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.

3

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