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[This post received some minor updates on July 26, 2017.]

This post is the eighth installment in my ten-part Minerals and Your Thyroid series, where I’m highlighting eight thyroid-supportive minerals (iodine is two parts) and one troublemaker: fluoride.

Prior posts: Calcium, Copper, Iron, Iodine (Part 1, Part 2), Magnesium, Manganese

Selenium symbol: Se
Atomic number: 34

If iodine is “the big daddy” thyroid mineral, then selenium is surely “the big mama.”

Many don’t realize the critical role that minerals play in thyroid function – however many are privy to the benefits of selenium specifically. In fact, a common question I get is, “How much selenium should I take?”

The short answer? Maybe none. But that’s not to say that selenium supplementation is never warranted. Let’s discuss.

The Triple Play
When it comes to a healthy thyroid, the importance of selenium simply can’t be underestimated. As such, I’ve nicknamed selenium “the thyroid triple play” because it:

1. Supports healthy thyroid hormone metabolism (Source)
2. Helps the body convert T4 (the inactive form of thyroid hormone) into T3
3. Helps to reduce Hashimoto’s antibodies

[I thoroughly address optimal thyroid nutrition in my best selling cookbook, The Essential Thyroid Cookbook: Over 100 Nourishing Recipes for Thriving with Hypothyroidism and Hashimoto’s. The educational component of the cookbook details not only thyroid-supportive minerals, but also vitamins and amino acids that help to optimize thyroid function. The mouthwatering recipes are chock full of these supportive nutrients.]

According to Chris Kresser, “Several research studies have demonstrated the benefits of selenium supplementation in treating autoimmune thyroid conditions. One study found that selenium supplementation had a significant impact on inflammatory activity in thyroid-specific autoimmune disease and reducing inflammation may limit damage to thyroid tissue.”

He continues, “Another study followed patients for nine months and found that selenium supplementation reduced thyroid peroxidase antibody levels in the blood, even in selenium sufficient patients.”

According to Dr. David Brownstein, “Selenium has been shown to slow the progression of autoimmune thyroid disorders.”

And generally, a little selenium goes a long way (see rich foods sources below).

Dr. Richard Shames recommends 100 micrograms per day (remember, micrograms, not milligrams) and some doctors recommend as much as 200 micrograms, which is the dose you’ll find in many multi-vitamins.

The short story is that selenium supplementation may not be a good idea for those already eating selenium-rich foods regularly. Why? Because when you consider that selenium boosts T3 – your active thyroid hormone – over-supplementation can cause…overstimulation. 

Note that I say over-supplementation. Too many read about the benefits of selenium and say, “Ooooh, I’m going to get myself a bottle of that!” and overdo it. More isn’t always more.

I’ve seen too many people fall prey to the “too much of a good thing” thing: anxiety, anxiousness, monkey mind, irritability, sleep issues, and even heart palpitations as a result of going gangbusters with supplementation.

But…this may be an oversimplification of what’s often happening for some people.

Firstly, it’s not a given that those supplementing with selenium, even in the face of a selenium-rich diet, will experience these symptoms. And there’s another significant factor that can contribute to this overstimulation.

Let’s harken back to Part 1 of my Your Thyroid + Iodine miniseries, where I stated that one well-publicized discovery was that if you have an excess or deficiency in selenium (the big mama), you’re likely to be intolerant of iodine (the big daddy) supplementation. That “intolerance” of iodine can lead to the same symptoms I list above.

Mama and Daddy in Balance
Given that iodine and selenium are the two thyroid-supportive minerals that get the most airtime, often, people are supplementing with both. Maybe it’s in the same “thyroid support” supplement (I’m always leery of these supplements). Or they’re taking iodine and selenium separately.

Regardless, here’s another situation where, as I’ve mentioned a few times in this Minerals series, there’s a checks and balances with mineral intake.

In my post on iodine, I quote Mario Renato Iwakura, a Brazilian engineer and Hashimoto’s patient who is thoroughly well-versed in Hashimoto’s literature. 1, 2.

He states, “…evidence emphasizes the need for balance between iodine and selenium. Just as iodine without selenium can cause hypothyroidism, so too can selenium without iodine. Both are needed for good health.”

Likewise, Kresser states, “If you do have Hashimoto’s or Graves’… and you’re considering taking iodine, you want to make sure that you’re getting at least 200 micrograms of selenium combined from food and supplements each day. Adequate selenium nutrition supports efficient thyroid hormone synthesis and metabolism and protects the thyroid gland from damage from excessive iodine exposure.”

The Gut: a Case for Selenium Deficiency
Those with autoimmune conditions have some level of leaky gut – even if it’s mild. But those with full-blown gastrointestinal disorders (Celiac, Crohn’s, ulcerative colitis, etc.) are at much greater risk of selenium deficiency due to compromised digestive absorption.

In these cases, I do recommend selenium supplementation while simultaneously healing the gut.

Reuse, Recycle
If you’ve been tuned into the world of Hashimoto’s and autoimmunity for any amount of time, you’ve likely heard of glutathione, a superpower antioxidant that significantly strengthens the immune system and is considered by many functional medicine doctors to be one of the pillars of fighting Hashimoto’s.

It also fights cancer, viruses, and bacterial infections and protects against inflammation and allergies.

It’s considered “the master antioxidant” and Dr. Mark Hyman says that it’s the most important molecule you need to stay healthy and prevent disease.

Glutathione can:

• Boost your body’s ability to modulate and regulate your immune system
• Dampen autoimmune flare-ups
• Protect and heal thyroid tissue

When free radicals begin to destroy your body’s tissue, glutathione will absorb the attack, sparing tissue and minimizing destruction.

And get this. It then gets recycled so it’s ready for action again. Amazing. And guess what helps with that recycling? That’s right – selenium. (And Vitamins C and E.)

Dr. Datis Kharrazian says, “The overall effect [of glutathione recycling] is to dampen both the autoimmune reaction and damage to body tissue. It also helps body tissue and the intestinal tract regenerate and recover.”

He continues, “Glutathione is like the bodyguard or Secret Service agent whose loyalty is so deep that she will jump in front of a bullet to save the life of the one she protects. When there is enough of the proper form of glutathione in the body to ‘take the bullet,’ no inflammatory response occurs. However when glutathione becomes depleted, it triggers a destructive inflammatory process.”

The foods that help the body make glutathione are: asparagus, broccoli*, avocado, spinach*, squash, grapefruit, peaches*, garlic, onions, kale*, collard greens*, cabbage*, cauliflower*, and watercress*, and raw eggs.

* These foods are considered “goitrogens,” but we bust the myth that they slow thyroid function here.

Troublemaker: Mercury
Mercury, like fluoride, which I’ll cover in two weeks, is a major troublemaker for the thyroid. The reasons are beyond the scope of this post, but let’s talk about mercury’s association with selenium.

Mercury has been shown to bind to thyroid tissue and inhibit proper thyroid function. According to Dr. David Brownstein, “Because mercury binds so tightly to our tissues and enzymes, the body has a very difficult time disposing of mercury. [And] selenium is one of the most potent chelators (binders) of mercury.”

Additionally, Brownstein states that “… the enzyme that converts the inactive thyroid hormone T4 into the active hormone T3 is an enzyme dependent on adequate selenium levels.”

But here’s the Catch-22. Mercury can displace selenium. So even if you’re getting adequate selenium, the mercury may be displacing it. So then the selenium doesn’t have the capacity to act as a mercury chelator.

My suggestion? Remove your mercury dental fillings…stat.

Many have reported significant improvement in their hypothyroidism/Hashimoto’s by removing their mercury/amalgam fillings. I had mine removed in 2003 and it wasn’t a big deal.

Just MAKE SURE that you work with a dentist who knows what the H-E-double hockey stick they’re doing. 

For one, they need to use a throat dam so that the mercury vapors aren’t inhaled during the removal process. Holy smokes, talk about high risk for serious recontamination.

Here are some resources for holistic dentistry: 1, 2, 3, 4

Summary
Again, don’t over-supplement with selenium. I think the same holds true for any form of supplementation.

According to Kresser, “Further research is needed to determine the long-term clinical effects of selenium treatment on inflammatory autoimmune thyroiditis. The long-term effects of supplementation on thyroid health are still unknown.”

He continues, “Long term consumption of high doses of selenium can lead to complications such as gastrointestinal upsets, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage.”

My suggestion is to make sure that you’re getting plenty of selenium from selenium-rich foods. ‘Tis true that our soils aren’t as mineral-rich as decades past, but when you consider that one Brazil nut is said to be an adequate daily dose of selenium, maybe you want to consider three. 

Other benefits of selenium:

• Helps to prevent and manage heart conditions
• Improves mood and a sense of wellbeing
• Helps to prevent free radical damage (it’s a powerful antioxidant)
• Helps to reduce the risk of prostate and secondary cancers
• Helps to prevent cataracts
• Up-regulates MnSOD expression (if you remember from my manganese post, MnSOD is an anti-inflammatory and has a calming effect on the immune system)
• Anti-carcinogenic (anti-cancer) properties
• Helps to normalize testosterone and estrogen
• Supplementation during pregnancy has been shown to alleviate the onset of postpartum Hashimoto’s

Other considerations: 

• Although it’s easy to get too much selenium, selenium toxicity is rare.
• Selenomethionine is plant-based selenium; selenocysteine is animal-based.
• Vitamin E helps to facilitate selenium absorption.
• According to Dr. Bruce Ames (per Dr. Andrew Weil), “Even modest selenium deficiency appears to be associated with age-related diseases and conditions such as cancer, heart disease and immune dysfunction.” (Source)
• Although supplementing with selenium is often recommended for those with autoimmune hypothyroidism, there may be some association between selenium supplementation and prostate cancer, although the studies aren’t definitive.
• Please don’t underestimate the importance of adrenal health…stress weakens the absorption of selenium.

Rich food sources of selenium include: tuna, shrimp, sardines, salmon, cod, scallops, mushrooms (crimini and shiitake), asparagus, mustard seeds, turkey, chicken, lamb, beef, barley, eggs, and tofu. **

** I’m not a fan of tofu. I’m not categorically against soy, but I believe it should be fermented, as in tempeh, miso, or natto, and only consumed in moderation.

Important note for this whole Minerals series: You may see some slight discrepancies in the list of foods in this post and the list of foods in my thyroid- and immune-supportive nutrition chart (which you can download for free here). This is because for the chart, we created a ranking system. If each thyroid- and immune-supportive food didn’t have a broad enough nutritional spectrum such that it represented enough nutrients, it didn’t make the cut. In other words, the list in this post may be slightly more inclusive.