Dietary fiber is the indigestible material that makes up the structure of much of the food we eat. Fiber is used by the foods we eat to lock-in nutrients & keep out pests. For example the skin of an apple or a tomato is made of fiber. The fiber helps keep out bacteria, allowing the fruit to last longer, giving it a better chance to be eaten.
Given that most of our food is packaged within a fibrous shell, our bodies have adapted to pass indigestible fiber through the body. Once inside our body the fiber helps move the food along the digestive tract as it breaks down and nutrients are absorbed. Fiber has direct health benefits. Studies have suggested that fiber intake helps lower bad cholesterol levels & regulates blood sugar.
There are two types of dietary fiber, soluble & insoluble. Soluble fiber turns into a gel like substance as it absorbs water and passes through the digestive tract. Soluble fiber will pick up sugars & carbohydrates as it passes through your digestive tract, it may eventually ferment in the later stages of the digestive process, causing gas & bloating. Insoluble fiber is mainly a bulking agent which makes up much of the contents of stools that eventually form later in the digestive process.
Fiber can be a double edged sword. While for most people with a normal digestive tract fiber is a good thing, for those with IBS it can be somewhat tricky. Since fiber can sometimes lead to further gas, bloating & urgency it may not be of benefit to someone with IBS.
Some have suggested those with IBS try to stick to a soluble fiber heavy diet. Those on a soluble fiber diet would need to ensure that any insoluble fiber foods are eaten with a large portion of soluble fiber foods as well.
There are soluble fiber supplements on the market which may help with symptoms. The goal is to provide padding for the food you eat while not causing you to bloat up. They are not guaranteed to work though & some people do not see improvement after starting a fiber regimen. If you do start taking a fiber supplement your symptoms may worsen initially, but improve over a few weeks. Most people try either Acacia Fiber or Psyllium Husk.
Some people have problems with either type of fiber & may experience symptoms from both soluble & insoluble fiber.
Soluble Fiber Foods: oats, rice, corn meal, white flour, peas, beans, apples, citrus fruits, carrots, barley and psyllium husk, cooked potatoes or carrots
Insoluble Fiber Foods: whole-wheat flour, wheat bran, whole grains nuts, leafy vegetables, citrus fruits, apples, whole kernel corn