Fiber: your Health’s overlooked hero
When we discuss or think about nutrition we often focus on the macronutrients: carbohydrate, fat, and protein. Or we attend to the micronutrients our food delivers such as vitamins and minerals. While these are undeniably essential to proper maintenance of daily physiological functioning, there is another less glamorous component of food that is often overlooked. One that “has never been formally proposed as an essential component of the diet.”(2) This constituent is fiber; the bulk of many fruits, vegetables, whole grains, and legumes that is not broken down in the digestive tract, and much of which exits the body through the stool. While that may suggest it lacks any real purpose, this couldn’t be further from the truth. Here we will explore the many roles of fiber, the requirements and average intake, and how to incorporate more fiber in your diet.
What is fiber?
Fiber is a type of carbohydrate that is not digested by the human body. It passes through the digestive system largely intact unlike other classes of carbohydrates. Fiber is derrived from fruits, vegetables, nuts, seeds, legumes and whole grains. It is classified as soluble or insoluble. Soluble means that it dissolves in water forming a gel-like substance in the digestive tract; insoluble refers to fiber that does not form this substance, and instead adds bulk to the stool. Oats, legumes and citrus are examples of soluble fiber, while fruits with the skin on, whole grains, and many vegetables are great sources of insoluble fiber. Often they can be found together.
The Role of Fiber and Its Many Benefits
Research demonstrates a “strong protective association against risk of developing several chronic diseases.” These include type 2 diabetes, colorectal cancer, cardiovascular disease, stroke, cardiovascular disease, and GI disorders such as Irritable Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS).(1) From aiding digestion to supporting weight management this nutrient has a host of applications that cannot be ignored. Highlighted below are some of the specific functions of fiber and the systems of the body it assists.
Digestive Wellness-By adding bulk and water to the stool, fiber promotes regular bowel movements, minimizing constipation, hemorrhoids, and other digestive-related challenges.
Blood Sugar Regulation-fiber slows the absorption of nutrients including glucose. This helps to minimize spikes and subsequent crashes that refined carbohydrates often cause leading to blood sugar dysregulation and even diabetes for some.
Weight Management-The mastication that high-fiber foods requires equates to more time and effort for these foods to be delivered to the digestive tract, allowing for satiety signals to catch up. This means that we experience fullness sooner reducing our energy intake. (2)
Heart Health-Soluble fiber traps and binds to cholesterol in the small intestine, blocking entry into the bloodstream and encouraging removal by way of the feces instead. Its positive effects on blood sugar also contribute to lowered risk of heart disease. The effect of soluble fiber on lowering LDL cholesterol is particularly significant. (3)
Gut Health and the Microbiome-Fiber is utilized by gut bacteria and metabolized into beneficial compounds such as short chain fatty acids (SCFAs). These contribute to a reduction in gastrointestinal diseases such as Irritable Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS), and have a positive effect on inflammation, obesity and metabolism(4)
How much fiber do we need?
According to the Recommended Dietary Allowance, fiber intake is dependent on gender, age, pregnancy, and lactation. Additional factors such as activity level, dietary restrictions, and other health conditions are also important to consider suggesting the nuance of this topic. And like we have learned for many other nutrients, the RDA often does not reflect optimal and instead hovers at the low end of what is needed to prevent overt deficiency. Nevertheless, here are the general guidelines according to the RDA:
Children- 19 grams from 1-3 years; 25 grams from 4-8 years
Males-31 grams from 9-13 years; 38 grams from 14-18 years; 38 grams from 19-50 years; 30 grams over 50 years
Females-26 grams from 9-13 years; 26 grams from 14-18 years; 25 grams from 19-50 years; 21 grams over 50 years
Pregnancy-28 grams during all 3 trimesters
Lactation-29 grams
It is believed that our ancestors may have consumed up to 100 grams of fiber a day. Comparably, North Americans today barely reach the RDA, averaging only 17 grams per day. Yet, even if we strive to meet the RDA, this puts us at just a fraction of what our ancestors consumed.
It is not surprising that 17 grams is the average. I know personally that unless I am thoughtfully aiming for 25 grams or more, 15-17 is about where I land. For this reason, I have been using a diet tracking app solely to track my fiber. This is what I have learned:
The cronometer app is my preferred choice because it offers a fairly comprehensive free version in the event that you choose to use it long-term
It only needs to be used short-term in order to get a sense of what it takes to meet your fiber goal
My daily smoothie alone gets me close to 15 grams of fiber
It can be best to go slow when increasing fiber as it can contribute to gas and bloating when attempted too rapidly
I feel much fuller and more satiated on the days my fiber is high
When diligently striving for high fiber I can average 35-40 grams per day
I challenge you to begin tracking your fiber too. Rather than tracking calories, macros, and all your micronutrients, try focusing on just this one aspect of diet. It takes the pressure off of trying to monitor everything at once and eliminates the goal as weight loss or caloric restriction, though these may be natural consequences of higher fiber intake.
Aim for whole foods based fiber over supplementation. Although some studies point to benefits of supplemental fiber too, they also indicate that whole food fruits and vegetables also bring with them micronutrients that provide additional benefits (2). Most Americans do not meet the recommended intake for fruits and vegetables either, which is presumable linked to low fiber intake.
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Carla Abate is a Board Certified Holistic Nutritionist in Lakewood, CO, specializing in functional nutritional strategies for women and families. She is a Restorative Wellness Solutions Practitioner, a Certified Nutrition Therapist Master, and a Postpartum Doula. She also holds a Master's degree in Counseling. Carla is dedicated to fostering health and wellness through evidence-based nutrition coaching. Contact her at Rebel Roots Nutrition.
Try my High Fiber Sunburst Smoothie!
References:
McKeown NM, Fahey GC Jr, Slavin J, van der Kamp JW. Fibre intake for optimal health: how can healthcare professionals support people to reach dietary recommendations? BMJ. 2022 Jul 20;378:e054370. doi: 10.1136/bmj-2020-054370. PMID: 35858693; PMCID: PMC9298262.
Rebello CJ, O'Neil CE, Greenway FL. Dietary fiber and satiety: the effects of oats on satiety. Nutr Rev. 2016 Feb;74(2):131-47. doi: 10.1093/nutrit/nuv063. Epub 2016 Jan 2. PMID: 26724486; PMCID: PMC4757923.
Ghavami A, Ziaei R, Talebi S, Barghchi H, Nattagh-Eshtivani E, Moradi S, Rahbarinejad P, Mohammadi H, Ghasemi-Tehrani H, Marx W, Askari G. Soluble Fiber Supplementation and Serum Lipid Profile: A Systematic Review and Dose-Response Meta-Analysis of Randomized Controlled Trials. Adv Nutr. 2023 May;14(3):465-474. doi: 10.1016/j.advnut.2023.01.005. Epub 2023 Feb 2. PMID: 36796439; PMCID: PMC10201678.
Guan ZW, Yu EZ, Feng Q. Soluble Dietary Fiber, One of the Most Important Nutrients for the Gut Microbiota. Molecules. 2021 Nov 11;26(22):6802. doi: 10.3390/molecules26226802. PMID: 34833893; PMCID: PMC8624670.