6 Benefits of Fiber

Written by Dr. Brian Bressler, MD, MS, FRCPC on June 9, 2020

We’ve all heard the advice that we should include fiber as part of a healthy diet. But you may be surprised to know that the benefits of fiber go well beyond what most people know. Let’s start with the basics and then cover the many benefits of fiber to help you stay healthy.

What is fiber?

Dietary fiber is a type of carbohydrate in plant-based foods that we cannot digest or absorb. Because of this, it performs many important functions along the whole length of the digestive system.

Different types of fiber

There are two main types of fiber: soluble and insoluble.

Soluble fiber absorbs water in the digestive system and forms a gel-like substance. Some types of bacteria in the large intestine ferment soluble fiber and it therefore acts as a food source for them. Examples of foods rich in soluble fiber are beans, oats, ground flaxseeds, and some fruits and vegetables.

Insoluble fiber does not dissolve in water. Some types of insoluble fiber are slowly fermented by bacteria in the large intestine, while other types are non-fermentable. Insoluble fiber is mostly found in whole grains, bran, legumes, nuts, seeds, peels/skins, and stringy and/or tough vegetables and fruits.

Most plant-based foods contain a combination of soluble and insoluble fiber.

Recommended daily intake of fiber

The recommended daily intake of fiber for most healthy adults is 38 grams for men and 25 grams for women. Most individuals consume far less than the recommended amount.

Benefits of fiber

1. Promotes a good balance of gut bacteria

We tend to think of bacteria as being associated with sickness or disease. But not all bacteria are unhealthy. In fact, a healthy immune system depends on a plentiful supply of “good” gut bacteria. It is estimated that we have about 500 different species of bacteria and 100 trillion bacteria living in our large intestine.

Getting adequate fiber intake from a variety of plant-based foods has been associated with an increased abundance and diversity of gut bacteria, which has been linked with positive health outcomes. If we do not feed our gut bacteria fiber, they will look for alternative fuel sources, such as the mucus lining of our large intestine. This can have negative health implications and has been tied to increased risk of gastrointestinal diseases.

2. Can help with appetite control

High-fiber meals stretch your stomach and result in delayed stomach emptying. These factors can make you feel full over longer periods. Overall, this may result in reduced food intake.

3. Can lower blood sugar levels

Approximately one-third of American adults have elevated blood sugar levels either because they have diabetes or prediabetes. A fiber-rich diet can help with blood sugar control by slowing the absorption of sugars into the blood.

4. Can reduce cholesterol

Some studies have shown that soluble fiber may help lower total blood cholesterol by reducing the low-density lipoprotein, or “bad” cholesterol. There are different ways in which fiber may do this. One of the ways is by binding to dietary cholesterol in the digestive tract, making it unavailable for absorption.

5. Impacts constipation

Constipation can be caused by stool moving through the large intestine too slowly. This often results in the fluid portion of the stool being absorbed back into the body making the stool hard, dry, and difficult to pass.

Fiber can help to reduce constipation by adding bulk to and softening stools. This helps move the stools along in the large intestine and makes them easier to pass.

6. May reduce the risk of colorectal cancer

Colorectal cancer includes both colon cancer and rectal cancer and is the third leading cause of cancer deaths. Studies have shown mixed results as to the efficacy of fiber on reducing the risks of colorectal cancer. One study found a 10% risk reduction in colorectal cancer for every 10 grams of fiber eaten a day. The more fiber study participants ate, the more risk reduction was found.

Researchers suggest that the potential reduced risk may be related to reduced transit time in the digestive tract, dilution of carcinogens, and the protective properties of some byproducts of bacterial fermentation of fiber.

Ways to increase your fiber intake

The best way to get more fiber in your diet is through increasing your intake of plant-based foods. The good news is that there are plenty of delicious high-fiber foods to choose from that can help you get the recommended daily amount.

Examples of high-fiber foods include:

  • Whole-grain products: whole-wheat breads, brown rice, bran, oatmeal
  • Fruits: pears, apples, berries, oranges, tangerines
  • Vegetables: broccoli, brussels sprouts, carrots, squash, potatoes
  • Legumes: beans, peas, lentils
  • Nuts and seeds: almonds, peanuts, sunflower seeds, walnuts

Whole foods tend to have more fiber than processed foods. For example, brown rice has more fiber than white rice. It is recommended to have whole foods more often than processed foods. Whole foods also have the added benefit of having micronutrients, like vitamins and minerals.

Getting enough fiber in your diet can produce many positive health outcomes. Since most of us are not getting enough fiber, it is important to consider how we can increase our intake. A good starting place could be aiming for half of your plate at lunch and dinner to be vegetables and/or fruits. Your gut bacteria will thank you!