Scripps Cancer Center

Fiber Types - Soluble and Insoluble

Medical Nutrition Therapy

 

About

Fiber is naturally found in plants and is in foods such as vegetables, fruits, whole grains, legumes, nuts, and seeds. Fiber is not digested by the body, so it passes through the digestive tract and out of the body relatively intact. A general rule of thumb is the more whole and unprocessed the plant food, the higher the fiber content.

Fiber is an important part of a healthy diet and can play a role in decreasing cancer risk, lowering cholesterol, controlling blood sugars, improving the gut microbiome, and can positively affect bowel function. There are two types of fiber: soluble and insoluble. Although both types provide health benefits, they are used differently by the body and therefore affect the digestive tract differently. All plant foods provide both types of fiber, but some will be higher in soluble fiber, and some will be higher in insoluble fiber.

If experiencing diarrhea, focusing on soluble fiber can be beneficial. If experiencing constipation, including both soluble and insoluble fiber is recommended. Fiber is beneficial for normalizing bowel function, but severe constipation or diarrhea may require medication adjustment and/or medical interventions. The information below includes nutritional interventions for less severe cases of diarrhea and constipation.

Soluble Fiber

In the body, soluble fiber attracts water to form a gel and gets "sticky" when wet. This slows digestion and can slow down the movement of stool through the digestive tract. It can also help make hard stools become softer and easier to pass. This type of fiber can help improve both diarrhea and constipation.

Foods to Include

Grains

Fruits & Vegetables

Nuts and Seeds

  • Refined grains

    • Examples of hot cereals: instant oatmeal, cream of rice, grits, cream of wheat

    • Other examples: white breads, bagels, noodles, pasta, rice, crackers, graham crackers

 

*If experiencing diarrhea, choose cereal, bread, and pasta products that have less than 2 grams of fiber per serving

  • Soft, canned, cooked

  • No skin or seeds

  • Examples, fruits:

    • Applesauce

    • Avocado

    • Banana, ripe

    • Pear, no skin

  • Examples, veggies:

    • Eggplant, no skin or seeds

    • Potatoes, no skin

    • Winter squash

  • Chia seeds

  • Nut butter, smooth

 

Insoluble Fiber

Insoluble fiber increases stool bulk and promotes movement of the stool through the digestive tract. It can help prevent and improve constipation, but only if insoluble fiber is consumed with an adequate amount of water. Be sure to increase fluid intake to prevent gas and bloating and to keep the stool soft as it moves through the digestive tract. 

 

Food Group

Foods to Include

 

 

Grains

 

 

  • Popcorn

  • Whole grains, examples:

    • Barley

    • Oats

    • Quinoa

    • Rice, brown or wild

    • Wheat bran (i.e., bran muffins)

  • Whole wheat products, examples:

    • Bread, pasta, cereal, crackers

 

 

Vegetables

 

 

  • Most vegetables, examples:

    • Broccoli

    • Cauliflower

    • Carrots

    • Green peas/beans

    • Spinach

    • Sweet potato

    • Potatoes with skin

 

 

 Fruits

 

  • Most fruits, examples:

    • Apple with skin

    • Banana, slightly unripe (some green)

    • Berries (i.e., raspberries, blueberries, blackberries)

    • Dried fruits (i.e., apricots, prunes, raisins, dates)

    • Grapes

    • Pear, with skin

Legumes

 

  • Beans (i.e., black, navy, kidney, etc.)

  • Lentils

  • Edamame

 

Nuts and Seeds

 

 

  • Nuts and nut butter, examples:

    • Almonds

    • Walnuts

  • Seeds, examples:

    • Flaxseed, ground

    • Sunflower seeds

 

Nutrition Tips

  • Foods with at least 2.5 grams of fiber per serving are "good sources" of fiber

  • Foods with at least 5 grams or more of fiber per serving are "excellent sources" of fiber

  • Increase fiber intake gradually and always increase fluid intake

    • Adding large amounts of fiber too quickly can cause abdominal discomfort or gas

    • If experiencing constipation, try adding a little more fiber to each meal by including a piece of fruit or switching processed or refined grains for whole grains

      • For example, try whole wheat pasta instead of white or whole wheat bread instead of sourdough

  • Prunes and prune juice

    • Prunes naturally contain a sugar alcohol called "sorbitol," which attracts water to the colon and can help initiate a bowel movement

      • Therefore, prunes or prune juice may be recommended for constipation

      • Speak to a Dietitian to know if this is recommended and how much is best for you

    • Apple juice also contains sorbitol, but in a lower amount

Fiber Supplements

  • Getting fiber from foods is the best choice

    • Whole foods contain vitamins, minerals, and phytochemicals in addition to fiber, which promotes long term health

  • If modifications to food choices are not enough, you may need to consider an over-the-counter fiber supplement

    • Speak with your doctor and health care team before taking

  • When using a fiber supplement, drink at least 8 ounces of water with the supplement and drink water throughout the day

    • Adding fiber without consuming adequate fluids can worsen constipation, bloating, and gas

Contact the healthcare team if:

  • Considering taking a fiber supplement or medication

  • Experience pain, fever, abdominal distention (bloating), or if vomiting occurs

  • Have not had a bowel movement in more than 3 days

  • Have bloody or black/tarry stool