Carbohydrates are one of the main types of nutrients. They are the most important source of energy for your body. Your digestive system changes carbohydrates into glucose (blood sugar). Your body uses this sugar for energy for your cells, tissues and organs. It stores any extra sugar in your liver and muscles for when it is needed.

Carbohydrates are called simple or complex, depending on their chemical structure. Simple carbohydrates include sugars found naturally in foods such as fruits, vegetables, milk, and milk products. They also include sugars added during food processing and refining. Complex carbohydrates include whole grain breads and cereals, starchy vegetables and legumes. Many of the complex carbohydrates are good sources of fiber.

Carbohydrates often get a bad rap, especially when it comes to weight gain. But carbohydrates are not bad at all. Because of their numerous health benefits, carbohydrates have a rightful place in your diet. In fact, your body needs carbohydrates to function well. But some carbohydrates may be better for you than others. Understand more about carbohydrates and how to choose healthy carbohydrates. 



Understanding Carbohydrates

Carbohydrates are a type of macronutrient found in many foods and beverages. Most carbohydrates are naturally occurring in plant-based foods, such as grains. Food manufacturers also add carbohydrates to processed foods in the form of starch or added sugar. The most basic carbohydrate is a sugar molecule, which joins together one or two units of carbon, hydrogen and oxygen. Other carbohydrates contain three or more units of the carbon-hydrogen-oxygen trio.

Types of Carbohydrates

There are three main types of carbohydrates: 


Sugar. Sugar is the simplest forms of carbohydrates. Sugar occurs naturally in some foods, including fruits, vegetables, milk and milk products. Sugars include fruit sugar (fructose), table sugar (sucrose) and milk sugar (lactose).


Starch. Starch is made of sugar units bonded together. Starch occurs naturally in vegetables, grains, and cooked dry beans and peas.


Fiber. Fiber also is made of sugar units bonded together. Fruits, vegetables, whole grains, and cooked dry beans and peas are among foods that are naturally rich in fiber. 


Common sources of naturally occurring carbohydrates include:

  • Fruits 
  • Vegetables
  • Milk 
  • Nuts 
  • Grains 
  • Seeds 
  • Legumes

Carbohydrates and Digestion

During digestion of carbohydrates, energy (sugar) is released and passed into the blood stream from the digestive system. The speed at which this happens varies from different carbohydrates; some carbohydrates release sugars very quickly into the blood stream (fast release carbohydrates) and other release sugar very slowly into the blood stream (slow release

The fast releasing (simple) carbohydrates include;

Table sugar, honey, sweets and most refined foods like white flour, white rice, etc and dried fruit like raisins, dates, as well as bananas. These are not recommended and should be consumed in very low quantities.


The slow releasing (complex) carbohydrates include;

whole grains, vegetables and some fruits like plums, berries, papaya, apples and pears


Simple Carbohydrates (Fast releasing carbohydrates)

Eating fast releasing foods will give you a quick energy boost followed by an energy slump and can affect your blood sugar balance quite negatively. If people eat more fast releasing carbohydrates than they need, the balance will go into storage and deposit on the body as fat. Most fast releasing (refined) foods also have very little vitamins and minerals as they have been removed by the refining process. Without vitamins and minerals our digestion becomes inefficient and we end up tired, without energy and loose the ability to control our weight. Other health problems usually follow.


Complex carbohydrates (Slow releasing)

Eating slow releasing carbohydrates on the other hand will give you a more even energy level and give your body less problems in adapting to energy swings. Unrefined foods such as brown flour, rice and whole beans and lentils etc also contain fibre - which is actually a very slow releasing carbohydrate that helps our digestive system stay healthy, assist bowel movements and helps in appetite control. The natural vitamins and minerals are also still present in whole foods, so if we would eat more whole foods and less refined ones, many of our so-called civilization diseases could be avoided.


So how do we know what is fast or slow releasing foods?

As mentioned above this is measured by the speed at which energy is passed from eating the food to the time energy is released into the blood stream in the form of glucose (sugar). This speed measure is also called GI - glycemic index and the GI can be used as a measure of quality of carbohydrates. This is a very critical knowledge to have for people living with diabetes - which is becoming a very common disease in modern day society.


However it is not only important to know how fast a food releases energy into the blood stream - it is also important to know how much of this fast releasing energy a food contains. Carrots for example release energy at about the same rate as chocolate, but of course you have to eat many carrots to get the same amount of energy as in a small piece of chocolate.


A more useful measure of carbohydrates is therefore the Glycemic load:


Glycemic Load (GL) = quantity of carbohydrate x quality of carbohydrate (GI)


GL value when added up from all the meals of the day will also tell you if you are likely to gain or loose weight with your current diet, always provided your total amount of calories is suitable for your age and build.

1. If your daily food has more than 50 GL points you are likely to gain weight, depending on build and level of exercise
2. If your food has an average of 50 GL points you will maintain your weight and 3. If you want to loose weight you should stay a bit below 50 Gl points a day depending on your level of exercise.

Your nutritionist or dietary adviser will assist you to make a good plan for a healthy diet that suits your special situation.


From the table below it can easily be seen that your diet should contain as many vegetables legumes and edible seeds as possible and as little as possible of French fries, soft drinks, cakes and other fast foods. Brown breads, rice and pasta etc are better than same amount of white. It is now up to everyone to apply common sense in putting together healthy diets, and consult a doctor or nutritionist for more specialized personal advice.


Some examples of GL values for food

(adapted from P. Holford 2007)

Carbohydrates and Health

Despite their bad reputation, carbohydrates are vital to your health for a number of reasons.


Providing energy

Your body uses carbohydrates as its main fuel source. Sugars and starches are broken down into simple sugars during digestion. They are then absorbed into your bloodstream, where they are known as blood sugar (glucose). From there, the glucose enters your body's cells with the help of insulin. Some of this glucose is used by your body for energy, fueling all of your activities, whether it is going for a jog or simply breathing. Extra glucose is stored in your liver, muscles and other cells for later use or is converted to fat.


Protecting against disease

Some evidence shows that whole grains and dietary fiber from whole foods helps reduce your risk of cardiovascular diseases. Fiber may also protect against obesity and type 2 diabetes. Fiber is also essential for optimal digestive health.

Controlling weight

Evidence shows that eating plenty of vegetables, fruits and whole grains can help you control your weight. Their bulk and fiber content aids weight control by helping you feel full on fewer calories. Contrary to what some weight-loss diets claim, very few studies show that a diet rich in healthy carbohydrates leads to weight gain or obesity.


Choosing Carbohydrates wisely

Carbohydrates are an essential part of a healthy diet, and they also provide many important nutrients. Still, not all carbs are created equal. Here's how to make healthy carbohydrates work in a balanced diet: 

  • Emphasize fiber-rich fruits and vegetables. Aim for whole fresh, and raw fruits and vegetables without added sugar. They are better options than are fruit juices and dried fruits, which are concentrated sources of natural sugar and therefore have more calories. Also, whole fruits and vegetables add fiber, water and bulk, and help you feel fuller on fewer calories.
  • Choose whole grains. All types of grains are good sources of carbohydrates. They are also rich in vitamins and minerals and naturally low in fat. But whole grains are healthier choices than are refined grains. Whole grains are better sources of fiber and other important nutrients, such as selenium, potassium and magnesium. Refined grains go through a process that strips out certain parts of the grain - along with some of the nutrients and fiber.
  • Stick to low-fat dairy products. Milk, cheese, yogurt and other dairy products are good sources of calcium and protein, plus many other vitamins and minerals. Choose the low-fat versions, though, to help limit calories and saturated fat. And beware of dairy products that have added sugar.
  • Do not forget beans and legumes. Legumes - beans, peas and lentils - are among the most versatile and nutritious foods available. Legumes are typically low in fat, contain no cholesterol, and are high in folate, potassium, iron and magnesium. They also have beneficial fats, and soluble and insoluble fiber. Because they are a good source of protein, legumes can be a healthy substitute for meat, which has more saturated fat and cholesterol. 
  • Limit added sugars. Added sugar probably is not harmful in small amounts. But there's no health advantage to consuming any amount of added sugar. In fact, too much added sugar, and in some cases naturally occurring sugar, can lead to such health problems as tooth decay, poor nutrition and weight gain.

Review Process

Supplied by: Dr Alice Ojwang-Ndong January 2012

Information Source Links

  • Holford, Patrich (2007): New Optimum Nutrition Bible. Piatkus books , An imprint of Little, Brown book group, 100 Victoria Embankment, London EC4Y ODY. ISBN No: 978-0-7499-2552-9
  • Carbohydrates. Centers for Disease Control and Prevention.  Accessed. Jan. 11, (2011).
  • The Encyclopedia of Foods: A Guide to Healthy Nutrition. San Diego, California: Academic Press; (2002).

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