Transcript DIGESTION and ABSORPTION

CARBOHYDRATES
Sugars, Starches, Fibers
Ch. 4
CARBOHYDRATES
Learning Objectives:
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Understand classes of carbs
•
Understand carb digestion and absorption
•
Discuss diabetes (Ch. 18) – types, risk
factors, long-term consequences, treatment
•
Function of carbohydrates in the diet, and
how they relate to health issues
WHAT ARE
CARBOHYDRATES?
•
Organic compounds
CARBON, HYDROGEN, and OXYGEN
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Two Main Classes:
SIMPLE (sugars)
COMPLEX (starches and fiber)
TYPES OF
CARBOHYDRATES
Simple Sugars
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Monosaccharides
– Glucose, fructose,
galactose
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Disaccharides
– Maltose, sucrose,
lactose
Complex

Polysaccharides
– Starch, fiber
SIMPLE SUGARS
MONOSACCHARIDES
Glucose
Galactose
Fructose
Monosaccharides
All have same chemical formula, C6H12O6
Different arrangements
MONOSACCHARIDES
GLUCOSE
– Blood sugar
– Essential energy source
– One of two sugars in every disaccharide
GALACTOSE
– Only in a few foods
– Common in milk as lactose – bound to glucose
FRUCTOSE
– Naturally occurs in fruit and honey
– Sweetest sugar
SIMPLE SUGARS
DISACCHARIDES
Sucrose
(glucose + fructose)
Lactose
(glucose + galactose)
Maltose
(glucose + glucose)
DISACCHARIDES
SUCROSE
– Simple table sugar
– Tastes sweet because of fructose
LACTOSE
– Milk sugar
MALTOSE
– Produced when starch breaks down
– In the grain barley
Condensation
Combining smaller
units to make larger
or longer molecules
Loss of water
Example: Combining
monosaccharides
to form disaccharides
Condensation
Hydrolysis
Hydro = water
Lysis = breaking apart
Breaking down long chains &
larger molecules into smaller
molecules
Addition of water
Example: Breaking down
starch into maltose and then
into 2 units of glucose
Occurs during digestion
Hydrolysis
COMPLEX CARBOHYDRATES
POLYSACCHARIDES
 Starch
 Glycogen
 Dietary
Fiber
COMPLEX CARBOHYDRATES
POLYSACCHARIDES
Starch - long chains of glucose molecules
from PLANTS
Storage form of energy in plants
•
Arrangement:
Unbranched (AMYLOSE)
Branched (AMYLOPECTIN)
POLYSACCHARIDE
STARCH
AMYLOSE
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30% of plant starches
Not as easily absorbed by humans
– Higher in grains, underground veggies, bananas
AMYLOPECTIN
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70% of plant starches
More soluble – branched ends
Major Sources of Starch….
Grains: rice, wheat, millet,
rye, barley, and oats
Legumes: soybeans, kidney
beans, black-eyed peas,
pinto beans, navy beans,
and garbanzo beans
Tubers: potatoes
Root crops: yams and
cassava
COMPLEX CARBOHYDRATES
POLYSACCHARIDES
Glycogen – animal form of stored glucose
Highly branched and composed of multiple
glucose molecules
 Used for glucose/energy in liver or muscle
 Food is NOT a significant source

Glycogen and Starch
Compared
COMPLEX CARBOHYDRATES
Polysaccharides
DIETARY FIBER
 Structural
part of plants found in all
plant derived food
Vegetables, fruit, whole grains, legumes
 Cannot
be broken down by human
digestive enzymes
CLASSIFICATION of FIBER
SOLUBLE – dissolve in water
Viscous – forms gel
» Found in legumes and fruit
INSOLUBLE – can’t dissolve in water
Nonviscous – do not form gels
» Found in grains and vegetables
CLASSIFICATION of FIBER
SOLUBLE
Easily fermented by bacteria in colon
 Protects against heart disease and diabetes

– Lowers cholesterol
– Lowers glucose

Found in
» Oats
» Barley
» Psyllium
» Legumes and peas
» Citrus fruits, apples, carrots
CLASSIFICATION of FIBER
INSOLUBLE
Less readily fermented by bacteria
 Helps alleviate constipation and prevent
diverticular disease

– Provides bulk to stools
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Found in
» Whole grains (bran)
» Vegetables
» Nuts
Foods rich in starch and fiber
offer many health benefits
Fiber in Foods
Health Benefits of Fiber

Normalizes bowel movements
» Provides bulk

Helps maintain bowel integrity and health
» ↓ risk of hemorrhoids and diverticula

Lowers blood cholesterol levels
» Soluble fibers may lower LDLs

Helps control blood sugar levels
» Slows absorption of sugar

Aids in weight loss
» More chewing, feel full longer, less energy dense

Possibly decrease colon cancer risk
Fiber Facts
Table 4-5 p117
Complex Carbohydrates
POLYSACCHARIDES
 Starch
– Storage form of energy in plants
 Glycogen
– Storage form of energy in the human body
 Dietary
Fiber
– Provide structure in stems, trunks, roots, leaves, and
skins in plants
Table 4-1 p101
CARBOHYDRATES
Learning Objectives:
•
Understand classes of carbs
•
Understand carb digestion and
absorption
•
Discuss diabetes (Ch. 18) – types, risk
factors, long-term consequences, treatment
•
Function of carbohydrates in the diet, and
how they relate to health issues
Whiteboard Activity
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This is what we’re
starting with – foods,
which contain
different types of
carbohydrates.
How does the body
digest and absorb
these types of carbs?
Carbohydrate Digestion
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MOUTH – Salivary Amylase (starch)
•
STOMACH – no chemical digestion
Why? No carb digesting enzymes here
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SMALL INTESTINE –
Pancreatic Amylase
Disaccharidases: maltase, sucrase, lactase
Carbohydrate Digestion
SMALL INTESTINE
 Pancreatic Amylase
– Enters SI from pancreatic duct
– Breaks polysaccharides
(starch) to shorter glucose
chains and maltose
Carbohydrate Digestion
SMALL INTESTINE

Disaccharidases – released from microvilli
– Maltase:
Maltose → glucose + glucose
– Sucrase:
Sucrose → glucose + fructose
– Lactase:
Lactose → glucose + galactose
Carbohydrate Digestion
LARGE INTESTINE
 Very little digestion occurs
– Most starches have been digested

Fiber remains
– Attract water, soften stool for passage

Bacteria in GI tract ferment some fibers
– Generates water, gases, and SCFAs
CARBOHYDRATE ABSORPTION
Fructose
Glucose
Galactose
CARBOHYDRATE ABSORPTION
SMALL INTESTINE
Fructose = Facilitated Diffusion

Specific carrier to transport across cell
membrane
Glucose & Galactose = Active Transport

Specific carrier to transport across cell
membrane + energy (ATP)
CARBOHYDRATE ABSORPTION
Monosaccharides enter bloodstream through
microvilli
 Travel to the liver via portal vein
 In liver, galactose and fructose converted to
glucose

– Each monosaccharide provides
at least one glucose molecule
Figure 4-9 p103
Food for Thought
IMPORTANCE OF GLUCOSE
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Energy – primary fuel for most cells in the body
The brain MUST have glucose!
Sparing body protein – if glucose is scarce, the
body will breakdown its own protein.
Preventing ketosis – with no carbohydrate, fat
breakdown produces ketone bodies. Can lead to
ketosis.
Storage as glycogen – liver stores are used to
maintain blood sugar, while muscle stores are
used to fuel activity.
Make fat - if energy needs met, will store excess
glucose as fat for later use
Modeling of Chemical Digestion
 Carbohydrate
Digestion Activity in
Small Groups (MP4 video)
Carb Digestion Review
Whiteboard
Now let’s finish this
activity –
What happens to
these foods and
different types of
carbohydrates in
the body?
Canvas - jpeg pics &
MP4 video
CARBOHYDRATES
Learning Objectives:
•Understand classes of carbs
•Understand carb digestion and absorption
•Discuss diabetes (Ch. 18) – types, risk
factors, long-term consequences, treatment
•Function of carbohydrates in the diet, and how
they relate to health issues
REGULATING BLOOD
GLUCOSE LEVELS
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Insulin: lowers blood glucose
• Released from pancreas
• Travels to cells (muscle and liver)
•
Glucagon: raises blood glucose
• Released from pancreas -> Travels to liver
• Break down glycogen and release glucose into blood
•
Epinephrine: “fight-or-flight” hormone
Diabetes
HIGH BLOOD SUGAR - Hyperglycemia
Type I – Insulin-Dependent Diabetes
Pancreas does not produce insulin
Type II – Non-Insulin Dependent
Cells fail to respond to insulin or
insufficient amounts produced
Type 1 Diabetes
5-10% of diagnosed cases
 Pancreas loses its ability to produce insulin
 Cause somewhat unclear - genetics
 Autoimmune disease
 Rate of destruction varies
 Occur at any life stage

– More common in younger individuals
Type 2 Diabetes
90-95% of cases
 Primary defect – cells fail to respond to
insulin (insulin resistance)
 Pancreas secretes more insulin – this
eventually wears the pancreas out
 Pancreas secretes insufficient insulin
 Linked with obesity and lifestyle
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Videos Regarding Type 1 and 2
Type 1 Diabetes
 http://www.youtube.com/watch?v=_OOWhuC_9Lw
Type 2 Diabetes
 http://www.youtube.com/watch?v=nBJN7DH83HA
Features of Type 1 and Type 2 Diabetes
Diabetes
 Prevalence
Among
Adults in US
 2000
- 2010
DIABETES – RISK FACTORS
Type I
Type II
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Unclear
 Genetics
 Injury
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Genetics
>40 years old
Certain Ethnic Groups
Overweight
Sedentary
Low HDL or high
triglycerides
Smoking, Excess Alcohol
Gestational diabetes
Decreasing Diabetes Risk
Lifestyle factors that lower diabetes risk:
Healthy body weight
 Physical Activity
 Diet that follows the Dietary Guidelines for
Americans
 Never smoking
 Limited alcohol intake
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Diabetes - Long Term
Consequences
 Deterioration
of the eye
– Blurred vision, blindness
– Diabetic Retinopathy
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Kidney Disease
– Diabetic Nephropathy
– Dialysis
Diabetes – Long Term
Consequences
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Peripheral vascular disease
– Damaged blood vessels, loss of circulation
– Infections progress rapidly
– Gangrene, leading to amputations
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Progressive nerve damage
– Diabetic Neuropathy – damaged neurons
– Painful, prickling sensation (arms & legs)
– Loss of sensation in hands and feet
Diabetes – Long Term
Consequences
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Heart disease
– Atherosclerosis develops early, progresses rapidly,
and is more severe
– 75% of people with diabetes actually die of heartrelated consequences
Treatment for Diabetes
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Diet
– Glycemic Response – refers to how quickly glucose is absorbed after a
person eats, how high BG rises, and how quickly it returns to normal
– Glycemic Index – method of classifying foods according to their
potential to raise BG; just a general guide, as it depends on many factors
Treatment for Diabetes
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Diet
– Consistent timing and composition of meals & snacks
from day to day is important
– Attention to all energy nutrients is important:
Carbs, Fat, & Protein
Treatment for Diabetes
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Physical activity
Type 2 – weight loss (even just 5-10%)
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Check blood glucose levels regularly
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Medications
– Type I
» Required: Insulin shots/pump
– Type II
» Oral meds and/or insulin shots
Hyperglycemia Symptoms
Blood glucose remains high
– Due to insufficient or ineffective insulin
Symptoms of Hyperglycemia include:
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Intense thirst and/or hunger
Increased urination
Blurred vision
Fatigue
Labored breathing
Acetone breath
LOW BLOOD SUGAR Hypoglycemia
Result of:
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Inappropriate
management of diabetes
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Strenuous physical
activity
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Skipped or delayed
meals
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Inadequate food intake
Symptoms:
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Hunger
Headache
Sweating
Shaking
Weakness
Nervousness, anxiety
Rapid heartbeat
Confusion, disorientation
Slurred speech
Treatment for Hypoglycemia
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Eat right away
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Consume smaller meals more frequently
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Replace refined carbs with fiber-rich carbs
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Seek medical help if severe
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Left untreated, could lead to coma and death
CARBOHYDRATES
Learning Objectives:
•
•
•
•
Understand the different classes of
carbohydrates
Understand the digestion and absorption of
carbohydrates
Discuss diabetes (Ch. 18) – types, risk
factors, long-term consequences, treatment
Learn about the function of
carbohydrates in the diet, and how
they relate to health issues
CARBOHYDRATES and HEALTH
US Intake of Sugar
Each person eats…
~ 75% of packaged foods in US contain
sweeteners…mostly added sugars
OR
~ 30 teaspoons of added sugar a day
= about 500 calories
CARBOHYDRATES and HEALTH
Sugar
Sugar and nutrient intake:
• Empty calories that can displace nutrients
Excess sugar promotes dental caries
CARBOHYDRATES and HEALTH
Sugar & Dental Caries
Bacteria produce acid that erodes tooth enamel
for 20-30 minutes after each exposure
– Promotes caries
Factors that effect erosion:
– How long food stays in mouth
– How often sugar is eaten
– Acidity of food/drink (i.e. soda, O.J., sports drinks)
CARBOHYDRATES and HEALTH
Sugar & Dental Caries
How to reduce damage to teeth?
– Consume non-sugary foods
– Consume sugar with meals, not between meals
– Milk & Cheese
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Neutralize acids
Stimulate salivary flow
Inhibit bacterial activity
Promote mineralization
Practice good oral hygiene
CARBOHYDRATES and HEALTH
A diet rich in COMPLEX carbohydrates may
lower the risk of:
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Obesity
Type II Diabetes
Cardiovascular Disease
Cancer
GI Disorders
What are some benefits of fiber?
Benefits of Fiber

Aids in weight loss/management
» More chewing, delays gastric emptying so you feel
full longer, less energy dense

Helps control blood sugar levels
» Slows absorption of glucose through small intestine

Lowers blood cholesterol levels
» Soluble fibers may lower LDL levels by binding to
bile and cholesterol in intestines and causing it’s
excretion
Benefits of Fiber

Normalizes bowel movements
» Provides bulk, increases stool weight

Helps maintain bowel integrity and health
» ↓ risk of hemorrhoids and diverticula

Decreases pressure and transit time within the colon,
reduced risk of diverticulosis

Possibly decreased colon cancer risk
Tips for Increasing Fiber

Increase gradually so GI tract can adapt
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Drink lots of fluids to soften fiber

Select from a variety of sources…
fruits, veggies, legumes, whole
grains, nuts/seeds
FDA Daily Value = 25 grams per day
Compared to Whole Wheat, White
Bread Is Missing:
75% of Fiber
72% of Magnesium
65% of Zinc
78% of Vitamin B6
White bread is enriched with….
Iron, Thiamin, Riboflavin, Niacin, Folate
Recommendations for CHO
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RDA = 130 gms to meet minimum amount
of glucose used by the brain
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45 – 65% of the Energy Requirement
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FDA set the Daily Value at 300 gms per day
(60% of kcals in ~2000 kcal diet)
Alternative Sweeteners
Table 4-4 p114
Artificial Sweeteners
Provide no kcals/energy in diet
 Large doses may have adverse effects on body
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Saccharin
Acesulfame-K
Sucralose
0 kcal/gram
0 kcal/gram
0 kcal/gram
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Aspartame
4 kcal/gram
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Artificial Sweeteners
Concerns:
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Chemicals created in a lab
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Full health effects are not known
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Trick body into thinking it’s receiving glucose –
when it doesn’t, body often craves food (highsugar foods), may cause to overconsume kcals
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Negatively affect our gut bacteria
Sugar Alcohols
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Provide bulk and sweetness
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These can be used in products that are
labeled “sugar-free”… NOT calorie free!
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Absorbed slowly – low glycemic response
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Cause gas, abdominal discomfort, diarrhea
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Don’t promote dental caries
– Beneficial in chewing gum, breath mints, etc.
Sugar Alcohols
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Isomalt
Lactitol
Maltitol
Mannitol
Sorbitol
2.0 kcal/gram
2.0 kcal/gram
2.1 kcal/gram
1.6 kcal/gram
2.6 kcal/gram
Stevia
Herbal sweetener
 Derived from a plant in South America
 “Healthier” option for non-nutritive
sweetener
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– Not practical in baked goods
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Most ideal for sweetening beverages
Sweeteners – Final Comments
All should be used in moderation
From whole-foods perspective:
– All (except stevia) are chemicals made in a lab
– Very far from what’s found in nature
– Using small amounts of real sugar and natural
sweeteners may be healthier in a balanced diet
» Honey, agave syrup, maple syrup, brown rice syrup