Chapter 4 Carbohydrates Sugars Starches and Fiber Carbohydrates

Chapter 4: Carbohydrates: Sugars, Starches, and Fiber

Carbohydrates in the Modern Diet n n n Carbohydrates are the basis of most modern diets. Carbohydrates in “whole foods, ” such as fresh fruit, diary or whole grains, are in their natural state. Refining carbohydrates separates the carbohydrates from their vitamins, minerals and fiber. Copyright 2010, John Wiley & Sons, Inc.

Whole versus Refined Carbohydrates Copyright 2010, John Wiley & Sons, Inc.

n What is Whole Grain? Copyright 2010, John Wiley & Sons, Inc.

Whole Grains versus Refined Grains n Whole or unrefined grains contain: n n n Bran layers: good source of fiber and vitamins Germ: good source of vegetable oils and vitamin E Endosperm: contains starch and some protein Copyright 2010, John Wiley & Sons, Inc.

n Which of the following nutrients are not added to enriched grains? q q

Whole Grains versus Refined Grains n n Refined grains, such as corn flakes or puffed rice, are made largely from the endosperm and are mostly starch. Refined grains may be enriched with thiamin, riboflavin, niacin and iron and fortified with folate. They do not contain the magnesium, some of the B vitamins or other nutrients of whole grains. Copyright 2010, John Wiley & Sons, Inc.

Choosing Whole Grains Copyright 2010, John Wiley & Sons, Inc.

Added Sugars in Our Diet Copyright 2010, John Wiley & Sons, Inc.

Carbohydrates n Carbohydrates in the diet are classified as: q q Simple carbohydrates, also known as sugars Complete carbohydrates, which include starch and fiber Copyright 2010, John Wiley & Sons, Inc.

Simple Carbohydrates n n n The basic unit of a carbohydrate is a single sugar molecule, known as a monosaccharide. The three most common monosaccharides in the diet are glucose, galactose and fructose. Glucose, also known as “blood sugar, ” is the most important carbohydrate fuel for the body. Copyright 2010, John Wiley & Sons, Inc.

Simple Carbohydrates Copyright 2010, John Wiley & Sons, Inc.

Disaccharides n n n Disaccharides are simple carbohydrates made of two monosaccharides linked together. Sucrose, or white table sugar, is formed by linking glucose with fructose. Sucrose is the only sweetener in the US that can be labeled “sugar. ” The chemical reaction that breaks sugar molecules apart is called a hydrolysis reaction. The chemical reaction that links two sugar molecules together is called a condensation reaction. Copyright 2010, John Wiley & Sons, Inc.

Structure of Disaccharides Copyright 2010, John Wiley & Sons, Inc.

Condensation and Hydrolysis Reactions Copyright 2010, John Wiley & Sons, Inc.

Complex Carbohydrates n n n Complex carbohydrates are made up of many monosaccharides linked together in chains. Oligosaccharides are short chains of less than ten monosaccharides. Polysaccharides are long chains of monosaccharides and include glycogen found in animals and starch and fiber found in plants. Copyright 2010, John Wiley & Sons, Inc.

n Which of the following sequences represents a monosaccharide followed by a disaccharide followed by a polysaccharide? q q fructose sucrose starch lactose glucose dietary fiber glucose maltose lactose galactose glycogen starch n Copyright 2010, John Wiley & Sons, Inc.

Dietary Fiber n n n Fiber includes certain complex carbohydrates that cannot be digested by human enzymes. Fiber cannot be digested or absorbed by the human body. Total fiber on a food label is the combined amount of functional fiber and dietary fiber found in the food. Soluble fiber dissolves in water and can be found in oats, apples and beans. Insoluble fiber does not dissolve in water and can be found in wheat bran and fruit and vegetable peels. Copyright 2010, John Wiley & Sons, Inc.

Digestion and Absorption of Carbohydrates Copyright 2010, John Wiley & Sons, Inc.

n The organ(s) which supply enzymes needed for starch digestion include the q q

Lactose Intolerance n n n The enzyme lactase is needed to digest lactose, the sugar found in milk. If lactose is not digested in the small intestine, it passes through to the large intestine. Undigested lactose in the small intestine can cause cramping, abdominal distention and diarrhea. Copyright 2010, John Wiley & Sons, Inc.

Indigestible Carbohydrates Slow Nutrient Absorption Copyright 2010, John Wiley & Sons, Inc.

Cellular Respiration n n To generate energy, glucose is metabolized through cellular respiration. Cellular respiration is also called aerobic metabolism. Cellular respiration produces ATP, a form of energy. This metabolic pathway uses six molecules of oxygen to convert one molecule of glucose into six molecules of carbon dioxide, six molecules of water and approximately thirty-eight molecules of ATP. Copyright 2010, John Wiley & Sons, Inc.

Gluconeogenesis Copyright 2010, John Wiley & Sons, Inc.

Availability of Carbohydrates Determines Fatty Acid Metabolism Copyright 2010, John Wiley & Sons, Inc.

Regulating Blood Glucose n n n In order to provide a steady supply of glucose to the cells, the concentration of glucose in the blood is regulated by the liver and by enzymes secreted from the pancreas. Glycemic response is how quickly and how high blood glucose rises after carbohydrates are consumed. The glycemic index is a ranking of how a food affects the glycemic response. Insulin is a hormone secreted by the pancreas in response to a rise in blood glucose levels. Glucagon is a hormone secreted by the pancreas in response to a decline in blood glucose levels. Copyright 2010, John Wiley & Sons, Inc.

n The _______ reflects a ranking of how specific foods affect blood glucose compared to the response of a reference food. q q glycemic response glycemic index gluconeogenic index solubility index Copyright 2010, John Wiley & Sons, Inc.

Abnormal Blood Glucose: Diabetes n n n Diabetes mellitus is the leading cause of blindness in the United States and accounts for 44% of all new cases of kidney failure. Gestational diabetes occurs in women during pregnancy. There may be an increased risk of developing type 2 diabetes later in life. Diabetes mellitus can be classified as: n n Type 1 Diabetes: Insulin is no longer made in the body Type 2 Diabetes: Insulin is present, but the cells do not respond Copyright 2010, John Wiley & Sons, Inc.

Diabetes Symptoms and Complications n Immediate Symptoms: excessive thirst, frequent urination, blurred vision and weight loss n Long Term Complications: damage to the heart, blood vessels, kidneys, eyes and nervous system. Infections are more common in patients with diabetes, and amputations may be necessary. Copyright 2010, John Wiley & Sons, Inc.

Diabetes Treatment n n n The goal of diabetes treatment is to keep blood glucose levels within normal ranges. Treatment includes a combination of diet, exercise, and, if necessary, medication, which can be oral or injected. Evidence is accumulating that refined sugar may play a role in the development of type 2 diabetes. Copyright 2010, John Wiley & Sons, Inc.

practice n n From what we’ve learned thus far, create some good meals to recommend to a diabetic Tips q q q Lower Carb Higher protein High fiber No sugar Nutritionally dense Copyright 2010, John Wiley & Sons, Inc.

Selecting Healthy Carbohydrates Copyright 2010, John Wiley & Sons, Inc.

Carbohydrates and Dental Caries n n n Dental caries occur when bacteria that live in the mouth form colonies on teeth known as plaque. If the plaque is not brushed or flossed away, the bacteria metabolize carbohydrates in the mouth and create acid. The acid dissolves tooth enamel and the underlying structures of the teeth and gums. Copyright 2010, John Wiley & Sons, Inc.

Low-Carbohydrate Weight Loss Diets n n n The rationale for low-carbohydrate diets is that foods high in carbohydrates stimulate the release of insulin. Insulin promotes energy storage, mostly from fat. The more insulin you release, the more fat you store. Low-carbohydrate diets cause less insulin to be released. With low-carbohydrate diets, the body produces more ketones. Ketones help suppress the appetite. Copyright 2010, John Wiley & Sons, Inc.

Carbohydrates and Heart Disease n n Diets high in sugar, or refined carbohydrates, have been shown to raise blood lipid levels and can lead to an increase in heart disease. Diets high in whole grains have been found to reduce the risk of heart disease. Copyright 2010, John Wiley & Sons, Inc.

High Fiber Intake and Bowel Disorders n Diets high in fiber, or indigestible carbohydrates, can relieve or prevent certain bowel disorders: n n Hemorrhoids Diverticulosis Diverticulitis Constipation Copyright 2010, John Wiley & Sons, Inc.

Colon Cancer and Fiber Intake n Epidemiological studies have shown that the incidence of

How Much Added Sugar Do We Eat? Copyright 2010, John Wiley & Sons, Inc.

n The acceptable range of carbohydrate intake for a healthy diet has been set

Reading Food Labels for Sugar and Fiber Content Copyright 2010, John Wiley & Sons,

n Why may sugar alcohols be used in products labeled “sugar free” or “no sugar added”? q q Sugar alcohols provide no kilocalaries Sugar alcohols are not derivatives of sugars Sugar alcohols are not monosaccharides or disaccharides Sugar alcohols are not absorbed into the body. Copyright 2010, John Wiley & Sons, Inc.

example n Joe Shmoe consumed 2500 calories yesterday, with 350 gm being from carbs. q q How many of his calories come from carbohydrate? What percentage of his energy is coming from carbohydrates? Copyright 2010, John Wiley & Sons, Inc.

Tools for Assessing Carbohydrate Intake Copyright 2010, John Wiley & Sons, Inc.

n How many kcalories (kcal) are there in 200 grams of carbohydrates? q q

Choosing Carbohydrates Wisely Copyright 2010, John Wiley & Sons, Inc.

Alternative Sweeteners n n Alternate sweeteners are also called nonnutritive sweeteners. Types of alternative sweeteners available in the US include: q q q Saccharin (the “pink packet”) Aspartame (the “blue packet”): cannot be used by people with phenylketonuria Sucralose (the “yellow packet”) Acesulfame K: sold as Sunette or Sweet One Neotame: can be used by people with phenylketonuria Copyright 2010, John Wiley & Sons, Inc.

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