How Mold Exposure Can Hurt Your Gut Health | Chris Kresser
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How Mold Exposure Can Hurt Your Gut Health

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Mold can develop in chronically moist areas, such as behind this kitchen cabinet. This kind of water damage can put residents in danger of mold exposure.
Mold exposure from a water-damaged home can cause serious gastrointestinal problems. iStock/Ekspansio

If you’ve encountered mold, either from a water-damaged building or contaminated foods, you’ve likely encountered mycotoxins—toxic byproducts of mold. They’re common environmental toxins, and they have adverse effects on many body systems, including the gastrointestinal tract.

While you’ve probably heard about the respiratory symptoms that can follow mold exposure, research indicates that mycotoxins can cause serious problems for your gut, as well. Read on to learn how mycotoxins impact gut health and the microbiota and what you can do to help restore your gut health if you’ve been exposed.

You know that mold exposure can cause major respiratory symptoms, but did you know it can hurt your gut, too? In this article, I explain how mold can hurt your GI tract and give my recommendations on how to get your gut healthy again. #optimalhealth #wellness #chriskresser

Did You Encounter Mold?

Unfortunately, mold exposure is far more common than we might expect. In the United States alone, 43 percent of buildings have current water damage, and 85 percent have past water damage. (1) Even homes that haven’t suffered water damage can house mold if indoor humidity levels are too high. Contaminated crops, including grains, as well as some fermented foods and dairy, can also carry mycotoxins.

Mycotoxins may play a crucial role in the development of chronic inflammatory response syndrome (CIRS), a complex, multifaceted illness. If you have CIRS brought on by mold exposure, you could be feeling any number of a wide range of symptoms: (2)

  • Malaise after exerting yourself
  • Weakness or fatigue
  • Memory problems
  • Headaches
  • Lightheadedness
  • Shortness of breath and other respiratory issues
  • Chronic abdominal problems
If you’re experiencing the symptoms above and you think you may have encountered mycotoxins, I recommend you get tested for CIRS. You can read more about CIRS and how to get tested in my article “5 Things You Should Know about Toxic Mold Illness.”

More about Mycotoxins

Mycotoxins are not molds, but rather the toxic compounds produced by specific types of fungi such as:

  • Aspergillus
  • Fusarium
  • Stachybotrys, or black mold
While a few mycotoxins have useful applications—the antibiotic penicillin is a toxin derived from Penicillium fungi, and the mycotoxin citrinin is used to produce cheese, sake, and miso—the vast majority of mycotoxins are harmful and capable of causing disease in humans.

The most frequently encountered harmful mycotoxins (which can ingested through consuming contaminated foods, inhaled or otherwise absorbed) are:

  • Trichothecenes
  • Fumonisins
  • Ochratoxins
  • Aflatoxins

Mycotoxins have a diverse array of harmful effects on the body. They are carcinogenic, mutagenic (capable of altering your DNA), and estrogenic (therefore triggering hormonal imbalance) and impair the normal function of the immune system, kidneys, liver, and nervous system. Emerging research indicates that mycotoxins also interact with the gut microbiota.

How Mold Can Hurt Your Gut Health

Mycotoxins produced by mold impair gut health on a structural and functional level. They disrupt the balance of beneficial and pathogenic bacteria in the gut, increase intestinal permeability, interfere with nutrient absorption (causing malnutrition), generate oxidative stress and inflammation, and increase your susceptibility to bacterial, viral, and parasitic gut infections.

It Changes Your Gut Microbiota

Mycotoxins can increase levels of harmful gut bacteria and deplete beneficial microbes. Research has found that exposure to deoxynivalenol (DON), a fumonisin mycotoxin, significantly increases levels of Bacteroides in the gut; also, a high proportion of Bacteroides is associated with inflammatory bowel disease (IBD). (3) Ochratoxin reduces levels of Lactobacillus reuteri and bifidobacteria; the reduction of beneficial lactobacilli and bifidobacteria decreases the intestinal production of short-chain fatty acids, leading to impaired gut immunity. (4)

Mycotoxins also promote the growth of pathogenic bacteria. In animal studies, ochratoxin ingestion increases the growth of a family of bacteria that includes Staphylococcus and Listeria. A combination of aflatoxins and fumonisins enhances the growth of Shiga-toxin-producing Escherichia coli, a type of E. coli that causes diarrhea, UTIs, and bloodstream infections. (5, 6)

It Can Lead to Leaky Gut

The intestinal epithelium—tightly packed epithelial cells that line the walls of your intestines—acts as a barrier to block the entry of pathogens, toxins, and foreign antigens into the bloodstream. Trichothecenes, fumonisins, and aflatoxins interfere with a protein that links epithelial cells together, weakening this barrier; they also decrease gut-protective mucin production and lower IL-8, a cytokine that assists with pathogen removal. (7) These effects increase intestinal permeability, causing leaky gut and rendering the gut vulnerable to infection.

It Can Cause Weight Loss and Even Malnutrition

Mycotoxins can damage your intestinal villi. Intestinal villi are small, finger-like projections that extend into the small intestine. They increase the surface area of the intestine and provide more pathways for nutrient absorption. Trichothecenes and ochratoxins degrade intestinal villi. (8) Shortened intestinal villi increase the risk of malnutrition by decreasing surface area available for nutrient absorption.

The mycotoxin deoxynivalenol (DON), a member of the trichothecene family, also blocks several nutrient transporters in the GI tract, including the D-glucose/D-galactose sodium-dependent transporter (SGLT1) and the D-fructose transporter (GLUT5). (9) Inhibition of these transporters impairs the absorption of carbohydrates and can promote small intestinal bacterial overgrowth (SIBO), malnutrition, and weight loss.

It Could Increase Oxidative Damage

People who have been exposed to mycotoxins require higher levels of antioxidants to combat free radical damage in their GI tracts. (10) Mycotoxins induce the production of reactive oxygen species (ROS), which oxidatively damage intestinal cells. (11)

Mold Increases Your Susceptibility to Gut Infections

Those who develop symptoms caused by mold often experience a variety of gastrointestinal issues, including gut infections. Mycotoxin exposure may directly increase your susceptibility to bacterial, viral, and parasitic gut infections by decreasing your intestinal immunity.

In animal studies, ochratoxin triggered viral gut infections and strengthened the virulence of intestinal parasites. In chickens, Fusarium decreases populations of CD4+ and CD8+ cells (helper T cells), increasing the risk of coccidiosis, an intestinal disease that easily spreads from bird to bird. Furthermore, the effectiveness of antiparasitic drugs is reduced by high levels of circulating mycotoxins, suggesting that mycotoxin exposure should be addressed first before attempting to treat parasitic infections. (12)

These Factors Can Worsen the Harmful Effects of Mold

Several factors may exacerbate the harmful effects of mycotoxins on your gut, including diet, antibiotic use, stress, exposure to other environmental toxins, and genetic background.

A diet high in grains, conventional dairy, and other processed foods that can become contaminated exponentially increases your exposure to mycotoxins. Mycotoxins can get into the food supply at various points in its production and distribution. For instance, grains sitting in storage, waiting to be transported or processed, can become damp and then moldy with mycotoxin-producing fungi. This is especially true with industrially farmed crops that are grown and harvested in vast quantities and then stored for long stretches of time before going to market.

Also, we know that antibiotic use and stress disrupt the gut flora, which can reduce the microbiome’s capacity to bind and detoxify mycotoxins. Exposure to other environmental toxins in water-damaged homes or other buildings—such as bacteria, Actinomycetes, endotoxins, and microbial volatile organic compounds (VOCs)—creates further toxicity in the GI tract. Finally, people with variants in CYP genes may be at an increased risk of mycotoxin-induced dysbiosis and intestinal epithelial damage; this is due to impaired processing of mycotoxins by cytochrome p450 enzymes in the liver. (13)

If You Have SIBO or IBS, Mold Exposure Might Make Things Worse

The gastrointestinal tract serves as the primary interface between ingested mycotoxins and the rest of the body.

Fascinatingly, researchers have discovered that mycotoxins and the gut microbiota engage in bidirectional crosstalk that ultimately influences the structure, function, and health of the gastrointestinal tract.

They have learned that while a healthy gut microbiota can bind and metabolize some ingested mycotoxins, mycotoxins can also alter the microbiota and reduce its natural detoxification capacity. This means that patients with pre-existing gut issues such as irritable bowel syndrome (IBS) and SIBO may be more severely impacted by mycotoxin exposure than people with a healthy gut microbiota, due to changes in their gut bacteria that reduce their capacity to process mycotoxins. (14)

Here’s How to Restore Your Gut Health after Mold Exposure

The first step in treating the side effects of mycotoxins is to stop your exposure to the mold in the first place and test your home for mold. Then you can focus on restoring your gut health.

Take Probiotics

Beneficial gut bacteria bind mycotoxins and prevent their absorption in the small intestine. Probiotic strains with mycotoxin-binding properties include Lactobacillus rhamnosus, L. plantarum, L. casei, and Propionibacterium freudenreichii. (15, 16, 17) If you’re trying to reduce your total mycotoxin load and detox, I encourage you to supplement with a multispecies probiotic containing these strains. Saccharomyces boulardii is another beneficial mycotoxin-binding probiotic that has been found to be effective in treating ochratoxin-exposed animals. (18)

Use Activated Charcoal or Another Sequestering Agent

Sequestering agents are compounds that bind mycotoxins in the GI tract and prevent them from being recirculated through the liver and GI tract. They help reduce the number of mycotoxins to which GI cells and microbes are exposed. Cholestyramine, activated charcoal, and bentonite clay are potent binding agents that can reduce the bioavailability of mycotoxins in the gut. (19, 20) However, these can cause constipation. I would only recommend them if you tend to have loose stools or you suffer from diarrhea. If you have constipation, chlorella also has mycotoxin-binding properties and may be a better option for you.

Switch to a Low-Mold Diet

Your diet can be a significant source of mycotoxins, especially if it is centered around grains, dairy, and other processed, packaged foods. Experimenting with a low-mold diet will reduce the amount of mycotoxins entering your GI tract and protect your intestinal epithelial cells and the gut microbiota. Here are some simple guidelines for implementing a low-mold diet.

You Should Avoid These Foods Entirely

Avoid high-sugar fruits:

  • Pineapple
  • Mango
  • Banana
  • Melons
  • Oranges
  • Grapes

Excess sugar fuels fungal overgrowth in the gut, a condition that often accompanies toxic mold illness; avoiding these fruits temporarily will starve and facilitate the eradication of fungal pathogens. I also recommend steering clear of packaged and processed foods, most grains, and fermented foods. And, of course, don’t consume foods that contain mold or yeast, such as:

  • Cheese
  • Alcoholic drinks
  • Processed and smoked meats
  • Edible fungi
  • Dried fruits

You Can Eat These Foods, but Only in Moderation

Consume moderate amounts of:

  • Rice
  • Quinoa
  • Buckwheat millet
  • Teff
  • Gluten-free oats
  • Potatoes
  • Sweet potatoes
  • Legumes
  • Squash
  • Low-sugar fruits such as apples and berries

Eat These Foods Whenever You Want

You’re free to eat organic and grass-fed meats and poultry, wild-caught seafood, non-starchy vegetables, fresh sprouted nuts and seeds, olive oil, coconut oil, ghee, and butter.

Bone broth, gelatin, and collagen peptides provide easily assimilated amino acids that can help repair damaged intestinal cells, so they’re another great addition to your low-mold diet.

Now I’d like to hear from you. Do you suffer from gut issues? Were you exposed to mold, or do you believe you were? Let me know in the comments below.

  1. Ana Rose,

    So are you only treating your mold exposure through diet? Were there any other steps you took to get rid of the mold? How are you doing now, which is about 6 months after your post? Hope you are doing better.

  2. Thanks for educating people about the devastating effects of mold poisoning. I dealt with severe mold poisoning a few years ago (it almost killed me, exacerbating all kinds of health problems like SIBO, insomnia, fibromyalgia, autoimmune skin issues, and extreme breathing difficulties). I believe it is impossible to rid the body of parasitic mold as long as you are consuming ANY plant sugars. There are many types of plant sugars–some are sweet, some are not (fructose, FODMAPS, alcohol, etc.)…all plants have carbs, and therefore some kind of sugar. So if you really want to starve the mold (and why bargain with it?), you have to abstain from ALL sugars for a good month. What does that mean? Fasting for a few days (ideal but not required) and then eating only meat, eggs and animal fats for one month. It is a very healing diet, in fact, in many ways. Beware, for a couple weeks you will experience carbohydrate withdrawal, which creates fatigue, sluggishness, and flu-like symptoms. But trust the process–it is profound. A good resource for thousands of amazing testimonials after having launched this way of eating (called the “carnivore” or “zero carb” diet) can be found at meatheals.com.