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chp4week2.pptxChapter 4 Carbohydrates: Simple Sugars and Complex Chains
What Are Carbohydrates?
Sugars, starches, and fibers
Major food sources: Plants
Produced during photosynthesis
Two main carbohydrate types
Simple (Sugars)
Complex (Starches and fibers)
Simple Sugars
Monosaccharides
Glucose
Fructose
Galactose
Simple Sugars
Disaccharides: Consist of two monosaccharides linked together
Sucrose
Lactose
Maltose
Monosaccharides
Glucose
Most abundant simple sugar in nature
Also called dextrose
Gives food a mildly sweet flavor
Usually joined to another sugar in foods
Provides energy to body cells
Body closely regulates blood sugar levels
Monosaccharides
Fructose
Also called levulose or fruit sugar
Tastes the sweetest of all the sugars
Occurs naturally in fruits and vegetables
Found in fruits, honey, and corn syrup
Monosaccharides
Galactose
Rarely occurs as a monosaccharide in food
Usually bonds to glucose to form lactose
Primary sugar in milk and dairy products
Disaccharides
Sucrose: glucose + fructose
“Table sugar”
Made from sugar cane and sugar beets
Listed as sugar on food labels
Lactose: glucose + galactose
“Milk sugar”
Found in milk and milk products
Disaccharides
Maltose: glucose + glucose
“Malt sugar”
Seldom occurs naturally in foods
Product of starch breakdown
Found in germinating cereal grains
Complex Carbohydrates
Chains of two or more sugar molecules
Oligosaccharides
Three to ten sugar molecules
Examples sources: dried beans, peas, and lentils
Polysaccharides
Long chains of monosaccharides
Structural differences affect how they behave in water and with heating
Digestible or nondigestible
Complex Carbohydrates
Starch
Plants store energy as starch
Found in grains, legumes, and tubers (potatoes and yams)
Long chains of glucose units
Amylose—straight chains
Amylopectin—branched chains
Resistant starch: A starch that is not digested
Complex Carbohydrates
Glycogen
Living animals store carbohydrate in the form of glycogen
Provides body glucose when blood glucose levels get low
Highly branched chains of glucose units
Most stored in our skeletal muscle and liver
Carbohydrate “loading”
Complex Carbohydrates
Fiber
Nondigestible carbohydrates and lignins
Dietary fiber: Found in plants
Fruits, vegetables, legumes, and whole grains
Functional fiber: Isolated and added to foods
Total fiber: Sum of dietary fiber and functional fiber
Complex Carbohydrates
Types of fiber
Cellulose
Indigestible by humans and a component of dietary fiber
Hemicelluloses
Variety of monosaccharides with many branching side chains
Pectins
Dietary fiber found in all plants, especially fruits
Complex Carbohydrates
Types of fiber
Gums and cilages
Gel-forming fibers that help hold plant cells together
Lignins
Indigestible substances that make up woody parts of vegetables and the seeds of fruits
Complex Carbohydrates
Types of fiber
Beta-glucans
Polysaccharides of branched glucose units
Found in barley and oats
Help decrease blood cholesterol levels
Chitin and chitosan
Primarily consumed in supplement form
Marketed as weight-loss supplements
May impair absorption of fat-soluble vitamins and some minerals
Carbohydrate Digestion and Absorption
Digestion breaks down carbohydrates to single sugars
Mouth
Salivary amylase begins digestion of carbohydrates
Stomach
Acidity of stomach juices halt action of salivary amylase and stops carbohydrate digestion
Carbohydrate Digestion and Absorption
Digestion
Small intestine
Pancreatic amylase continues starch digestion
Brush border enzymes digest disaccharides
Other digestive enzymes
Maltase, sucrase, and lactase split maltose, sucrose, and lactose, respectively
Carbohydrate Digestion and Absorption
Digestion
Bonds that link glucose molecules
Alpha bonds
Broken down by human enzymes
Starch
Beta bonds
Bonds remain unbroken by human enzymes
Cellulose
Carbohydrate Digestion and Absorption
Digestion
Enzymes
Highly specific
Examples include lactase and Beano
Some carbohydrates remain intact, such as fiber and resistant starch
Carbohydrate Digestion and Absorption
Absorption: The small intestine swings into action
End products of carbohydrate digestion
Glucose
Galactose glucose
Fructose glucose
Liver
Stores and releases glucose as need to maintain blood glucose levels
Carbohydrates and Glucose in the Body
Glucose is our primary fuel
Needed to burn fat efficiently
When we eat food, our bodies
Immediately use some glucose to maintain normal blood glucose levels
Store excess glucose as glyocgen in liver and muscle tissue
Carbohydrates and Glucose in the Body
Using glucose for energy
Liver glycogen
Maintains normal blood glucose levels
Muscle glycogen
Fuels muscle activity
Carbohydrates and Glucose in the Body
Sparing body protein
Adequate carbohydrates prevent body from making glucose from body proteins
Preventing ketosis
Ketone bodies ketosis dehydration
Body needs a minimum of 50 to 100 grams of carbohydrate/day to prevent ketosis
Carbohydrates and Glucose in the Body
Regulating blood glucose
To maintain an adequate supply for cells
Controlled by hormones
Insulin
Key “unlocking” body cells and allowing glucose to enter and fuel them
Glucagon
Breaks down glycogen to glucose
Epinephrine
“Fight-or-flight” hormone
Carbohydrates and Glucose in the Body
Regulating blood glucose
Glycemic index
Foods vary in their effect on blood glucose levels
Index measures the effect of food on blood glucose levels
The Role of Carbohydrates in Our Diet
Recommended Carbohydrate Intake
RDA = 130 grams per day
Dietary Guidelines
“Reduce the intake of added sugars”
AMDR for added sugars = < 25% of daily energy intake
Choose whole grains, vegetables, fruits, and cooked dried beans and peas
Consume > ½ of all grains as whole grains
The Role of Carbohydrates in Our Diet
Current Consumption: How much are we eating?
AMDR = 45–65% of kcal
Average American adult = 49–50% of kcal
13% of population has added sugar intake > 25% of kcal
High soft drink consumption
Milk consumption and vitamin and mineral quality of diet is declining
The Role of Carbohydrates in Our Diet
Choosing Carbohydrates Wisely
Increase fruit, vegetables, whole grains, low-fat milk
Strategies
Eat peel fruit/vegetables
Eat legumes
Choose brown rice
Choose high-fiber cereal
Drink plenty of water!
The Role of Carbohydrates in Our Diet
High intake of foods rich in dietary fiber offers many health benefits, including reduced risk of
Obesity
Type 2 diabetes
Cardiovascular disease
Gastrointestinal disorders
Increase fiber intake gradually while drinking plenty of fluids
Carbohydrates and Health
Fiber and obesity
Possible role in weight control
Fiber and type 2 diabetes
Better control of blood glucose
Fiber and cardiovascular disease
Can lower blood cholesterol levels
Fiber and gastrointestinal disorders
Healthier gastrointestinal functioning
Carbohydrates and Health
Negative effects of excess fiber
Gradual intake and increased water consumption
Can bind small amounts of minerals
Carbohydrates and Health
Moderating sugar intake
Use less added sugar
Limit soft drinks, sugary cereals, candy, ice cream, and sweet desserts
Choose fresh fruits or those canned in water or juice
Carbohydrates and Health
Nutritive sweeteners
Monosaccharides, disaccharides, and sugar alcohols
Natural vs. refined
Non-nutritive sweeteners
Saccharin
Aspartame
Acesulfame K
Sucralose
Carbohydrates and Health
Sugar and dental caries promoted by:
Carbohydrate remaining in the mouth
Food that sticks to teeth
Frequent consumption
Sip high sugar drinks over time
