What is Insoluble Fiber? - Sources, Benefits & Examples

Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

This lesson will cover information on insoluble fiber. We will look at the sources and some of the benefits of consuming insoluble fiber. There is a short quiz to follow the lesson.

What is Insoluble Fiber?

Let's first start by defining the term insoluble. You may recollect learning about solubility years ago in a chemistry class. Solubility refers to the ability of a liquid or solid to be dissolved into another liquid to the point where the newly created substance has a consistent composition throughout the substance. A soluble is something that can dissolve in water or another liquid. So for something to be insoluble, this would mean that it cannot be dissolved into a liquid.

Insoluble fiber is a fiber than cannot be dissolved in water or another liquid. Think about it this way, it's almost like when you make a bowl of cereal.

The cereal is insoluble in milk
Picture of bowl of cereal

This is in comparison to lemonade. When you squeeze the lemons and add sugar to water, everything dissolves and creates a new substance, which is the lemonade.

The lemon juice and sugar are soluble in water
Picture of lemonade

Sources of Insoluble Fiber

Foods that contain insoluble fiber are things such as whole grains and most beans. Lentils are another source of insoluble fiber. The bowl of cereal that we talked about earlier would also contain insoluble fiber if it is an all bran cereal. There are some vegetables that are composed of insoluble fiber, too.

Benefits of Insoluble Fiber

There are some great benefits to having a diet that contains insoluble fiber. These fibers are known to be able to help cleanse the intestinal tracts. For this reason, they make for a great natural laxative. As a matter-of-fact, some laxatives are created using the extracts from sources of insoluble fiber. Consuming insoluble fiber regularly can also help to prevent constipation since insoluble fiber promotes bowel movements. The other benefit of insoluble fiber is that is that it helps to push other foods through the digestive tract a lot quicker than normal.

Examples of Insoluble Fiber

Have you ever had a bowel movement and noticed the corn that you ate earlier or yesterday come out looking exactly the same as when you ate it? Of course, we all have done that at some point. This brings us to our first example of insoluble fiber.

Corn is composed of insoluble fiber
Picture of corn

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