The addition of fiber to your diet is a fundamental nutrition concept. Fiber is most commonly thought about when talking about keeping things moving in the bathroom. However, fiber is important for a variety of reasons. In this article we will talk about an overview of fiber.

The American Diet is known for being inadequate in fiber. In fact, most Americans consume 10-13 grams of fiber daily. The recommended amount of fiber is 38 grams for men and 25 grams for women per day.  

an overview of fiber

What is fiber?

Fiber is known as a non-digestible form of carbohydrates.

Fiber only comes from plant based foods.

Most animals can digest fiber through enzymes, but humans lack the enzymes to break down all plant fibers

Plants contain two types of fibers classified by their ability to dissolve in water – soluble fiber and insoluble fiber. Both are important and have different uses.

Soluble Fiber

Soluble fiber is known for slowing the digestive tract down. It promotes the feeling of fullness, decrease the glycemic effect of meals, reduce the absorption of fat and cholesterol, and binds to estrogen to allow for it’s remove through the digestive system.

Soluble fibers include pectin, gums, mucilage, fructans, and some resistant starches. Foods that contain soluble fibers are some fruits, vegetables, oats, and barley. 

By dissolving in water, soluble fiber forms a viscous gel. Think about the type of gel that is formed when making jelly or jam with pectin. Or if you add chia seeds to water, the way it thickens. That is because of the soluble fiber.

The watery-gel fiber mixture, or bolus,  is moved through the digestive system without being broken down because humans lack enzymes to break down plant matter. 

Fortunately, bacteria in the gut do have the enzymes to break down plants. The gut microbiota feeds off the gelatinous fibers in the large intestine. 

As a by-product, the bacteria releases gasses and a small number of fatty acids absorbed directly into the bloodstream as fat-soluble vitamins.  The gas is released through breath, flatus, and feces.  

Gradually increase dietary fiber over time to avoid bloating and discomfort.  Healthy bacteria in the gut grow by the billions and become more efficient once a diet is adequate in fiber. In summary, the gut will normalize a high-fiber diet, and bloating will be kept at a minimum. 

Insoluble Fiber 

Insoluble fiber increases gut motility by decreasing intestinal transit time and increasing fecal bulk. This promotes digestive regularity. Less fat is absorbed when combined with insoluble fiber due to the faster digestion rate. 

Insoluble fibers include lignin, cellulose, and hemicellulose. Food forms include whole grains such as barley, oats, or millet, bran, nuts, and seeds.  Because this type of fiber does not dissolve in water, it remains unchanged while moving through the digestive tract.  

Dietary Fiber and Functional Fiber 

The Institute of Medicine classifies fiber into two categories: dietary and functional fibersDietary fiber is the combined soluble and insoluble fiber found in plants. In addition to dietary fiber, functional fiber is isolated, extracted, and purified carbohydrates that are non-digestible. Functional fiber is added to food during processing for its beneficial health effects. 

Boosting Fiber Intake 

Due to the lack of fiber in the American Diet, food manufacturers add different types of fibers to their food and beverages to increase consumption. Some of the functional fibers added to foods are soluble corn fiber, polydextrose, and soluble fiber dextrin. Even though these are considered safe, some people may be sensitive to the fiber additive. Sensitivity to added fiber may include symptoms such as gas and bloating, and generalized abdominal cramping.

If your diet does not contain enough fiber, the addition of supplements may be useful. Here are some supplemental fiber that you can try to see if it works for you;

  • psyllium husk powder
  • chia seeds
  • Garden of Life’s Raw Organic Fiber contains both soluble and insoluble fibers through various seeds and grains
  • “Bob’s Red Mill’s Organic High Fiber Hot Cereal which increases fiber through oat bran

Whole Foods Approach

Some plant based foods are naturally high in dietary fiber. These include:

  • nuts and seeds
  • peas and beans
  • whole grains
  • fruits and vegetables

Some of my favorite fibrous foods are chia seeds, flax seeds, pistachios, boiled peanuts, white beans, any berry, oatmeal, green peas, turnip greens, broccoli, cauliflower, kale, brussels sprouts, delicata squash, parsnips, sweet potatoes, bananas, figs, peaches, and jicama. 

Think outside the Box

Flaxseeds are one of my favorite way to add fiber to foods without altering the taste. Since I was 17, I have added milled flax seeds to my pizza as a topping. Add milled flaxseeds to soups, spaghetti, chili, salads, on a hamburger, or your favorite foods. One ounce of flaxseed is 8 grams of fiber. Milled flaxseed is sold in stores, but I highly recommend buying whole flaxseeds and grinding them a week’s worth at a time. The flax oil is extracted and sold separately or depleted from the milled.

My babies love chia seeds in their yogurt. My son says, “I want seeds!” Chia seeds taste crunchy, and that’s it unless soaked in water. Then, that is an entirely different mouth feel of chewy. Add chia seeds to smoothies, nut butter, oatmeal, cereal, protein bars, cookies, and salad or salad dressing.

In summary, plants make edible food from solar energy. Celebrate by eating and sharing plant-based food with you and your family. The fiber is rewarding to the body. Chronic underutilization of plant-based foods may result in heart disease, imbalances in blood sugar, some cancers. 


Leila is a wife and mom of two littles. She has a Masters of Science and is working toward completing a dietetic internship to become a registered dietitian. Leila has a enjoys using foods in their most natural form, along with herbs, to optimize the nutrients the body uses for day-to-day performance.