Back to Blog


Why You Should Add Fiber To Your Diet

Theresa Hardy, PhD, RN
Onegevity

Why is fiber so good for you?


Do you feel like most dietary recommendations sound like sweeping generalizations? “Eat less sugar”, “Eat more vegetables”, “Eat fewer carbohydrates”. And then, even worse, it can feel like we receive recommendations that contradict each other. “Eat less fat.” “Eat more good fat.” It’s no wonder that many of us find it hard to decipher what we should incorporate into our daily diet routines. 

It’s easier to make dietary changes if we understand the ‘why’ behind the ‘what’. 

One recommendation we have likely all heard is “eat more fiber”, especially if we struggle with any sort of gut complaint. Why fiber? Our science team at Onegevity is here to give you the why.

What is dietary fiber? 

Dietary fiber is defined as nondigestible carbohydrates found in foods that support the growth of health-promoting bacteria that colonize the gastrointestinal tract. Fibers are classified according to several characteristics, including their food source, chemical structure, water solubility (the ability of a substance to dissolve), viscosity (the “thickness” of a substance), and fermentability. 

There are two main forms of fiber, soluble and insoluble. Insoluble fibers are not digested, or only slowly digested by gut bacteria, so they have a fecal bulking effect. 

Soluble forms, on the other hand, are fermented by gut bacteria and give rise to metabolites, such as short-chain fatty acids (SCFA), which provide important health benefits.1,2

Why should you include fiber in your diet? 

1. Fiber adds bulk. 

Perhaps the reason most of us are familiar with (and why many of us already include fiber in our diets) is that fiber helps to bulk stool, making it easier to pass, and therefore decreasing issues of constipation. Fiber can also help if you experience more diarrhea because it absorbs water and adds bulk to loose stool. In addition to this better-known effect, fiber also helps to lower cholesterol and regulate our body’s blood glucose response.3


2. Fiber is a prebiotic. 

Fiber also works in ways that are less immediately obvious, but equally important. It serves as an important energy source for specific gut microbes that have the specialized machinery required to produce metabolites like short-chain fatty acids (SCFAs). Among other important functions, SCFAs play a vital role in regulating our metabolism and immune system. Studies have found very high protein, low-carbohydrate diets not only lead to a significant reduction in the production of SCFAs, but also increase the production of potentially harmful metabolites. These harmful substances can increase inflammation and contribute to the development of chronic diseases.2 So think about your absolute and relative dietary intake in regards to your gut next time you’re tweaking your diet! 


3. Fiber regulates immune response. 

SCFAs, which are produced when gut bacteria break down fiber, promote the generation and maturation of regulatory T cells. If your memory of biology is failing you, regulatory T cells suppress the body’s immune response, helping to maintain homeostasis and preventing autoimmunity.2


4. Fiber maintains gut integrity. 

Another important effect of fiber is its role in helping to protect the mucus layer that lines the gut and serves as a barrier from harmful bacteria. Dietary fiber helps to stimulate the gut lining to secrete mucus. Diets that are low in fiber can lead the mucus layer to deteriorate and breakdown, making the gut more vulnerable to bacterial invasion and increasing susceptibility to infection


5. Fiber has positive effects beyond the gut. 

Reduced fiber intake is linked with a whole host of chronic health issues, including diseases of the gut, like inflammatory bowel disease and colorectal cancer. But the actions of the gut metabolites produced from fiber are not limited to the gut. Studies have found that reduced fiber intake affects the lungs, increasing risk of asthma and chronic obstructive pulmonary disease. Additionally, it has been shown that increasing fiber intake increases the good bacteria in our gut and helps to maintain body weight.2 Do you need any more reasons to include fiber in your diet? 


Let’s get practical

Although fiber is present in a wide range of plant-based foods, Western diets typically contain very little fiber. Use these tips to increase your fiber intake. 

  • Dose matters. The average American consumes only about 17 g/day of dietary fiber. The recommended daily intake is 38 g/day for men and 25 g/day for women. To really see the beneficial health effects of fiber, you need to start by making sure you are getting enough.4 
  • Fiber is not one size fits all. There are many types of fiber, and while all fiber will lead to shifts in the composition of the gut microbiome (the bacterial community present in our gut), not all these shifts have the same health benefits. For example, soluble fibers, such as psyllium and fibers found in oat products can lower cholesterol concentrations and normalize blood sugar levels, whereas, insoluble fibers (e.g., wheat bran) can have a laxative effect. If you are looking for a specific health effect, it may help to speak to a nutritionist or another health professional to determine what type of fiber would be best to include in your diet.4
  • Go slow. Increasing your fiber intake too quickly can lead to abdominal discomfort and other undesirable symptoms, like bloating, diarrhea and constipation. While fiber is good for your health, it can take some time for your body to adjust to the increased intake.2 Be sure to drink plenty of water.
  • Fiber effects are personal. Studies have shown that not everyone responds the same to increased fiber intake. Researchers suggest that the differences may be due to the response of the gut microbiome to fiber being highly individualized. Some individuals may lack the bacterial species necessary to utilize fiber.2  Therefore, knowing which type of fiber you need based on your microbiome may produce greater beneficial effects and less unwanted effects.

  • Test your gut microbiome using Onegevity’s Gutbio microbiome kit. Learn about which bacteria you have present and which fibers can support optimal gut health, motility, and effects beyond the gut. With your report, you will receive personalized recommendations for a diet, supplements, and lifestyle that can help you maintain gut integrity, improve gut diversity, support optimal digestion and absorption, and promote overall health. 



1.        So D, Whelan K, Rossi M, et al. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. Am J Clin Nutr. 2018;107(6):965-983. doi:10.1093/AJCN

2.        Makki K, Deehan EC, Walter J, Bäckhed F. The Impact of Dietary Fiber on Gut Microbiota in Host Health and Disease. Cell Host Microbe. 2018;23(6):705-715. doi:10.1016/j.chom.2018.05.012

3.        Fuller S, Beck E, Salman H, Tapsell L. New Horizons for the Study of Dietary Fiber and Health: A Review. Plant Foods Hum Nutr. 2016;71(1):1-12. doi:10.1007/s11130-016-0529-6

4.        Fiber. Linus Pauling Institute. https://lpi.oregonstate.edu/mic/other-nutrients/fiber. Published 2019. Accessed March 13, 2020.