What are Carbohydrates?

What Are Carbohydrates?
In a number of my previous articles I have stated that you should go for complex carbohydrates where possible and minimise your consumption of simple carbohydrates.  After thinking about this for some time I realised that I had never fully understood or explained the difference between the two.  That’s why today I am going to be discussing carbohydrates in greater detail.


Carbohydrates are one of three macronutrients with fats and protein being the other two.  They are made from a combination of carbon, hydrogen and oxygen hence the name ‘carbo’ (meaning carbon) ‘hydrate’ (meaning water which is made from hydrogen and oxygen).  Carbohydrates are your body’s primary energy source.  If they are not needed a small amount can be stored in the liver and muscles as glycogen and the rest is stored as fat.


Simple carbohydrates (also known as simple sugars) are chemically made of one or two sugars.  There are two main types:

1) MONOSACCHARIDES:- These are the simplest type of sugar hence the name ‘mono’ (meaning one) and ‘saccharide’ (meaning sugar).  Monosaccharides are used to form more complex carbohydrates and there are three different types:
– Fructose:- This is often referred to as fruit sugar because it is found naturally in many fruits and honey (often in combination with glucose).
– Galactose:- This is formed when lactose (a disaccharide discussed below) is broken down during digestion.
– Glucose:- This is often referred to as blood sugar because it is the main carbohydrate that travels through the bloodstream.  It is found naturally in fruits, vegetables and honey.

2) DISACCHARIDES:- These are made of two monosaccharide units that are linked together hence the name ‘di’ (meaning two) and ‘saccharide’ (meaning sugar).  There are many types of disaccharide and some of the most common are listed below:
– Lacctose (Glucose + Galactose):- This is often referred to as milk sugar.
– Maltose:- (Glucose + Glucose):- This is often referred to as malt sugar.
– Sucrose (Glucose and Fructose):- This is often referred to as table sugar or cane sugar.


Complex carbohydrates are chemically made of three or more chemically linked sugars.  There are again two main types:

1) OLIGOSACCHARIDES:- These are made from a few monosaccharide units that are linked together (usually between three and ten) hence the name ‘oligo (meaning few) and ‘saccharide’ (meaning sugar).  Oligosaccharides are found in various plant foods including onions and wheat.  The human digestive system struggles to break down this type of carbohydrate with 90% not being digested in the small intestine.

Apart from being a carbohydrate, oligosaccharides also act as prebiotics meaning that they support the growth of various bacteria in the large intestine (colon).  These bacteria have a number of health benefits.  For starters they are believed to produce a number of short chain fatty acids (SCFA) and small amounts some of the B complex vitamins.  They are also thought to promote further absorption of certain minerals.

2) POLYSACCHARIDES:- These are made from longer chains of monosaccharides or disaccharides that are linked together hence the name ‘poly’ (meaning more than one) and ‘saccharide’ (meaning sugar).  Although they are made from simple sugars they do not taste sweet.  There are four main main types of polysaccharide:
– Starch:- This is the stored form of carbohydrate in plants.  It can be further broken down in to rapidly digesting starch (RDS) which breaks down in to simple sugars quickly, slow digesting starch (SDS) which breaks down in to simple sugars over a longer period of time and resistant starch which passes through the small intestine and reaches the large intestine (colon) without being broken down in to simple sugars at all.  The speed at which starch is digested also depends on other factors including how processed the food is (processing generally does the same job that our digestive system would do so the more processed a food is the easier it becomes to digest), the starch structure (the arrangement of the sugar molecules that make up the starch affect how easy it is to digest) and how the starch is cooked (cooking time of pasta is believed to affect how easy it is to digest).
– Glycogen:- This is the stored form of carbohydrate in humans and animals.
– Cellulose:- An indigestible form of carbohydrate that comes from the cell walls of plants.  It is better known as dietary fibre.
– Dextrin:- This is produced when long chains of starch are digested and broken down in to shorter chains.


As I mentioned above carbohydrates are your body’s primary choice when it comes to getting energy.  When you eat carbohydrates they are broken down in your digestive tract and then released into the blood as glucose which causes blood glucose levels to rise.  The rate and speed at which they rise depends upon the type of carbohydrate ingested.  Eating simple sugars or RDS causes glucose levels to increase rapidly whilst eating SDS causes sugar to be released in to the blood in a more controlled way and keeps glucose levels stable.

When your blood sugar levels rise your pancreas releases insulin, a hormone that helps your cells take glucose from the blood and either use it for energy, store it as glycogen or store it as fat.  As your body’s cells take glucose from the blood and your blood sugar levels become low your pancreas stops releasing insulin and starts releasing glucagon.  Glucagon is a hormone that helps your liver convert stored glycogen back in to glucose and release it in to the bloodstream.

If your glycogen stores become depleted your body can then convert protein and fat in to glucose through a process called gluconeogenesis.  However, this is a much more complicated and inefficient process.  On top of this fat’s primary function is to help protect the cells and vital organs whilst protein’s primary function is to help repair and build them.  If your body uses these macronutrients for energy then they cannot perform their intended functions properly.  For these reasons carbohydrates are your body’s preferred energy source.


So far I have explained the different types of carbohydrate and also how your body uses carbohydrates.  With the exception of fibre, oligosaccharides and resistant starch all carbohydrates end up being broken down in to sugar (glucose) which then provides your body’s cells with energy.  So if they all end up as sugar why should you worry about which type of carbohydrate you consume?

Well although all carbohydrates eventually become sugars some are digested a lot more quickly than others.  Carbohydrates that are easy to digest are released in to the blood rapidly and cause a quick surge in glucose levels.  Your body responds to this surge by releasing additional insulin which then causes your glucose levels to crash.  This can result in fluctuating energy levels, increased fat storage, poor appetite control and in the worst cases damage to your vital organs.  Constrastingly, carbohydrates that are more difficult to digest are released in to the blood slowly which means glucose levels remain relatively stable and the above problems are avoided.

Also certain carbohydrate sources are more nutritionally dense than others.  For example, table sugar provides you with carbohydrates and not much else.  However, a fruit or vegetable provides you with carbohydrates, fibre and vitamins meaning that you get much more nutritional value from a 100 calorie piece of fruit than you would from 100 calories of table sugar.  Therefore, slow digesting, nutritionally dense carbohydrates are the best choice for your body.


In the past I referred to complex carbohydrates as those that were high in fibre, rich in vitamins and minerals and more difficult to digest.  However, after researching and writing this article I realise that this was a mistake.  Whilst this definition is true of some complex carbohydrates it is not true of them all.  All carbohydrates (with the exception of fibre, some oligosaccharides and resistant starch) are essentially sugars.  Some complex carbohydrates actually break down more quickly than simple carbohydrates.  Instead of looking at simple and complex carbohydrates we should instead be looking to consume carbohydrates that digest slowly and are rich in fibre, vitamins, minerals and other nutrients.

In my next few articles I am going to be discussing some of methods you can use to choose the best carbohydrate sources.  Until then I hope that this article has given you a good understanding of the different kinds of carbohydrates and cleared up the confusion surrounding simple and complex carbohydrates.

Now I want to hear from you guys.  Do you agree with what I have said about carbohydrates?  Are you currently consuming the right type of carbohydrates?  Let me know by leaving a comment.

Carbohydrate Basics (How Stuff Works)
Understanding Carbohydrates (About.com)
What’s the Difference between Simple and Complex Carbohydrates? (About.com)

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  1. Stu says


    I just read your article after seeing it linked from GohealthGoFit.com

    I was a little aprehensive when I saw you start with the old simple/complex descriptions. That would have a piece of white bread preferred over an apple simply because it contains complex carbs. It’s with great relief that I see you’ve correct that view.

    I have to admit that I’m predisposed to a paleo approach to carbs. In any case I look forward to your future expolorations on carbs.


    Tom Reply:

    Thanks for the comments Stu. Glad you liked the article. Although I am not completely against carbohydrates as some other fitness blogs seem to be, I have considerably reduced my intake of carbs since reading more and more about healthy eating. My opinion on carbohydrates at the moment is that most people do eat too many carbs and very often eat poor quality carbs. Therefore, most people could do with reducing their carbohydrate intake and making more sensible carbohydrate choices. However, I still haven’t decided what I think the optimal level of carbohydrates is in my diet.

    I think in the end people are always going to have different opinions on carbohydrates, just as they do with protein and fat. My goals is to try and present all the facts and information through these blog posts and then come to a conclusion based on these.


  2. Scott N says

    Hey Tom quick question Insulin stores glucose in the muscles as glycogen, then starts releasing glucagon to change glycogen to glucose. Okay now with the glucose in your bloodstream, where does it go now? From what Ive read your body doesn’t want glucose in the blood stream as it sees it as a sort of toxic sludge. It has to go somewhere after that, but where?

    Thanks in advance.


  3. says

    Timothy – Thanks for your comments. Always great to receive positive feedback.

    Scott – Your body doesn’t want too much glucose in the blood as this can cause long term damage to your organs, veins, arteries and nerves. However, it still needs some glucose in the bood so that your cells can use it for energy.

    When your blood sugar levels become too low your body releases glucagon to convert stored glycogen into glucose. This glucose is then released into the bloodstream and used for energy by the cells that need it. Hope this makes it a little clearer.


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