How Mold Affects the Gut, Immune System, and Thyroid

Welcome to Healthy Gut Healthy Thyroid!

This is your weekly roundup of the BEST actionable steps for those people with thyroid and autoimmune thyroid conditions who want to restore their health…by healing their gut. Whether you have hyperthyroidism or Hashimoto’s you will benefit from the content in this newsletter.

In today's issue:

• Main Topic: How Mold Affects the Gut, Immune System, and Thyroid

• Podcast Review: What Role Do Your Genes Play in Thyroid Health?

• Ask Dr. Eric: What should I do when I can't improve my thyroid numbers through diet?

How Mold Affects the Gut, Immune System, and Thyroid

Mold is a significant issue, and while more people are becoming aware of how it can impact overall health, not everyone understands how it can affect the gut microbiome.

Just as is the case with many other toxins and toxicants, the mycotoxins produced by mold can negatively affect the gut. Research has shown that mycotoxins can disrupt the integrity of the intestinal lining through mechanisms such as tight junction impairment, oxidative stress, apoptosis (cell death), and inflammation (1). In other words, the mycotoxins from mold can cause a leaky gut.

In some ways, mold is similar to gluten. Just because you don’t experience noticeable symptoms when consuming gluten doesn’t mean it isn’t affecting your intestinal barrier. The same concept applies to mold exposure. Even if someone doesn’t feel significantly symptomatic, mycotoxins can still quietly disrupt the gut and immune system.

That said, individual susceptibility varies. Some people have a reduced ability to detoxify and eliminate mycotoxins, which can lead to more noticeable symptoms. Others may appear relatively asymptomatic, but this doesn’t mean mold exposure isn’t having a negative effect beneath the surface.

Mold and the Gut Microbiome

According to the company RealTime Laboratories, a number of studies suggest that mycotoxins can alter the composition of the gut microbiome.

For example, one study found that exposure to a specific mycotoxin called ochratoxin A (OTA) led to the complete disappearance of certain beneficial bacteria, including Lactobacillus reuteri. This is concerning because L. reuteri plays an important role in reducing inflammation, supporting immune balance, and helping to maintain healthy digestion.

In addition, other mycotoxins such as aflatoxins have been shown to reduce the overall diversity of the gut microbiome. This is important because a diverse microbiome is associated with better immune function, improved metabolism, and greater resilience to stressors.

When beneficial bacteria decrease and microbial diversity is reduced, this can create an environment where opportunistic organisms are more likely to thrive. Over time, this imbalance—known as dysbiosis—can contribute to digestive symptoms, immune dysfunction, and even metabolic disturbances.

How Mold Affects the Immune System and Thyroid

Beyond its effects on the gut, mold exposure can also have a significant impact on the immune system—and this is where the connection to thyroid health becomes especially important.

Mycotoxins can dysregulate the immune system in multiple ways. They can increase inflammatory cytokines, suppress certain immune responses, and in some cases contribute to immune overactivation. This imbalance can make it more difficult for the body to maintain proper immune tolerance, which is essential in preventing autoimmune conditions. I discussed immune tolerance in Newsletter 50.

Since both Graves’ disease and Hashimoto’s are autoimmune conditions, anything that disrupts immune balance—such as mold exposure—has the potential to play a role as a trigger or contributing factor.

In addition, chronic inflammation driven by mold exposure can place added stress on the body. This can affect the hypothalamic-pituitary-adrenal (HPA) axis, blood sugar regulation, and detoxification pathways—all of which indirectly influence thyroid function.

From a clinical standpoint, I have worked with a number of patients where mold exposure appeared to be one of the “missing pieces” preventing them from fully restoring their health.

Addressing Mold Colonization of the Gut

Another concern with mold is that, in some cases, it can colonize the gut. This is different from simply being exposed to mold in the environment, as colonization suggests that fungi are actively residing and growing within the body.

Because of this, some practitioners who focus on mold will recommend antifungal treatment for all patients with suspected mold exposure. Others take a more targeted approach and will first perform testing—such as an organic acids test—to determine whether fungal overgrowth is present.

I tend to fall into the latter category. If I recommend a urinary mycotoxins test and it comes back positive, I don’t automatically recommend antifungal agents. However, if an organic acids test shows elevated fungal markers—or if the person has clear gastrointestinal symptoms suggestive of fungal overgrowth—then antifungal support may be appropriate.

When it comes to addressing fungal overgrowth or potential colonization, there are a few options to consider. Undecylenic acid is one supplement I commonly recommend, as it has natural antifungal properties. I also frequently use Saccharomyces boulardii, which is a beneficial yeast that can help balance the gut microbiome and inhibit the growth of pathogenic fungi.

It’s also important to remember that simply “killing off” fungi isn’t the entire solution. You also want to create an environment in the gut that discourages overgrowth in the first place. This includes supporting digestion, improving gut barrier integrity, and restoring microbial balance. And of course you also need to eliminate the source of the mold.

Supporting the Gut After Mold Exposure

If mold has negatively impacted the gut, part of the recovery process involves rebuilding and supporting the intestinal environment.

This can include:

✔️ Supporting gut barrier integrity (i.e., nutrients such as L-glutamine, zinc, and vitamin A)

✔️ Restoring microbial diversity (through diet, prebiotics, and probiotics when tolerated)

✔️ Supporting bile flow and detoxification pathways

✔️ Reducing ongoing exposure to mold and other environmental toxins

In many cases, improving gut health will also help improve immune balance, which in turn can support thyroid health.

Final Thoughts

Mold exposure is often an overlooked factor when it comes to gut health, immune function, and thyroid conditions. While not everyone exposed to mold will experience obvious symptoms, mycotoxins can still have subtle but meaningful effects on the gut microbiome and intestinal barrier.

Over time, these changes can contribute to immune dysregulation and, in some cases, play a role in autoimmune thyroid conditions such as Graves’ disease and Hashimoto’s.

The good news is that, with the right approach, it is possible to address mold-related gut imbalances and restore a healthier internal environment. This typically involves a combination of reducing exposure, supporting detoxification, and rebuilding gut health.

If you feel like you’ve addressed many of the common factors—such as diet, stress, and basic gut support—but still aren’t where you want to be, mold exposure might be something worth considering.

Not All Gut Healing Supplements Are The Same

Since most of the immune cells are located in the gut, a healthy gut is essential for a healthy immune system. In fact, Hippocrates himself said that “all disease begins in the gut”. And so whether someone has Graves’ disease, Hashimoto’s thyroiditis, or another health condition, having a healthy gut is important to achieve optimal health.

When choosing a gut healing supplement you want one that does the following:

• Promotes optimal function of the GI lining

• Rejuvenates health of intestinal mucosa

• Supports healthy inflammatory response

• Builds immune support

• Thyroid-friendly ingredients

The Gut Healing Bundle includes the following:

SMT-GI Restore. Combines effective clinical levels of well-researched (and thyroid-friendly) nutrients and botanicals specifically formulated to support optimal gastrointestinal health and function without any added flavors, colors, sweeteners, gums or common allergens.

Enzymes Plus. Comprised of a proprietary blend of digestive enzymes along with betaine HCL and ox bile to support optimal digestion of proteins, fats, and carbohydrates. Also contains the special protease DPP IV (dipeptidyl peptidase IV), which aids in the breakdown of the peptides gluteomorphin (from gluten) and casomorphin (from casein). Although you don’t need to be experiencing digestive symptoms to use Enzymes Plus, it may be helpful for those who experience gas and bloating after eating, occasional constipation or diarrhea, or a feeling of fullness after eating.

SMT-Probio. Choosing a good quality and effective probiotic can be a challenge, as there are so many probiotic supplements on the market. Unfortunately many probiotic supplements only list the species, and not the specific strains. Others list the strains but aren’t diverse or potent enough. SMT-Probio Complete provide 18 different strains belonging to 13 different species of three different genera. For consumer convenience, this formula is available encapsulated at a maintenance dose of 45 billion CFUs per capsule. The HOWARU and FloraFIT strains that comprise these formulas are stable, proven, and trusted worldwide.

To learn more about The Gut Healing Bundle visit www.guthealingbundle.com

Save My Thyroid Podcast Review

I have a podcast called "Save My Thyroid", where I discuss how people with hyperthyroidism and Hashimoto's can save their thyroid and regain their health. And during each edition of this newsletter I'll briefly discuss a recent podcast episode.

In a recent podcast episode I chatted with Justin Harris, a certified functional genomics practitioner, who explains how understanding your genetic blueprint can unlock personalized strategies for managing thyroid health. We dive into how genetics influences key factors like oxidative stress, detox pathways, and autoimmune conditions such as Hashimoto’s and Graves’ disease. Justin also shares how genetic testing can offer insights into your body’s unique response to food, exercise, and environmental factors.

By understanding your genetic makeup, you can make more informed decisions about nutrition, supplements, and lifestyle changes. We also touch on the role of epigenetics in how your genes express themselves and how modifying your lifestyle can improve thyroid function and overall health.

Tune in to find out how your genes could be the missing piece.

Ask Dr. Eric

During every issue I'll answer a question or two that I think can benefit most people with a thyroid or autoimmune thyroid condition. If you'd like for me to consider your question for a future edition of this newsletter email your question to [email protected].

QUESTION: WHAT SHOULD I DO WHEN I CAN’T IMPROVE MY THYROID NUMBERS THROUGH DIET?

Dr. Eric, I purchased your excellent book The Hyperthyroid Healing Diet and followed a strict Level 3 diet for three months, as you suggested in your book. However, my thyroid panel hasn’t improved. What else would you recommend?

Thanks for your question! This is a very common situation. There’s no doubt that eating a healthy diet is an important piece of the puzzle, and some people will see improvements in their thyroid hormones—and even antibodies—through diet alone.

That said, many people need to go beyond diet and lifestyle in order to truly optimize their thyroid numbers. So while I realize it can be discouraging to make significant dietary changes and not see improvements in your thyroid panel, this doesn’t mean the diet isn’t helping. It simply means that additional factors likely need to be addressed.

In fact, in my book I have a separate section titled “Beyond The Hyperthyroid Healing Diet,” where I dedicate chapters to the following:

✅Optimizing your adrenals
✅Healing your gut
✅Improving sleep quality and duration
✅Exercise and hyperthyroidism
✅Reducing your toxic burden
✅Correcting nutrient deficiencies
✅Bioengineered foods and glyphosate concerns
✅Testing options to consider

So while I commend you for following a Level 3 diet (which is a modified AIP diet), it sounds like it’s time to incorporate some of these additional strategies.

This doesn’t mean you should go back to your previous way of eating. However, depending on your progress, you might consider reintroducing certain foods and transitioning to a Level 2 diet while continuing to address these other key areas.

Additional Thyroid-Related Resources

Click Here for What Role Do Your Genes Play in Thyroid Health? (episode 234)

Click Here to access hundreds of thyroid-related articles and blog posts

Click Here to join the Graves’ disease and Hashimoto’s community

Click Here to purchase one of Dr. Eric’s thyroid-related books

Click Here to work with Dr. Eric and his team

📚References:

(1) https://pmc.ncbi.nlm.nih.gov/articles/PMC12656439/

(2) https://realtimelab.com/how-mycotoxins-affect-the-gut/

That’s a wrap