Carbohydrates
• Functions:
• 1) Primary function = provide Energy
• 2) Structural components of body:
• I.e., cartilage
• 55- 60% of kcal of diet
• General Formula: CH20
Classes of Carbohydrates
• 1) Simple CHO’s
• Single or double sugar units (saccharides)
• 2) Oligosaccharides
• 3 to 10 saccharide units
• 3) Complex CHO’s
• Usu 1,000’s of saccharide units long
Simple CHO’s
• Monosaccharides
– Glucose
– Fructose
– Galactose
• Disaccharides
– Maltose
– Lactose
– Sucrose
Complex CHO’s
• Starch
• Glycogen
• Fiber
• Oligosaccharides
• Inulin
• fructoligosaccharide
Simple CHO’s
• Almost exclusively in plant foods
• Found in fruits, sweets, milk and milk
products, table sugar
Monosaccharides
Simplest CH O’s
• Building blocks of all CHO’s
• Glucose: most common
– aka dextrose, blood sugar
• Fructose: fruits, honey, high-fructose
corn sugar
• Galactose: part of milk sugar (lactose)
6
H
4
HO
CH2OH
H
5
H
H
2
O
HOCH2
O
OH
3
6
6
H
1
OH
O
H
Glucose
-mildy sweet
1
5
CH2OH
2
H H
4
OH
HO OH
3
H
Fructose
-Intensely sweet
HO
4
H
CH2OH
5
O
OH
H
H
3
H
2
H
1
OH
OH
Galactose
-hardly sweet
Disaccharides
CH 2OH
CH 2OH
O
O
O
Glucose + glucose
maltose
6 CH
5
2OH
6 CH
O
5
1
4
3
2
O
2OH
O
1
4
3
2
6 CH
2OH
O
5
Galactose + glucose
lactose
1
4
3
6
2
O
O
HOCH 2
5
2
3
CH 2OH
1
4
Glucose + fructose
sucrose
CH 2OH
CH 2OH
O
CH 2OH
O
O
maltase
O
2OH
6 CH
O
5
5
1
4
3
OH
2OH
O
1
4
O
2
3
lactase
glucose
6 CH
6 CH
2OH
O
5
4
2
Lactose
O
5
1
1
4
2
3
2
galactose + glucose
O
1
4
3
sucrase
2
O
O
HOCH 2
2OH
2OH
5
6
OH
HO
glucose +
3
6 CH
O
HO
Maltose
6 CH
CH 2OH
6 CH
5
1
4
5
2
3
2
CH 2OH
4
2
3
O
HOCH 2
O
3
5
6
2OH
CH 2OH
4
Sucrose
1
glucose + fructose
1
Complex CHO’s
aka Polysaccharides
• Starch
– In plant foods
– major E reserve for plants
– = glucose + glucose + glucose etc.
– About 3,000 glucose’s bonded together
• 2 Forms of starch:
– 1) amylose
– 2) amylopectin
Amylose
• Straight chain of glucose’s
• a1--> 4 bonds
O
O
O
O
O
O
O
Amylopectin
• Branched chains of glucose’s:
• a1--> 4 bonds
• a1--> 6 bonds at branch points
O
O
O
O
O
O
O
O
O
Complex CHO’s
aka Polysaccharides
• Glycogen
– Animals synthesize this and store it in liver
and muscle
– = glucose + glucose + glucose etc.
– a1-->4 bonds and a1-->6 bonds
O
O
O
O
O
O
O
O
O
Amylopectin
vs.
Glycogen
Made by plants
Made by animals
Branched
VERY HIGHLY Branched
a1 --> 4
a 1 --> 4
a 1-->6
a 1 --> 6
Plant
Cell
Wall
Non-cell
wall
plant
parts
Protein
Lipids
Inorganic substances
Lignin
Cellulose
Hemicellulose
Pectins
Gums
Mucilages
Algal polysaccharides
Suberin
Cutin
Dietary
Fiber
Complex CHO’s
aka Polysaccharides
• Fiber
– Cellulose = very common fiber
– = glucose + glucose + glucose etc.
– b 1-->4 bonds
Etc...
CH2 OH
CH2 OH
CH2 OH
O
O
O
CH2 OH
O
O
O
O
Etc...
Fiber
• NO Human enzymes can break down fiber
• Bacterial enzymes in intestines can break
down fiber
Dietary Fiber
Soluble
Pectin
Insoluble
Mucilages
Some
Gums
Hemicellulose
Cellulose
Lignin
Some
Hemicellulose
Soluble
Fibers
Bile
acids
adsorption
or binding
of
Lipid
Fecal bile acids
Lipid absorption
Serum cholesterol
Minerals
Altered mineral balance
Soluble
Fibers
Gel
Formation
Gastric Emptying
Slow Glucose
Absorption
Nutrient Absorption
Transit Time
Feeling of
Fullness
Insoluble & soluble
Fibers
 Water-holding
capacity
Fecal volume
Colon Transit Time
(speed movemn’t thru gut)
Defecation Frequency
( constipation)
Insoluble & Soluble
Fibers
Enterocyte
Energy
Fermentability/
Degradability
Lactate
GI Lumen
acidification
2˚ bile acid
synthesis
Inhibit Tumor
Formation
Short Chain
Fatty Acids
Mucosal Cell
Proliferation
 Colonic Na+ and
H2O absorption
Fiber in Foods:
• In general, whole, unprocessed foods
contain more fiber than their processed
versions
• Most fiber-rich foods have a mix of
various types of fibers
• Require about 25 to 35 grams/day
Fiber in Foods:
Processing of foods
Apple = 5 g
Applesauce = 2 g
Apple juice = 0.2 g
Increasing Fiber in the Diet:
• Consumption of veggies, fruits, beans,
whole-grain products
• Whole fruits instead of fruit juice
• Use whole-grain flour instead of white
flour
• Brown rice instead of white rice
Dilute CHO’s
vs.
Sugar in Fruit
vs.
This Sugar comes
with
Vitamins,
Minerals and Fiber
Concentrated CHO’s
Sugar in Candy
NO fiber or very little
Typically few
Vitamins and
Minerals/kcal
Ingredients List:
•
•
•
•
•
•
Sucrose
Glucose
Maltose
Dextrose
Fructose
High-fructose Corn
Syrup
• Brown Sugar
• Honey
• Confectioner’s
Sugar
• Invert Sugar
• Levulose
• Raw Sugar
• Turbinado Sugar
Sugar Intake Guideline
• < 10% of total kcal
• This applies to concentrated refined
sugars (I.e., candies, sweets),not fruits
or milk products
Suggestions to Reduce Sugar
Intake:
• Substitute Water or Fruit Juices for soft
drinks
• Unsweetened cereals
• Reduce sugar in recipes
• Use sweet spices, I.e., allspice, anise,
cinnamon, ginger, vanilla, coconut
Dental Caries
• Bacteria feast on sugars and release
acids that decay tooth enamel
• Not only the amount of sugar eaten
• How much the food clings to teeth
• How frequently eaten
• Baby bottle syndrome
Digestion of CHO’s
• Digestion begins in mouth, w/ salivary
amylase
• Fiber delays gastric emptying
• Pancreatic amylase
• Lactase, maltase, sucrase are brush border
enzymes (made by sm. Intestines)
The Fate of CHO’s in your body:
• 1) satisfy immediate energy needs of
all your cells
• 2) Extra CHO’s converted to glycogen
and stored in muscles and liver
• 3) Extra CHO’s converted to fat in liver
and stored in adipose cells
Maintaining Blood Glucose Levels
• Critical to maintain blood glucose
• Too low ---> shaky, weak, headache
• Too high ---> sleepy, chronically high
causes organ damage
Eat a Meal
Blood Glucose
Pancreas releases
Insulin
Liver picks
up glucose
Muscle picks
up glucose
Adipose picks
Up glucose
Results in Blood Glucose
Fasted
Blood Glucose
Pancreas releases
Glucagon
Liver breaks
down glycogen
Muscle breaks
down glycogen
Adipose
releases fat
Results in Blood Glucose
When Blood Glucose is Low, A Snack with
CHO, Fat and Protein is Best:
• CHO: good source of glucose and
stimulates insulin secretion
• Protein: stimulates glucagon which
opposes insulin to prevent the body
cells from picking up too much glucose
too fast
• Fat:slows digestion --> slows absorption
Serum Cholesterol:
• Strongest Hypocholesterolemic Effect:
– Psyllium, Guar Gum, Oat Gum
• Moderate Hypocholesterolemic Effect:
– Oat Bran, Soybean fibers
• No Hypocholesterolemic Effect:
– Wheat, Corn, Rice Brans
Hypoglycemia
• Abnormally low blood glucose level
• Symptoms =
• Recommend:
Diabetes
• IDDM (insulin-dep.
diabetes mellitus)
• Aka: juvenile onset,
type I
• About 10% of all
cases
• NIDDM (non-insulin
dep. Diabetes mellitus)
• Aka: adult-onset, type
II
• About 90% of all
cases
• 2x the risk to heart dx.
• Majority obese
- a major cause of blindness, kidney failure,
amputations, male impotence
Diabetes Risk for Women:
• Overweight women 8 times more likely to
get diabetes than normal weight women
• Obese women 20 times more likely to get
diabetes than normal weight women
• Women who do ≥ 7 hours moderate
exercise/wk, 30% lower risk than women
who exercise < 1/2 hour / wk
• Diets: high fiber & PUFA’s, low in SFA
and trans fats 50% lower risk
NEJM, 2001, 345, 785, 829; J Nat Cancer Inst, 2001, 93, 937
Number of New Diabetes Cases (NIDDM) 0-19 years
J Pediatr, 1996, 128,608-615
Number of New Diabetes Cases (NIDDM) 10-19 years
J Pediatr, 1996, 128,608-615
Percentage of New Diabetes (NIDDM) Cases, 0 - 19 years
J Pediatr, 1996,128,608-615
Rising Incidence of NIDDM in Youth
• 0-19 year olds:
– Before 1992, 3-4% of all new cases of diabetes were
NIDDM
– After 1992, 16% of all new cases of diabetes were
NIDDM
– 4 - fold INCREASE
• 10-19 year olds:
– Before 1992, 3-4% of all new cases of diabetes were
NIDDM
– After 1992, 33% of all new cases of diabetes were
NIDDM
– 10 - fold INCREASE
Increased risks for Diabetics:
• Hypertension
• Amputations
• Coronary Heart
Disease
• Blindness
• Stroke
• Kidney, liver damage
Blood Glucose Levels:
• Normal: 70 - 110 mg/dL of blood
• Below 40 mg/dL (2.2mmol/L) --> coma,
seizure, death
• Above approx. 180 mg/dL (10 mmol/L) -->
– Immediate effects: glycosuria, caloric loss,
thirst, hunger
– Chronic effects: renal, retinal, nerve, blood
vessel damage
Blood glucose (mg/dL)
250
200
Diabetes
150
100
Normal
50
Reactive
Hypoglycemia
1
Time (hours)
2
Glycemic Index
• = a quantitative ranking of foods based on
their postprandial blood glucose response
(above fasting glucose) compared to a
reference food
• The reference food is either:
– White bread (50 g available cabohydrate)
– Glucose (50 g)
Factors that affect a food’s GI
•
•
•
•
•
•
Particle size: as particle size  :  GI
Differences in cooking
Starch composition: amylose v. amylopectin
Fiber content
Ripeness
Food processing
Application of GI
• Diabetes: the GI helps in control of blood
glucose and insulin responses
• Sports performance: Different GI foods
more effectively replenish glycogen stores
after exercise: High GI foods replenish
glycogen better than low GI foods
• Appetite Research: Low GI foods produce
greater satiety than high GI foods
Obese Children
High GI meal
(instant oatmeal)
Low GI meal
(steel cut oats)
(Identical energy &
macronutrient intake)
Ad libitum energy consumption
monitored throughout rest of day
Result:
Energy intake 53% HIGHER in High GI group
Ludwig et al., Pediatrics, 1999, 103, E261-66