There is a lot of misinformation regarding carbohydrates and low carb diets. Most of the time people are told to limit the amount of carbs that they eat with each meal but it is never explained what this means. The question, Is Fiber A Carbohydrate, is a good example of the confusion that can result when things are not explained well.
The answer is, fiber is a form of carbohydrate but it reacts differently in our bodies than sugar or starches do.
A carbohydrate is a molecule that is manufactured in a plant from the three main building blocks of life: Carbon, Oxygen, and Hydrogen. You can think of the word carbohydrate as a combination of these three words. CARB from carbon. O from oxygen. And Hyd from hydrogen. This is how I remember what these molecules are made of. If you are interested in a more pure organic chemistry definition then a great article can be found at Wikipedia.
Plants use simple carbohydrates called sugars as fuel. These sugars are manufactured when sunlight shines on the plant and the plant then uses the energy from the sun to fuel the process of combining carbon from the air, found in carbon dioxide, and water which of course is made up of oxygen and hydrogen. The plant combines these into a new molecule, a carbohydrate, that can then be used for energy.
So sugar is a carbohydrate
But, it is hard for the plant to store sugar for later use. It is bulky and the plant needs to save all the room that it can. So, most of the sugar in some plants is combined into larger molecules called starch. A starch molecule is just a whole bunch of sugar molecules which are stuck together. But the sugar molecules in starch are not stuck together very strongly so it is easy for the plant to turn the starch back into sugar when it needs it.
What is really interesting is the fact that humans, and all animals, also use sugar for energy to make our bodies work. When we eat foods with sugar or starch our intestines absorb the sugar into our blood stream where it can be moved around the body and used by our cells as fuel. Our intestines also break down the starch molecules into simple sugar and absorb that.
If we get too much sugar in our blood then it is stored in the liver for further use. But if the liver gets full then we convert the sugar into fat storage. So, if you are overweight then one cause is eating too much food with sugars in it.
What About Fiber As A Carbohydrate
The plant has a very basic need besides just storing and using energy created by the sun and the combination of water and carbon dioxide. It also needs to be able to stand up. If a plant didn’t have some type of structure then it would lust lay on the ground. It turns out the skeleton of a plant is also made of carbohydrates but they are different than starches. These carbohydrates are also made by using the energy of the Sun to combine Carbon Dioxide and water into sugars but these sugars are little different and they stick together very strongly. That makes sense because the plant needs to have a strong skeleton to stand up. This type of carbohydrate is known as fiber.
Unlike starches, when we eat foods that contain fiber our intestines can not break them down into sugar because they are held together so tightly. This is why fiber adds bulk to our body waste.
So even though fiber is a carbohydrate, it does not increase the sugar levels in our blood and thus won’t cause us to gain weight and it won’t cause problems if we are diabetic. That is why food labels now show fiber content. A food may have 20 grams of carbs total but if 5 of those grams are actually fiber then you really only need to worry about 15 grams if you are watching your weight or you are trying to control your diabetes.