How do carbohydrates work?

We hear about carbohydrates in the news constantly -- the complex carbs are supposed to be better than the simple ones, but why? In fact, what exactly is a carbohydrate? Listen in and learn more in this podcast.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house Stuff works dot com where
smart happens. Hi. I'm Marshall Brain with today's question, how
do carbohydrates work and why do we hear about them
all the time? In the news? Carbohydrates are something we

(00:21):
hear about constantly in American culture. There are simple carbohydrates
and complex carbohydrates, where complex carbohydrates are supposed to be
better for your health than the simple ones. There are
low carb diets like the Atkins diet or the Ducan diet,
and they're supposed to help you lose lots of weight
by somehow eliminating the bad effects of carbohydrates. Then there's

(00:44):
the more esoteric things like the glycemic index of foods,
and this has to do with carbohydrates as well. Let's
take a look at how carbohydrates work and why you
should care about them. You've probably heard of things like
glucose and pctoes. These are the simplest carbohydrates. They are
molecules containing six carbon atoms, six oxygen atoms, and twelve

(01:08):
hydrogen atoms, and this is where the name carbohydrate comes from.
Carbo represents the carbon atoms, while the oxygen and hydrogen
atoms represent water or hydrates. Plants make carbohydrates from sunlight,
and animals eat the plants. Pure glucose or pure fructose,
being the simplest carbohydrates, can be immediately absorbed by the

(01:32):
small intestine into the bloodstream. Table sugar or sucrose is
a die sacc ride. One glucose and one fructose molecule
are bonded together to make a molecule of sucrose. And
enzyme in your small intestine can break the pair apart
and then they can be immediately absorbed in your small
intestine and they enter the bloodstream. A starch, like the

(01:55):
starch found in wheat or potatoes or rice, is a
longer chain of glucose molecules connected together. Your body has
enzymes that can break apart the chain into individual glucose
molecules for absorption. Starch molecules are known as complex carbohydrates,
and this is where the idea of the glycemic index
comes from. In general, things like glucose and table sugar

(02:19):
come into your body and enter the bloodstream very very quickly.
They have a high glycemic index and cause a spike
in the amount of glucose in your bloodstream. White bread,
because the wheat is so highly processed, also has a
high glycemic index. Whole grains, beans, nuts, and vegetables do
contain carbohydrates, but these carbohydrate chains take much longer to

(02:43):
break down in the small intestine, so the glucose from
these foods enters the bloodstream much more slowly and evenly.
These foods have a low glycemic index and therefore are
much healthier because they don't cause such intense spikes in
blood sugar. Many diet it's are low carb diets. They
ask you to restrict the carbohydrates you eat. Why do

(03:05):
they do that? Keep in mind that what a typical
American diet looks like is things like a bowl of
cereal or a slice of pizza, or a can of ravioli,
or a bottle of soda, potato chips, packages of cookies,
bowls of ice cream. These are common foods in the
typical American diet. These foods typically contain something like forty

(03:28):
to fifty grams of carbohydrates per serving. Therefore, a typical
American eating a typical American diet can easily consume three
hundred grams of carbs per day or more without even
thinking about it. A lunch consisting of two slices of pizza,
chocolate chip cookie, and a big soda. That's two hundred
grams of carbs right there, and it all comes in

(03:51):
in just a few minutes. The surge of glucoast that
a meal like this pumps into the bloodstream requires your
body to use a lot of insulin to handle the spike.
Over the years, the spikes can cause type two diabetes,
where your body becomes resistant to the effects of the
insulin that your pancreas is putting into the bloodstream. In addition,
a meal like that contains a lot of calories, leading

(04:13):
to obesity over time, and that causes its own set
of health effects. A low carb diet restricts your carbohydrate intake,
say fifty grams of carbs per day rather than three hundred.
This restriction can decrease the spikes in blood sugar, which
tends to lower hunger pangs and reduce the calories you
consume per day. Will a low carb diet hurt you?

(04:35):
For example, you may know that your brain and nervous
system require glucose. If you take in no carbohydrates, will
your brain die No. Your body, when necessary can manufacture
its own carbohydrates in your liver through a process called
gluco neogenesis. This process is important if say, you're lost
in a forest with no food for three days, or

(04:58):
if you're fasting for some reason, or if you get
so sick that you can't eat for a few days,
or if you're living in an extremely cold climate and
meat is your only source of food. In all those cases,
there's no glucose coming in, so obviously your body has
to have a way to deal with it. Glucose is essential,
so your body is able to supply the glucose even

(05:19):
if you have no carbohydrates coming in through your food.
This whole thing is fascinating really. Carbohydrates are one source
of food energy, but there are all these different aspects
to it, and carb consumption can have a huge impact
on your overall health. The more you learn about carbohydrates,
the more interesting it gets. For more on this and

(05:41):
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