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Chapter 2

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Introduction
Source of carbohydrates
Types of carbohydrates and metabolism:
◦ Simple
◦ Complex
◦ Fiber

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A carbohydrate is an organic compound with the
formula C6H12O6
Carbohydrates, proteins, and fats supply 90% of
the dry weight of the diet and 100% of its energy
...


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These nutrients also differ in how quickly they
supply energy
...


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carbohydrates are broken down into sugars,
proteins into amino acids,
fats into fatty acids and glycerol
...

Milk and milk products are the only foods derived
from animals that contain a significant amount of
carbohydrates
Sugars are found in jams, soft drinks, and milk, while
starches are found in cereals, breads, and
vegetables
...
Monosaccharides

2
...
sucrose = glucose + fructose
2
...
maltose = glucose + glucose

Amylose

Simple
Carbohydrates
(Sugars)

1
...
fructose
3
...

Contains about 6000 glucose residues

1
...
Delays absorption of sugar
3
...
Decreases transit time

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Simple carbohydrates, sometimes called
simple sugars, include:
◦
◦
◦
◦

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fructose (fruit sugar),
sucrose (table sugar),
lactose (milk sugar),
as well as several other sugars
...
C
...

They quickly increase the level of blood
glucose (blood sugar)
...

Fruits are one of the richest natural sources
of simple carbohydrates
...

Complex

carbohydrates

Starches

Amylose

fiber

Amylopectin

Soluble

Insoluble

Complex carbohydrates must be broken down into
simple carbohydrates before they can be absorbed

They tend to provide energy to the body more
slowly than simple carbohydrates but still more
quickly than protein or fat
...


They increase blood sugar levels more slowly and to
lower levels than simple CHO but for a longer time

Figure 3-11 p78

Figure 3-11a p78

Figure 3-11b p78

Table 3-03a p79

Table 3-03b p79

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Complex carbohydrates include starches and
fibers, which occur in wheat products (such
as breads and pastas), other grains (such as
corn), beans, and root vegetables (such as
potatoes)
...

Except for fiber, which cannot be digested,
both simple and complex carbohydrates are
converted into glucose
Glucose is a major fuel for all of the body's
cells and the only source of energy for the
brain and red blood cells
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If people consume more carbohydrates than they
need at the time, the body stores some of these
carbohydrates within cells (as glycogen) through a
process called Glycogenesis and converts the rest to
fat
...

◦ is stored in the liver and the muscles
...

◦ The amount of carbohydrates stored as glycogen can
provide almost a day's worth of calories
...


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Fiber : is a tough complex carbohydrate
...

◦ Or insoluble: It does not dissolve in water, and the body
cannot digest it
...
Meat and dairy
foods do not contain fiber
...

Only a relatively small amount of fiber is
digested or metabolized in the stomach or
intestines
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1
...


3
...

A high-fiber diet also reduces the risk of colon
cancer, perhaps by speeding the rate at which stool
passes through the intestine and by keeping the
digestive tract clean
...
In this way, a high-fiber diet helps lower
blood cholesterol levels, reducing the risk of heart
disease
...
It is made up of a number of complex
carbohydrates called non-starch polysaccharides
(NSP)
...

Dietary fibre cannot be broken down by digestive
enzymes, although micro-organisms that line the
large intestine are able to digest some of the dietary
fibre
...

Foods such as meat, fish and dairy products do not
contain any dietary fibre
...

This type of dietary fibre has also been thought to
slow down the digestion of carbohydrate in sugars
and starches, which results in better glucose
metabolism
...


Insoluble dietary fibre binds with water in the intestine
and helps remove waste from the body
...

Some researchers suggest it may also help prevent
haemorrhoids (piles), diverticular disease, polyps and
cancer of the colon or large intestine
...
g
...


Adults should aim for an intake of around 18 grams a
day, or even a little more
...

Very high fibre intakes are not recommended because
there are some substances in dietary fibre, e
...
phytate
which can reduce the absorption of minerals from food
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Comparing Soluble and Insoluble Fiber
Type of Fiber

Sources

Functions

Soluble

Apples

Helps moderate the changes in blood sugar
and insulin levels that occur after eating a
meal

Barley
Beans
Citrus fruits
Lentils
Oat bran
Pectin (from fruit)

Helps reduce cholesterol levels
May reduce the risk of coronary artery
disease

Rice bran
Strawberries

Insoluble

Apples
Brown rice
Pears
Prunes

Many vegetables, including cabbage, root
vegetables, and zucchini
Whole grains and whole-grain breads and
pastas

Provides bulk to feces and thus helps food
move through the digestive tract,
preventing constipation
Helps eliminate cancer-causing substances
produced by the bacteria in the large
intestine
Reduces pressure in the intestine, helping
prevent diverticular disease
Is helpful in losing weight because the body
processes it slowly



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