Fiber is a topic that has been discussed in nutrition for a long time, yet there are still many questions. Here I answer some FAQ about fiber for you.

FAQ about Fiber

If fiber can’t be digested how is it useful?

Our human bodies do not have the specific enzymes needed to break down fiber. However, fiber still has many uses. Here is a list of why, although not digestible, fiber is necessary for a whole foods diet.

  • Fiber binds to cholesterol in your intestines, not allowing your body to absorb cholesterol. This aids with decreasing coronary blockages and heart disease.
  • Fiber also binds to estrogen in the GI tract. This allow for estrogen to be moved through your body so it does not get reabsorbed, contributing to estrogen dominance.
  • Fiber creates bulk (size and weight) in your stool, which stimulates peristalsis, the wave-like movement of the large intestines. This movement aids in pushing everything through so it can get out easier. This also aids with decreasing colon cancer.
  • It slows down how quickly other non-fiber carbohydrates are absorbed, thus aids with controlling blood sugar.
  • Since fiber is not broken down, it stays in your stomach longer, creating a feeling of fullness. This is useful for weight loss.
  • Fiber feeds the digestive microbiome. This allows the beneficial microbes to thrive supporting a healthy digestive system.

How much fiber do I need and what foods have fiber in them?

The recommended amount of fiber is 21-25g for women and 25-38g for men. Unfortunately, most Americans are getting only about half of that amount. Any food with 5g of fiber or more is considered “high fiber” and can be labeled so on a package. Using the “math” of getting enough fiber, a person needs approximately four or five servings of high fiber foods every day.

Foods naturally high in fiber include:

  • beans and legumes
    • navy beans 1/2 cup = 10g fiber
    • black beans 1/2 cup = 8g fiber
    • lima beans 1/2 cup = 7g fiber
  • seeds and some nuts
    • chia seeds 1 Tablespoon = 5g fiber
    • almonds 1/4 cup = 4g fiber
    • flax seeds 1 Tablespoon = 3g fiber
  • whole grains
    • quinoa 1 cup = 5g fiber
    • oatmeal 1 cup = 4g fiber
    • brown rice 1 cup = 4g fiber
  • fruits and vegetables
    • collard greens 1/2 cup (cooked) = 4g fiber
    • artichoke 1 small = 7g fiber
    • raspberries 1 cup = 8g fiber
    • pomegranate 1 cup = 7g fiber

Can I take fiber supplements if I know my diet doesn’t have enough fiber?

Ideally you would get fiber from your diet, however additional fiber supplements can be useful. There are various ways to add in fiber. My favorites include psyllium husk (such as Metamucil or Citrucel), inulin fiber, wheat dextrin (which is safe for people with gluten sensitivity or celiac disease such as Benefiber), or a combination of various fiber sources (such as Garden of Life Organic Raw Fiber).

While increasing fiber supplements, it is also a good idea to work toward gradually increasing the fiber through your food choices.

Does fiber cause constipation?

While fiber is important there is a possibility that it can cause constipation. Remember that fiber creates bulk, both weight and size, to your stool. There are two likely scenarios where fiber may contribute to constipation.

First, a gradual increase in fiber allows your digestive system to slowly accommodate the changes. Since fiber feeds the gut microbiome it allows for a slow shift to the “community” in your digestive system.

Second, an increase in fiber also needs and increase in fluid. Increasing bulk needs to be accompanied by an hydration to support the adequate wave-like motion to keep your stool moving.

If fiber is a type of carbohydrate, should I avoid fiber if I am eating to keep my carbs lower?

Technically fiber is considered a carbohydrate because of its structure. However, fiber is indigestible which means it does not break down into sugar molecules in your gastrointestinal tract. This means that it passes through your digestive system.

Also, when monitoring carbohydrates, often the amount of fiber is subtracted from the total carbohydrate count when calculating “net carbs.”

How is fiber related to prebiotics?

All prebiotics are fiber, but not all fiber is a prebiotic.

Prebiotics are certain types of soluble fiber. They serves as food for the microbial community that lives in your gastrointestinal tract, also known as your gut microbiota. Because they are fiber, humans can not digest prebiotics, however the beneficial gut microbes can. The microbes consume these prebiotic fibers and produce beneficial compounds that support a health GI tract and immune system, among other health benefits.


I hope you gain some insight from these FAQ about fiber to remind you of the importance of fiber. It’s not just to keep your bowels moving, but fiber is an overlooked, yet useful food for overall wellness.