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Types of Fiber: The Difference Between Soluble and Insoluble Fiber

We get it. You’ve been having some digestive issues and you need information on fiber, stat. Well, we’re here to help. Fiber plays an important role in many biological processes in your body, but the simplest way to explain dietary fiber is to break it down into two basic types of fiber: ​soluble​ and ​insoluble​.

Soluble Fiber

When you think of ​soluble fiber​, remember these three qualities:

  • Absorbs water
  • Becomes gel-like
  • Slows digestion

Put simply, soluble fiber is a form of fiber found naturally in many foods (and supplements) that slows digestion and can help ​relieve constipation​ and ​lower cholesterol​. A few examples of ​high-fiber foods​ that contain soluble fiber are:

  • Grains such as barley and oat bran.
  • Nuts such as Brazil nuts, almonds, and peanuts.
  • Seeds such as sesame seeds, sunflower, and flaxseed.
  • Fruits such as strawberries, pears, and apples.
  • Lentils, Lima beans, kidney beans, and navy beans.

Insoluble Fiber

When you think of ​insoluble fiber​, remember these three qualities:

  • Does not absorb water
  • Adds bulk to your digestive tract
  • Speeds up or helps “move along” digestion

Insoluble fiber, as the name suggests, does not absorb (or dissolve in) water. Just as with soluble fiber, it can be found in a variety of different foods and can help with constipation​. Some ​high-fiber foods​ that contain insoluble fiber are:

  • Beans such as kidney, pinto, and navy beans.
  • Grains such as wheat bran, wheat germ, and popcorn.
  • Most vegetables such as green beans, Brussels sprouts, and okra.
  • Certain fruits like raspberries and strawberries.

Additionally, many foods contain both types of fiber such as varieties of beans, grains, fruits, and vegetables. For a full resource of the dietary fiber content in food, please refer to the ​USDA Food Composition Database​.

Next time you're staring at items in the grocery store trying to remember the different types of fiber and which foods contain them, you can breathe easy knowing our guide is just a click away. Bon Appetit!