carbohydrates. carbohydrates glucose provides energy for the brain and ½ of energy for muscles and...
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CarbohydratesCarbohydrates
CarbohydratesCarbohydrates
glucose provides energy for the brain and ½ glucose provides energy for the brain and ½ of energy for muscles and tissuesof energy for muscles and tissues
glycogen is stored glucoseglycogen is stored glucose glucose is immediate energyglucose is immediate energy glycogen is reserve energyglycogen is reserve energy
CarbohydratesCarbohydrates
all plant foodall plant food milkmilk
carbohydrates are not equalcarbohydrates are not equal
– simple carbohydratessimple carbohydrates
– complex carbohydratescomplex carbohydrates
Simple CarbohydratesSimple Carbohydrates
sugarssugars
– monosaccharides – single sugarsmonosaccharides – single sugars
– disaccharides – 2 monosaccharidesdisaccharides – 2 monosaccharides
Complex CarbohydratesComplex Carbohydrates
starches and fibersstarches and fibers polysaccharidespolysaccharides
– chains of monosaccharideschains of monosaccharides
Simple CarbsSimple Carbs monosaccharidesmonosaccharides
– all are 6 carbon hexesall are 6 carbon hexes6 carbons6 carbons12 hydrogens12 hydrogens6 oxygens6 oxygensarrangement differsarrangement differs
–accounts for varying accounts for varying sweetnesssweetness
– glucose, fructose, glucose, fructose, galactosegalactose
GlucoseGlucose
mild sweet flavormild sweet flavor known as blood sugarknown as blood sugar essential energy sourceessential energy source found in every found in every
disaccharide and disaccharide and polysaccharidepolysaccharide
FructoseFructose
sweetest sugarsweetest sugar found in fruits and honeyfound in fruits and honey added to soft drinks, added to soft drinks,
cereals, desertscereals, deserts
GalactoseGalactose
hardly tastes sweethardly tastes sweet rarely found rarely found
naturally as a single naturally as a single sugar sugar
DisaccharidesDisaccharides
pairs of the monosaccharidespairs of the monosaccharides– glucose is always presentglucose is always present– 22ndnd of the pair could be fructose, galactose of the pair could be fructose, galactose
or another glucoseor another glucose– taken apart by hydrolysistaken apart by hydrolysis– put together by condensationput together by condensation– hydrolysis and condensation occur with all hydrolysis and condensation occur with all
energy nutrientsenergy nutrients– maltose, sucrose, lactosemaltose, sucrose, lactose
CondensationCondensation
making a disaccharidemaking a disaccharide– chemical reaction linking 2 chemical reaction linking 2
monosaccharidesmonosaccharides
HydrolysisHydrolysis
breaking a disaccharidebreaking a disaccharide
– water molecule splitswater molecule splits
– occurs during digestionoccurs during digestion
MaltoseMaltose
2 glucose units2 glucose units produced when starch breaks downproduced when starch breaks down not abundantnot abundant
SucroseSucrose fructose and fructose and
glucoseglucose tastes sweettastes sweet
– fruit, vegetables, fruit, vegetables, grainsgrains
table sugar is table sugar is refined sugarcane refined sugarcane and sugar beetsand sugar beets
brown, white, brown, white, powderedpowdered
LactoseLactose
glucose and galactoseglucose and galactose main carbohydrate in main carbohydrate in
milkmilk– known as milk sugarknown as milk sugar
Complex CarbohydratesComplex Carbohydrates
polysaccharidespolysaccharides
– glycogen and starchglycogen and starchbuilt entirely of glucosebuilt entirely of glucose
– fiberfibervariety of monosaccharides and other variety of monosaccharides and other
carbohydrate derivativescarbohydrate derivatives
GlycogenGlycogen limited in meat and not found in plantslimited in meat and not found in plants
– not an important dietary source of not an important dietary source of carbohydratecarbohydrate
BUTBUT– all glucose is stored as glycogenall glucose is stored as glycogen– long chains allow for long chains allow for hydrolysis and releasehydrolysis and release of energyof energy
StarchesStarches
stored in plant cellsstored in plant cells body hydrolyzes plant starch to glucosebody hydrolyzes plant starch to glucose
FiberFiber
structural parts of plantsstructural parts of plants
– found in all plant derived foodfound in all plant derived food bonds of fibers cannot be broken down bonds of fibers cannot be broken down
during the digestive processduring the digestive process
– minimal or no energy availableminimal or no energy available
Fiber typesFiber types
cellulosecellulose
pectinspectins ligninslignins resistant starchesresistant starches
– classified as fibersclassified as fibers
– escape digestion and escape digestion and absorptionabsorption
Fiber CharacteristicsFiber Characteristics soluble fibers, viscous, fermentablesoluble fibers, viscous, fermentable
– easily digested by bacteria in coloneasily digested by bacteria in colon
– associated with protection against heart associated with protection against heart disease and diabetesdisease and diabetes lower cholesterol and glucose levelslower cholesterol and glucose levels
– found in legumes and fruitsfound in legumes and fruits
FiberFiber
insoluble and not easily fermentedinsoluble and not easily fermented
– promote bowel movementspromote bowel movements
– alleviate constipationalleviate constipation
– found in grains and vegetablesfound in grains and vegetables
DRI and FiberDRI and Fiber
distinguish fibers by sourcedistinguish fibers by source
– dietary fibers: naturally in intact plantsdietary fibers: naturally in intact plants
– functional fibers: extracted from plants or functional fibers: extracted from plants or manufacturedmanufactured
– total fiber: sum of the 2total fiber: sum of the 2
Carbohydrate DigestionCarbohydrate Digestion
break down into glucosebreak down into glucose– body is able to absorb and usebody is able to absorb and use
large starch moleculeslarge starch molecules– extensive breakdownextensive breakdown
disaccharidesdisaccharides– broken oncebroken once
monosaccharidesmonosaccharides– don’t need to be broken downdon’t need to be broken down
Carbohydrate DigestionCarbohydrate Digestion begins in mouthbegins in mouth
– chewing releases salivachewing releases saliva
– enzyme amylase hydrolyzes starch to enzyme amylase hydrolyzes starch to polysaccharides and maltosepolysaccharides and maltose
stomachstomach
– no enzymes available to break down no enzymes available to break down starchstarch
– acid does some breakdownacid does some breakdown
– fibers in starch provide feeling of fullnessfibers in starch provide feeling of fullness
small intestinesmall intestine– majority of carbohydrate digestion majority of carbohydrate digestion
takes place heretakes place here– pancreatic amylase reduces carbs to pancreatic amylase reduces carbs to
glucose chains or disaccharidesglucose chains or disaccharides– specific enzymes finish the jobspecific enzymes finish the job
maltasemaltase–maltose into 2 glucosemaltose into 2 glucose
sucrasesucrase–sucrose into glucose and fructosesucrose into glucose and fructose
lactaselactase–lactose into glucose and lactose into glucose and
galactosegalactose
large intestinelarge intestine– 1-4 hours for sugars and 1-4 hours for sugars and
starches to be digestedstarches to be digested– only fibers remainonly fibers remain
attract water, which softens attract water, which softens stoolstool
– bacteria ferment some fibersbacteria ferment some fiberswater, gas, short-chain water, gas, short-chain
fatty acids (used for fatty acids (used for energy)energy)
Carbohydrate AbsorptionCarbohydrate Absorption
glucose can be absorbed in the mouthglucose can be absorbed in the mouth majority absorbed in small intestinemajority absorbed in small intestine
– active transportactive transportglucose and galacticglucose and galactic
– facilitated diffusion facilitated diffusion fructosefructosesmaller rise in blood glucosesmaller rise in blood glucose
Lactose IntoleranceLactose Intolerance more lactose is consumed than can be more lactose is consumed than can be
digesteddigested
– lactose molecules attract waterlactose molecules attract watercause floating, abdominal discomfort, cause floating, abdominal discomfort,
diarrheadiarrhea
– intestinal bacteria feed on undigested intestinal bacteria feed on undigested lactoselactoseproduce acid and gasproduce acid and gas
Lactose IntoleranceLactose Intolerance
age, damage, medication, diarrhea, age, damage, medication, diarrhea, malnutritionmalnutrition
management requires dietary changemanagement requires dietary change
– 6 grams (1/2 cup) usually tolerable6 grams (1/2 cup) usually tolerable
– take in graduallytake in gradually
– hard cheeses & cottage cheesehard cheeses & cottage cheese
– enzyme drops or tabletsenzyme drops or tablets lactose free diet is extremely difficult to lactose free diet is extremely difficult to
accomplishaccomplish
Carbohydrate MetabolismCarbohydrate Metabolism 1/3 of body’s glycogen is stored in liver1/3 of body’s glycogen is stored in liver
– released as glucose to bloodstreamreleased as glucose to bloodstream1.1. eat – intake glucoseeat – intake glucose2.2. liver condenses extra glucose to glycogenliver condenses extra glucose to glycogen3.3. blood glucose fallsblood glucose falls4.4. liver hydrolyzes glycogen to glucoseliver hydrolyzes glycogen to glucose
Glycogen is bulky, so we store only so much: Glycogen is bulky, so we store only so much: short term energy supplyshort term energy supply
Fat is the long term energy supply.Fat is the long term energy supply.
Glucose for EnergyGlucose for Energy
enzymes break apart glucose – yielding enzymes break apart glucose – yielding energyenergy
inadequate supply of carbohydratesinadequate supply of carbohydrates– ketone bodies (fat fragments) are an ketone bodies (fat fragments) are an
alternate energy source during starvationalternate energy source during starvation– excess ketones can lead to ketosis: excess ketones can lead to ketosis:
imbalance of acids in bodyimbalance of acids in body minimum of 50 – 100 grams of carbs/day minimum of 50 – 100 grams of carbs/day
are needed to avoid ketosisare needed to avoid ketosis
Glucose HomeostasisGlucose Homeostasis
maintaining an even balance of glucose is maintaining an even balance of glucose is controlled by insulin and glucagoncontrolled by insulin and glucagon
– insulininsulinmoves glucose into the bloodmoves glucose into the blood
– glucagonglucagonbrings glucose out of storagebrings glucose out of storage
maintaining balancemaintaining balance
– balanced meals at regular intervalsbalanced meals at regular intervals fiber and some fat slow the digestive fiber and some fat slow the digestive
process downprocess downglucose gets into the blood slow and glucose gets into the blood slow and
steadysteady
Maintaining Blood
Glucose Homeostasis
IntestineWhen a person eats,blood glucose rises.
1
2
Insulin stimulates the uptake of glucose into cells and storageas glycogen in the liver andmuscles. Insulin also stimulatesthe conversion of excessglucose into fat for storage.
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4
5
6
7 Blood glucose begins torise.
a The stress hormoneepinephrine and other hormonesalso bring glucose out of storage.
GlucoseInsulinGlucagonGlycogen
Glucagon stimulates livercells to break down glycogenand release glucose into theblood.a
Liver
Low blood glucose stimulatesthe pancreas to releaseglucagon into the bloodstream.
As the body's cells useglucose, blood levels decline.
Glucagon
Pancreas
Fat cell
Liver
Muscle
High blood glucose stimulatesthe pancreas to release insulin.
Pancreas
Insulin
ImbalanceImbalance
diabetesdiabetes– after food intake, blood glucose rises and after food intake, blood glucose rises and
is not regulated because insulin is is not regulated because insulin is inadequateinadequate
hypoglycemiahypoglycemia– blood glucose drops dramaticallyblood glucose drops dramatically
too much insulin, activity, inadequate too much insulin, activity, inadequate food intake, illnessfood intake, illness
diet adjustment includes fiber-rich carbs diet adjustment includes fiber-rich carbs and proteinand protein
Glycemic IndexGlycemic Index
way of classifying way of classifying food according to food according to their ability to raise their ability to raise blood glucoseblood glucose
much controversymuch controversy
SugarSugar
½ comes from natural sources, ½ from ½ comes from natural sources, ½ from refined and addedrefined and added
– sucrose, corn syrup, honeysucrose, corn syrup, honey excess can lead to nutrient deficiencies excess can lead to nutrient deficiencies
and tooth decayand tooth decay
– empty caloriesempty calories
– sugar and starch break down in the sugar and starch break down in the mouthmouth
SugarSugar
recommended intakerecommended intake
– added sugar = no more than 10% of energy added sugar = no more than 10% of energy intakeintake
Starch and FiberStarch and Fiber
diet that includes starch, fiber and natural diet that includes starch, fiber and natural sugarssugars
– whole grains, vegetables, legumes, fruitswhole grains, vegetables, legumes, fruitsmay protect against heart disease and may protect against heart disease and
strokestroke reduces the risk of type 2 diabetesreduces the risk of type 2 diabetesenhances the health of the large enhances the health of the large
intestineintestinecan promote weight losscan promote weight loss
Starch and FiberStarch and Fiber starch intakestarch intake
– 45-65%45-65%
– 225 – 325 grams (DV is 300 225 – 325 grams (DV is 300 grams)grams)
– 900-1300 kcal/2000 kcal900-1300 kcal/2000 kcal
– RDA is 130 gramsRDA is 130 grams fiber intakefiber intake
– Daily Value is 25 grams/2000 Daily Value is 25 grams/2000 kcalkcal
GroceriesGroceries
grains: 1 serving = 15 gramsgrains: 1 serving = 15 grams vegetablesvegetables
– ½ cup starchy = 15 grams½ cup starchy = 15 grams– ½ cup nonstarchy = 5 grams½ cup nonstarchy = 5 grams
fruit: 1 serving = 15 gramsfruit: 1 serving = 15 grams milk: 1 cup = 12 gramsmilk: 1 cup = 12 grams meat: none or littlemeat: none or little legumes: ½ cup = 15 gramslegumes: ½ cup = 15 grams
Artificial SweetenersArtificial Sweeteners
help keep sugar and energy intake downhelp keep sugar and energy intake down anything we eat has FDA approvalanything we eat has FDA approval
– saccharinsaccharin
– aspartameaspartame
– acesulfame potassiumacesulfame potassium
– sucralosesucralose
– neotameneotame
Sugar ReplacersSugar Replacers
sugar alcoholssugar alcohols
– provide bulk and sweetnessprovide bulk and sweetnesscookies, gum, candy, jellycookies, gum, candy, jelly
– do contain minimal kcaldo contain minimal kcal
– low glycemic responselow glycemic responseabsorbed slowlyabsorbed slowly
– do not cause dental cariesdo not cause dental caries