What are Mycotoxins? A Primer on Mold Exposure and the Gut Microbiome



It has been estimated that as many as 47% of buildings in the United States have some amount of mold exposure [1]. Unfortunately, that means there’s a good chance your environment has a bit of mold. 

In this article you will  learn about mycotoxins and the possible health effects of mold exposure, including how it may affect your gut. Exposure to mold across the lifespan, but especially in the early life period (and even during pregnancy!) may increase your risk of atopic disorders, such as eczema, allergies, and asthma. The good news is, a strong gut microbiome can help protect you against the side effects of mold. Read on to learn more!

Mycotoxins and how mold enters the body 

You may recognize the names of a few common molds, like Aspergillus and Penicillium, but there are many others that can affect you depending on your environment or exposures. Wet or humid environments can easily lead to the growth of a variety of molds [2]. All mold needs to thrive is a bit of moisture and some nutrients. Nutrients can come in many forms, but home materials like carpet, wood, or even ceiling tiles can support mold growth. Moisture often shows up after a major rain storm or even a flood, but can also accumulate over time in high humidity environments. You can also be exposed to molds through contaminated foods [3]. 

So what are mycotoxins? Many molds have the potential to cause harm, and do so by producing metabolites called mycotoxins (“myco” means fungus, so mycotoxins are toxins from fungi like mold). Once these toxins enter your body they can cause damage to many different body systems. 

Molds release spores to reproduce, so a common way to be exposed to mycotoxins is through inhalation of these mold spores [4]. When this occurs, these mycotoxins are likely to affect body systems such as your lungs, blood stream, immune system, and even your brain [5]-[8]. This is often the route that mold affects people when it is found in their homes.

If mycotoxins are eaten on a piece of moldy food, their first line of attack will be in your gut, before traveling to the rest of your body [9]. Studies have shown that they can open up passage through your protective gut barrier by reducing the mucus layer and breaking down your epithelium [10], [11], [12] as well as dysregulate the immune system in your gut by throwing off the balance of pro- and anti-inflammatory cytokines [13]. They may also hurt your gut microbiome. 

The role of mold and mycotoxin exposure in health conditions 

Early life mold exposure may sensitize the immune system, increasing the risk of atopic disorders such as eczema, allergies, as well as asthma [14]. This happens when components of the mold structure, like mold spores for example, are detected by your body as allergens, leading to a larger than necessary response by your immune system [15]. These mold components can also cause inflammation throughout your body. 

Eczema is associated with exposure to molds, such as Aspergillus [16] in the first year of life [17] [18] [19]. It is also possible for exposure to mold during pregnancy to increase the risk of eczema later in childhood [20]. 

Allergies, whether to food [21], [22] or to other irritants like pet dander or tree pollen [23], can all be worsened by exposure to mold. In addition, mold exposure in a damp household is associated with an increased risk of allergic rhinitis in both children and adults [24], [25].

Asthma has the strongest association with mold exposure. Several studies have shown that exposure to mold during the first two years of life increases the risk of asthma development by the end of childhood [2], [26]-[30]. 

Research shows that early life mold exposure before 1 years old has the highest risk for asthma. One study showed that mold exposure at 1 year of age, but not 7 years of age, increased the risk of asthma at 7 years of age [31]. Common indoor molds like Penicillium, Aspergillus, and Cladosporium may be specifically responsible for the increased risk of asthma [32].

The season of your baby’s birth may play a role in their exposure to mold. This is because the fall and winter months are when molds and fungi release their spores into the air. Babies born during this period are more likely to be exposed to mold during the crucial, early life period. Babies born in these winter months are also at increased risk for atopic conditions [30], potentially due to their exposure to mold, alongside other factors like pollen exposure, and incidence of illness. 

Can mycotoxins hurt—or even help—my microbiome? 

Research on the effects of mycotoxins on the human microbiome is extremely limited. However, knowledge from studies in animal models can help us to understand the possible effects of mold exposure on the human gut microbiome. 

Notably, not all molds are harmful. Penicillin, a significant medical breakthrough, was discovered by Alexander Fleming on a moldy Petri dish in 1928. This accidental discovery highlighted the potential benefits of molds. 

Antibacterial properties 

It is possible for mycotoxins themselves to have antibacterial properties, meaning that they can kill bacteria. In some cases, we’ve been able to use this to our advantage. The life-saving antibiotic Penicillin was originally derived from a mold, Penicillium, by Alexander Fleming because of its natural ability to kill pathogenic bacteria [33]. Today, penicillin is synthetically produced in labs, bypassing the need for mold altogether. Other molds, such as Myxomycetes and Fusarium [34], [35], also have this unique antibacterial ability.  

Unfortunately, this means that it is also possible for environmental exposure to mycotoxins to degrade the beneficial bacteria in your gut. When mycotoxins attack your gut barrier, this sends alarm signals in the gut. Unfortunately, in many cases these signals may degrade your gut microbiome [13].

Support of pathogens

After the beneficial bacteria in your gut are killed off, a niche is left open that often is filled by more unfriendly bacteria. Animal studies have shown that mycotoxin exposure can increase the likelihood of these unfriendly bacteria taking root in your microbiome [36]. 

Luckily, a robust gut microbiome is a great defense against invading mycotoxins [37]. We’ll cover this more in detail later! 

Ways to protect yourself from mold exposure

Control indoor moisture. The number one cause of household mold is moisture, whether that be from a high humidity climate or a leaky pipe. Attacking the source of moisture within your home should be your first step to preventing mold. 

Test for mold. If you have noticed a damp area or a musty smell in a certain room of your home, it may be wise to test for mold. Both at-home and professional tests are available. 

Filter out the spores. If a mold problem is already present at home, spores from that mold will circulate in the air, potentially increasing the overall fungal load in your home. Consider a HEPA-grade air purifier to remove these microscopic spores from the air in your home. 

Seek mycotoxin treatment. If you feel you may be having a reaction to mold in your home, a visit to your healthcare provider may be in order. 

Because of how common mold is in our environment, chances are you have been exposed at some point in your life. Keep reading to learn how your gut microbiome plays a role in keeping you healthy.

Your gut microbiome: bacteria, viruses, and…fungi? Meet your mycobiome!

So, we've talked about bad mold exposure, what about good fungi? Are there any fungi that are supposed to be in your gut? The answer is yes! This little known microbial community is sometimes referred to as the “mycobiome.” In most cases, this group of fungal species makes up less than 1% of your microbiome, and often don’t show up on a shotgun metagenomics test because the individual species may make up such a small fraction of your sample. This may sound scary, but at low levels most fungal species can actually coexist with the rest of your microbiome without causing any harm. 

Researchers have made efforts to understand what fungal species populate a healthy gut during the first months of life. Here’s what they’ve found:

  • Babies in the first month of life likely have mostly Candida [38], Cryptococcus, and Saccharomyces [39] in their mycobiome. 
  • Babies between 1 and 3 months begin to grow Malassezia and Cystofilobasidium [38], as well as Debaryomyces during the period that they are still relying on breastmilk or formula for nutrition [40]. 
  • Babies up to 1 year and older may have higher levels of Trichosporon [38], but Saccharomyces may dominate instead if they were born by a c-section birth. 

Even though fungi make up a small portion of your microbiome, their composition can have a big impact on your health. Unsurprisingly, a shift in your mycobiome can cause negative gastrointestinal symptoms [41], but they can also have impacts on your immune system and metabolism [42], [43] or even your brain [44], [45].  

Strengthen your microbiome defense against mycotoxins

If all this talk about mold and toxins has you worried, you’re not alone. We come bearing good news! Having a healthy gut can help protect you from the side effects of mold exposure. 

Your gut microbiome can actually tamper the toxic effects of mycotoxins—by either holding them captive so they can’t infiltrate your gut barrier and reach the rest of your system, or by transforming the mycotoxins into new forms that are no longer toxic to you [13]. Isn’t that amazing?

More good news: you don’t have to guess if your gut health is strong. A great place to start is a gut health test from Tiny Health, giving you a comprehensive look into your microbiome. You’ll learn about your (or your child’s) unique mix of beneficial and disruptive microbes and health conditions associated with any imbalances. Then you’ll get a personalized action plan with recommendations for foods, probiotics or supplements, and lifestyle changes you can make to get your gut health on track. Get started today! 


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