PHED 2015- Nutrition for Life 4e

1. CHAPTER
3
Carbohydrates: Plant-Derived
Energy Nutrients
Chapter 3 Outline
I. What Are Carbohydrates?
A. Carbohydrates are one of the three macronutrients that provide energy to our bodies.
1. Carbohydrates contain carbon, hydrogen, and oxygen.
B. Most carbohydrates come from plant foods.
1. Plants make glucose through photosynthesis.
C. Simple carbohydrates are sugars.
1. The three monosaccharides are glucose, fructose, and galactose.
a. Glucose is the preferred source of energy for the brain and is an important energy
source for all cells.
b. Fructose is the sweetest natural sugar and occurs naturally in fruits and vegetables.
c. Galactose occurs as part of the disaccharide lactose.
2. The three disaccharides are lactose, maltose, and sucrose.
a. Lactose is made up of one glucose molecule and one galactose molecule and is
found in milk.
b. Maltose is made up of two glucose molecules and is a by-product of the breakdown
of larger molecules.
c. Sucrose is made up of one glucose molecule and one fructose molecule and is the
sweetest disaccharide.
D. Complex carbohydrates are polysaccharides.
1. Starch is a polysaccharide stored in plants.
2. Fiber is a polysaccharide that gives plants their structure.
a. Dietary fiber is the indigestible parts of plants that form the support structures of
plants.
b. Functional fiber is manufactured and added to foods and fiber supplements.
c. Total fiber is the sum of dietary fiber and functional fiber.
d. Fiber may also be classified as soluble and insoluble.
e. Soluble fiber is viscous and may reduce risk for cardiovascular disease and type 2
diabetes.
f. Insoluble fiber is not digested and promotes regularity.
g. Not all complex carbohydrate foods are fiber-rich.
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2. 3. Glycogen is a polysaccharide stored by animals.
II. Why Do We Need To Eat Carbohydrates?
A. Carbohydrates provide energy.
1. Carbohydrates and fat fuel daily activity; carbohydrates deliver 4 kilocalories (kcal) of
energy per gram.
2. As the intensity of exercise increases, the percentage of carbohydrate used to fuel the
exercise increases.
3. Carbohydrates spare protein.
a. Gluconeogenesis is the generation of glucose from the breakdown of proteins into
amino acids.
B. Fiber-rich carbohydrates have health benefits.
1. Possible benefits of fiber consumption include:
a. Reduced risk of colon cancer
b. Prevention of hemorrhoids and constipation
c. Reduced risk of diverticulosis
d. Reduced risk of obesity
e. Reduced risk of heart disease
f. Reduced risk of type 2 diabetes
III. What Happens To The Carbohydrates We Eat?
A. Digestion breaks down most carbohydrates into monosaccharides.
1. Starch digestion begins in the mouth through the action of salivary amylase.
2. Most carbohydrate digestion occurs in the small intestine.
a. Pancreatic amylase digests any remaining starch to maltose.
b. Additional enzymes break down disaccharides into monosaccharides.
c. Lactose intolerance is an inability to digest lactose.
B. The liver converts all monosaccharides into glucose.
1. The liver releases glucose into the bloodstream if needed for immediate energy.
2. If there is no immediate demand for glucose, it is stored as glycogen.
C. Fiber is excreted from the large intestine.
1. Fiber enters the large intestine.
a. Bacteria break down some previously undigested carbohydrates, including soluble
fiber.
b. The fiber remaining in the colon provides bulk to stools.
D. Insulin and glucagon regulate the level of glucose in blood.
1. Insulin lowers blood sugar by facilitating uptake of glucose by body cells.
2. Glucagon raises blood glucose by causing the liver to convert its stored glycogen into
glucose.
3. Hypoglycemia refers to lower-than-normal blood glucose levels.
E. The glycemic index shows how foods affect our blood glucose levels.
a. Foods with a high glycemic index cause a sudden spike in blood glucose.
b. The glycemic load of a food is the carbohydrate it contains multiplied by its
glycemic index.
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3. IV. How Much Carbohydrate Should We Eat?
A. The current RDA for carbohydrates is 130 g per day for adults 19 years of age and older.
B. The AMDR for carbohydrates is 45 to 65 percent of total energy intake.
C. Most Americans eat too much refined carbohydrate.
1. Added sugars are sugars and syrups that are added to food during processing.
a. The most common source of added sugars in the U.S. diet is sodas and soft drinks.
2. Sugar causes tooth decay.
3. There is no proven link between sugar and hyperactivity in children.
4. High sugar intake can lead to unhealthful levels of blood lipids.
5. High sugar intake is associated with diabetes and obesity.
D. Most Americans eat too little fiber-rich carbohydrate.
1. We need at least 25 grams of fiber daily.
a. It is important to drink more fluids as fiber intake is increased.
2. Excessive fiber intake is possible and can lead to:
a. Intestinal gas and bloating
b. Dehydration
c. Reduced absorption of certain nutrients
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4. d. Malnutrition in some populations such as children, the elderly, and the chronically
ill
3. A shopper’s guide: hunting for fiber.
a. Select breads and cereals made with whole grains.
b. Buy fresh fruits and vegetables whenever possible and leave the skin on.
c. Frozen fruits and vegetables are healthy alternatives to fresh produce.
d. If choosing canned produce, look for products stored in their own juice.
e. Eat legumes frequently–every day if possible.
V. What’s The Story on Alternative Sweeteners?
1. Sweeteners such as sucrose, fructose, honey, and brown sugar contribute energy when
digested and are therefore nutritive sweeteners.
2. Sweeteners such as mannitol, sorbitol, isomalt, and xylitol are termed sugar alcohols
and feature a reduced glycemic response, decreased risk of dental decay, and slower
absorption in the intestines.
3. Numerous other products are used to sweeten foods without promoting tooth decay
and weight gain. Because they provide little to no energy, they are termed non-
nutritive sweeteners.
A. Limited use of alternative sweeteners is not harmful.
1. Saccharin: branded as “Sweet n’ Low”
2. Acesulfame-K: (ascesulfame potassium) branded as “Sunette” or “Sweet One”
3. Aspartame: branded as “Equal”
4. Sucralose: branded as “Splenda”
5. Neotame and stevia
B. Using artificial sweeteners does not necessarily prevent weight gain.
1. Ultimately, body weight is a function of Calories consumed versus Calories expended.
VI. What Is Diabetes, And Why Has It Become A Public Health Concern?
A. Diabetes is a chronic disease in which the body can no longer regulate glucose.
1. In type 1 diabetes, the body does not produce enough insulin.
a. Uncontrolled diabetes can lead to ketoacidosis.
b. Type 1 diabetes may be an autoimmune disease.
c. The only treatment is daily insulin injections.
2. In type 2 diabetes, cells become less responsive to insulin.
a. In most cases, obesity is the trigger for type 2 diabetes.
b. Insulin insensitivity often precedes type 2 diabetes.
c. A cluster of risk factors referred to as the metabolic syndrome also increases risk for
type 2 diabetes.
3. Lifestyle choices can help control or prevent type 2 diabetes.
a. Eat a balanced diet with plenty of whole grains, fruits, legumes, and vegetables
b. Engage in moderate daily exercise.
c. Maintain an appropriate body weight.
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