Dietary Fiber for Detox: Understanding Soluble vs Insoluble Fiber

Dietary fiber is especially important for proper detoxification of exogenous and endogenous compounds in our bodies. These compounds can be toxins, heavy metals, even our own hormones… and they all rely on fiber to bind and complete elimination outside of the body (mostly via the feces).

High fiber meal oats and berries - fiber for detox
Oats and Raspberries: High-Fiber and Nutritious!

What is Fiber?

Dietary fiber is plant material that is undigestible. There are two main types of fiber: soluble and insoluble. Plant foods typically contain a combination of both types in different degrees, depending on the plant’s makeup.

INSOLUBLE FIBER, mostly found in whole grains, absorbs water in the GI tract, helping to hydrate the waste material into soft, bulky stools that easily pass through the system. We cannot digest insoluble fiber, but the commensal bacteria in the gut partially digest it! This fermentation turns the fiber into beneficial short-chain fatty acids that provide energy to our intestines.

SOLUBLE FIBER, mostly found in seeds, legumes and certain starches, adds bulk to the stool by delaying gastric emptying and also acts as a binder with bile, toxins, and other undigested material. Soluble fiber controls blood glucose metabolism by delaying absorption of glucose and also lowers cholesterol by binding with bile acids. Certain soluble fibers (inulin, FOS) stimulate the growth of beneficial bacteria and act as prebiotics.

All fruits and vegetables contain fiber, but some have more than others. The American Dietetic Association suggests 20-35g of fiber per day. Not sure where you stand? Use a simple tracking app like MyFitnessPal to see what your intake is. Then, slowly start to increase fiber by choosing more fiber-rich foods.

The Role of Fiber in Detox

Dietary fiber, both soluble and insoluble, plays a large role in the detoxification process.  The phytonutrients in fiber, such as metallothionein, bind to toxic elements (e.g., mercury, lead, cadmium, arsenic) and prevent their interaction with other molecules to reduce reactive oxygen species (ROS) production, (Lamb, et al., 2011). In addition, the gastrointestinal fermentation of fiber increases short chain fatty acid production which results in byproducts such as butyrate, acetate, and propionate, (Lin, et al., 2012). Butyrate specifically increases glutathione S-transferases and other enzymes which also bind toxic compounds for elimination (Stein, Borowicki, Scharlau & Glei, 2010).  

Commercially prepared fibers can be made from the derivatives of food production.  For example, sugarcane bagasse is a non-soluble remnant left over after sugar cane has undergone juice extraction (Sangeetha et al., 2011).  Commercially prepared fiber tends to have a significantly higher glycemic index compared to whole foods with similar levels of fiber (Atkinson, Foster-Powell, & Brand-Miller, 2008; Mozaffarian, 2013). However, a fiber supplement can still bring benefit for individuals eating a restricted diet.

Many studies support any combined increase of dietary fiber intake in reducing all-cause mortality, heart disease, and cancer (Benisi-Kohansa, 2016; Fungwe, Bente, & Hiza, 2007; Park, Subar, Hollenbeck, & Schatzkin, 2011). However, when individual foods are compared, advantages can be seen in consuming more intact foods versus fiber-enriched foods. Increasing fiber intake from a variety of whole foods like berry fruits and green leafy vegetables has been attributed to improved glucose metabolism due to the wide array of nutrients and antioxidants (Wang, Fang, Gao, Zhang, & Xie, 2016). 

High-fiber Salad based on Whole Foods legumes and plants

Is Dietary Fiber the secret cure-all?

One meta-analysis concluded that many of the measured health benefits in people who eat high fiber diets might be due to their associated healthy lifestyle patterns, including consumption of whole fruits, vegetables, and legumes containing these synergistic micronutrients, rather than the fiber itself (Park et al., 2011).

When we have a low-fiber diet, instead of being eliminated, toxins get recirculated into the bloodstream. Symptoms of toxic burden can include mood swings, weight gain, low-libido, and fibroids.

Often, our body compensates for poor detoxification capacity and it shows up as sugar cravings, caffeine dependence, and weight gain.

Symptoms of low-fiber diet include fatigue and hormone issues. Fiber helps restore detox capacity
Feed me some FIBER!

Signs that you may need to improve your detoxification capacity:

  • food allergies,
  • fatigue,
  • poor stress management,
  • acne and breakouts,
  • hormone imbalance,
  • poor sleep,
  • brain fog,
  • autoimmune disease.

Eating adequate fiber can start to address these issues by ensuring regular elimination, a balanced microbiome, and plenty of phytonutrients for metabolic health. Some of my favorites? The Hormone-Healing Diet or The Anti-Inflammatory Diet.

When is a low-Fiber Diet appropriate?

However, many individuals suffer from gastrointestinal consequence from high-fiber foods. This mostly occurs in the case of SIBO/SIFO, when there is an overgrowth of bacteria in the small intestine. As these fibers pass through the stomach to the small intestine, they are fermented by these bugs leading to gas, bloating, constipation, and pain.

The most obvious culprits are often the cruciferous vegetables (Brussels sprouts, Broccoli, Cauliflower), alliums (Raw Onion, Garlic), and legumes (Beans, Lentils, Peas).

In order to address this overgrowth, a period of avoidance is necessary to starve out these bacteria. A low-FODMAP diet is a therapeutic diet that removes fermentable fibers for a period of time, and then systematically reintroduces them. The Carnivore Diet is another low-Fiber diet than can be especially therapeutic for functional gut disorders.

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Final Thoughts on Dietary Fiber

Ultimately, if tolerated, fiber deserves a paramount place in any well-rounded diet. A healthy individual is regularly eliminating, supporting metabolic processes with their diet, and not spilling over into adverse symptoms. Fiber can improve each of these pillars of health–in the right application.

For individuals who struggle with disordered eating, simply counting fiber can be a great way to assess the diet while avoiding a calorie-counting trigger. Also, bringing more awareness to choosing high-fiber whole foods over processed fake food products is an easy place to start.

Want to work with a functional nutritionist to personalize your diet? Struggling with hormone imbalance, IBS, weight gain, mood changes? Let’s look at FOOD FIRST. Read more about Functional Nutrition at The Facility here.

CLICK HERE to schedule a FREE 15-Minute Nutrition Consult with Kate to determine your best course of action!


Atkinson, F. S., Foster-Powell, K., & Brand-Miller, J. C. (2008). International tables of glycemic index and glycemic load values: 2008. Diabetes Care, 31(12), 2281-2283. doi:10.2337/dc08-1239. Retrieved from

Benisi-Kohansa, S., Saneei, P., Salehi-Marzijarani, M., Larijani, B., Esmaillzadeh, A., & Benisi-Kohansal, S. (2016). Whole-Grain Intake and Mortality from All Causes, Cardiovascular Disease, and Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Advances In Nutrition, 7(6), 1052-1065. doi:10.3945/an.115.011635. Retrieved from

Fungwe, T. V., Bente, L., & Hiza, H. (2007). The Food Supply and Dietary Fiber: Its Availability and Effect on Health. Retrieved August 1, 2018, from

Lamb, J., Konda, V., Quig, D., Desai, A., Minich, D., Bouillon, L., & … Tripp, M. (2011). A program consisting of a phytonutrient-rich medical food and an elimination diet ameliorated fibromyalgia symptoms and promoted toxic-element detoxification in a pilot trial. Alternative Therapies In Health & Medicine17(2), 36-44. Retrieved from

Lin, H. V., Frassetto, A., Kowalik Jr, E. J., Nawrocki, A. R., Lu, M. M., Kosinski, J. R., … & Marsh, D. J. (2012). Butyrate and propionate protect against diet-induced obesity and regulate gut hormones via free fatty acid receptor 3-independent mechanisms. PloS one7(4), e35240.  Retrieved from:

Mozaffarian, R. S., Lee, R. M., Kennedy, M. A., Ludwig, D. S., Mozaffarian, D., & Gortmaker, S. L. (2013). Identifying whole grain foods: a comparison of different approaches for selecting more healthful whole grain products. Public Health Nutrition, 16(12), 2255-2264. doi:10.1017/S1368980012005447. Retrieved from

Park, Y., Subar, A. F., Hollenbeck, A., & Schatzkin, A. (2011). Dietary fiber intake and mortality in the NIH-AARP diet and health study. Archives Of Internal Medicine, 171(12), 1061-1068. doi:10.1001/archinternmed.2011.18. Retrieved from

Sangeetha A., Mahadevamma, S., Begum, K. and Sudha, M. (2011). International Journal of Food Sciences & Nutrition. Vol 62(5). Pp457-8. Retrieved from

Stein, K., Borowicki, A., Scharlau, D., & Glei, M. (2010). Fermented wheat aleurone induces enzymes involved in detoxification of carcinogens and in antioxidative defence in human colon cells. British Journal Of Nutrition104(8), 1101-1111. doi:10.1017/S0007114510001881 Retrieved from

Thompson, S. V., Hannon, B. A., An, R., & Holscher, H. D. (2017). Effects of isolated soluble fiber supplementation on body weight, glycemia, and insulinemia in adults with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. The American Journal Of Clinical Nutrition106(6), 1514-1528. doi:10.3945/ajcn.117.163246 Retrieved from:

Yang, J., Wang, H. P., Zhou, L., & Xu, C. F. (2012). Effect of dietary fiber on constipation: a meta analysis. World journal of gastroenterology: WJG18(48), 7378. Retrieved from:


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