What are complex Carbohydrates & simple Carbohydrates?

Carbohydrates are one of the 3 macro-nutrients which make up the majority of our diet, and are the most consumed of the macro-nutrients in the Western world, and they...

Carbohydrates are one of the 3 macro-nutrients which make up the majority of our diet, and are the most consumed of the macro-nutrients in the Western world, and they can are found in a variety of foods such as grains, fruits, vegetables and dairy. This article will explain what carbohydrates are, explore the differences between types of carbohydrates and investigate the effects of carbohydrates on our health.


The basics of carbohydrates

All carbohydrates are made up of chains of  single units called saccharides (sugars). These chain lengths can vary from one or two of these molecules to hundreds. Small chains of one or two saccharides (called monosaccharides or disaccharides) are often referred to as sugars or simple carbohydrates, whereas longer chains (called polysaccharides) are known as complex carbohydrates or fibre.

Carbohydrates fulfil fewer roles in the body than the other two macro-nutrients (proteins and fats), and are primarily used for a source of energy in the body, and are readily converted into ATP (usable energy) by our cells.


Common monosaccherides

There are 3 common naturally occurring monosaccherides which we can obtain through our diet:


Glucose is produced by plants, and is the most commonly consumed and well recognised sugar molecule in the western world. It is readily absorbed by the digestive system into the blood stream, and all cells in the body are able to convert glucose into energy.

If large amounts of glucose are consumed, it will be rapidly absorbed, and our blood sugar levels will increase above a desired level, causing insulin to be produced. This causes cells in the liver and muscles to convert glucose into glycogen, which is simply long chains of sugar molecules bonded together. This acts as a medium-long term storage for glucose, and when blood glucose levels start to deplete, our body will break down glycogen back into glucose – providing energy for our cells. This allows us to maintain even energy levels.

If large amounts of glucose are regularly consumed and glycogen stores in our muscles and liver are full, excess glucose will be stored as fat, which is an even longer term store of energy for sugars. Regular consumption of large amounts of glucose can also cause our cells in our body to become resistant to the effects of insulin, which if not remedied, can result in the development of type 2 diabetes.


Fructose is also very commonly consumed and recognised in the Western world, and is often found alongside glucose in foods. Fructose is also very easily absorbed by the digestive system, but only the cells in the liver are able to utilize fructose as a source of energy.

Any fructose consumed will be stored in the liver as glycogen, which can quickly fill up the glycogen holding potential of the liver. Fructose does not stimulate an insulin response by the body, and does not have an immediate effect on the energy levels in the body. However, because fructose is stored in the liver as glycogen, there is less storage capacity throughout the body for other moosaccherieds such as glucose, which will increase the risk of developing fat cells and also increases the risk of developing type 2 diabetes.


Galactose is the least well recognised of the 3 monosaccherides, and is not as abundant in our diets as the previous two. Galactose can be found primarily in dairy, and is significantly less sweet than glucose or fructose.

Research on galactose is limited, but it fulfils more roles in the body than just providing energy. Galactose has been shown to be critical in the communication between cells, especially the immune cells, and it is needed for optimal immune support. There is also evidence that galactose can inhibit the growth of tumours (which may be a result of its immune-supportive properties) and can protect against Alzheimer’s disease. Galactose can also be converted into glucose in the body, and used as a source of energy in our cells.


Common disaccherides

Disaccherides are 2 types of monosaccherides bonded together. There are a number of variations of disaccheriedes, but the most abundant in our diet are explained bellow:


Sucrose is made up of glucose and fructose, and is commonly recognised as table sugar. This form of sugar is most abundant in our diet, and it is very quickly absorbed in our digestive system.  When sucrose is consumed it is broken down into glucose and fructose very quickly, and the two molecules are absorbed just as quick if they were consumed separately. Regular consumption of sucrose alongside inactivity is associated with weight gain and type 2 diabetes.


Maltose is made up of two glucose molecules bonded together and is derived from cereals. Its break down into two glucose molecules also happens very quickly in the digestive system, and consumption of maltose has a similar effect on the body as just consuming glucose. As with sucrose, consumption of maltose alongside inactivity is associated with weight gain and type 2 diabetes.


Lactose is made up of a glucose and galactose molecule, and is the least abundant of the 3 discussed disaccharides on our diet. It is derived from milk and dairy, and the two molecules are easily broken apart and quickly absorbed.

Polysaccherides/ complex carbohydrates

Polysacherides are long chains of the mentioned monosaccherides in any combination and are often bonded to other molecules such as amino acids. Complex carbohydrates can typically be split into 2 categories: digestible/soluble fibre or indigestible/insoluble fibre:

Digestible/ soluble fibre:

This type of complex carbohydrate can be broken down by enzymes into smaller units, and ultimately disaccherides and monosaccherides, which can then be absorbed through the digestive system. Break down of soluble fibre can take a long period of time, and monosaccherides are steadily released over this time, which effectively ‘drip feeds’ our body with energy. This causes very little insulin to be produced, and is a much more preferable source of sugars than simple carbohydrates. For this reason soluble fibre can help prevent the development of type 2 diabetes and can help control weight gain. Soluble fibre also absorbs water, which slows down digestion and stomach emptying, which prolongs the feeling of satiety after a meal.

Indigestible/ insoluble fibre:

This type of complex carbohydrate cannot be broken down by enzymes, and passes through the digestive system relatively intact. Some insoluble fibre can be fermented in the gut, and broken down by our resident microflora, but the majority cannot. This type of fibre aids with the passage of food and waste through the digestive system, and helps prevent constipation. Insoluble fibre can also help lower circulating LDL cholesterol in the blood.



Due to the rapid absorption of simple sugars (monosaccherides and disaccherides) and the resulting negative effects on our health, consumption should be minimised unless you regularly partake in exercise which demands large amounts of energy.

Complex carbohydrates are a preferred source of energy for the body, and slowly release energy over an extended period of time – avoiding insulin spikes and minimising the risk of diabetes and weight gain, and assisting with the passage of food and waste through the digestive system.

I hope you enjoy the site, and like what we have worked hard to create, any feedback is very much welcome, after all this site is for you! Graduate of Nutrition & Food Science (Bsc) at Reading Uni.

    The Health Cloud was created in December 2011 by Craig and Morg who have been friends since high school. Our focus is to educate our readers with unbiased health articles and on the side we run our own online health shop. This website is for you, so drop us a comment or send us a tweet, we always take the time to reply!