Carbohydrates and Its Types
Carbohydrates and Its Types
Carbohydrates and Its Types
Sugars, Starches
and Fiber
Figure 4.2
Disaccharides
➢ Three Disaccharides
• Sucrose
- Most common
• Lactose
• Maltose
- Least common
- Formed from digestion of starches
Figure 4.3
Polysaccharides
➢ Starch
• Plants store glucose in chains of starch
- Amylose
- Straight chain
- More resistant to digestion
- Resistant starch
✓ May improve health of digestive tract
✓ May improve glucose tolerance
✓ May stimulate growth of beneficial intestinal
bacteria
- Amylopectin
- Branched chains
- Easier to digest
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Polysaccharides
➢ Fiber
• Nondigestible polysaccharides
• Provides no energy
• Classification
- Soluble
- Pectins, beta-glucan, some gums, mucilage
- Easily fermented by intestinal bacteria
• Carbon dioxide, methane, some fatty acids
- Insoluble
- Cellulose, lignin, some hemicelluloses
- Not easily fermented
© 2010 Pearson Education, Inc.
Fiber Health Benefits
➢ Soluble fibers
• Slow gastric emptying and may delay absorption of some
nutrients
- Helps reduce serum cholesterol
- Improve appetite control
- Normalize blood glucose levels
• May help protect against colon cancer
➢ Insoluble fibers
• Relieves constipation
➢ Most plant foods contain both soluble and insoluble fibers
BG → glycogen breakdown → BG
Figure 4.4
Oligosaccharides
➢ Similar in length to simple carbohydrates
➢ Similar in makeup to polysaccharides
➢ Humans lack the enzymes necessary to digest them
➢ Intestinal microflora digest and ferment them
• Cause bloating, discomfort, and flatulence
➢ Food sources
• Legumes, beans, cabbage, brussels sprouts, broccoli
Figure 4.7
Quick Review
➢ Complex carbohydrates
• Polysaccharides: starch, fiber, glycogen
• Fiber
- Soluble – fermented by intestinal bacteria; moves
slowly
- Insoluble – moves quickly through and reduces
constipation
- Functional – added to foods
➢ Oligosaccharides
• Contain three to ten units
• Part of cellulose in cell walls
Figure 4.9
Quick Review
➢ Digestion of carbohydrates begins in the mouth
➢ Most carbohydrate digestion takes place in the small
intestine
➢ Carbohydrates are broken down to monosaccharides for
absorption
➢ Monosaccharides are converted to glucose in the liver and
• Used as energy
• Stored as glycogen in the liver and muscle cells
• Stored as glycerol and fatty acids in the adipocytes
➢ Fiber travels to the colon undigested and most is eliminated
from the body
Figure 4.10
How to Maintain Blood Glucose Levels
➢ Epinephrine and norepinephrine – increases blood glucose
• Stimulate glycogenolysis and gluconeogenesis
➢ Cortisol – increases blood glucose
• Stimulates gluconeogensis
• Reduces uptake of glucose by the muscle cells
➢ Growth hormone – increases blood glucose
• Stimulates fat breakdown for energy
• Reduces uptake of glucose by the muscles
• Increase glucose production in the liver
Figure 4.14
Food Sources of Fiber
Figure 4.15
Quick Review
➢ Best sources of carbohydrates are
• Fresh fruits and vegetables • Legumes
• Whole grains • Low-fat dairy products
➢ Excellent sources of fiber are
• Whole grains • Legumes
• Fruits • Nuts
• Vegetables • Seeds
➢ Packaged foods can be good sources of starch and fiber
• Read label carefully
• Avoid too much sugar, fat, and kilocalories
Liver Breaks
Down Glycogen
Blood Glucose and Produces Cell
Rises Glucose from Starves
Non-
Carbohydrate
Sources
Body
Ketoadicosis Uses Fat
for Fuel
Forms of Diabetes
➢ Type 1
• Usually begins in childhood or early adulthood
• 5–10% of diabetics
• Immune system destroys beta cells of the pancreas
- No insulin produced
• Common symptoms of elevated blood sugar
- Polydipsia
- Polyuria
- Polyphagia
• Require insulin and frequent blood glucose monitoring
Figure 4.17
Fasting Hypoglycemia
➢ Occurs in the morning after an overnight fast
➢ Occurs during long stretches between meals or after
exercise
➢ May be caused by
• Medications
• Illness
• Drinking too much alcohol
• Certain tumors
• Hormone imbalances
Figure 4.18
Added Sugar
➢ Reasons sugar is added to foods
• To keep product moist
• To turn pastries a golden brown
• Preservative
• Thickening agent
• Make yeast rise
• Make foods taste sweet
Figure 4.19
Americans Drink the Majority of Their Sugar
Figure 4.20
Health Effects of Sugar
➢ Sugar can contribute to
• Dental carries
• Elevated level of fat in the blood
• Lowing of HDL cholesterol
➢ Sugar does not cause
• Increased risk of diabetes
• Hyperactivity in children
➢ Sugar is not considered an addictive substance