Chapter 4

The Carbohydrates: Sugars

StarchesFiber

Objectives for Chapter 4• Explain why the body needs carbohydrates.• Distinguish between simple carbohydrates and

complex carbohydrates.• Explain the process of carbohydrate digestion.• Define the role of insulin in regulating the blood

glucose level in the body.• Determine your daily carbohydrate and fiber

needs.• Know health benefits of fiber.• How to identify added sugar in the diet.• Describe the difference between type 1 and type 2

diabetes.• Know the complications of poorly controlled

diabetes.

What Are Carbohydrates?

Found primarily in plant-based foods– Grains, vegetables, fruits, nuts, legumes– Carbohydrate-based foods are staples in

numerous cultures around the world.

Most desirable form of energy for body– In form of glucose (-ose = carbohydrate)– Brain and red blood cells especially rely only

on glucose for fuel source.– Glucose is most abundant carbohydrate in

nature.

What are Carbohydrates?

• Carbohydrates are made of carbon, hydrogen and oxygen atoms (CHO)

• These atoms form chemical bonds that follow the laws of nature.

Carbohydrates

Types of Carbohydrates• Simple carbohydrates

– Monosaccharides – glucose fructose and galactose• contain 6 carbon atoms, 12 hydrogen

atoms and 6 oxygen atoms

– Disaccharides – maltose, sucrose, lactose

Monosaccharides• Glucose -

– hexagon, blood sugar

– One of the 2 sugars in every disaccharide

– Unit from which the polysaccharides/ complex carbohydrates are made

MonosaccharidesFructose• Has same chemical formula as glucose, but

different structure• Sweetest sugar (this is why it is the most commonly

found sugar in soft drinks)• Found naturally in honey and fruits

Monosaccharides• Galactose

– Binds with glucose to form lactose, found in milk

– Does not exist alone, always with glucose

Disaccharides

• 2 monosaccharides bonded together to form disaccharides

• Occur through 2 chemical reactions:

• Condensation – water molecule joins 2 monosaccharides together

• Hydrolysis – water molecules splits to break apart a disaccharide into two monosaccharides

Disaccharides

Sucrose - Found in table sugar, cane sugar, fruits and vegetables

• glucose + fructose

DisaccharidesMaltose - Glucose and glucose combine together to

form • Found only in small amount in foods• It is a product of starch/polysaccharide breakdown

Disaccharides

Lactose - Glucose and galactose bonded together

• Milk sugar

Complex Carbohydrates?

Polysaccharides

• Long chains and branches of sugars linked together.

• There are three types:– Starch, fiber, and glycogen

– Starch is the storage form in plants.• Amylose: straight chains of glucose units• Amylopectin: branched chains of glucose

units

Complex Carbohydrates

Glycogen• Storage form of carbohydrate in

animals and human• Found in liver and muscles• Important source of glucose for blood• Not a significant food source of carbs• Highly branched (easy to breakdown to

glucose for energy)

Complex Carbohydrates

Starches• Storage form of glucose in plants• Found mainly in starchy vegetables,

fruits, grains, legumes and tuber (Yams and potatoes)

• Branched and unbranched

Complex Carbohydrate

Fiber is part of plant that we eat but can’t digest– Examples: cellulose, hemicellulose, lignins,

gums, pectin– Humans lack digestive enzyme needed to break

down fiber.– Dietary fiber: naturally found in foods– Functional fiber: added to food for beneficial

effect• Example: Psyllium added to cereals

– Total fiber = dietary fiber + functional fiber

Complex CarbohydrateFibers• Slows down the process of

chewing and stimulates production of saliva

• Fiber is classified by its affinity for water:

– Soluble fiber– Non-soluble/insoluble fiber

Complex Carbohydrate

Soluble fiber: • found in fruits, oats, barley, beans• dissolves in water and is fermented

by intestinal bacteria• Many are viscous, have thickening

properties• Move more slowly through GI tract• Delays glucose absorption• Decrease Cholesterol

Complex Carbohydrate

Non-soluble/insoluble fiber – • found in whole grains, cereals, vegetables

• cellulose, hemicellulose, lignins• Move more rapidly through GI tract, laxative

effect• Increase fecal weight which promotes

bowel movements• Slows starch breakdown and delays

glucose absorption in the blood

Why Is Fiber So Important?

Fiber helps lower risk of developing:• Constipation • Diverticulosis, diverticulitis• Obesity: high-fiber foods add to

satiation• Heart disease: soluble fibers lower

elevated blood cholesterol levels• Colorectal cancer• Diabetes mellitus: slow digestion and

absorption of glucose

Digestion of CHOThe goal of carbohydrate digestion is to make

glucose for energy– You digest carbohydrates in your mouth and

intestines.

Mouth• Chewed and moistened with saliva to

become bolus• Saliva contains amylase enzyme (-ase =

enzyme) starts the breakdown of starch into smaller polysaccharides

Digestion of CHO• Stomach

– Gastric acid (HCL) deactivate amylase– HCL help break down starch further– No enzymes are active here on

carbohydrate– Fiber sits here and delays stomach

emptying– Food has now become Chyme

CHO DigestionSmall intestine• Performs most of the carbohydrate

breakdown• The pancreas secretes pancreatic amylase to

break down polysaccharide into glucose chains

• Maltase, sucrase, lactase enzymes breaks down the disaccharides

• The intestinal cells then absorb the monosaccharides which go to the blood and then to the liver via the vascular system

CHO Digestion

Large intestine• 1-4 hrs after eating, most sugar and

starch is digested• A small amount of starch and fiber

remain• Fiber attracts water which softens

the stool• Rectum

– Holds waste until excretion

From Carbohydrates to Glucose

Absorption of CHO

• Some CHO is absorbed through the lining of the mouth (mostly maltose)

• Most absorption takes place in the small intestine

• Then goes into the blood and liver where the cells take up fructose and galactose and convert it to glucose

Lactose IntoleranceLactose: • principal carbohydrate found in dairy products• People with a deficiency of the enzyme lactase

cannot digest lactose properly.• Lactose maldigestion is natural part of aging

– As soon as baby stops nursing, body makes less lactase

Lactose intolerance: • when lactose maldigestion results in nausea,

cramps, bloating, diarrhea and flatulence• Common mostly with Native Americans and

African Americans

Lactose Intolerance

Dietary Changes• Gradually add dairy products to your diet• Eat smaller amounts throughout day rather than

large amount at 1 time• Try reduced-lactose milk and diary products• May tolerate up to 1 cup of milk per day• May tolerate yogurt, acidophilus milk, hard

cheese and cottage cheese• Increase intake of calcium fortified foods

How the Body Use Carbohydrates?

• Glucose supplies energy for body, required for brain, nervous system, red blood cells– Fat can provide fuel for muscle, other tissues

• Hormones regulate amount of glucose in blood • Insulin is released by pancreas in response to high

blood glucose levels after a carbohydrate-heavy meal– Directs conversion of glucose in excess of immediate

energy needs into glycogen in liver and muscle cells (limited capacity)

– Rest of excess glucose converted to fat

Glucose in the body

Stored as glycogen in the body• 1/3 in the liver

– Liver glycogen stores depleted after about 18 hours

• 2/3 in the muscle• Glycogen can be broken down easily to

make glucose for energy• Glycogen in the muscle stays there to fuel

exercise and day-to-day activities

Glucose in the BodyLiver can make glucose from protein in

the absence of adequate glucose• Gluconeogenesis – breaking down of

protein from muscle by the liver to make glucose liver

Protein-sparing action• having adequate carbohydrate in the diet to

prevent the breakdown of protein for energy.

Glucose in the Body

• Without glucose, fat can’t be broken down completely and ketone bodies are produced, which are acidic.– Ketosis: elevated blood levels after fasting

about two days

• The brain uses glucose only for energy.– Brain switches to using ketone bodies for fuel

to spare protein-rich tissues.• If fasting continues, protein reserves are depleted

and death is inevitable.

Maintaining Normal Blood Glucose

• Normal blood glucose –– 70-110mg/dL

• Regulating hormones– Insulin – moves glucose from blood

stream after a meal– Glucagon – brings glucose to the blood stream– Epinephrine (adrenaline) increases blood glucose

levels at times of stress.• Fight or flight” hormone: stress, bleeding, low blood glucose

levels trigger its release

Insulin Directs Excess Glucose

into Storage

High Blood Glucose Levels

Glucagon Directs

release of Glucose

into blood stream

Low Blood Glucose Levels

What Is Diabetes Mellitus?

Diabetes mellitus: • individual has high blood glucose levels due to

insufficient insulin or insulin-resistance• Glucose can’t enter cells, which burn fat for fuel• Without glucose, acidic ketone bodies build up,

causing life-threatening diabetic ketoacidosis: untreated can result in coma, death

• Type 1 diabetes: 5-10% of cases– Autoimmune disease: insulin-producing cells in pancreas

destroyed - insulin injections required– Develops in childhood, early adult years

What Is Diabetes Mellitus

Type 2 diabetes: 90-95% of cases

• Cells are resistant to insulin,

• pancreas decreases production of insulin and medication and/or insulin is required

• People 45 and older or at risk for diabetes

• Now seen in increasing number among overweight and obese children

• Prediabetes: glucose intolerance– Blood glucose higher than normal but not high

enough to be classified as Diabetes

What Is Hypoglycemia?

Hypoglycemia: blood glucose level below 70 mg/dl– Symptoms: hunger, shakiness, dizziness,

perspiration, light-headedness– May occur in people with diabetes when they

don’t eat regularly to balance effects of insulin or blood glucose-lowering medication• Can cause fainting, coma

Interpreting Blood

Glucose Levels

What Is Diabetes Mellitus?

Diabetes can result in long-term damage

• High blood glucose levels damage vital organs.– Nerve damage, numbness, poor circulation

• Infections, leg and foot amputations

– Eye damage, blindness– Tooth and gum problems– Kidney damage– Increased risk of heart disease

What Is Diabetes Mellitus?

Blood glucose control is key

• Nutrition and lifestyle goals:– Physical exercise– Well-balanced diet containing:

• High-fiber carbohydrates from whole grains, fruits, vegetables

• Low-fat milk• Adequate lean protein sources• Unsaturated fats• Total calories important for weight management

What Is Diabetes Mellitus?

Cases of diabetes are on the rise.– Sixth leading cause of death in the U.S.– Over 200,000 Americans die from diabetic

complications annually– Rapidly rising in children

• Obesity, overweight, and physical inactivity increase risk

Preventing type 2 diabetes:– Losing excess weight, physical exercise, heart-

healthy, plant-based diet

Health effects Sugars

• Accusations against Sugar– Causes obesity– Causes heart disease– There is no scientific evidence that sugar

causes misbehavior in children and criminal behavior in adults

– There is a theory that sugar increases serotonin levels, which can lead to cravings and addiction

Recommended Intakes • Added sugars –

– DRI - No more than 25% of total daily energy intake

– WHO/FDA – less than 10% of total daily energy– For active women = 8 tsp of sugar daily– For active men = 18 tsp of sugar daily

• Americans average over 30 tsp of added sugars daily.

• Starch– Minimum - 130 g/day for brain function

• 45% - 65% total daily energy intake

Recommended Intakes

• Fiber– 14 grams of fiber per 1,000 calories to

promote heart health– Most Americans fall short: about 15g/day – Daily Value: 25 g/day– American Dietetic Association recommends

20-35 g per day.– World Health Organization suggests no more

than 40 g per day.

Health Effects of Starch and Fiber

• Heart disease• Type II Diabetes• Fiber block the absorption of unwanted

particles in the GI tract• Colon Cancer – removes cancer causing

agents from the body• Weight mgt• Excessive fiber can cause malabsorption,

gas, diarrhea and abdominal distention

GrainsGrains:• Three edible parts: bran, endosperm, germ• Refined grains: milling removes bran and

germ– Some B vitamins, iron, phytochemicals and

dietary fiber lost as a result– Examples: wheat or white bread, white rice

• Enriched grains: folic acid, thiamin, niacin, riboflavin and iron added to restore some of the lost nutrition

• Whole grain foods contain all three parts of kernel

• Examples: brown rice, oatmeal, whole-wheat bread

From Wheat Kernel to

Flour

Increasing Intake of Complex carbohydrate

– Grains – encourage whole grains– Vegetables – starchy and non-starchy vegetables

differ in carbohydrate content– Fruits – vary in water, fiber and sugar content– Milks and Milk Products – contain carbohydrate;

cheese is low– Meat and Meat Alternates – meats are low but

nuts and legumes have some carbohydrate– Food labels list grams of carbohydrate, fiber and

sugar; starch grams can be calculated.

• Whole grains at the supermarket

• Sugar and Processed Foods

Natural and Added Sugars?

• Naturally occurring sugars found in fruits and dairy– Usually more nutrient-dense; provide more

nutrition per bite

• Added sugars are added by manufacturers and are often “empty calories” (provide little nutrition).– Examples: soda, candy

Health effects of Added Sugars

Carbohydrates play a role in dental caries– Fermentable sugars and starch feed bacteria

coating teeth, producing acid to erode tooth enamel

– To minimize tooth decay: • Eat three balanced meals daily

– Keep snacking to a minimum, choosing whole fruits and raw vegetables

• Include foods that fight dental caries: cheese, sugarless gum

• Regular dental care and good dental hygiene

Slices of an Orange versus Orange Slices

Added Sugars

Finding the added sugars in your foods:– Sugars on food labels appear under

numerous different names.• Honey and fructose are not nutritionally superior to

sucrose.

– Naturally occurring sugars are not distinguished from added sugars on the Nutrition Facts panel.

Finding Added Sugars on the Label: The Many Aliases of Added

Sugar

Added Sugars on the Label

Where Are The Added Sugars?

The Many Sizes of Soft DrinksA bottle or can of soda can provide from 6 to 17 teaspoons of added sugars, depending on the size of the container.

Alternatives to SugarSugar substitutes are as sweet or sweeter

than sugar, but contain fewer calories.– Must be approved by FDA and deemed safe

before allowed in food products in U.S.– Saccharin (Sweet’N Low): 200-700% sweeter

than sugar– Aspartame (Nutrasweet, Equal): 200% sweeter

• People with PKU need to monitor all dietary sources of phenylalanine, including aspartame.

– Acesulfame-K (Sunette): 200% sweeter– Sucralose (Splenda): 600% sweeter– Neotame: 7,000-13,000% sweeter

Sugar Alternatives

• Artificial Sweeteners and Weight Control– Much research still being done– Using artificial sweeteners will not

automatically reduce energy intake.

Sugar Replacers

• Also called nutritive sweeteners, sugar alcohols, and polyols

• Maltitol, mannitol, sorbitol, xylitol, isomalt, and lactitol

• Absorbed more slowly and metabolized differently in the body

• Low glycemic response

• Side effects include GI discomfort

Homework/Extra Credit

10 points – Extra credit

Find someone who has either type 1 or type 2 diabetes and interview them by asking the following questions. Write a one page typed summary of your interview.

1. How did you first find out you have diabetes

2. What symptoms, if any do you have

3. What do you have to do to control your diabetes (e.g. insulin, medications, exercise, diet)?

4. How else does diabetes affect your day-to-day life

Bring a food label of your favorite cereal to class