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Insoluble Fiber and Mycotoxin Binding: The Gut's Natural Defense

Written by Portland Clinic of Natural Health on October 13, 2023

Mycotoxins, harmful compounds produced by certain fungi, are an increasing concern due to their potential health risks. They can contaminate various foods, such as cereals, nuts, fruits, and even some animal products. Consuming contaminated foods can lead to various health issues, including digestive disturbances, weakened immune function, and even carcinogenic effects in some cases.

Recent studies suggest that dietary insoluble fiber may play a pivotal role in binding these mycotoxins in the gut, thereby reducing their harmful effects. Let’s dive deeper into the role of insoluble fiber in this protective mechanism. (1)

What is Insoluble Fiber?

Insoluble fiber is one of the two main types of dietary fiber, the other being soluble fiber. As the name suggests, insoluble fiber does not dissolve in water. Instead, it remains largely unchanged as it moves through the digestive tract. This characteristic is beneficial for adding bulk to stool and aiding in regular bowel movements. (2, 3)

Some primary sources of insoluble fiber include:

  • Whole grains (e.g., wheat bran, brown rice)
  • Nuts and seeds
  • Vegetables (e.g., carrots, broccoli, cauliflower)
  • Fruit skins

How Does Insoluble Fiber Bind Mycotoxins?

Physical Binding: Insoluble fiber has a unique porous structure. As mycotoxins come into contact with insoluble fiber, they can become trapped or "adsorbed" in these pores, reducing their bioavailability and preventing their absorption in the gut.

Alteration of Gut Transit Time: Insoluble fiber increases stool bulk, which can speed up the transit time of food and waste through the digestive system. This reduced transit time may provide less opportunity for mycotoxins to be absorbed.

Support of Beneficial Gut Bacteria: Some studies suggest that certain gut bacteria can modify or degrade mycotoxins, rendering them less toxic. While insoluble fiber isn't directly fermented by gut bacteria like soluble fiber is, the presence of insoluble fiber can promote a healthier gut environment, indirectly supporting these beneficial microbes. (4)

The Role of Insoluble Fiber in Binding and Reducing Adverse Effects of Mycotoxins

While more research is needed, especially on human subjects, existing evidence suggests that insoluble fiber has a potential role in binding and reducing the harmful effects of mycotoxins in the gut. Incorporating foods rich in insoluble fiber into our daily diet not only offers digestive benefits but may also provide an added layer of defense against dietary mycotoxins.

However, it’s essential to remember that while insoluble fiber may help mitigate the impact of mycotoxins, it's always best to prevent or limit exposure in the first place. Proper food storage, regular inspection, and consumption of high-quality food products are primary measures everyone should consider.


  1. López-Ruiz R, Marin-Saez J, Cunha SC, Fernandes A, de Freitas V, Viegas O, Ferreira IMPLVO. Investigating the Impact of Dietary Fibers on Mycotoxin Bioaccessibility during In Vitro Biscuit Digestion and Metabolites Identification. Foods. 2023 Aug 23;12(17):3175. doi: 10.3390/foods12173175. PMID: 37685107; PMCID: PMC10486935.
  2. McRorie JW Jr, McKeown NM. Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber. J Acad Nutr Diet. 2017 Feb;117(2):251-264. doi: 10.1016/j.jand.2016.09.021. Epub 2016 Nov 15. PMID: 27863994.
  3. Williams BA, Mikkelsen D, Flanagan BM, Gidley MJ. "Dietary fibre": moving beyond the "soluble/insoluble" classification for monogastric nutrition, with an emphasis on humans and pigs. J Anim Sci Biotechnol. 2019 May 24;10:45. doi: 10.1186/s40104-019-0350-9. PMID: 31149336; PMCID: PMC6537190.
  4. McCormick SP. Microbial detoxification of mycotoxins. J Chem Ecol. 2013 Jul;39(7):907-18. doi: 10.1007/s10886-013-0321-0. Epub 2013 Jul 12. PMID: 23846184.

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