carbohydrates functions: 1) primary function = provide energy 2) structural components of body:...
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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 Complex CHO’s
• Monosaccharides– Glucose– Fructose– Galactose
• Disaccharides– Maltose– Lactose– Sucrose
• Starch • Glycogen• Fiber
• Oligosaccharides• Inulin• fructoligosaccharide
Simple CHO’s
• Almost exclusively in plant foods
• Found in fruits, sweets, milk and milk products, table sugar
MonosaccharidesSimplest CHO’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)
O
O H
H
C H 2 O H
H O
O H
HH
H O C H 21
2
34
5
6
O
1
23
4
5
6C H
2O H
O H
HO HH O O
H
H
H
HH
O
1
23
4
5
6C H
2O H
O H
HO H
H O
O H
H
H
H
H
Glucose Fructose Galactose-mildy sweet -hardly sweet-Intensely sweet
O
1
2
6
3
4
5
C H 2 O H
O
1
2
6
3
4
5
C H 2 O H
O
O
1
2
6
3
4
5
C H 2 O H
OH O C H 2
C H 2 O H
O
1
2
6
3
4
5
O O
O
C H 2 O H C H 2 O H
Glucose + glucosemaltose
Galactose + glucoselactose
Glucose + fructosesucrose
Disaccharides
Maltose
Lactose
Sucrose
maltase
lactase
sucrase
O
O H
C H 2 O H
O
H O
C H 2 O H
O H H O
glucose + glucose
O
1
2
6
3
4
5
C H 2 O H
O
1
2
6
3
4
5
C H 2 O H
galactose + glucose
O
1
2
6
3
4
5
C H 2 O H
O
1
2
6
3
4
5
C H 2 O H
O
O
1
2
6
3
4
5
C H 2 O H
OH O C H 2
C H 2 O H
O
1
2
6
3
4
5
O O
O
C H 2 O H C H 2 O H
O
1
2
6
3
4
5
C H 2 O HOH O C H 2
C H 2 O H1
2
6
3
4
5
glucose + fructose
Complex CHO’saka 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
• 1--> 4 bonds
O O O OO O O
Amylopectin
• Branched chains of glucose’s:
• 1--> 4 bonds
• 1--> 6 bonds at branch points
O O O OO O O
O O
Complex CHO’saka Polysaccharides
• Glycogen– Animals synthesize this and store it in liver
and muscle– = glucose + glucose + glucose etc.– 1-->4 bonds and 1-->6 bonds
O O O OO O O
O O
Amylopectin vs. Glycogen
Made by plants Made by animals
Branched VERY HIGHLY Branched
1 --> 4 1 --> 4
1-->6 1 --> 6
ProteinLipidsInorganic substances
LigninCelluloseHemicellulosePectins
GumsMucilagesAlgal polysaccharidesSuberinCutin
PlantCell Wall
Non-cell wall plant parts
DietaryFiber
Complex CHO’saka Polysaccharides
• Fiber– Cellulose = very common fiber– = glucose + glucose + glucose etc.– 1-->4 bonds
O
O O
C H 2 O H C H 2 O H
O O
O
C H 2 O H C H 2 O H
O Etc...Etc...
Fiber
• NO Human enzymes can break down fiber
• Bacterial enzymes in intestines can break down fiber
Dietary Fiber
Soluble Insoluble
SomeHemicellulose
Pectin
Gums
MucilagesLignin
CelluloseSome
Hemicellulose
Soluble Fibers
adsorptionor binding
of
Fecal bile acids
Lipid absorption
Serum cholesterol
Bileacids
Lipid
Minerals
Altered mineral balance
Soluble Fibers
GelFormation
Transit Time
Nutrient Absorption
Gastric Emptying
Slow Glucose Absorption
Feeling ofFullness
Insoluble & soluble Fibers
Water-holdingcapacity
Fecal volume
Colon Transit Time(speed movemn’t thru gut)
Defecation Frequency( constipation)
Insoluble & Soluble Fibers
Fermentability/Degradability
Colonic Na+ and H2O absorption2˚ bile acid
synthesis
Lactate
GI Lumenacidification
Short ChainFatty Acids
Inhibit TumorFormation
EnterocyteEnergy
Mucosal CellProliferation
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. Concentrated CHO’s Sugar in Fruit vs. Sugar in Candy
This Sugar comes with
Vitamins, Minerals and Fiber
NO fiber or very little
Typically fewVitamins 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 releasesInsulin
Liver picksup glucose Muscle picks
up glucose
Adipose picksUp glucose
Results in Blood Glucose
Fasted
Blood Glucose
Pancreas releasesGlucagon
Liver breaksdown 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
• Coronary Heart
Disease
• Stroke
• Amputations
• Blindness
• 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
Blo
od g
luco
se (
mg/
dL
)250
200
150
100
50
Time (hours)1 2
Diabetes
Normal
ReactiveHypoglycemia
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)
Glycemic Response
White BreadSpaghetti
50
25
0
-25Δ , /Plasma Glucose mg
dL
InsulinemicResponse,Time min
,Time min
0306090120150180
030609012015018050 g CHO
Eur J Clin Nutr,1991,45,489-99,,JAMA 2002,287,2414-23
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
Energy intake 53% HIGHER in High GI group
Result:
Ludwig et al., Pediatrics, 1999, 103, E261-66