CarbohydratesCarbohydrates

CarbohydratesCarbohydrates

Most easily metabolized nutrient for the Most easily metabolized nutrient for the body, converted into glucosebody, converted into glucose

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

Compounds composed of carbon, oxygen Compounds composed of carbon, oxygen and hydrogen that are arranged to make and hydrogen that are arranged to make different variations of sugar moleculesdifferent variations of sugar molecules

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 Mono = oneMono = one Saccharides = sugarSaccharides = sugar

– 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

in starchy foods in starchy foods

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 sugarsugar

one of the sugars in one of the sugars in milk milk

DisaccharidesDisaccharides

pairs of the monosaccharides (di = two)pairs of the monosaccharides (di = two)

– maltose, sucrose, lactosemaltose, sucrose, lactose

MaltoseMaltose

2 glucose units2 glucose units known as malt sugarknown as malt sugar not abundant in foods not abundant in foods

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

milk, depending on milk, depending on milk's fat content milk's fat content lactose contributes 30-lactose contributes 30-50% of milk's energy50% of milk's energy– 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

StarchesStarches

stored in plant cells (grains, vegetables, stored in plant cells (grains, vegetables, potatoes and legumes)potatoes and legumes)

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 CharacteristicsFiber Characteristics soluble fibers (dissolves in water) soluble fibers (dissolves in water)

– 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 (does not dissolve in water) insoluble (does not dissolve in water)

– promote bowel movementspromote bowel movements

– alleviate constipationalleviate constipation

– found in grains and vegetablesfound in grains and vegetables

– associated with reduced cancer rates associated with reduced cancer rates

Meeting Fibre NeedsMeeting Fibre Needs

Choose whole grain more than refined Choose whole grain more than refined products such as white breadproducts such as white bread

Males aged 14 to 50 need 38g of fibre dailyMales aged 14 to 50 need 38g of fibre daily Females aged 14 to 18 need 36g of fibre Females aged 14 to 18 need 36g of fibre

daily (decreased to 25g at age 19) daily (decreased to 25g at age 19)

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

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

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

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

– enzyme drops or tabletsenzyme drops or tablets lactose free diet is extremely difficult to lactose free diet is extremely difficult to

accomplishaccomplish

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

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

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