It is important to understand how
carbohydrates different one from another
to understand how they impact the
structure and taste of food and
ultimately our health.
The first step in setting
carbohydrates is learning the methods
for classifying them.
Unfortunately there are many terms and
it can lead to confusion.
We're going to look at the two most broadly used methods for classifying
carbohydrates, carbohydrates, and how
they relate to each others.
The first method is using chemical
terminology.
This is the clearest one if you know the
molecular structure of the carbohydrate
That's a big if, but we're going to start
there.
The smallest chemical unit considered a
carbohydrate is called a sugar. When
a molecule a carbohydrate composes of a
single sugar unit is called a
monosaccharide, with just means one sugar unit.
There are three common monosaccharides. There is fructose; there is glucose; and
there's galactose. Fructose would be
commonly found in fruit.
Glucose is also found in fruits and some
vegetables, but probably the cleanest
example of where you get glucose is corn
syrup. Corn syrup is composed naturally
of a hundred percent glucose. Galactose
is not commonly found in food by itself.
The next category carbohydrates using
chemical terminology is disaccharides.
Disaccharides are composed of two
monosaccharides, so two sugar units, that
are chemically linked together. For
example, we have sucrose. Sucrose is
formed by taking a glucose and fructose
molecule together and chemically link them
together to be a distinct molecule.
There are three common disaccharides the sucrose another is maltose and then lactose.
Sucrose is just a fancy name for
table sugar.
Maltose is not commonly found in foods, and then lactose is found in milk, and that's
in cow's milk, human milks, and
all milk made by mammals. It comes
from the same root word as lactating.
The last category of carbohydrates using
chemical terminology is polysaccharide
and that just stands for many sugar
units.
It's interesting to note that the sugar
units making up these large molecules
are all glucose. When we looked at each
one of those units is a glucose molecule
but how they are linked together
is that what makes one from the other. There are three major polysaccharides,
the starch, the fiber and then glycogen. If we look at the starch, starch is found
in foods such as breads and rice,
potatoes, legumes, beans.
Our bodies able to chemically break down
each one of those
so we end up those single glucose
molecules and then can absorb it.
If we look at fiber, it also has made a
single units linked together of
glucose.
But, in this instance we cannot break it
down. So we're going to take it
from that small intestines and it will
passed into that large intestines.
We would find that again in plants. We are going to find it in the structural part of
plants are the fruits and the vegetables
and the whole grains and legumes are
going to be rich in both starch and
fiber. The starch can be broken down to
those glucose molecules absorbed, the fiber can't be. The last category then is glycogen.
Glycogen is not found in our
foods, but it is found on our body.
We're going to find it specifically in
our liver and in our muscles.
So, we actually consume starch and fiber, but we have glycogen on our bodies
Knowing the chemical structure of
carbohydrate provides clues to how it
impacts foods and health.
Generally, those mono and disaccharides… these groups here… tend to be sweet
and polysaccharides are not. Although lactose is an
exception. It is disaccharide, but not
sweet.
And, if the carbohydrates is digested, such as those mono and disaccharides, and the starches
it provides four kcalories per gram. So,
it's helpful to know the chemical
structure and the corresponding chemical
terminology for classifying
carbohydrates.
However, most people do not know the
chemical structure of the carbohydrates they eat.
The more common terms used for classifying carbohydrates is common
terminology are going to be simple and
complex carbohydrates. Pretty much if
it's a mono or disaccharide, it is going
to be a simple carbohydrate and if it is
a polysaccharide, which are those starches and fibers found in our foods,
they're going to be complex carbohydrate.
It would be nice if we could just stop
there,
but the problem is too often with those
simple carbohydrates they are collectively
called "sugars." It is common to
believe that all sugars are unhealthy.
Yet, no one believes that fruits and milk,
which we find here fruits and our milk
which we find from the simple mono and
disaccharides, are unhealthy.
So, we have to subdivide it into
further categories. We divided into
the two categories of added sugar and
naturally occurring sugar. So, sugar made
by the food itself is considered
naturally occurring. We think about
the lactose in milk, you think about that
fructose in the fruits and some
vegetables, like tomatoes. But if you added to food, such as making
in soda pop, that would be
considered added sugar.
It is interesting to note, however, that
you can have the same molecule can be
considered a naturally occurring in
one food, but considered an added sugar
and another. For example here we again
have that lactose in milk and it's a
naturally occurring sugar, but we would
also see lactose over here on the
list of added sugars. The difference
is if you take that lactose out of milk
and you put it into its own little pile,
which we can do, and then you add it to
another food like bread, which is common
to do, it is now considered an added sugar.
So, defining added sugar sometimes can be confusing. The Food and Drug Administration,
which has the jurisdiction over nutrition food labels,
defines added sugars as sugar added
during the processing of the food, or
packaged as such, which include sugars as free and mono and disaccharides sugars
from syrups, such as
honey, which some people are sometimes
surprised to find it's an added sugar,
and also from the concentrated fruits
and vegetables if it's added in levels
that are higher than expected naturally.
Although current nutrition food labels
do not distinguish between added and
naturally occurring sugars, future nutrition food labels will be
required to provide that information. So, chemical terminology is one method for
categorizing carbohydrate and then we
have the more common terminology.
When studying carbohydrates, it is important to know how these two methods for classifying
carbohydrates work and how
they relate to each to the other.

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