Chapter 4 Carbohydrates: Sugar, Starch, Glycogen, and Fiber Nutrition: Concepts & Controversies, 12e Sizer/Whitney

Learning Objectives Describe the major types of carbohydrates, and identify their food sources. Describe the various roles of carbohydrates in the body, and explain why avoiding dietary carbohydrates may be ill-advised. Summarize how fiber differs from other carbohydrates and how fiber may contribute to health.

Learning Objectives Explain how complex carbohydrates are broken down in the digestive tract and absorbed into the body. Describe how hormones control blood glucose concentrations during fasting and feasting. Explain the term glycemic index and how it may relate to diet planning.

Learning Objectives Describe the scope of the U.S. diabetes problem and educate someone about the long- and short-term effects of untreated diabetes and prediabetes. Name components of a lifestyle plan to effectively control blood glucose and describe the characteristics of a diet that can assist in managing type 2 diabetes.

Learning Objectives Compare the symptoms of postprandial hypoglycemia with those of fasting hypoglycemia, and name some diseases associated with the latter type. Discuss current research regarding the relationships among dietary carbohydrates, obesity, diabetes, and other ills.

Carbohydrates Ideal nutrients Energy needs Feed brain and nervous system Keep digestive system fit Keep your body lean Digestible and indigestible carbohydrates Complex vs. simple carbohydrates

A Close Look at Carbohydrates Contain the sun’s radiant energy Green plants Photosynthesis Glucose Plants do not use all of the energy stored in their sugars Carbohydrate-rich foods Plants Milk

Carbohydrate – Mainly Glucose – Is Made by Photosynthesis

A Close Look at Carbohydrates - Sugars Six sugar molecules Monosaccharides Glucose, fructose, galactose Disaccharides Lactose, maltose, and sucrose Digestion of mono- and disaccharides Chemical names end in -ose

How Monosaccharides Join to Form Disaccharides

A Close Look at Carbohydrates – Starch Polysaccharides Starch Plant’s storage form of glucose Glycogen Fiber Nutrition For a plant For a human

How Glucose Molecules Join to Form Polysaccharides

A Close Look at Carbohydrates – Glycogen Storage form of glucose Animal bodies Chains are longer than starch More highly branched Undetectable in meats

A Close Look at Carbohydrates - Fibers Human digestive enzymes cannot break bonds Bacteria in large intestine Fermentation Soluble vs. insoluble fibers

The Need for Carbohydrates Critical energy source Nerve cells and brain Preferred dietary sources Starchy whole foods Complex carbohydrates Vital roles in the functioning body

The Need for Carbohydrates Weight loss Caloric contribution Conversion into fat storage Refined sugars Increase fiber-rich whole foods Reduce refined white flour and added sugars

Why Do Nutrition Experts Recommend Fiber-Rich Foods? Health benefits Reduced risk of heart disease Reduced risk of hypertension Reduced risk of diabetes Reduced risk of bowel disease Promotion of healthy body weight Sources of fiber

Characteristics, Sources, and Health Effects of Fibers

Fiber Composition of Common Foods

Why Do Nutrition Experts Recommend Fiber-Rich Foods? Lower cholesterol and heart disease risk Complex carbohydrates More than just fiber Viscous fiber Cholesterol synthesis Blood glucose control Whole grains Soluble fibers

One Way Fiber in Food May Lower Cholesterol in the Blood

Why Do Nutrition Experts Recommend Fiber-Rich Foods? Maintenance of digestive tract health All kinds of fiber Ample fluid intake Benefits of fiber Constipation, hemorrhoids, appendicitis, diverticulosis

Diverticula

Why Do Nutrition Experts Recommend Fiber-Rich Foods? Digestive tract cancer and inflammation Ways fiber works against cancer Dilution Folate Resident bacteria Butyrate Recommended dietary sources Healthy weight management Appetite control

Fiber Recommendations and Intakes Few people in U.S. meet recommendations 20-35 grams of fiber daily Based on energy needs, age, and gender Adding fiber to diet Too much fiber? Dangers of excess Binders in fiber Chelating agents Cause of deficiencies

Usefulness of Carbohydrates

Refined, Enriched, and Whole-Grain Foods Bread supplies much carbohydrate for many people Kernel (whole grain) has four main parts Germ Endosperm Bran Husk

A Wheat Plant and a Single Kernel of Wheat

Refined, Enriched, and Whole-Grain Foods U.S. Enrichment Act of 1942 Required additives Addition in 1996 Advantages of whole grains vs. enriched grains Finding the whole grains in foods

Nutrients in Whole-Grain, Enriched White, and Unenriched White Breads

Bread Labels Compared

From Carbohydrates to Glucose – Digestion & Absorption Starch and disaccharides are broken down Monosaccharides for absorption Starch Begins in the mouth Splits starch into maltose Digestion ceases in the stomach Digestion resumes in small intestine Pancreas Resistant starch

From Carbohydrates to Glucose – Digestion & Absorption Sugars Split to yield free monosaccharides Enzymes on small intestine lining Travel to the liver Fiber Fermented by bacteria in the colon Odorous gas Gradually increase fiber intakes

How Carbohydrate in Food Becomes Glucose in the Body

Why Do Some People Have Trouble Digesting Milk? Ability to digest milk carbohydrates varies Lactase Made by small intestine Symptoms of intolerance Nausea, pain, diarrhea, and gas Milk allergy Nutritional consequences Milk tolerance and strategies

The Body’s Use of Glucose Basic carbohydrate unit used for energy Body handles glucose judiciously Maintains an internal supply Tightly controlling blood glucose concentrations Brain, nervous system, red blood cells

Splitting Glucose for Energy Glucose is broken in half Can reassemble Broken into smaller molecules Irreversible Two pathways

Splitting Glucose for Energy Glucose can be converted to fat Fat cannot be converted to glucose Dependence on protein when insufficient carbohydrate Protein-sparing action Ketosis Shift in body’s metabolism Disruption of acid-base balance DRI minimum of digestible carbohydrate

How Is Glucose Regulated in the Body? Two safeguard activities Siphoning off excess blood glucose Replenishing diminished glucose Two hormones Insulin Signals body tissues to take up glucose Glucagon Triggers breakdown of glycogen Epinephrine

Handling Excess Glucose Body tissue shift Burn more glucose Fat is left to circulate and be stored Carbohydrate storage as fat Liver breakdown and assembly Costs a lot of energy Weight maintenance Dietary importance and composition

Glycemic Index of Food Elevation of blood glucose and insulin Diabetes Food score compared to standard food Diabetes Glycemic load (GL) Lower GL = less glucose guild up and less insulin needed Limitations of glycemic index Resist notion of “good” or “bad” foods

Glycemic Index of Selected Foods

Diabetes Prevalence of diabetes Prediabetes Perils of diabetes Adults Children Prediabetes Importance of testing Perils of diabetes Toxic effects of excess glucose Inflammation Circulation problems

Prevalence of Diabetes Among Adults in the United States

Warning Signs of Diabetes

Type 1 Diabetes 5 to 10 percent of cases Common age of occurrence Autoimmune disorder Own immune system attacks pancreas Lose ability to produce insulin External sources of insulin Fast-acting and long-acting forms

Type 2 Diabetes Predominant type of diabetes Lose sensitivity to insulin Obesity underlies many cases Other factors foreshadowing development Middle age and physical inactivity Body fat accumulation Genetic inheritance Prevention

Type 1 and 2 Diabetes Compared

An Obesity-Diabetes Cycle

Management of Diabetes Controlling blood glucose is key Monitoring blood glucose levels Taking medications Control body fatness Establish good eating patterns

Management of Diabetes Nutrition Goal: blood glucose levels in normal range Control carbohydrate intake Amount rather than source seems to matter Carbohydrate recommendations Varies with glucose tolerance Exchange system

Management of Diabetes Nutrition Carbohydrate timing Evenly spaced Sugar alcohols Advantages Artificial sweeteners Weight control

Management of Diabetes Physical activity Benefits of regular activity Type 2 diabetes vs. type 1 diabetes

Hypoglycemia Rare, but true disease Postprandial hypoglycemia Abnormally low blood glucose Postprandial hypoglycemia Requires test to detect Fasting hypoglycemia Symptoms Methods to reduce symptoms

Finding Carbohydrates in Foods Fruits Vary in water, fiber, & sugar concentrations Juice Vegetables Breads, grains, cereals, rice, & pasta Brown color does not equal whole grain Low-fat and low-sugar choices

Finding Carbohydrates in Foods Meat, poultry, fish, dry beans, eggs, & nuts Nuts and legumes Milk, cheese, & yogurt High-quality protein Oils, solid fats, & added sugars Naturally occurring vs. added sugars Honey

Finding Carbohydrates in Foods The nature of sugar Teaspoon values High-fructose corn syrup Concentrated juice sweeteners Ways to magnify sweetness without calories

Are Carbohydrates “Bad” for Health Controversy 4

Accusation 1: Carbohydrates Are Making Us Fat Americans are fatter Greater consumption of calories 300-500 per day Epidemiological studies Weight loss

Percentage of Calories from Energy Nutrients, U.S., 1977-2006

Daily Energy Intake Over Time

Accusation 2: Carbohydrates Cause Diabetes Obesity and diabetes Refined carbohydrates and diabetes Native Americans Glycemic load and diabetes Whole foods

Accusation 3: Added Sugars Cause Obesity and Illness Current trends Daily Per year Relationship with disease

Added Sugars: Average U. S Added Sugars: Average U.S. Supply per Person Compared with USDA Prudent Upper Intake Limits

Accusation 4: High-Fructose Corn Syrup Harms Health Villainy has been exaggerated Nature of HFCS Half of added sugar in U.S. food supply Obesity HCFS not a proven cause Liquid sugar and calorie control Appetite regulation Fructose does not stimulate insulin release

Accusation 4: High-Fructose Corn Syrup Harms Health Effects on lipid metabolism Fructose causes fats to accumulate in blood and liver Metabolic activities of concern

Accusation 5: Blood Insulin Is To Blame Presence of insulin Body tends to store energy Claims made about insulin Expert standing on insulin Insulin does not cause accumulation of excess body fat