The Nutritional Magic of Dietary Fiber

Shannon Miller

November 18, 2021

Scientific contributor, Heather Huntsman, Ph.D., CSCS, is back again discussing one of the most overlooked aspects of nutrition: Fiber. Read on to discover the myriad of benefits increasing fiber intake can have on overall health.

What if I told you that there was one nutrient that could help lower cholesterol to improve heart health, control blood sugar levels, improve digestive and bowel health, manage body weight, and even prevent certain types of cancer? And that there is a wealth of scientific evidence to back it up? I’d assume you would want 2 servings!1,4 Dietary fiber, a complex carbohydrate and the structural part of a plant that ironically, the body cannot digest or absorb, is actually one of the few nutrients that lives up to all of its hype. Unfortunately, the average adult in the United States eats less than half of the recommended levels, and this is even lower in individuals that adhere to many of the popular low-carbohydrate diets.2

In an effort make sure you are as informed as possible when making nutrition decisions that are best for you and your family, let’s unpack some of the facts about fiber. The first question to answer is how much fiber is “enough.” The table below summarizes the daily requirements by age and life stage.3 It is important to note that like many nutrient requirements, age, sex, and life stage are important factors to consider.



If you are like most Americans and you aren’t meeting your daily recommend amounts, you may need to boost your fiber intake by increasing your consumption of whole grains, fruits, vegetables, legumes, or nuts and seeds, which are all good sources of fiber. While processed foods do have some fiber, the overall amount per calorie tends to be lower, as the refining process often removes a good portion of fiber content.1 That said, if you want to know how much fiber is in the processed foods you eat, you can find fiber listed on the food label directly under Total Carbohydrates as a sub-category.



Perhaps the most intriguing question, in my opinion, is how can a nutrient that you don’t even digest have such a profound effect on health? To answer that question, you need to know a couple of key features of the structure of fiber. First, and I mentioned this earlier, fiber is a complex carbohydrate. What makes a carbohydrate simple or complex is the number or sugar molecules that are linked together in one structure. The figure below illustrates what the body sees when metabolizing each.


This structure is important because the harder the body has to work to break complex structures down, the slower the simple carbohydrates can get into the blood stream and affect your blood sugar levels.4 Secondly, with a more complex structure, fiber takes longer to break down which means that it can lead to longer lasting satiety.2 The longer you feel satiated, or full, the less likely you will eat more calories. This is why fiber is considered an important part of weight loss or weight maintenance.

Finally, the most fascinating quality about fiber: because our body does not fully digest and absorb fiber, it moves very slowly from the stomach to the intestine, then on to the colon and finally out of our body. It does this to help promote the movement of material through your digestive system by increasing stool bulk. For this reason, a higher fiber diet has been shown to decrease the risk of colon cancer.5 Additionally, although we can’t technically absorb fiber, as it moves through the gastrointestinal tract, our microbiota is able to digest it which is why fiber is classified as a prebiotic. Although our understanding of the microbiome is still in its infancy, what we do know is that a healthy microbiome can impact our health in a multitude of ways, and that properly feeding your microbiome is an important part of the equation.6

So, know your facts about fiber and don’t let your fear of too many carbs scare you away from getting the recommended daily amount. Your heart, digestive system, gut microbiome, and your body weight will thank you.

Article Sources
  1. Dietary Fiber: Essential for a healthy diet. Mayo Clinic Staff. Mayo Clinic.
  2. Salvin JL. (2005) Dietary fiber and body weight. 21(3):411-418. doi. 10.1016/j.nut.2004.08.018.
  3. Dahl WJ and Stewart ML. (2015) Position of the Academy of Nutrition and Dietetics: Health implications of dietary fiber. Journal of the Academy of Nutrition and Dietetics. 115(11):1861-1870. doi. 10.1016/j.jand.2015.09.003.
  4. Improving your health with fiber. Cleveland Clinic medical professional, Cleveland Clinic.
  5. Kunzmann, A. T., Coleman, H. G., Huang, W.-Y., Kitahara, C. M., Cantwell, M. M., & Berndt, S. I. (2015). Dietary fiber intake and risk of colorectal cancer and incident and recurrent adenoma in the prostate, lung, colorectal, and ovarian cancer screening trial. The American Journal of Clinical Nutrition, 102(4), 881–890.
  6. Holscher HD. (2017) Dietary fiber and prebiotics and the gastrointestinal microbiota. Gut Microbes. 8(2):172-184. doi. 10.1080/19490976.2017.1290756.

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