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 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.

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

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

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

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

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

Type 1 and 2 Diabetes Compared

An Obesity-Diabetes Cycle

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

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