Carbohydrates – Simple or Complex, That is the Question


There is probably no greater debate today than the one over the role of Carbohydrates in our diets. The one man, whose name springs to mind when discussing this topic, is Dr Atkins of “The Atkins Diet” who popularised the No or Low carbohydrate weight loss programme. Because of his writings people worldwide have developed the erroneous belief that carbohydrates are inherently bad and should therefore be avoided. They have been blamed as the cause of all body fat and excess weight.

There are others who take the take the contrary view and say that ” you can’t go wrong with carbohydrates”.

So who is right ?

We now know that  carbohydrates , the staple of most diets, aren’t all good or all bad. Some kinds promote health while others if eaten often and in large quantities can increase the risk of developing diseases such as Diabetes and Coronary Heart Disease.

Carbohydrates are the body’s preferred fuel source. Carbohydrates are the only fuel source for many vital organs , including the brain, central nervous system and kidneys

What are Carbohydrates?

Carbohydrates are an important part of a healthy diet. They are found in a wide array of naturally occurring and prepared foods  such as bread, cereal grains, legumes, rice, corn, pasta, vegetables, fruit, milk, yoghurt, sugar, honey, biscuits, cakes, soft drinks and sweets. The most common and abundant forms are sugars , starches and fibres

Almost all the starches and sugars that humans burn for energy come from Plants; the only major exception is lactose,  the sugar in milk.

The basic building block of every carbohydrate is a sugar molecule, a simple union of carbon, hydrogen and oxygen.

Carbohydrates were once grouped into two main categories according to their chemical structure and digestibility:

Simple carbohydrates or sugars, can generally form crystals, dissolve in water and are easily digested. They  include naturally occurring sugars such as fruit sugar (Fructose ), corn or grape sugar (dextrose or glucose) and 2010-01-14_1527processed sugars, such as table sugar ( Sucrose ),brown sugar and molasses.

Complex carbohydrates include everything made of three or more linked sugars.They have a range of textures, flavours, colours and molecular structures. complex_carbohydrates1

These are further classified into Starches or Fibres. Starches and fibres are essentially chains of sugar molecules; some contain hundreds of sugars.

Our  digestive system deals with all carbohydrates in much the same way; it beaks them down ( or attempts to do so ) into single sugar molecules, because only these are small enough to pass from our stomach and intestines into the blood stream. Most digestible carbohydrates are converted into glucose ( often referred to as blood sugar ) because cells are designed to use this as a universal energy source.

Our digestive system however lacks the enzymes that are necessary to break down dietary fibre, including cellulose and other parts of the woody skeleton of plants so it passes through the body undigested. Dietary fibre is very important because is aids in proper colon function, thus reducing the incidence of constipation.

Fibre comes in two forms:

  • Soluble fibre which dissolves in water and binds to fatty substances in the intestines and carries them out as waste, thus lowering low density lipoprotein (LDL or bad cholesterol). It also helps regulate the body’s use of sugars, helping to keep hunger and blood sugar in check.
  • Insoluble fibre helps push food through the intestinal tract, promoting regularity and helping to prevent constipation. It may help prevent some types of cancer and other diseases

Carbohydrates our Energy Source

So how do we get energy from carbohydrates?  As we have discussed above, the digestive system breaks down carbohydrate containing foods into simple sugars, mainly glucose. These are absorbed from our intestine into our blood stream. As blood sugar levels rise, special cells in the pancreas secrete a hormone called Insulin that signals cells to absorb blood sugar for energy or storage. Any glucose that is not needed for immediate energy is converted into Glycogen, a large molecule composed of a chain of glucose units. This is stored in the liver and muscle tissue, ready to supplement the blood sugar levels should they drop between meals or during physical activity.

When this system does not work properly, people so affected can develop Diabetes (That’s a story for another day)

Today the emphasis has switched from the terms simple or complex carbohydrates to the concept of Glycaemic Index ( GI ). Carbohydrate containing foods are compared with glucose.Foods are rated on a scale, based on their effect on the blood sugar over a period of time, usually 2 hours. Foods that break down quickly during digestion and therefore cause a rapid rise in blood glucose, have the highest GI score.

For example , white bread, which breaks down rapidly, has a high glycaemic index. Foods  such as whole grain bread, oats, lentils, apples and yoghurt are digested more slowly and therefore result in a slower and more sustained change in blood sugar levels. Foods such as these have a low GI.

Foods with a score of 70 or above are high GI foods ,while those with a score of 50 or less are defined as low GI foods.

Categorising foods in this way makes much more sense. Diet can therefore be tailored to the needs of the individual

Vitalicious Natural Muffins-100 Delicious Calories

In  my next article I will discuss the role of  FATS in our diet

Doctor Bill

Acknowledgements:  Wikipedia :
Better Health Channel
Harvard School of Public Health