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The Carbohydrates
Sugars
Starches
Fiber
Carbohydrates (CH2O)n
• Simple carbohydrates
–Monosaccharides
–Disaccharides
• Complex carbohydrates
Simple Carbohydrates
• Monosaccharides
–C6H12O6
•Glucose (dextrose, blood sugar)
•Fructose
•Galactose
Glucose
Fructose & Galactose
Condensation
Hydrolysis
Disaccharides
• Maltose = glucose + glucose
• Sucrose = glucose + fructose
• Lactose = glucose + galactose
Complex Carbohydrates
• Polysaccharides
– Glycogen (animal)
– Starches (plant)
– Fibers (non-starch polysaccharides)-not
digested well.
Glycogen & Starch Molecules Compared
(small Segments)
Complex Carbohydrates
• Fibers
–Cellulose
–Hemicelluloses
–Pectins
Complex Carbohydrates
• Fibers
–Gums and mucilages
–Lignin
–Resistant starches
Complex Carbohydrates
• Fibers
–Soluble fibers
•Viscous-Gums, pectins
•Fermentable
Complex Carbohydrates
• Fibers
–Insoluble fibers
•Nonviscous-cellulose, lignins,
resistant starches
• (Phytic acid)
Digestion
• Mouth
–Salivary amylase
• Stomach
–Fibers and satiety
Digestion
• Small intestine
–Maltase, sucrase, lactase
• Pancreas
–Pancreatic amylase
Carbohydrate
Digestion in the
GI Tract
Digestion
• Large intestine
–Fermentation of viscous fibers
•Water, gas, short-chain fatty
acid production
Absorption
Lactose Intolerance
• Symptoms-gas production,
nausea, etc.
• Causes
–Lactase deficiency
Lactose Intolerance
• Prevalence-variable
• Dietary changes
–Does not require the elimination
of milk/milk products
–Acidophilus milk
Glucose in the Body
• Energy
• Glycoproteins
• Glycolipids
Carbohydrate Metabolism
• Storing
glucose as
glycogen
(1/3)
• Using glucose
for energy
Carbohydrate Metabolism
• Making glucose from protein
–Gluconeogenesis
–Protein-sparing action of
carbohydrates
Carbohydrate Metabolism
• Making ketone bodies from fat
fragments
–Ketone bodies
•Ketosis
–Acid-base balance
Carbohydrate Metabolism
• Converting glucose to fat
–Energetically expensive
Constancy of Blood
Glucose
• Regulating hormones
–Insulin-uptake of sugar
–Glucagon-release of sugar
–Epinephrine-release (fight or
flight)
Maintaining Blood
Glucose Homeostasis
Constancy of Blood
Glucose
• Diabetes
–Type 1 diabetes
•Failure of insulin production
–Type 2 diabetes-fat cells are
insulin resistant!
•Obesity
Constancy of Blood
Glucose
• Hypoglycemia
–Rare in healthy people
Constancy of Blood
Glucose
• Glycemic response
–Glycemic index
Sugars
• Added sugars
–Sucrose, invert sugar, corn
syrups, etc.
Sugars
• Health effects
of sugars
–Nutrient
deficiencies?
Sugars
• Health effects of
sugars
–Dental caries
•Dental plaque
Accusations
Against Sugars
• Sugar causes
obesity?
• Sugar causes
heart disease?
Accusations
Against Sugars
• Sugar causes misbehavior in
children and criminal behavior in
adults?
• Sugar causes cravings and
addictions?
–serotonin
Recommended Intakes of
Sugars
• DRI
–No more than 25% of total daily
energy intake
Carbs. Part II: Practical Aspects of
Starches and Fibers
Starch and Fiber
• Health effects
–Heart disease
–Diabetes
–GI health
Starch and Fiber
• Health effects
–Cancer
–Weight management
–Harmful effects of excessive fiber
intake
Viscous Fibers
Nonviscous Fibers
Starch and Fiber
• RDA for carbohydrate
–130 g/day
–45% - 65% total daily energy
intake
• Daily Value: 300 g/day
Starch and Fiber
• Fiber
–Daily Value: 25 g/day
–AI: 14 g/1000 kcal/day
Guidelines
to Groceries
• Grains
Alternatives to Sugar
• Saccharine and cancer
• Aspartame and PKU
Artificial Sweeteners
• Also called nonnutritive sweeteners
– Saccharin
• Used primarily in soft drinks and as a tabletop
sweetener
• Rapidly excreted in the urine
• Does not accumulate in the body
• Has been removed from list of cancer-causing
substances
Artificial Sweeteners
• Aspartame
– General purpose sweetener
– Warning about phenylalanine for those with
PKU
– Controversial finding that aspartame may have
caused cancer in rats
– Excessive intake should be avoided by those
with epilepsy
Artificial Sweeteners
• Acesulfame-K (acesulfame potassium)
– Research confirms safety
Artificial Sweeteners
• Sucralose
– Made from sugar
– Passes through digestive tract
• Neotame
– Most recent on the market
– Very sweet
– Phenylalanine not an issue
Artificial Sweeteners
• Tagatose
– Used for foods and beverages
– Provides less kcalories than sugar
– High doses can cause flatulence and loose
stools.
• Alitame and Cyclamate
– Pending FDA approval
– Approved in other countries
Artificial Sweeteners
• Acceptable Daily Intake (ADI) is the level of
consumption, maintained every day and still safe
by a wide margin.
– Moderation and variety are still recommended.
• Artificial Sweeteners and Weight Control
– Much research still being done
– Using artificial sweeteners will not automatically
reduce energy intake.
Stevia – An Herbal Alternative
• Lacks research
• Classified as a dietary supplement
• Not required to have testing and FDA
approval
Sugar Replacers
• Also called nutritive sweeteners, sugar
alcohols, and polyols
• Maltitol, mannitol, sorbitol, xylitol, isomalt,
and lactitol
• Absorbed more slowly and metabolized
differently in the body
• Low glycemic response
• Side effects include GI discomfort