Dietary fibers (or roughage) are carbohydrates that cannot be digested. Fiber is often classified as either soluble fiber or insoluble fiber based on whether the plant components they come from dissolve in water or not.
There are many types of dietary fibers. The various types of dietary fiber differ by the type of plant they come from, and the components of the fiber. There are both soluble and insoluble fibers, as well as fermentable and non-fermentable types. Fermentable fibers provide food for bacteria in the digestive tract.
Dietary fibers may also be classified on the basis of their relationship with health or disease states. In addition to being classed as soluble or insoluble, fibers may be categorized as prebiotics for their ability to promote the growth of favorable microorganisms in the body and probiotics for their direct effect on host bacterial populations.
A 2009 European Journal of Clinical Nutrition review found that greater consumption of cereal fiber is associated with a significantly reduced risk of coronary heart disease and cardiovascular disease, while greater consumption of fruit fiber was associated with a significantly reduced risk of cancer.
The review also found that higher dietary fiber intakes were associated with lower body weights and serum total cholesterol concentrations.
Soluble fibers tend to swell in the stomach and slow the movement of food along the digestive tract which increases fullness after eating and may be related to lowering cholesterol levels.
Some soluble fibers can also be prebiotic and metabolically ferment in the colon into short-chain fatty acids which may affect the health of bowel tissues and regulate glucose and lipid metabolism.
Insoluble fibers tend to speed up or slow down food passing through the digestive tract, depending on the substance. They may decrease the rate at which nutrients and other chemicals are absorbed in the intestines. Insoluble fibers can also increase bulk and soften stools, making them easier to pass.
How to incorporate dietary fiber
There are many reasons to include dietary fiber in your diet. Some of the most important ones are: