Carbohydrates

Will BrownLecture 4

1/12/2012

Outline and Content

• Objective – To identify basic structure, sources, and digestion of carbohydrates. Also to identify how carbohydrates affect blood glucose and some of the issues associated with to little or to much

• Content– Eat This, Not That– Carbohydrate

• Simple• Complex

Which should you eat?

Nutrition Facts

Serving Size:32 pieces

150 cal

9g fat (1.5g saturated)

290 mg Sodium

Nutrition Facts

Serving Size: 15 chips

120 cal

3.5 g fat (0.5g saturated)

220 mg sodium

In addition, the Dorito's come with 2 g of fiber.

Introduction

• What are carbohydrates?– Sugar molecules arranged in various ways

• Why do we love carbohydrates do much? • One of the primary flavors was developed for

carbohydrates – sweet!• Provide the main energy source for the body– 4 kcal/gram– Stored in either liver or muscles as glycogen– Also available in the blood as glucose

Where are carbohydrates produced?

• Primarily made by green plants• Plants are able to transform solar energy into

chemical energy– What is the name of this process?

6 CO2 + 6 H2O → C2H12O6 + 6 O2

So 6 carbon dioxides along with 6 water molecules and some energy from the sun results in 1 glucose molecule and oxygen

SIMPLE CARBOHYDRATES

Simple Carbohydrates

• Two main forms of simple carbohydrates– Monosaccharides – One sugar– Disaccharides – Two sugars

• Can anybody give an example of a simple carbohydrate?

• Food labels list both mono and di under “Sugars”

Monosaccharidesglucose, fructose, galactose

Disaccharides

Sucroseglucose+fructose Maltose

glucose+glucose

Lactoseglucose+galactose

Monosaccharides

• Single unit of sugar• Three most basic forms– Glucose – Fructose – Galactose

Glucose

• Most common form of sugar found in the body

• AKA: Dextrose• Not common in food as single sugar– Most comes from breakdown of sucrose

• Most forms of sugar are converted to glucose once in the body

Fructose• AKA: Fruit sugar• After absorption transported to liver– Either converted to glucose or converted to other

compounds, i.e.: fat• Most fructose comes from the refined product

high-fructose corn syrup• Forms the other half of the sucrose molecule

Galactose

• Very similar in structure to Glucose• Not found in large amounts in nature • Forms half of the disaccharide Lactose– Glucose forms the other half

• Converted to Glucose or Glycogen in the liver

Disaccharides

• Two molecules of sugar• Sucrose

– Glucose and Fructose bonded together– Sources: honey, sugarcane, sugar beets, and maple sugar– Not produced by animals

• Lactose– Glucose bonded to Galactose– Produced in milk synthesis

• Maltose– Glucose bonded to Glucose– Comes from breakdown of starch– Important sugar in fermentation process

COMPLEX CARBOHYDRATE

Polysaccharides

StarchesMade in plants

Digestible

FiberMade in plants

Indigestible

GlycogenMade by animals

Stored in muscle + liver

AmyloseStraight chain

AmylopectinBranched

PectinsSoluble

CelluloseInsoluble

Polysaccharides

StarchesMade in plants

Digestible

FiberMade in plants

Indigestible

GlycogenMade by animals

Stored in muscle + liver

AmyloseStraight chain

AmylopectinBranched

PectinsSoluble

CelluloseInsoluble

Digestible Complex Carbohydrates

• AKA: Polysaccharides and starch• Long chains of sugar molecules bonded

together – can be >1000 molecules of sugar• Plants store CC in 2 main forms– Amylose

– Amylopectin

Digestible Complex Carbohydrate

• Enzymes breakdown starch at the end of the chain• Amylose is slower to digest than amylopectin– As a result amylopectin raises blood sugar faster

• All carbs are listed on nutrition labels as “Other Carbohydrates”

• Glycogen is primary sugar found in the body– Stored in muscles and liver– Glucose molecules bonded together– Highly branched; even more so than amylopectin

• Can quickly raise blood glucose levels

Polysaccharides

StarchesMade in plants

Digestible

FiberMade in plants

Indigestible

GlycogenMade by animals

Stored in muscle + liver

AmyloseStraight chain

AmylopectinBranched

PectinsSoluble

CelluloseInsoluble

Complex Carbohydrates: Fiber

• Made up primarily of polysaccharides• Can not be digested by humans• 6 types of Fiber– Cellulose– Hemicellulose– Pectins– Gums– Mucilages– Lignin

-- Carbohydrate fibers

-- Non-carbohydrate fiber

Polysaccharides

StarchesMade in plants

Digestible

FiberMade in plants

Indigestible

GlycogenMade by animals

Stored in muscle + liver

AmyloseStraight chain

AmylopectinBranched

PectinsSoluble

CelluloseInsoluble

Soluble fibers

• Pectins, gums and mucilages• AKA: viscous fiber• Dissolve or swell when placed in water• Source: found around and inside plants• Readily digested by bacteria – fermentable• Found in foods under various names– Guar gum– Gum arabic– Locust bean gum– Pectin for jam and jellies

Soluble fiber

• Pectin– Galacturonic acid– Also others

• Mucilages– Galactose– Manose– And others

Polysaccharides

StarchesMade in plants

Digestible

FiberMade in plants

Indigestible

GlycogenMade by animals

Stored in muscle + liver

AmyloseStraight chain

AmylopectinBranched

PectinsSoluble

CelluloseInsoluble

Insoluble Fiber

• Comprised of cellulose, hemicellulose, and lignin• AKA: nonfermentable fiber• Do not readily dissolve in water• Sorce: form the structural parts of plants– Cell wall, bark, etc.

• Not readily metabolized by commensal bacteria• Bran is rich in hemicellulose and lignin– Outer covering of all whole grains

Insoluble Fiber

• Cellulose– Glucose

• Hemicellulose– Xylose– Galactose– Glucose– Small amounts of other monosaccharides

• Lignin– Multi-ringed alcohols

• That is why it is called a “noncarbohydrate”

Carbohydrates on Food Labels

• Sugars = all mono and disaccharides

• Dietary fiber = fiber present in the food– Does not include added or

“functional” fiber– Now you can find “total fiber”

• Number of complex carbs is total carbs – DF – sugars

Carbs in the Diet

• Recommended Daily allowance of Carbohydrate = 130g

• Should comprise 45-65% of daily calories– Example: for 2000 calorie diet that is between 900

to 1300 calories• Look for nutrient dense carbohydrates– Fruit, vegetables, beans, etc.

• Avoid processed carbohydrates– Refined sugars and refined grains

Carbs in the Diet

• Why is it necessary to eat whole grains?• What is a whole grain?

• During the refinement process the bran is removed

• Leaves very little if any fiber – mostly starch

• Why is this a problem?

Easily digestible carbohydrates quickly raise blood sugar

Which should you eat?

Nutrition Facts

Serving Size: 1/2 cups dry

150 cal

3 g fat (0.5 g saturated)

1 g Sugar

4 g fiber

Nutrition Facts

Serving Size: 2 packets

200 cal

0 g fat

2g Fiber

Process of making grits has high concentration of starch and reduced fiber

Carbs in the Diet: Sweeteners

• Two categories– Nutritive– Alternative

• Nutritive sweeteners provide calories– Sugars – Used in many types of food– Sugar alcohols – limited uses

• Alternative sweeteners provide no calories– Saccharin– Aspartame

• Alternative sweeteners are “sweeter” on a per gram basis compared to nutritive sweetners

Carbs in the Diet: Nutritive Sweeteners

• All monosaccharides and disaccharides • Sucrose is the benchmark to measure relative sweetness– Sucrose = 1.0– If >1 then sweeter than sucrose– If < 1 then not as sweet as sucrose

• High Fructose Corn Syrup (HFCS) is used extensively as a sweetener is food– ~55% Fructose– Made by refining corn– As sweet as sucrose but cheaper to make

Carbs in the Diet: Nutritive Sweeteners

• Other types of sugars found in food– Brown Sugar – sucrose with molasses– Turbinado sugar – partially refined sugar; AKA: raw

sugar– Honey – plant nectar enzymatically broken down

by bees• Can cause botulism in infants – recommended to not

give to children under the age of 2

– Inverted sugar – sucrose that is heated until “inverted”

Which should you eat?

Nutrition Facts

Serving Size: ¼ cup

240 cal

0 fat

40 g Sugar

Nutrition Facts

Serving Size: ¼ cup

210 cal

0 g fat

50g Sugar

Natural maple syrup not only has fewer calories but also is high in manganese.

Carbs in the Diet: Nutritive Sweeteners

• Sugar Alcohols– Sorbitol and Xylitol are examples– Much lower calorie content than sugars

• Sugar = 9 kcal/g• Sugar alcohol = ~2.6 kcal/g

– Converted to glucose much slower; resides longer in SI– If consumed in large amounts can cause diarrhea– Found in sugarless gum, breath mints, and candy– Must be listed on food labels

• If one is used, must be listed by name• If 2 or more than “sugar alcohol” is listed

Carbs in the Diet: Alternative Sweeteners

• AKA: artificial sweeteners• Found in many forms and many brand names• Yield little to no calories when eaten• No RDA, instead have ADI – Acceptable Daily Intake

– The amount 100 times less than the no harmful effect level in animal studies

• 6 are approved in the US– Saccharin – Aspartame– Sucralose– Neotame– Cyclamate– Acesulfame-K

Saccharine

• The oldest alternative sweetener• First produced in 1879• Approved for use in over 90 countires• Sold in pink packets – Brand name Sweet ‘N Low®• 50% of market share in USA• Originally thought to increase cancer risk– No longer listed as carcinogen – Studies had the rats consuming a crazy amount of it

and saw marginal increases in bladder cancer

Aspartame

• Sold in blue packets – brand name Equal®• Approved in over 90 countries• Endorsed by numerous diet and medical groups• 200 times sweeter than sucrose• Yields 4 kcal/g• Made of phenylalanine, aspartic acid and methanol

– Because more protein than sugar, looses sweetness with prolonged heating, not good for cooking

• ADI – 50mg/kg of body weight– ~80 packets of Equal®

• Some adverse effects have been reported• Considered safe for pregnant women – consult your physician

Sucralose

• Sold as the brand name Splenda®• 600 times sweeter than sucrose• Made by adding 3 Cl to sucrose• Does not breakdown when heated• Not readily absorbed so most excreted in

feces– Small amounts taken up secreted by kidneys

Neotame

• Recently approved by FDA• Approved for use in many applications– Not meat or poultry

• 7000-13,000 times sweeter than sucrose• Does not breakdown when heated• Similar in structure to aspartame• Safe in general population and does not carry

the PKU warning of aspartame

Acesulfame-K

• Sold under the brand name Sunette®• 200 times sweeter than sucrose• Heat stable• Approved by FDA in 1988 – in Europe since ’83• Not digested by the body• K stands for potassium

Tagatose

• Brand name = Naturlose®• Altered form of fructose• Poorly absorbed • Yields 1.5 kcal/g• Eventually fermented in LI so thought to act as

prebiotic

Stevia

• Brand name = Sweet Leaf®• Derived from South American shrub• 100-300 times sweeter than sucrose• Provides no energy• Available in Japan since ‘70s but not approved

in US till 2008