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Your Thyroid: What Happens When The Foods You Love…Bite You Back?

omega 3, gluten-free, anti-inflammatory foods, thyroid hormones

Quiz time…

Which of the following foods could harm your critically important thyroid gland?

  1. Flaky, buttery croissant
  2. Chewy chocolate chip cookie
  3. Oven-roasted Brussels sprouts
  4. Organic spinach salad
  5. Roasted sweet potato

If you answered that the croissant and the chocolate chip cookie could damage your thyroid, you’re right…

These foods both contain gluten, which can damage the thyroid in a number of ways. And these two foods also raise your blood sugar, promoting inflammation, oxidation and metabolic imbalances (all of which can directly affect the thyroid).

But the correct answer to the quiz is: ALL OF THE ABOVE

What most people don’t realize is that even many so-called “superfoods” – including Brussels sprouts… spinach… sweet potatoes… and MANY more – can damage the thyroid and lead to full-blown disease.

And this is no small, isolated issue…

thyroid hormones, medication, thyroid

It is estimated that 20 million Americans have some type of thyroid disease (with tens of millions more worldwide). As further proof of how common this condition is, the drug with the most prescriptions written annually is a thyroid medication.

But there is good news…

It is much safer (and importantly, more EFFECTIVE) to treat a thyroid condition by determining the root causes and correcting those conditions with a personalized diet that avoids potential triggers.

Foods and environmental factors can harm your thyroid in six key ways:

  1. Promoting Leaky Gut (Intestinal Permeability)
  2. Destroying Thyroid Tissue
  3. Blocking Manufacture of Thyroid Hormones
  4. Hampering Metabolism of Iodine (required to produce thyroid hormones)
  5. Cross-Reactions with other foods, compounds or tissues
  6. Raising Thyroid Antibodies

Before we get to specific harmful compounds in our foods and environment, it’s important to note…

One Size Does NOT Fit All when it Comes to Your Diet

Of course, there are some foods that negatively impact almost everyone with thyroid disease…

(I’m talking to you, Gluten!)

We have to remember that we are all unique. And there are personal health and genetic differences between every one of us. That means a certain trigger could cause severe symptoms for one person… and have no effect on another.

But there are four compounds, which are “common denominators” when it comes to the thyroid:

  1. Lectins
  2. Goitrogens
  3. Oxalates
  4. Heavy Metals

Let’s learn a about these key thyroid-harming compounds and what they do…


Lectins are proteins that protect plants from being consumed by microorganisms, pests, insects and other predators… including YOU! These compounds resist digestion and pass through the tract unchanged (a survival mechanism for seeds).

Lectins have the potential to promote leaky gut. They increase bad bacteria (and bacterial toxins) in the gut. And they also bind to tissues (including the thyroid). All of these mechanisms can damage the thyroid and trigger autoimmune disease.


Goitrogens are found in a wide variety of foods. These compounds can block your ability to manufacture of thyroid hormones. They also hamper iodine metabolism, which reduces thyroid function.

And while some people handle goitrogens just fine, others can be severely affected. The New England Journal of Medicine recently pointed to a case of a woman who put herself into a hypothyroid coma by eating raw bok choy daily for several months (even though she previously had no previous history of thyroid disease).

The good news is that cooking goitrogenic foods can help deactivate them, thereby reducing or eliminating risk of harm. In fact, a recent study in Human Toxicology found that consuming 150g of cooked and drained Brussels sprouts daily for four weeks had no impact on thyroid function.


Oxalates are compounds that can form damaging and painful oxalic acid crystals in the body.

Those at risk for oxalate toxicity include: people who have taken antibiotics, those with autoimmune disease, gut imbalances, autism, or other health issues. It has also been shown that many people in the Western world don’t have the bacteria to break oxalates down.[1]

In addition to damaging the thyroid directly, build-up of oxalic crystals can lead to a wide variety of symptoms, including joint and bone problems, anemia, gout, kidney stones, muscle pain, vulvodynia and kidney disease.[2]

In a similar case to the woman who consumed too much bok choy, another woman was recently admitted to the hospital with severe kidney damage, due to the oxalates she was consuming as part of a “green smoothie cleanse.”[3]

Heavy Metals

As you most certainly know, the list of harmful effects from heavy metals – including mercury, cadmium, lead, aluminum and arsenic – extends well beyond the thyroid.

We tend to think of these metals as “pollutants” that end up in soil, water, plants and animals as an aspect of our modern industrialized world. And while this is certainly true, many of these compounds occur organically and can enter the food supply naturally.

Heavy metals harm the thyroid in myriad ways…

For example, the thyroid gland needs the mineral iodine to produce thyroid hormones. But when mercury is present, the thyroid can absorb it in place of iodine. This can directly cause hypothyroidism[4] and increases the risk of autoimmune thyroid disease.[5]

Heavy metals have also been shown to:
  • Promote goiter[6]
  • Increase risk of thyroid cancer[7]
  • Elevate levels of thyroid-stimulating hormone (TSH)[8]
  • Removing iodine from the thyroid hormone, thyroxine[9]
  • Cause oxidative damage to the thyroid
  • Reduce production of beneficial thyroid hormones[10]

Heavy metals can also trigger an immune response, which can lead to production of antibodies which target and destroy thyroid tissue.[11]

And it doesn’t take much…

One recent study of the effects of arsenic on the thyroid suggests that it can “profoundly affect the thyroid hormone receptor (TR) at very low concentrations” as well as impact the genes that can affect thyroid function.[12]

Keep in mind: Most of these thyroid-harming compounds come from plants… with the exception of heavy metals. That’s why it’s important to choose wild, low-toxin seafood (like mackerel, sardines and wild salmon), as well as grass-fed and pasture-raised meats.

anti-inflammatory foods

So, now you know which compounds can damage your thyroid and what kind of harm they can cause. Please stay tuned for my next article, where I will discuss the common foods that contain these compounds and how to create the personalized diet that’s best for YOU!

Kelley HerringED NOTE: Kelley Herring is the co-founder of Wellness Bakeries, makers of grain-free, gluten-free, low-glycemic baking mixes for cakes, cookies, breads, pizza and much more.

Kelley’s academic background is in biology and chemistry and for the last 15+ years, she has focused on the study of nutritional biochemistry…and the proven powers of compounds in foods to heal the body.