Chapter 4 presents the following content: What are carbohydrates?simple sugars, complex carbohydrates, carbohydrate digestion and absorption, carbohydrates and glucose in the body, the role of carbohydrates in our diet, carbohydrates and health,...
Trang 1Chapter 4
Carbohydrates
: Simple
Sugars and Complex
Chains
Trang 2What Are Carbohydrates?
• Sugars, starches, and
Trang 5• 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
Trang 6• 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
Trang 7• Galactose
– Rarely occurs as a monosaccharide in food
– Usually bonds to glucose to form lactose
• Primary sugar in milk and dairy products
Trang 8• 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
Trang 9• Maltose: glucose + glucose
– “Malt sugar”
– Seldom occurs naturally in foods
– Product of starch breakdown
– Found in germinating cereal grains
Trang 10Complex Carbohydrates
and lentils
behave in water and with heating
Trang 11Complex Carbohydrates
(potatoes and yams)
digested
Trang 13Complex Carbohydrates
form of glycogen
glucose levels get low
liver
Trang 14Complex Carbohydrates
Trang 16Complex Carbohydrates
component of dietary fiber
branching side chains
especially fruits
Trang 18Complex Carbohydrates
cells together
woody parts of vegetables and the seeds of fruits
Trang 19vitamins and some minerals
Trang 20Carbohydrate Digestion and
Trang 21Carbohydrate Digestion and
• Brush border enzymes digest disaccharides
• Other digestive enzymes
– Maltase, sucrase, and lactase split maltose, sucrose, and lactose,
respectively
Trang 22Carbohydrate Digestion and
Trang 23Carbohydrate Digestion and
Absorption
• Digestion
• Enzymes
– Highly specific
» Examples include lactase and Beano
• Some carbohydrates remain intact, such
as fiber and resistant starch
Trang 25Carbohydrate Digestion and
Trang 27Carbohydrates 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
Trang 28Carbohydrates and Glucose in
Trang 29Carbohydrates 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
Trang 30Carbohydrates and Glucose in
the Body
• Regulating blood glucose
– To maintain an adequate supply for cells
Trang 31Carbohydrates and Glucose in
Trang 33The 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
Trang 34The 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
Trang 35The 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!
Trang 36The Role of Carbohydrates in
• Increase fiber intake gradually while
drinking plenty of fluids
Trang 37Carbohydrates 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
Trang 38Carbohydrates and Health
• Negative effects of excess fiber
– Gradual intake and increased water
consumption
– Can bind small amounts of minerals
Trang 39Carbohydrates 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
Trang 40Carbohydrates and Health
Trang 41Carbohydrates 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