Medically reviewed by Natalie Butler, R.D., L.D. — Written by Jennifer Huizen on August 31, 2017
Dietary fiber, the indigestible part of plant material, is made up of two main types. Soluble fiber easily dissolves in water and is broken down into a gel-like substance in the part of the gut known as the colon. Insoluble fiber does not dissolve in water and is left intact as food moves through the gastrointestinal tract.
The term fiber refers to all the parts of plant-based foods that cannot be digested or absorbed by the body. Unlike simple carbohydrates, including most breads and sugars, fiber is a complex carbohydrate and does not raise blood sugar levels.
Fiber is commonly found in vegetables, fruits, whole grains, and legumes. It is also sometimes called roughage or bulk. It is an essential nutrient, which means it must be eaten in the diet.
Fast facts on soluble and insoluble fiber:
- Soluble and insoluble are the two main types of fiber. Many fiber-rich foods contain some of both.
- Both forms of fiber have health benefits.
- Humans have been using fiber as a dietary aid since ancient times.
- In a society built on refined carbohydrates, or white breads, pastas, and sugar sweeteners, getting enough fiber can take effort.
