Download Unit 1/Carbohydrates Fall 2011.pdf

Carbohydrates
© 2009 Cengage - Wadsworth
The Chemist’s View of Carbohydrates
 Carbohydrates are made of carbon, hydrogen
and oxygen atoms.
 These atoms form chemical bonds that follow
the laws of nature.
 The chemical formula for carbohydrates are
similar, Cn(H2O)n
 In other words, for every carbon, there is a molecule
of water, hence the name “carbo-hydrates” or
“hydrated carbons”
© 2009 Cengage - Wadsworth
Common Carbohydrates in Human
Nutrition
Sucrose (table
sugar)
glucose
fructose
Lactose (milk
sugar)
Maltose
glucose
Glucose
Galactose
Glucose
Oligo/
Polysaccharides;
Starch and
Glycogen
Glucose
Fiber
Soluble
(fermentable)
Insoluble
Two Monosaccharides:
Glucose and Fructose
© 2009 Cengage - Wadsworth
Two Monosaccharides:
Glucose & Galactose
© 2009 Cengage - Wadsworth
The Simple Carbohydrates
 Disaccharides
 Maltose consists of two glucose units. It is
produced during the germination of seeds
and fermentation.
 Sucrose is fructose and glucose combined. It
is refined from sugarcane and sugar beets,
tastes sweet, and is readily available.
 Lactose is galactose and glucose combined.
It is found in milk and milk products.
© 2009 Cengage - Wadsworth
The Complex Carbohydrates
 Few (oligo-) or many (poly-) saccharides
 Multiple glucose units linked together in straight or
branched chains.
 Glycogen (carbohydrate storage in animals)
 Storage form of glucose in the body
 Provides a rapid release of energy when needed
 Starches
 Storage form of glucose in plants
 Found in grains, tubers, and legumes
© 2009 Cengage - Wadsworth
The Complex Carbohydrates
 Dietary fibers provide structure in plants, are
very diverse, and cannot be broken down by
human enzymes.
 Soluble fibers are viscous and can be digested by
intestinal bacteria (fermentable). These fibers are
found in fruits and vegetables.
 Insoluble fibers are nonviscous and are not digested
by intestinal bacteria. These fibers are found in
grains and vegetables.
© 2009 Cengage - Wadsworth
© 2009 Cengage - Wadsworth
The Complex Carbohydrates
 Fiber Sources
 Dietary fibers are found in plant foods.
 Functional fibers are health-benefiting fibers that
are added to foods or supplements.
 Total fiber considers both dietary and functional
fibers.
 Resistant starch is starch that escapes digestion
in the small intestine and that may be
fermented in the large intestine.
© 2009 Cengage - Wadsworth
The Complex Carbohydrates
 Resistant Starch
 Starches physically inaccessible to digestive
enzymes: partly milled grains & seeds
 Starch resistant to digestion due to the nature of the
starch granule: raw potato, unripe banana, some
legumes and high amylose starches (e.g., high
amylose corn)
 Starch that forms from retrograded amylose &
amylopectin during food processing: e.g. potatoes,
bread, cornflakes
 Starch produced by chemical modification
Glucose in the Body
 Primary role
 Energy
 Red blood cells and cells of the nervous system
require glucose for energy
 Other Roles
 Glycoproteins (e.g. intrinsic factor)
 Glycolipids
© 2006 Thomson-Wadsworth
Glucose in the Body
 The body stores glucose as glycogen in liver
and muscle cells.
 The body uses glucose for energy if glycogen
stores are available.
© 2009 Cengage - Wadsworth
Glucose in the Body
 If glycogen stores are depleted, the body
makes glucose from protein.
 Gluconeogenesis is the conversion of protein
to glucose.
 Protein-sparing action is having adequate
carbohydrate in the diet to prevent the
breakdown of protein for energy.
 Body fat is metabolized more efficiently
when some carbohydrate is available
© 2009 Cengage - Wadsworth
Glucose in the Body
 In fasting, starvation or situations of
carbohydrate depletion, the body can obtain
energy by mobilizing fat stores.
 In the absence of carbohydrate, however this
can lead to a condition known as “ketosis”.
 The body can use glucose to make body fat
when carbohydrates are consumed
excessively.
© 2009 Cengage - Wadsworth
Glucose in the Body
 The Constancy of Blood Glucose
 The Regulating Hormones



Insulin moves glucose into the cells and helps to
lower blood sugar levels.
Glucagon brings glucose out of storage and raises
blood sugar levels.
Epinephrine acts quickly to bring glucose out of
storage during times of stress.
 Blood glucose can fall outside the normal range
with hypoglycemia or diabetes.
© 2009 Cengage - Wadsworth
Glucose in the Body
 The Constancy of Blood Glucose
 Maintaining Glucose Homeostasis



Low blood glucose may cause dizziness and weakness.
High blood glucose may cause fatigue.
Extreme fluctuations can be fatal.
 Normal blood glucose levels (fasting)

70-100 mg/dl
© 2009 Cengage - Wadsworth
Maintaining
Blood
Glucose
Homeostasis
© 2009 Cengage - Wadsworth
Glucose in the Body
 Diabetes
 Type 1 diabetes is the less common type with
no insulin produced by the body.
 Type 2 diabetes is the more common type
where fat cells resist insulin.
 Prediabetes is blood glucose that is higher
than normal but below the diagnosis of
diabetes.
 Hypoglycemia is low blood glucose and can
often be controlled by dietary changes.
© 2009 Cengage - Wadsworth
Health Effects and
Recommended Intakes of Sugars
 Dental caries
 Caused by bacteria residing in dental plaque
 Bacteria ferment the sugars from food and
the breakdown of starches in the mouth,
producing an acid that erodes tooth enamel

Factors involved
 Length of time sugars are in contact with the
teeth.
 Stickiness of the sugar-containing food
© 2009 Cengage - Wadsworth
Health Effects and
Recommended Intakes of Sugars
 Excessive sugar intake can contribute to the
development of body fat by adding to
excess kcalorie intake.
 Sugar may be able to alter blood lipid
levels and contribute to heart disease in
some.
 E.g. a high intake of simple carbohydrates is
associated with elevations of blood triglycerides
© 2009 Cengage - Wadsworth
Health Effects and
Recommended Intakes of Sugars
 Excessive intakes of sugar may displace nutrients
and contribute to obesity.
 “Natural” does not always mean nutritious. (e.g.,
honey)
 Foods with added sugars are part of discretionary
kcalories
 Foods with added sugars have sugars listed as a first
ingredient.
 Naturally occurring sugars from fruits, vegetables
and milk are acceptable sources.
© 2009 Cengage - Wadsworth
Health Effects and
Recommended Intakes of Sugars
 There is no scientific evidence that sugar causes
misbehavior in children and criminal behavior in
adults.
 Sugar consumption per se does not cause diabetes.
© 2009 Cengage - Wadsworth
Health Effects and
Recommended Intakes of Sugars
 Recommended Intakes of Sugars
 The USDA Food Guide states that added sugars
can be included in the diet as part of
discretionary kcalories.
 Dietary Guidelines for Americans 2010:

Limit SoFAS (Solid Fats and Added Sugars)
 DRI suggest added sugars should contribute no
more than 25% of a day’s total energy intake.
© 2009 Cengage - Wadsworth
Look for these ingredients as added
sugars on food labels
 Brown sugar
 Invert sugar
 Corn sweetener
 Lactose
 Corn syrup
 Maltose
 Dextrose
 Malt syrup
 Fructose
 Molasses
 Fruit juice concentrate
 Raw sugar
 Glucose
 Sucrose
 High-fructose corn syrup
 Sugar
 Honey
 Syrup
© 2009 Cengage - Wadsworth
Health Effects and Recommended
Intakes of Starch and Fibers
 Health Effects of Starch and Fibers
 May be some protection from heart disease and
stroke


Soluble fibers bind with and increase excretion of
bile. Since bile is made from cholesterol, the body
must use its cholesterol stores to make new bile
acids. As a result, blood cholesterol levels are
decreased.
Fiber may also displace fat in the diet.
© 2009 Cengage - Wadsworth
Health Effects and Recommended
Intakes of Starch and Fibers
 Reduce the risk of type 2 diabetes by decreasing
glucose absorption
 Enhance the health of the GI tract which can then
block the absorption of unwanted particles
 May protect against colon cancer by removing
potential cancer-causing agents from the body
© 2009 Cengage - Wadsworth
Dietary Fiber
Soluble Fiber
Insoluble Fiber
 Oatmeal
 Whole wheat bread
 Oat bran
 Barley
 Nuts & seeds
 Brown rice
 Most fruit (e.g.,
 Couscous
strawberries, blueberries,
pear, apples)
 Dry beans & peas
 Bulgur or whole grain




© 2009 Cengage - Wadsworth
cereals
Wheat bran
Seeds
Most vegetables
Fruits
Health Effects and Recommended Intakes of
Starch and Fibers
 Promote weight control
 Complex carbohydrates provide less fat and
added sugar.
 High fiber increases viscosity of GI contents &
results in slower transit time (greater time in
contact with satiety receptors)
© 2009 Cengage - Wadsworth
Health Effects and Recommended
Intakes of Starch and Fibers
 Recommended Intakes of Starch and Fibers
 RDA for carbohydrate is 130 g per day
 AMDR for carbohydrate is 45-65% of total
kcalories
 Dietary Guidelines for Americans 2010
encourage a variety of whole grains,
vegetables, fruits and legumes daily.
© 2009 Cengage - Wadsworth
Health Effects and Recommended
Intakes of Starch and Fibers
 Recommended Intakes of Fiber
 FDA: 25 grams for a 2,000-kcalorie diet.
 DRI: 14 g per 1000 kcalorie intake (28 grams for a
2,000 kcalorie diet)
 American Dietetic Association: 20-35 g per day.
 World Health Organization suggests no more
than 40 g per day.
© 2009 Cengage - Wadsworth
Health Effects and Recommended
Intakes of Starch and Fibers
 Harmful effects of excessive fiber intake
Displaces energy and nutrient-dense foods
 Abdominal discomfort and distention
 May interfere with nutrient absorption

© 2009 Cengage - Wadsworth
© 2009 Cengage - Wadsworth
Comparison
of Bread
Labels
© 2009 Cengage - Wadsworth
Voluntary Whole Grain Stamps from
the Whole Grain Council
 Whole grain stamp – for products offering ½ serving
or more of whole grain
 100% whole grain stamp – for products where ALL of
the grain is whole grain
 http://www.wholegrainscouncil.org