glyconogenesis Ø Prevents ketosis © 2010 Pearson Education, Inc.

How to Maintain Blood Glucose Levels Ø Ø Ø Goal for blood glucose is 70– 100 mg/dl Insulin – lowers blood glucose levels • Needed for glucose to enter the cell from the blood stream - Exception: liver, kidney, and brain cells • Helps convert glucose to glycogen through glycogenesis • Helps convert glucose to fatty acids through lipogenesis • Inhibits lipolysis Glucagon – increases blood glucose levels • Stimulates the release of glucose into the blood • Stimulates glycogenolysis • Stimulates gluconeogensis © 2010 Pearson Education, Inc.

Insulin and Glucagon Regulate Glucose Metabolism Figure 4. 10

How to Maintain Blood Glucose Levels Ø Epinephrine and norepinephrine – increases blood glucose • Stimulate glycogenolysis and gluconeogenesis Ø Cortisol – increases blood glucose • Stimulates gluconeogensis • Reduces uptake of glucose by the muscle cells Ø Growth hormone – increases blood glucose • Stimulates fat breakdown for energy • Reduces uptake of glucose by the muscles • Increase glucose production in the liver © 2010 Pearson Education, Inc.

Quick Review Ø Ø Glucose is the body’s preferred source of energy • Especially the brain and red blood cells Adequate carbohydrate intake • Maintains blood glucose levels • Spares protein • Prevents ketosis Blood glucose levels are maintained by two hormones • Insulin which lowers blood glucose levels • Glucagon which raises blood glucose levels Epinephrine, norepinephrine, corisol, and growth hormone raise blood glucose levels. © 2010 Pearson Education, Inc.

Glycemic Index Ø Classifies the effects of carbohydrate-containing foods on blood glucose Ø May be helpful for diabetics Ø Glycemic index (GI) refers to the measured upward rise, peaks, and falls of blood glucose following consumption of high-carbohydrate food • Ranks foods according blood glucose © 2010 Pearson Education, Inc.

Glycemic Load Ø Glycemic load (GL) – adjust GI by taking into account the amount of carbohydrate consumed in a typical serving of food Ø Factors affecting GI • Ripeness of fruit • Cooking • Processing • Size of food pieces • Amount of fiber • Combinations of food eaten © 2010 Pearson Education, Inc.

Glycemic Index and Glycemic Load Ø Usefulness of GI and GL for disease prevention and weight management is controversial Ø Is helpful in educating people about • Carbohydrate content of foods • Portion sizes • Serving numbers © 2010 Pearson Education, Inc.

Dietary Fiber Ø Benefits • Helps lower risk of - Bowel irregularity - Obesity

Dietary Fiber Ø Chronic constipation can lead to diverticulosis and diverticulitis Ø Prevention of constipation and diverticulosis • Insoluble fiber helps reduce transit time of foods in the colon • Soluble fiber helps make stool easier to pass by increasing bulk and softening texture © 2010 Pearson Education, Inc. Figure 4. 12

Dietary Fiber Ø Prevention of heart disease and diabetes • Viscous, soluble fiber helps lower elevated blood cholesterol levels - Interferes with reabsorbtion of bile acid © 2010 Pearson Education, Inc. Figure 4. 13

Dietary Fiber • Slow moving, viscous, soluble fiber may reduce the rate which fat and carbohydrate are absorbed - Decreasing level of fat in blood and improving insulin sensitivity, decrease risk of heart disease • Insoluble fiber has been shown to promote heart health • Viscous soluble fiber helps slow digestion and absorption helping control blood glucose levels © 2010 Pearson Education, Inc.

Dietary Fiber Ø Ø Fiber helps reduce the incidence of several cancers • Decreases the amount of time cancer-promoting substances spend in contact with the intestinal lining • Encourages the growth of colon-friendly bacteria • Reduces acid in the colon Helps prevent obesity • Increase satiety • Reduce food intake Caution: Increase dietary fiber and fluid intake gradually © 2010 Pearson Education, Inc.

Quick Review Ø Ø Glycemic index (GI) ranks foods according to effects on glucose levels compared to white bread or pure glucose Glycemic load adjust for serving size Foods that contain high fiber or are eaten with protein and fat generally have a lower GI. High-fiber diet health benefits include reduced risk of • Constipation • Diverticulosis • Heart disease • Obesity • Diabetes Mellitus • Cancer © 2010 Pearson Education, Inc.

Importance of Whole Grains

Carbohydrate Sources Ø Best choices should include nutrient-dense, low-saturated fat foods, simple carbohydrates, fiber,

Food Sources of Carbohydrates Figure 4. 14

Food Sources of Fiber Figure 4. 15

Quick Review Ø Ø Ø Best sources of carbohydrates are • Fresh fruits and vegetables • Legumes • Low-fat dairy products • Whole grains Excellent sources of fiber are • Legumes • Whole grains • Nuts • Fruits • Seeds • Vegetables Packaged foods can be good sources of starch and fiber • Read label carefully • Avoid too much sugar, fat, and kilocalories © 2010 Pearson Education, Inc.

Diabetes Mellitus Ø Occurs when an individual either doesn’t make enough, or is unable to utilize, the hormone insulin to regulate blood glucose levels Ø Epidemic • Sixth leading cause of death in the United States • Costs the U. S. almost $100 billion annually • Number of people with diabetes is rising annually © 2010 Pearson Education, Inc.

Diabetes Mellitus Consume Carbohydrates Blood Glucose Rises Liver Breaks Down Glycogen and Produces Glucose from Non. Carbohydrate Sources Ketoadicosis No Insulin Available or Cells Resistant Cell Starves Body Uses Fat for Fuel

Forms of Diabetes Ø Type 1 • Usually begins in childhood or early adulthood • 5– 10% of diabetics • Immune system destroys beta cells of the pancreas - No insulin produced • Common symptoms of elevated blood sugar - Polydipsia - Polyuria - Polyphagia • Require insulin and frequent blood glucose monitoring © 2010 Pearson Education, Inc.

Forms of Diabetes Ø Type 2 • Overweight individuals develop this form frequently • 90– 95% of diabetics • Can go undiagnosed - Damages vital organs without individual being aware of it Ø Polycystic ovary syndrome • Hormonal imbalance in women • Have higher incidence of insulin resistance and hyperinsulinemia - Increased risk of developing type 2 diabetes © 2010 Pearson Education, Inc.

Forms of Diabetes Ø Prediabetes • Impaired glucose tolerance • Fasting blood sugar between

Diabetes Ø Ø Long-term damage from diabetes • Nerve damage • Tooth loss • Leg and foot amputations • Gum problems • Kidney disease • Eye diseases • Heart disease • Blindness Slowing of onset of complications • Control level of blood glucose through - Diet - Insulin or oral medication - Monitoring blood glucose - Regular healthcare visits © 2010 Pearson Education, Inc.

Diabetes Ø Slowing of onset of complications • Control level of blood glucose through - Diet - Insulin or oral medication - Monitoring blood glucose - Regular health care visits © 2010 Pearson Education, Inc.

Quick Review Ø Diabetes involves inadequate regulation of blood glucose levels Ø Type 1 diabetes – inadequate production of insulin Ø Type 2 diabetes – insulin resistance Ø Chronic high blood glucose can damage vital organs Ø Diabetics need medications and/or insulin to manage blood glucose Ø High-fiber diet and routine exercise play a key role in managing and preventing diabetes Ø Polycystic ovary syndrome increases the risk of developing type 2 diabetes © 2010 Pearson Education, Inc.

Hypoglycemia Ø A blood glucose level that is too low (usually below 70 mg/dl) Ø Signs and symptoms • Hunger • Nervousness • Dizziness • Light-headed Ø • • Confused Weak Shaky Sweaty Eating or drinking carbohydrate rich foods • Relieves symptoms • Raises blood glucose © 2010 Pearson Education, Inc.

Change in Blood Glucose After Eating a High-Carbohydrate Meal Figure 4. 17

Fasting Hypoglycemia Ø Occurs in the morning after an overnight fast Ø Occurs during long stretches between meals or after exercise Ø May be caused by • Medications • Illness • Drinking too much alcohol • Certain tumors • Hormone imbalances © 2010 Pearson Education, Inc.

Quick Review Ø Symptoms of hypoglycemia • Hungry, nervous, light-headed, shaky, and/or sweaty Ø Diabetics who take medications and/or insulin and do not eat properly are at risk Ø Individuals without diabetes may experience reactive hypoglycemia several hours after meals Ø Fasting hypoglycemia may occur upon awaking in the morning Ø Can be caused by medications, illnesses, hormone imbalances, or excessive consumption of alcohol © 2010 Pearson Education, Inc.

Natural versus Added Sugar Ø Naturally occurring sugar • Sugars such as fructose and lactose found naturally in foods • Tend to be nutrient dense Ø Added sugar • Sugars added to processed foods and sweets • Empty calories © 2010 Pearson Education, Inc.

Slices of an Orange versus Orange Slices Figure 4. 18

Added Sugar Ø Reasons sugar is added to foods • To keep product moist • To turn pastries a golden brown • Preservative • Thickening agent • Make yeast rise • Make foods taste sweet © 2010 Pearson Education, Inc.

Finding Added Sugars on the Label Figure 4. 19

Americans Drink the Majority of Their Sugar Figure 4. 20

Health Effects of Sugar Ø Sugar can contribute to • Dental carries • Elevated level of fat in the blood • Lowing of HDL cholesterol Ø Sugar does not cause • Increased risk of diabetes • Hyperactivity in children Ø Sugar is not considered an addictive substance © 2010 Pearson Education, Inc.

Quick Review Ø Taste buds do not distinguish between naturally occurring sugar and added sugar Ø Foods with naturally occurring sugar provide more nutrition and satiation than empty-calorie sweets Ø There are numerous names for added sugar Ø Soft drinks are the number-one contributor of added sugars to U. S. diets © 2010 Pearson Education, Inc.

Putting It All Together Ø Carbohydrates are an important part of a healthy diet Ø Whole grains, fruits, vegetables, and lean dairy products • Provide carbohydrates and vitamins and minerals • Should be the predominant source of carbohydrates Ø Whole grains, fruits, and vegetables are a good source of fiber and phytochemicals • Adequate amounts of these can prevent many chronic disease Ø Sugary foods should be eaten in moderation © 2010 Pearson Education, Inc.