Chapter 4
The Carbohydrates:
Sugars
Starches
Fiber
Objectives for Chapter 4
• Explain why the body needs carbohydrates.
• Distinguish between simple carbohydrates and
complex carbohydrates.
• Explain the process of carbohydrate digestion.
• Define the role of insulin in regulating the blood
glucose level in the body.
• Determine your daily carbohydrate and fiber
needs.
• Know health benefits of fiber.
• How to identify added sugar in the diet.
• Describe the difference between type 1 and type 2
diabetes.
• Know the complications of poorly controlled
diabetes.
What Are Carbohydrates?
Found primarily in plant-based foods
– Grains, vegetables, fruits, nuts, legumes
– Carbohydrate-based foods are staples in
numerous cultures around the world.
Most desirable form of energy for body
– In form of glucose (-ose = carbohydrate)
– Brain and red blood cells especially rely only
on glucose for fuel source.
– Glucose is most abundant carbohydrate in
nature.
What are Carbohydrates?
• Carbohydrates are made of carbon,
hydrogen and oxygen atoms (CHO)
• These atoms form chemical bonds that
follow the laws of nature.
Carbohydrates
Types of Carbohydrates
• Simple carbohydrates
– Monosaccharides – glucose fructose
and galactose
• contain 6 carbon atoms, 12 hydrogen
atoms and 6 oxygen atoms
– Disaccharides – maltose, sucrose,
lactose
Monosaccharides
• Glucose – hexagon, blood
sugar
– One of the 2 sugars
in every
disaccharide
– Unit from which the
polysaccharides/
complex
carbohydrates are
made
Monosaccharides
Fructose
• Has same chemical formula as glucose, but
different structure
• Sweetest sugar (this is why it is the most commonly
found sugar in soft drinks)
• Found naturally in honey and fruits
Monosaccharides
• Galactose
– Binds with glucose to form lactose, found in
milk
– Does not exist alone, always with glucose
Disaccharides
• 2 monosaccharides bonded together
to form disaccharides
• Occur through 2 chemical reactions:
• Condensation – water molecule joins
2 monosaccharides together
• Hydrolysis – water molecules splits to
break apart a disaccharide into two
monosaccharides
Disaccharides
Sucrose - Found in table sugar, cane sugar,
fruits and vegetables
• glucose + fructose
Disaccharides
Maltose - Glucose and glucose combine together to
form
• Found only in small amount in foods
• It is a product of starch/polysaccharide breakdown
Disaccharides
Lactose - Glucose and galactose bonded
together
• Milk sugar
Complex Carbohydrates?
Polysaccharides
• Long chains and branches of sugars
linked together.
• There are three types:
– Starch, fiber, and glycogen
– Starch is the storage form in plants.
• Amylose: straight chains of glucose units
• Amylopectin: branched chains of glucose
units
Complex Carbohydrates
Glycogen
• Storage form of carbohydrate in
animals and human
• Found in liver and muscles
• Important source of glucose for blood
• Not a significant food source of carbs
• Highly branched (easy to breakdown
to glucose for energy)
Complex Carbohydrates
Starches
• Storage form of glucose in plants
• Found mainly in starchy vegetables,
fruits, grains, legumes and tuber
(Yams and potatoes)
• Branched and unbranched
Complex Carbohydrate
Fiber is part of plant that we eat but can’t
digest
– Examples: cellulose, hemicellulose, lignins,
gums, pectin
– Humans lack digestive enzyme needed to break
down fiber.
– Dietary fiber: naturally found in foods
– Functional fiber: added to food for beneficial
effect
• Example: Psyllium added to cereals
– Total fiber = dietary fiber + functional fiber
Complex Carbohydrate
Fibers
• Slows down the process of
chewing and stimulates production
of saliva
• Fiber is classified by its affinity for
water:
– Soluble fiber
– Non-soluble/insoluble fiber
Complex Carbohydrate
Soluble fiber:
•
found in fruits, oats, barley, beans
•
•
Delays glucose absorption
Decrease Cholesterol
• dissolves in water and is fermented by
intestinal bacteria
• Many are viscous, have thickening
properties
• Move more slowly through GI tract
Complex Carbohydrate
Non-soluble/insoluble fiber –
• found in whole grains, cereals, vegetables
• cellulose, hemicellulose, lignins
• Move more rapidly through GI tract, laxative
effect
• Increase fecal weight which promotes
bowel movements
• Slows starch breakdown and delays
glucose absorption in the blood
Why Is Fiber So Important?
Fiber helps lower risk of developing:
• Constipation
• Diverticulosis, diverticulitis
• Obesity: high-fiber foods add to
satiation
• Heart disease: soluble fibers lower
elevated blood cholesterol levels
• Colorectal cancer
• Diabetes mellitus: slow digestion and
absorption of glucose
Digestion of CHO
The goal of carbohydrate digestion is to make
glucose for energy
– You digest carbohydrates in your mouth and
intestines.
Mouth
• Chewed and moistened with saliva to
become bolus
• Saliva contains amylase enzyme (-ase =
enzyme) starts the breakdown of starch
into smaller polysaccharides
Digestion of CHO
• Stomach
– Gastric acid (HCL) deactivate amylase
– HCL help break down starch further
– No enzymes are active here on
carbohydrate
– Fiber sits here and delays stomach
emptying
– Food has now become Chyme
CHO Digestion
Small intestine
• Performs most of the carbohydrate
breakdown
• The pancreas secretes pancreatic amylase to
break down polysaccharide into glucose
chains
• Maltase, sucrase, lactase enzymes breaks
down the disaccharides
• The intestinal cells then absorb the
monosaccharides which go to the blood and
then to the liver via the vascular system
CHO Digestion
Large intestine
• 1-4 hrs after eating, most sugar and
starch is digested
• A small amount of starch and fiber
remain
• Fiber attracts water which softens
the stool
• Rectum
– Holds waste until excretion
From Carbohydrates to Glucose
Absorption of CHO
• Some CHO is absorbed through the
lining of the mouth (mostly maltose)
• Most absorption takes place in the small
intestine
• Then goes into the blood and liver where
the cells take up fructose and galactose
and convert it to glucose
Lactose Intolerance
Lactose:
• principal carbohydrate found in dairy products
• People with a deficiency of the enzyme lactase
cannot digest lactose properly.
• Lactose maldigestion is natural part of aging
– As soon as baby stops nursing, body makes less lactase
Lactose intolerance:
• when lactose maldigestion results in nausea,
cramps, bloating, diarrhea and flatulence
• Common mostly with Native Americans and
African Americans
Lactose Intolerance
Dietary Changes
• Gradually add dairy products to your diet
• Eat smaller amounts throughout day rather than
large amount at 1 time
• Try reduced-lactose milk and diary products
• May tolerate up to 1 cup of milk per day
• May tolerate yogurt, acidophilus milk, hard
cheese and cottage cheese
• Increase intake of calcium fortified foods
How the Body Use Carbohydrates?
• Glucose supplies energy for body, required for
brain, nervous system, red blood cells
– Fat can provide fuel for muscle, other tissues
• Hormones regulate amount of glucose in blood
• Insulin is released by pancreas in response to high
blood glucose levels after a carbohydrate-heavy
meal
– Directs conversion of glucose in excess of immediate
energy needs into glycogen in liver and muscle cells
(limited capacity)
– Rest of excess glucose converted to fat
Glucose in the body
Stored as glycogen in the body
• 1/3 in the liver
– Liver glycogen stores depleted after about 18 hours
• 2/3 in the muscle
• Glycogen can be broken down easily to
make glucose for energy
• Glycogen in the muscle stays there to fuel
exercise and day-to-day activities
Glucose in the Body
Liver can make glucose from protein in
the absence of adequate glucose
• Gluconeogenesis – breaking down of
protein from muscle by the liver to
make glucose liver
Protein-sparing action
• having adequate carbohydrate in the diet to
prevent the breakdown of protein for
energy.
Glucose in the Body
• Without glucose, fat can’t be broken down
completely and ketone bodies are
produced, which are acidic.
– Ketosis: elevated blood levels after fasting
about two days
• The brain uses glucose only for
energy.
– Brain switches to using ketone bodies for fuel
to spare protein-rich tissues.
• If fasting continues, protein reserves are depleted
and death is inevitable.
Maintaining Normal
Blood Glucose
• Normal blood glucose –
– 70-110mg/dL
• Regulating hormones
– Insulin – moves glucose from blood
stream after a meal
– Glucagon – brings glucose to the blood stream
– Epinephrine (adrenaline) increases blood glucose
levels at times of stress.
• Fight or flight” hormone: stress, bleeding, low blood glucose
levels trigger its release
High Blood Glucose Levels
Insulin
Directs
Excess
Glucose
into
Storage
Low Blood Glucose Levels
Glucagon
Directs
release of
Glucose
into blood
stream
What Is Diabetes Mellitus?
Diabetes mellitus:
• individual has high blood glucose levels due to
insufficient insulin or insulin-resistance
• Glucose can’t enter cells, which burn fat for fuel
• Without glucose, acidic ketone bodies build up,
causing life-threatening diabetic ketoacidosis:
untreated can result in coma, death
• Type 1 diabetes: 5-10% of cases
– Autoimmune disease: insulin-producing cells in pancreas
destroyed - insulin injections required
– Develops in childhood, early adult years
What Is Diabetes Mellitus
Type 2 diabetes: 90-95% of cases
• Cells are resistant to insulin,
• pancreas decreases production of insulin and
medication and/or insulin is required
• People 45 and older or at risk for diabetes
• Now seen in increasing number among
overweight and obese children
• Prediabetes: glucose intolerance
– Blood glucose higher than normal but not high
enough to be classified as Diabetes
What Is Hypoglycemia?
Hypoglycemia: blood glucose level below
70 mg/dl
– Symptoms: hunger, shakiness, dizziness,
perspiration, light-headedness
– May occur in people with diabetes when they
don’t eat regularly to balance effects of insulin
or blood glucose-lowering medication
• Can cause fainting, coma
Interpreting
Blood
Glucose
Levels
What Is Diabetes Mellitus?
Diabetes can result in long-term damage
• High blood glucose levels damage vital
organs.
– Nerve damage, numbness, poor circulation
• Infections, leg and foot amputations
–
–
–
–
Eye damage, blindness
Tooth and gum problems
Kidney damage
Increased risk of heart disease
What Is Diabetes Mellitus?
Blood glucose control is key
• Nutrition and lifestyle goals:
– Physical exercise
– Well-balanced diet containing:
• High-fiber carbohydrates from whole grains, fruits,
vegetables
• Low-fat milk
• Adequate lean protein sources
• Unsaturated fats
• Total calories important for weight management
What Is Diabetes Mellitus?
Cases of diabetes are on the rise.
– Sixth leading cause of death in the U.S.
– Over 200,000 Americans die from diabetic
complications annually
– Rapidly rising in children
• Obesity, overweight, and physical inactivity increase
risk
Preventing type 2 diabetes:
– Losing excess weight, physical exercise, hearthealthy, plant-based diet
Health effects Sugars
•
Accusations against Sugar
– Causes obesity
– Causes heart disease
– There is no scientific evidence that sugar
causes misbehavior in children and criminal
behavior in adults
– There is a theory that sugar increases
serotonin levels, which can lead to cravings
and addiction
Recommended Intakes
• Added sugars –
– DRI - No more than 25% of total daily energy
intake
– WHO/FDA – less than 10% of total daily energy
– For active women = 8 tsp of sugar daily
– For active men = 18 tsp of sugar daily
• Americans average over 30 tsp of added sugars
daily.
• Starch
– Minimum - 130 g/day for brain function
• 45% - 65% total daily energy intake
Recommended Intakes
• Fiber
– 14 grams of fiber per 1,000 calories to
promote heart health
– Most Americans fall short: about 15g/day
– Daily Value: 25 g/day
– American Dietetic Association recommends
20-35 g per day.
– World Health Organization suggests no more
than 40 g per day.
Health Effects of Starch
and Fiber
• Heart disease
• Type II Diabetes
• Fiber block the absorption of unwanted
particles in the GI tract
• Colon Cancer – removes cancer causing
agents from the body
• Weight mgt
• Excessive fiber can cause malabsorption,
gas, diarrhea and abdominal distention
Grains
Grains:
• Three edible parts: bran, endosperm, germ
• Refined grains: milling removes bran and
germ
– Some B vitamins, iron, phytochemicals and
dietary fiber lost as a result
– Examples: wheat or white bread, white rice
• Enriched grains: folic acid, thiamin, niacin,
riboflavin and iron added to restore some of
the lost nutrition
• Whole grain foods contain all three parts of
kernel
• Examples: brown rice, oatmeal, whole-wheat bread
From Wheat
Kernel to
Flour
Increasing Intake of Complex
carbohydrate
– Grains – encourage whole grains
– Vegetables – starchy and non-starchy vegetables
differ in carbohydrate content
– Fruits – vary in water, fiber and sugar content
– Milks and Milk Products – contain carbohydrate;
cheese is low
– Meat and Meat Alternates – meats are low but
nuts and legumes have some carbohydrate
– Food labels list grams of carbohydrate, fiber and
sugar; starch grams can be calculated.
• Whole grains at the supermarket
• Sugar and Processed Foods
Natural and Added Sugars?
• Naturally occurring sugars found in fruits
and dairy
– Usually more nutrient-dense; provide more
nutrition per bite
• Added sugars are added by
manufacturers and are often “empty
calories” (provide little nutrition).
– Examples: soda, candy
Health effects of Added
Sugars
Carbohydrates play a role in dental caries
– Fermentable sugars and starch feed bacteria
coating teeth, producing acid to erode tooth
enamel
– To minimize tooth decay:
• Eat three balanced meals daily
– Keep snacking to a minimum, choosing whole fruits and raw
vegetables
• Include foods that fight dental caries: cheese,
sugarless gum
• Regular dental care and good dental hygiene
Slices of an Orange versus
Orange Slices
Added Sugars
Finding the added sugars in your foods:
– Sugars on food labels appear under
numerous different names.
• Honey and fructose are not nutritionally superior to
sucrose.
– Naturally occurring sugars are not
distinguished from added sugars on the
Nutrition Facts panel.
Finding Added Sugars on the
Label: The Many Aliases of Added
Sugar
Added Sugars on the Label
Where Are The Added Sugars?
The Many Sizes of Soft Drinks
A bottle or can of soda can provide from 6 to 17
teaspoons of added sugars, depending on the size of the
container.
Alternatives to Sugar
Sugar substitutes are as sweet or sweeter
than sugar, but contain fewer calories.
– Must be approved by FDA and deemed safe
before allowed in food products in U.S.
– Saccharin (Sweet’N Low): 200-700% sweeter
than sugar
– Aspartame (Nutrasweet, Equal): 200% sweeter
• People with PKU need to monitor all dietary sources
of phenylalanine, including aspartame.
– Acesulfame-K (Sunette): 200% sweeter
– Sucralose (Splenda): 600% sweeter
– Neotame: 7,000-13,000% sweeter
Sugar Alternatives
• Artificial Sweeteners and Weight Control
– Much research still being done
– Using artificial sweeteners will not
automatically reduce energy intake.
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
Homework/Extra Credit
10 points – Extra credit
Find someone who has either type 1 or type 2
diabetes and interview them by asking the
following questions. Write a one page typed
summary of your interview.
1. How did you first find out you have diabetes
2. What symptoms, if any do you have
3. What do you have to do to control your diabetes (e.g.
insulin, medications, exercise, diet)?
4. How else does diabetes affect your day-to-day life
Bring a food label of your favorite cereal to class