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Lecture 6:
Carbohydrates
Nutrition 150
Shallin Busch, Ph.D.
Chemical Structures
Atom: The smallest components of an
element that have all of the
properties of an element (Whitney
and Rolfes)
Element: A type of atom, has unique
properties (for ex. iron, oxygen)
Molecule: Two or more atoms of the
same or different elements joined by
chemical bonds
Carbohydrates
“Hydrated carbons”
Molecules that are made up of water
(hydrogen and oxygen) and carbon
Simple CarbohydratesMonosaccharides
• Glucose: Form of energy used in body
• Fructose: From fruits and honey
• Galactose: Part of lactose
Disaccharides
• Maltose = glucose + glucose
• Sucrose = glucose + fructose
• Lactose = glucose + galactose
+
+
+
Complex Carbohydrates
“Polysaccharides”
• Chains made of hundreds to
thousands of glucose molecules
• Glycogen - made in the body of
animals to store glucose
• Starch – digestable, from plants
• Fiber – undigestable, from plants
Glucose:
The bodies energy currency• All cells in body use glucose for
energy
• Brain and nervous system use glucose
almost exclusively
• Red blood cells use only glucose
(Fat is also used as an energy source)
Enzymes for Carbohydrate
DigestionAmylase: Facilitates the break down of
starch to small polysacchrides anddisacchrides; in saliva and pancreatic juices
Maltase: Facilitates the break down ofmaltose; on wall of small intestine
Sucrase: Facilitates the break down ofsucrose; on wall of small intestine
Lactase: Facilitates the break down oflactose; on wall of small intestine
Carbohydrate Absorption• Glucose and Galactose: active transport
(fast)
• Fructose: facilitated diffusion (slower)
• Starches: must be broken into
monosaccharides before absorption (slow)
Consequences of fast or slow absorption of
monosacchrides…How to maintain constant
blood glucose levels?
Liver and Carbohydrates
• Converts fructose and galactose to
glucose
• Stores glucose as glycogen (70g or
280kcal)
• Converts excess glucose to fat and
sends it to fat stores in the body
Muscles and Carbohydrates
• Muscles use glucose for energy
• Can store glucose as glycogen (120g
or 480 kcal of energy)
• Uses glycogen stores when necessary
Fate of Absorbed Glucose
Review of Actions of Insulin and GlucagonWhen a person eats,
blood glucose rises.
Liver
Pancreas
Key:
Fat cell
High blood glucose stimulates
the pancreas to release insulin.
Glucose
Insulin
Glucagon
Glycogen
Intestine
Insulin stimulates the uptake of
glucose into cells and storage
as glycogen in the liver and
muscles. Insulin also stimulates
the conversion of excess
glucose into fat for storage.
As the body's cells use
glucose, blood levels decline.
Low blood glucose stimulates
the pancreas to release
glucagon into the bloodstream.
Glucagon stimulates liver
cells to break down glycogen
and release glucose into the
blood.a
Blood glucose begins to
rise.
Liver
Insulin
Glucagon
a The stress hormone
epinephrine and other hormones
also bring glucose out of storage.
Muscle
Pancreas
1
2
3
4
5
6
7
Run out of Carbohydrates?
• When the body runs out of glucose
and glycogen store, it creates its own
glucose!
• Converts amino acids (proteins) into
glucose (gluconeogenesis)
Carbohydrate Deficit in Diet
• Fat is converted into ketone bodiesas an alternative energy source forthe brain
• Lots of ketone bodies in the bloodcauses ketoacidosis, which makes theblood acidic
• Ketoacidosis alters body’s basicfunctions and damages organs
Exercise and Energy Source
(Use of fat is not necessarily through conversion to ketones.)
Carb Intake
• Recommended Dietary Allowance (RDA) is130 grams/day just to supply the brainwith glucose.
• 45-65% of daily calorie intake should be inthe form of carbohydrates.
• Focus on foods high in fiber and low inadded sugars.
Names of Foods that are
Carbohydrates?
Homework and In-Class Activity• On Thursday, bring in a food label (original packaging
or a photocopy) of a food which has lots of differentingredients (cereal, granola bar, candy etc.)
• With a partner you will fill out the worksheetentitled “Finding carbs in your food” (on website)which will help you 1) find carbs in your food and 2)compare the carbs in two foods.
• If class is cancelled on Thursday, use the time youwould spend in class to fill out the sheet bycomparing two foods from your pantry. Turn in thesheet on Friday.
Added Sugar
• Sugar that is added to food which already
has natural sugars in it (for ex,
caramelized popcorn)
• DRI suggests intake should be less than 25%
of total energy intake
• WHO and FAO suggests that should be
less than 10% of total energy intake
• Why?
Diets high in simple sugars
Can cause dental problems such as
cavities, tooth decay, and gum disease
Diets high in simple sugars
• Associated with increased levels of“bad cholesterol”
• Associated with decreased levels of“good cholesterol”
• Can lead to poor nutrition, due tofailure to obtain necessary vitamins,minerals, fiber, etc. (empty calories)
Fiber Intake
• The Adequate Intake (AI) of fiber is
14 grams for every 1,000 kcal in the
diet
• Most Americans eat only half the
recommended amounts of fiber
• Too much fiber (VERY RARE) can lead
to malnourishment, GI distress,
limited nutrient absorption
2 Types of Fiber
1) Viscous: Soluble, more fermentable
2) Nonviscous: Insoluble, less fermentable
Viscous Fiber
• Gums, mucilages, pectins, psyllium
• Found in: whole grain products (barley,oats, rye), fruits, legumes, seeds,vegetables,
• Also extracted and used as foodadditives
Viscous Fiber
• Lowers blood cholesterol by binding bileand blocking absorption of cholesterol
• Slows glucose absorption
• Slows transit of food in upper GI tract
• Holds moisture in stools (softening them)
• Digested by bacteria and yield fatty acidsthe colon uses for energy
Lowers risk of both heart disease anddiabetes
Insoluble Fiber
• Cellulose, Lignins, Resistant starches,psyllium, many hemicelluloses
• Brown rice, fruits, legumes, seeds,vegetables, wheat bran, whole grains
• Also extracted and used as foodadditives
Insoluble Fiber• Increase fecal weight and speed of
fecal passage through colon
• Provides bulk and feeling of fullness
• Alleviates constipation
• Lowers risk of diverticulosis,hemorrhoids, and appendicitis
• May help with weight management
DiverticulosisHealth Problems and Carbs
Three health disorders related to
carbohydrate metabolism are
– Diabetes
– Hypoglycemia
– Lactose intolerance
Lactose intolerance
• Insufficient lactase productioncauses an inability to digest lactosefound in dairy products
• Symptoms include intestinal gas,bloating, nausea, cramping, diarrhea
• Lactose intolerant people may need tofind alternate sources of calcium
Diabetes
• Inability to regulate blood glucose levels
• Untreated diabetes can cause ketoacidosis,nerve damage, kidney damage, blindness,and can be fatal
• Three types:– Type 1 diabetes
– Type 2 diabetes
– Gestational diabetes
Type I Diabetes
• Accounts for 10% of all cases
• Patients do not produce enough insulin
• Causes hyperglycemia – high bloodsugar (glucose)
• Requires insulin injections andlifestyle management(diet, exercise,sleep)
• May be an autoimmune disease
Type 2 Diabetes
• Most diabetics have Type 2 diabetes
• Body cells are insensitive orunresponsive to insulin
• Excess insulin is often produced
• Causes hyperglycemia because cellscannot take in the glucose from theblood
Type 2 Diabetes cont.
Cause is unclear but obesity, genetics,
and physical inactivity play a role
Diabetes and Genetics
Type 2 Diabetes cont.
• Treated with diet, exercise, and
possibly oral medications
• Healthy lifestyle choices may prevent
or delay onset of type 2 diabetes
Symptoms of Diabetes
Type 1 Diabetes
Frequent urination
Unusual thirst
Extreme hunger
Unusual weight loss
Extreme fatigue
Irritability
Type 2 Diabetes
Any of the type 1symptoms
Frequent infections
Recurring skin, gum orbladder infections
Blurred vision
Cuts/bruises that areslow to heal
Tingling/numbness in thehands and feet
Hypoglycemia
• Low blood sugar (glucose)
• Fasting hypoglycemia results whentoo much insulin is produced evenwhen the patient has not eaten
• Reactive hypoglycemia results whentoo much insulin is produced after ameal
• Causes shakiness, sweating, anxiety
Graph Blood Sugar after
Meals
1) Healthy Individual
2) Diabetic
3) Individual with Hypoglycemia