MargiAnne Isaia, MD MPH

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Advanced Nutrition
Carbohydrates
MargiAnne Isaia, MD MPH
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CARBOHYDRATES
CHO (CARBOHYDRATES) General formula Cn (H20)n
CHO 121 exception sugar alcohols
(Sorbitol, Maltitol, Manitol,
Galactitol,Lactitol) oligosaccharides
polysaccharides CHO classification - simple
monosaccharides, hexose Glucose, Galactose,
Fructose, pentose
Ribose disaccharides Maltose, Sucrose,
Lactose - complex oligosaccharides (3-10
monosaccharides) polysaccharides (gt10
monosaccharides) starch/glycogen, pectines,
cellulose, gums Physiologically important
sugars Glucose, Galactose, Fructose, Ribose
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CARBOHYDRATES
CHO FUNCTIONS Energy 50 of dietary energy
(polysaccharides) starch/glycogen Structure
- connective tissue - plasma
membrane Signal transduction - cell
communications Gastro-intestinal health
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CARBOHYDRATES
CHEMISTRY
Simple
Complex
SUGARS
STARCHES
G L U C O S E
GLYCOGEN (glucose storage)
FAT (excess glucose)
ENERGY (1 g 4 Kcal)
Liver
Skeletal muscle
Heart
Kidneys
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CARBOHYDRATES
DIETARY CHO w Grains, millet, roots, tubers -
polysaccharides starch Breakdown starch
Maltose - Glucose Inulin (Fructosan) starch
from tubers -
hydrolysis to Fructose w Legumes, soy Starch,
oligosaccharides (Raffinose, Stachyose) w Beets,
fruits, honey, high fructose corn syrup
(HFCS) Sucrose Fructose Glucose w
Dairy Lactose Glucose Galactose
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CARBOHYDRATES
SOURCES
S i m p l e
MONOSACCHARIDE (Hexose)
SOURCES
SIGNIFICANCE
D - Glucose

• Found naturally in few foods (corn syrup),
  fruit juices

body sugar found in blood and tissue fluids
(older name Dextrose)

• Hydrolysis of maltose, cane sugars, lactose,
  starches

cell fuel
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CARBOHYDRATES
SOURCES
S i m p l e
MONOSACCHARIDE (Hexose)
SOURCES
SIGNIFICANCE
D - Fructose

• Honey, fruits, juices

changed to G in the liver, serves as basic
body fuel

• Hydrolysis of Sucrose from cane sugar

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CARBOHYDRATES
SOURCES
S i m p l e
MONOSACCHARIDE (Hexose)
SOURCES
SIGNIFICANCE
D - Galactose

• Hydrolysis of Lactose (milk sugar)

changed to G in the liver, cell fuel,
synthesized in mammary gland to make lactose of
milk
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CARBOHYDRATES
SOURCES
S i m p l e
DISACCHARIDE
SOURCES
SIGNIFICANCE
Maltose
hydrolyzed to D Glucose. Basic body
fuel

• Germinating cereals

• Malt products by hydrolysis of starch

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CARBOHYDRATES
SOURCES
S i m p l e
DISACCHARIDE
SOURCES
SIGNIFICANCE
Sucrose

• Cane, beet sugar, maple sugar, molasses,
  carrots, pineapple

Hydrolyzed to G and F, body fuel
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CARBOHYDRATES
SOURCES
S i m p l e
DISACCHARIDE
SOURCES
SIGNIFICANCE
Lactose

• Milk

Hydrolyzed to G and Gal, body fuel, milk
production during lactation
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CARBOHYDRATES
SOURCES
POLYSACCHARIDES
SOURCES
SIGNIFICANCE
Starch

• Cereals, buckwheat, legumes, cassava, potatoes
  or other vegetables

• The storage form for CHOs in plant
• / Digested soluble starch Dextrin, Maltose
  Glucose
• / Undigested resistant starch promote health

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CARBOHYDRATES
SOURCES
POLYSACCHARIDES
SOURCES
SIGNIFICANCE
Dextrin

• Formed as intermediate products in the
  breakdown of starch

Dextrin hydrolyzed Maltose, Glucose
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CARBOHYDRATES
SOURCES
POLYSACCHARIDES
SOURCES
SIGNIFICANCE
Oligosaccharides

• Partially digested starch (size 3-10 G
  molecules)

formed naturally through starch
digestion Commercially used in special formula
for infants, persons with GI problems, sport
drinks

• Stachyose Raffinose in legumes (beans,
  soybeans)

indigestible PREBIOTICS Fermentation by
bacterial flora Short Chain Fatty Acids, gas,
GI tract health
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CARBOHYDRATES
SOURCES
POLYSACCHARIDES
SOURCES
SIGNIFICANCE
Glycogen

• Meat

The storage form of CHOs in animals
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CARBOHYDRATES
POLYSACCHARIDES Classification (chemical)
homo vs. hetero-polysaccharides
(mucopolysaccharides) Storage plant vs.
animal Structure - amylose
(plant, linear structure) - amylopectine (plant,
branched structure) - glycogen (animal, branched
structure) - cellulose (linear,
plant, undigested) - hemicelluloses (plant,
branched, xylose) - pectin (plant, from fruit
and jellies, non absorbable) Hetero-polysaccharid
e (Mucopolysaccharides) - chondroitin sulfate,
heparin, hyalluronic acid
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CARBOHYDRATES
DIGESTION Starch the major CHO made of Glucose
unitshomopolysaccharide - linear a-1, 4
glycosidic branch, Amylose - linear a-1,4
branched, and a-1,6 glycosidic bonds
Amylopectin Salivary and pancreatic amylase act
on interior a-1,4 glycosidic linkages Starch
after partial digestion g limit Dextrin (8-10
C) Limit Dextrin g Maltose Isomaltose
(enzyme Dextrinase) Isomaltose g 3 Glucose
(enzyme Isomaltase) Maltoseg 2 Glucose
(Maltase brush border disaccharidase)
Sucrose g Glucose Fructose (Sucrase brush
border disaccharidase) Lactose g Glucose
Galactose (Lactase brush border
disaccharidase) Isomaltase g the only enzyme
that digests a-1,6 glycosidic bonds.
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CARBOHYDRATES
DIGESTION a amylase active after first month
following birth Cellulose b-1,4 Glucose units
No human enzyme can break this bond
Undigested CHOs escape to large intestin
Raffinose, Stachyose Prebiotics Prebiotics
food ingredients - stimulate the growth and/or
activity of Bifidobacteria and Lactic
bacillus This group of bacteria beneficial
effects on the host Prebiotics bifidogenic
factor Prebiotics typically are carbohydrates
(oligosaccharides) Many forms of dietary fiber
(soluble fiber) exhibit prebiotic effect. Health
benefits same with Bifidobacteria and Lactic
bacillus positive effects on Ca and other
mineral absorption, immune system
effectiveness and strength, bowel pH,
-reduction of Inflammatory Bowel Diseases and
Colo-rectal Cancer risk (
bifidogenic effect, plus production of SCFA)
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CARBOHYDRATES
DIGESTION Starch the most important
polysaccharide (homopolysaccharide) Glucosan
GLUCAN - eaten after cooking (the
heat of cooking gelatinizes the starch granules
and increases their susceptibility to enzymatic
digestion ( a amylase) Resistant starch
indigestible starch Sources cereals, potatoes,
legumes Gelatinization heat applied to starch
granules suspended in a liquid g the starch
granules absorb water and swell. Smaller Amylose
molecules diffuse out of the swollen starch
granules and form a 3D network which trap
additional water.
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CARBOHYDRATES
DIGESTION Resistant starch (RS) - sum of
starch and degradation products not absorbed
in the small intestine of a healthy
person. RS 1- physically enclosed Starch
(partially milled grains) RS 2 - ungelatinized
crystalline granules (banana, potatoes) RS 3 -
retrograde amylose - formed during the cooling
of starch gelatinized by moist heating RSs -
escape digestion in the small intestine, enter
the colon g fermentation (in this respect
RS-similar to dietary fiber) The end product of
the fermentation of RS in colon SCFA (propionic,
acetic and butiric acid) C02, H2, methane
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CARBOHYDRATES
DIETARY FIBERS are all from plant food -
polysaccharides - non-polysaccharides,
lignin resistant to digestive enzymes Insoluble
fiber - cellulose (b-1,4 Glucose, cell-wall) -
hemi-cellulose (polymer of pentose hexose) -
lignin (non CHO, woody wall of plants) Soluble
fiber - pectin (gel forming, intracellular
cement) - gum (viscous, from the seeds of
fruits) - mucilage (plant seed, viscous,
thickener)
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CARBOHYDRATES
SUGARS Impact on human taste because they
are sweet primarily Sucrose, Glucose,
Fructose Degree of sweetness - Sucrose 100
sweetness (standard) - Glucose 61-70 -
Fructose 130-180 - Maltose 43-50 -
Lactose 15-45 Functions of sugar in cooking
- provide sweetness, texture, bulk,
preservation (by raising the osmotic pressure),
fermentation (bread, alcoholic beverages.)
Properties of sugar - browning reaction -
reducing sugar - sugar alcohol Non-caloric
sweeteners Saccharin, AceK, Aspartame, Splenda
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CARBOHYDRATES
ABSORBTION - Facilitated transport - use
carrier proteins, Glucose Transport Protein GLUT
(integral protein), from high to low
concentration, with gradient - allows Glucose to
enter and exit - Active transport - against
gradient, co-transport, ATP required - brush
border cells and renal tubule Active transport
of - Glucose - Galactose - Co-transport
with Na - Na/K ATPase dependent - GLUT-5
mediated
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CARBOHYDRATES
GLUT TRANSPORTERS Human facilitated - diffusion
Glucose transporter family (GLUT1-5) GLUT 1 Km
for hexose uptake 1-2 (red cells) (major
expression sites placenta, brain, kidney,
colon) GLUT 2 Km for hexose uptake 15-20
(hepatocytes) (liver, pancreatic b cell,
kidney, small intestine) GLUT 3 Km 10 (brain,
testis) GLUT 4 Km 47 (muscle skeletal and
heart brown white fat) GLUT 5 Km 6-11
(small intestine, specific for Fructose) Km,
MICHAELIS- MENTEN constant Km - affinity of a
protein for a particular substrate Km - small
high affinity
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CARBOHYDRATES
GLUT TRANSPORTERS GLUT 1 (erythroid brain
carrier) - RBC, heart, kidney, adipose, brain
- constituent of blood brain barrier - Km for
uptake in RBC less than Km for exit, asymmetric
transport - low Km enables uptake when blood
Glucose is low (and intracellular demand is
high) - Insulin independent in some cells GLUT
2 (liver Glucose transporter)
Liver, kidney, small intestine, b-cells of
pancreas - low affinity for Glucose, symmetric
transport - rapid efflux following
gluconeogenesis - useful during absorption of
Glucose, Galactose - Insulin independent
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CARBOHYDRATES
GLUT TRANSPORTERS GLUT 3 (brain Glucose
transporter) - adult brain, kidney, placenta,
spermatozoa - mainly expressed in neurons - low
affinity for Glucose, but higher than GLUT 1 -
Insulin independent GLUT 4 (Insulin responsive
Glucose transporter) - adipocyte, skeletal and
cardiac muscle - increased maximum velocity for
Glucose, Insulin dependent GLUT 5 (Fructose
transporter) - mainly expressed by jejunum,
kidney, skeletal muscle - transports Fructose
better than Glucose - High in spermatozoa which
uses Fructose as fuel GLUT 6-7 6 similar to 3
7 similar to 2
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CARBOHYDRATES
GALACTOSE - uses GLUT 2 proteins like
Glucose - cleared by the liver rapidly, hence
high blood Galactose is not common - most
Galactose in the cell is used as structural CHO
or connected to Glucose and stored as
glycogen - body can convent Glucose to
Galactose, hence not essential
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CARBOHYDRATES
FRUCTOSE - Cleared rapidly by liver - Converted
to glucose and used in glycolysis or stored as
glycogen in a relatively small amount Uses GLUT
5 Larger amount contributes to weight
gain, could exacerbate hyperlipidemia
or insulin resistance induces
protein fructosylation and/or oxidative damage
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CARBOHYDRATES
METABOLIC REGULATION Normal Glucose in blood is
70-105 mg/dl Following a meal it increases and
during fasting decreases Tightly regulated, so
brain can always access Glucose (140g/day
minimum for brain working properly)
Mono-saccharides from digested meal enter liver
through portal circulation Glucose
phosphorylated by hexokinase/glucokinase
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CARBOHYDRATES
METABOLISM Hexokinase in a fasting state -
subject to feed back inhibition - high affinity
(low Km) Glucokinase - used in a well fed
state - not regulated - has low affinity, high
Km, high Vmax Fructose and Galactose converted
to Glucose
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CARBOHYDRATES
METABOLISM IN PHYSIOLOGIC STATE Well fed
(Insulin released) - 30 -60 min following a
meal, blood Glucose increases - size of meal,
fiber content, influent this - Glucose uptake,
glycolysis, Glycogen synthesis, and
lipogenesis increases - muscle and liver
Glycogen store replenished - within 2 hours
blood Glucose and Insulin levels return to normal
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CARBOHYDRATES
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CARBOHYDRATES

• POST ABSORPTION STATE
• - Following over night fast or skipping meals
• Gluconeogenesis is ()
• liver uses glucogenic amino acids, lactate
• and glycerol to synthesize Glucose
• - Brain continues to use Glucose
• - Liver Glycogen depleted

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CARBOHYDRATES
GLUCOSE METABOLISM
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CARBOHYDRATES
GLUCOSE METABOLISM

1. Glucose transported into cell
2. Conversion of Glucose into Glycogen

hBlood glucose
Pancreas releases Insulin
Glucose how CHOs circulate in the blood
stream Normal Blood Glucose 100 mg / dl
(70-105 mg/dl)

1. Breakdown of Glycogen to Glucose
2. Increased synthesis of Glucose

Pancreas releases Glucagon
iBlood Glucose
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CARBOHYDRATES
STARVATION - Available Glucose spared for
brain and RBC - Glycogen breakdown 4-24 hours
following fast - Gluconeogenesis starts 8-40
hrs following fast - Ketone synthesis occurs
after 1-2 days and becomes an important fuel
source
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CARBOHYDRATES
BLOOD GLUCOSE LEVEL, HORMONES TIME
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CARBOHYDRATES
CHARACTERISTICS
Simple
Complex
SUGARS
STARCHES
UNREFINED
REFINED
REFINED
UNREFINED
ABSORPTION
longer
quickly
longer
quickly
INSULIN RELEASE
BLOOD SUGAR LEVEL
VOLUME EATEN
large
small
large
small
ENERGY DENSITY (Calorie/ Volume)
small
large
small
large
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CARBOHYDRATES
GLUCOSE METABOLISM
DIETARY GLUCOSE

• BLOOD GLUCOSE

h GLYCOGENOLYSIS
h INSULIN
h GLUCONEOGENESIS
h LIPOLYSIS
h G OXIDATION
h FFA
h GLYCEROL

• LIPOGENESIS, g FFA

i OXIDATION
h GLYCOGEN SYNTHESIS
h GLUCAGON
i INSULIN
h SOMATOSTATIN
( GLUCONEOGENESIS

• BLOOD GLUCOSE

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CARBOHYDRATES
GLUCOSE METABOLISM Food intake energy
expenditure are under - long term signals
(Insulin, Leptin, Ghrelin) - short term signal
(Colecystokinine) Insulin (I) secreted by
pancreatic b-cells Stimuli - Glucose and Amino
Acids circulating in the blood - Incretin
hormons - Glucose dependent insulino-tropic
polypeptide (GIP) - Glucagon-Like Peptide 1
(GLP-1) Insulin indirectly stimulates Leptin
production Leptin secreted by adipose cells
Insulin and Leptin act on CNS and (-) Food
intake () energy expenditure Ghrelin -
secreted by stomach endocrine cells, () food
intake
(-) fat oxidation
-normally suppressed after meals
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CARBOHYDRATES

• FRUCTOSE METABOLISM HEALTH IMPACT
• Differences in hepatic metabolism of Glucose and
  Fructose
• Fructose more lipogenic than Glucose
• TG levels increase postprandial, effect more
  pronounced in persons with existing
  hyperlipidemia or Insulin resistance
• - Fructose does not stimulate Insulin secretion
• It results in decreased level of circulating
  Leptin
• Fructose does not suppress Ghrelin secretion
  after meal
• Chronic consumption of a diet high in Fructose
  (sugar, high fructose corn syrup) associated with
  dietary fat and inactivity involved in increasing
  energy intake, weight gain and obesity

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CARBOHYDRATES
RECOMMENDATIONS Glucose intake Infants 0-6
months AI 60 g/day 7-12 months AI95
g/day Children lt18 years AI130
g/day Adults at least AI140 g/day
in order to provide adequate CHO for brain, CNS
need not to depend on ketones or
TAG Recommendation 45-65 energy coming from
CHO
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CARBOHYDRATES
DAILY AMOUNT
C a l o r i e s p e r d a y
PROTEINS
CARBOHYDRATES
15
60
E x a m p l e
FATS
A person of 150 lb (70 kg)
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Needs 1,260 Calories from glucose
1,260 /4 315 grams glucose/day
G l u c o s e e q u i v a l e n t s
100 g whole wheat bread
50 g glucose
100 g potatoes- cooked
20 g glucose
100 g banana
20 g glucose
100 g grapes
20 g glucose
100 g fruit
5-10 g glucose
100 g vegetables
lt/5 g glucose
100 g table sugar
100 g glucose
100 g honey
100 g fructose
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CARBOHYDRATES
RIGHT DECISION
Eat more!
100 g wheat bread
50 g Glucose
100 g potatoes- cooked
20 g Glucose
100 g banana
20 g Glucose
100 g grapes
20 g Glucose
100 g fruit
5-10 g Glucose
100 g vegetables
lt/5 g Glucose
Eat less!
100 g table sugar
100 g Glucose
100 g honey
100 g Fructose
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CARBOHYDRATES
GLYCEMIC INDEX (how G rises after a meal)
90
85
Depends on - type of CHOs, cooking methods,
commercial food processing
80
75
P l a s m a g l u c o s e l e
v e l
Apple
70
Apple Sauce
65
Apple Juice
60
55
30
60
90
120
150
180
M i n u t e s a f t e r m e a l
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CARBOHYDRATES
RIGHT DECISION
Glycemic Index (GI)
(rate at which Glucose is absorbed and delivered
to the blood)
Low GI
- Low rate constant blood Glucose level after
meal
- Best food has low GI
Examples brown rice, barley, whole wheat bread,
legumes
High GI
- Increased blood Glucose, increased Insulin
delivery to the blood, decreased blood Glucose
shortly after the meal
Examples white bread, potatoes, juices,
processed foods smaller particles (potatoes)
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CARBOHYDRATES
COMPARISON
8 apples 4 ounce chocolate, 1 ounce 28
g
25 med carrots 1 can soft drink 1 can
240 ml
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CARBOHYDRATES
A variety of plant based foods help prevent
wide fluctuation in blood glucose levels
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REFERENCES Modern Nutrition in Health and
Disease, 10 th. Ed www. Pubmed.com http//
cme.medscape.com
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