Transcript The Liver - University of Akron

Chapter 4:
Carbohydrates
Plants Synthesize
Glucose
Simple Sugars
Monosaccharides
Single sugar molecules
Disaccharides
Pairs of monosaccharides
Monosaccharides
Glucose
Fructose
Galactose
Glucose (Dextrose)
Not used as a sweetener
Source: breakdown of starch and
other sugars
Glucose in the Body
Form of sugar found
in the blood
Only energy source
for the brain
Quick energy for
muscles
Fructose (fruit sugar)
Sweetest monosaccharide
Metabolized to glucose in the liver
Found in fruit, honey, and high fructose
corn syrup
Is in sucrose (table sugar)
Galactose
Not used as sweetener
Usually bound with glucose (lactose or
milk sugar)
Converted to glucose in the liver
Available fuel source
Disaccharides:
Pairs of Sugars
“Simple sugars”
Linked monosaccharides
Always contain glucose
Sucrose
Glucose + Fructose
Table sugar
Soft drinks, candy, ice cream
Baked goods, jelly, cereal
Lactose
Galactose +
Glucose
Dairy products
Increases calcium
absorption
Maltose (malt sugar)
Glucose + Glucose
Sprouting seeds
Digestion of starch
Fermentation
Alcohol production
Complex Carbohydrates
Polysaccharides: Starch & Glycogen
Amylose: straight chain digestible
starch
Amylopectin: branched chain
digestible starch
Dietary fiber: non-digestible
Oligosaccharides
3-10 monosaccharides
Found in beans and legumes
Not digested
Metabolized by bacteria in the large
intestine
Beano®
Polysaccharides: Starch
3,000 or more monosaccharides bound
together
Plant storage of glucose
Two forms
Amylose--straight chain polymer
 Amylopectin--highly branched polymer

Polysacchai\rides
Sources of Starch
Grain products:
bread, cereal,
pasta
Some “starchy”
vegetables:
corn, peas,
carrots,
potatoes
Glycogen
Storage form of CHO for animals and human
Structure similar to amylopectin
More sites for enzyme action
Found in the liver and muscles
Glycogen Sources
Dietary: insignificant
Made in the body
Stored in the liver and muscles
Dietary Fiber
Plant cells
Cannot be digested by humans
Humans lack necessary enzymes to
break the bonds
Dietary Fiber
Found only in plants
Whole grains
Fruits
Vegetables
Types of Fiber
Insoluble fiber
Cellulose, hemicellulose, lignin
Does not dissolve in water
Not fermented by bacteria in the colon
Tough, fibrous parts of vegetables
Cereal bran, whole grains, fruit
Types of Fiber
Soluble fiber
Gum, Pectin,
Mucilage
Fermented in colon
Sources: Fruits,
vegetables, oats,
beans, rice bran,
psyllium seed
Soluble and Insoluble
Fiber
Health Benefits of
Insoluble Fiber
Decreases intestinal transit time
Promotes regularity, softer stools
Reduces constipation
Reduces risk of hemorrhoids (varicose
veins in the rectum) caused by
constipation
Health Benefits of
Insoluble Fiber
Reduces risk of diverticulosis
Outpouching of intestinal wall
 Diverticulitis: inflamed pouches

High fruit and vegetable intake seems to
reduce risk of colon cancer, though fiber
may not be the factor
Diverticula
Health Benefits of
Soluble Fiber
Associated with reduced risk of
cardiovascular disease
Slows absorption of glucose from the
small intestine
Appears to reduce risk of diabetes
May help with blood glucose control (but
requires very large amounts of fiber)
Health Benefits of
All Fiber
Weight management
Bulky, high-fiber foods fill you up
Have low energy density
May reduce risk of obesity
Negative Effect of
Excessive Fiber
>60 g/day
Bind minerals (calcium, zinc, iron)
Satiety without adequate nutrients,
especially in children
Diarrhea
Constipation: if inadequate water can
result in bowel obstruction
CHO in Food
Carbohydrate
Digestion
Effects of Cooking
Softens fibrous tissues
Easier to chew and swallow
Digestion of
Carbohydrate in the
Mouth
Saliva contains amylase
Starch is broken down to shorter
saccharides
Taste the sweetness with prolong
chewing
Proceeds down the esophagus
Digestion of
Carbohydrate in the
Stomach
The acidic environment stops the
action of salivary amylase
No further starch digestion occurs
In the Small Intestine
Pancreatic amylase is released
Intestinal cells release enzymes
Maltose + maltase
Sucrose + sucrase
Lactose + lactase
glucose + glucose
glucose + fructose
glucose + galactose
Monosaccharides are absorbed
Lactose Intolerance
Reduction in lactase
Lactose is undigested and not absorbed
 Lactose is metabolized by large intestinal
bacteria


causes gas, bloating, cramping, discomfort
Primary lactose intolerance disease
Secondary lactose intolerance disease
What To Do If You Are
Lactose Intolerant
Determine amount you can tolerate
Eat dairy with fat
Cheese & yogurt are usually tolerated
well
Use of Lact-Aid
CHO Digestion
CHO Absorption
Glucose and Galactose
Active absorption
Energy is expended
Going from low to high concentration gradient
Fructose
Facilitated diffusion using a carrier
No energy expended
Portal Vein
Transport absorbed monosaccarhides
Delivers them to the liver
Liver can:
transform fructose/galactose into
glucose
release them into the blood stream
store as gylcogen (or fat)
Uses of Glucose
Energy
Brain’s only source
Muscle – quick energy
Glycogen
Muscle: used by individual muscle
Liver: maintain blood sugar
Excess converted to fat
Stored in fat cells
Future energy use as fat
Regulation of Blood
Glucose
Hyperglycemia
 Hormone
regulates
 Insulin
Hypoglycemia
 Hormones
regulate
 Glucagon
 Epinephrine
Blood Glucose Control
Role of the liver
 Regulates glucose that enters
bloodstream
Role of the pancreas
 Release of insulin
 Release of glucagon
Functions of Insulin
Promotes glycogen synthesis
Increases glucose uptake by the
cells
Reduces gluconeogenesis
Net effect: lowers the blood
glucose
Functions of Glucagon
Breakdown of glycogen
Enhances gluconeogenesis
Net effect: raises blood glucose
Epinephrine/
Norepinephrine
“fight or flight” response
breakdown glycogen
raises blood glucose
Diabetes Mellitus-Type 1
Genetic link
Immunological disorder
Associated with early introduction of
cow’s milk
Absence of insulin
Insulin dependent
Hyperglycemia
Treatment for Type 1
CHO counting
Insulin therapy
Risk for heart disease, kidney damage,
other complications
Diabetes Mellitus-Type 2
Genetic link
Associated with obesity
Non-insulin dependent to start
Accounts for majority of cases of DM
Defective insulin receptors on the cells
Over secretion of insulin to compensate
Leads to beta cells failure
Treatment: medication and diet therapy
(weight loss)
Consequences of Poor
Blood Glucose Control
Acute: Hypoglycemia; Ketosis leading to ion
imbalances, dehydration, coma, death
Chronic
Nerve damage
Heart disease
Kidney disease
Blindness
Atherosclerosis
Wound infections
Amputations
Hypoglycemia
Reactive hypoglycemia
 Occurs 2-4 hours after eating a meal
 Possibly due to over secretion of
insulin
Fasting hypoglycemia
 Usually caused by pancreatic cancer
 Leads to overproduction of insulin
Sweeteners
Sucrose--benchmark of all sweeteners
Same caloric content (4 kcals/gm)
No health benefit over another
Consumption ranges: 14-48 lbs/yr per
person
Types of Sweeteners
High-fructose corn syrup




cornstarch treated with acid and enzymes
conversion of glucose into fructose
same degree of sweetness as sucrose
cheaper and used in many food products
Brown sugar
Maple syrup
Honey
Sugar alcohols



1.5-3 kcal/g
Absorbed and metabolized slower
Large amount causes diarrhea
Low Calorie Sweeteners
Saccharin (Sweet’N Low®)
Aspartame (NutraSweet®)
Acesulfame potassium,
acesulfame-K (Sweet One®)
Sucralose (SPLENDA®)
Neotame
Saccharin
First produced in 1879
180-200x sweeter than sucrose
Excessive intake is linked to bladder
cancer in lab animals
Not a potential risk in humans in
amounts normally used
Aspartame
(NutraSweet)
Composed of phenylalanine and aspartic acid
180-200x sweeter than sucrose
4 kcal/gm, but only a trace amount is needed
to sweeten foods
Not heat stable
Complaints of sensitivity to aspartame

headaches, dizziness, seizures, nausea, etc.
Not recommended for people with
phenylketonuria (PKU)
Aspartame
(NutraSweet)
FDA recommended limits 50 mg/kg
body weight/day in adults
=14 cans diet soft drink
80 packets Equal
Acesulfame-K (Sunette)
FDA approved 1988
200x sweeter than sucrose
Not digested by the body
Heat stable
Diabetisweet used in baking; gum,
Kool-Aid, puddings, gelatin, candy
Sucralose (Splenda)
FDA approved 1998
600x sweeter than sucrose
Substitute chlorines for hydroxyl groups
on sucrose
Heat stable
Tiny amount digested
Used in soft drinks, gum, baked goods,
frozen desserts, fruit drinks
Sweetener Function
Enhances flavor
Use in moderation
CHO Recommended
Intake
No RDA (yet)
Consume at least 50 gm to prevent
ketosis
National Cholesterol Education Program
recommends 50-60% of kcal from CHO
Current intake is ~50%
Recommended Fiber Intake
Choose fiber-rich fruits, vegetables, and
whole grains often (2005 US Dietary
Guidelines)
Adults ≤50 years 38 grams (men) and 25
grams (women). Adults >50 who eat less
food, 30 grams (men); 21 grams (women).
(U.S. DRIs)
Children >1 years: AI’s range from 19 g (age
1-3) 25 g (4-8); adolescent boys 31-38 g;
adolescent girls 26 g
The Average American eats 14-15 grams of
fiber a day
Recommended Dietary
Fiber Intake
20-35 gm of fiber/day (10-13 gm/1000 kcals)
Children: age +5gm/day
Ave. U.S. intake: ~16 gm/day
Too much fiber (>60 gm/d) will:




require extra intake of fluid
bind to some minerals
develop phytobezoars
fills the stomach of a young child quickly
Recommendation for
Simple Sugar Intake
Low nutrient density
Displaces other foods
Recommends no more than 10% of
total kcal/day
Ave. U.S. intake: 16% of total kcal/day
Added to food and beverages
during processing
Names for Added Sugars that
Appear on Food Labels
Major Sources of Added Sugar
(Caloric Sweeteners)
in the American Diet
Sugar and ADD/ADHD
There is no evidence that sugar is a
cause of ADD/ADHD or exacerbates
symptoms
U.S. Dietary Guidelines
Choose and prepare foods
and beverages with little
added sugars or caloric
sweeteners
Reduce the incidence of
dental caries by practicing
good oral hygiene and
consuming sugar and starchcontaining foods and
beverages less frequently
Glycemic Index
The blood glucose response of a given
food compared to a standard (typically
glucose or white bread)
Glycemic Index
The concept of Glycemic Index has
been highlighted in popular diet books
Sugar Busters
 The South Beach Diet

Glycemic Index
Influenced by various factors
Starch structure
Fiber content
Cooking methods
Degree of processing
Whether it is eaten in the context of a meal
Presence or absence of fat
A given food can elicit highly variable
responses
Glycemic Index of
Selected Foods
Food
Brown rice
White long grain rice
GI
55
56
White short grain rice
Spaghetti
Whole Wheat bread
72
41
69
White bread
Sucrose
Carrots
70
65
49
Potatoes, mashed
73-83
Wardlaw. Contemporary Nutrition, p. 134
Glycemic Index
Epidemiological studies suggest that high
glycemic index diets are associated with
health consequences such as increased risk
for diabetes
However, the American Diabetes Association
states the total amount of CHO is more
important than the GI
Combining low GI foods with high GI foods at
meals will reduce blood glucose response
Functions of CHO
Provide energy
4 kcals/gram
 Brain, nerves, red blood cells
 With low cho intake, proteins converted to
glucose

Protein-sparing

~100 g CHO/day
Functions of CHO
Source of fiber
Indigestible plant cells
 Health benefits

Adds flavor, texture, color

Makes food appetizing
Needed for proper fat metabolism

Avoid ketosis
Functions of
Carbohydrate
Supplies energy
Protein sparing
Prevent ketosis
Sweetener