Download Carbohydrates

Chapter Three
The
Carbohydrates:
Sugars, Starch
& Fiber
NUT SCI 242 Spring 05
© Karen Lacey, MS ,RD, CD
I. Carbohydrate Basics
Compounds composed of carbon,
hydrogen, and oxygen atoms.
 The primary role: energy source
– 4 cal/gram
 Ideal fuel for the body
 Two types:
– Simple
– Complex

II. Simple Carbohydrates

Structure:
–
–
A single sugar (Monosaccharide)
A pair of two sugars linked together
(Disaccharide)
6 carbons in ring form
 All are chemically similar to glucose and
can be converted into glucose

A. Monosaccharides
1.
2.
Glucose
 “blood sugar”
used for energy
 Found in fruits,
vegetables, honey
Fructose
 Sugar of fruits,
honey, maple &
corn syrup
Cont’d
3.
Galactose
 Part of milk
sugar
B. Disaccharides (double
sugars)

1.
Two sugar units
linked together
Sucrose
 Glucose +
Fructose
 Table Sugar
Cont’d
1.
2.
Lactose
 Glucose + Galactose
 Milk sugar
Maltose
 Glucose + Glucose
 Product of starch
breakdown

After eating sugar,
intestinal enzymes split
the double sugars into
single sugars.
C. Sugar & Health



Guidelines recommend limiting
sugar in the form of sweets to
less than 10% of calories.
Sugar is an “empty calorie” food.
Evidence on sugar
– Causes dental decay & gum
disease
– Low nutrient content
– Promotes and maintains
obesity
D. Keeping Sweetness in the
Diet




Read food labels for
clues on sugar content
Use less added sugar
Limit soda, surgary
cereals, candy
Choose fresh fruits or
those canned in water
or juice
III. Complex Carbohydrates
Long chains of sugars (glucoses)
arranged as starch or fiber
 Also called polysaccharides
 Two types

–
–
Starch
Fiber
A. Starch



A plant
polysaccharide
composed of
hundreds of glucose
molecules, digestible
by human beings
The storage form of
glucose in plants
Found in grains,
vegetables, legumes
B. Adding Whole Foods to the
Diet
A whole food is one that is altered as
little as possible from the plant or
animal tissue from which it was taken.
 Whole foods have a nutritional
advantage over their empty-calorie
processed forms.

Parts of a Wheat Kernel




Germ: the nutrient-rich and fat-dense inner
part of a whole grain
Endosperm: the bulk of the edible part of a
grain; contains starch & protein
Bran: the fibrous protective covering of a
whole grain & the chief source of fiber
Husk: the outer, inedible covering of a
grain
C. The Bread Box

Terms:
– Refined: the process by which the
coarse parts of food products are
removed
–
Enriched: the process by which the B
vitamins thiamin, riboflavin, niacin, folic
acid & the mineral iron are added to
refined grains & grain products at levels
specified by law
Cont’d
–
–
Fortified Foods: foods to which nutrients
have been added
 Commonly eaten foods are fortified
with nutrients such as iodine, vitamin
D or calcium to help prevent a nutrient
deficiency or to reduce the risk of
chronic disease
Whole grains: a grain that is not refined
D. Fiber




The indigestible residues of food,
composed mostly of polysaccharides
Yields few calories, if any
Helps support plant structure
Two types:
– Insoluble
– Soluble
Cont’d


Insoluble fiber
– Does not dissolve in water
– Cellulose, hemicellulose & lignin
Soluble fiber
– Either dissolves or swells in water
– Pectin, gums, mucilages & some
hemicelluloses
E. Health Effects of Fiber


Fiber in the diet is associated with several
diseases
– Digestive tract: Maintain health & function
– Cardiac: Helps control blood cholesterol
– Diabetes: Moderates blood glucose levels
– Cancer: Hinders action of cancer-causing
agents
– Obesity: May help prevent obesity
Different forms of fiber have different health
effects
Cont’d

TOO MUCH FIBER?
– No RDA; recommended is 20-35 grams
per day
– Too much fiber can:
 Cause dehydration
 Carry minerals out of the body
 Cause nutrient and energy deficiencies
from eating too much bulk in the
malnourished, elderly and children
F. Adding Fiber to Your Diet

Foods that are high
in fiber include:
– Plant foods
(especially those
with skins &
seeds)
– Whole grains
– Fruits
– Vegetables
IV. How the Body Handles
Carbohydrates
Maintaining blood glucose
levels
B. Hypoglycemia
C. Hyperglycemia (Diabetes)
A.
V. Alternatives to Sugar



Minimal or no calories
Many times sweeter than sugar
Current products:
– Saccharin
– Aspartame
– Sucralose
– Acesulfame