Myth About Thyroid Health: "Brazil Nuts Provide the Daily Selenium I Need"

supplements thyroid health Jan 12, 2020

Brazil nuts are delicious, and they contain more selenium by weight than any other food. One ounce of Brazil nuts provides a whopping 990% of your recommended daily value! So why not eat a few nuts every day to get your selenium rather than pop one more pill? Let’s do a little myth-busting about that.


What Does Selenium do for You?

Selenium is an essential mineral for thyroid health. It’s a trace mineral, one that’s dosed in micrograms. Yet, at these seemingly minuscule amounts, a selenium deficiency can be a direct cause for hypothyroidism and even a trigger for Hashimoto’s thyroiditis, the autoimmune condition that damages your thyroid gland and causes hypothyroidism.

Selenium serves many functions throughout your body, but your thyroid gland tends to get center stage with this mineral.

Selenium is essential in converting your inactive T4 hormone that your thyroid gland produces into the active T3 that your cells can use.

Your body also converts selenium into the master antioxidant - glutathione. This goes on to protect your thyroid gland from oxidative stress, inflammation, and supports your overall immune function. That’s definitely something you want to have going for you!

Selenium works with vitamin E to support normal cell function and fertility. 

Proper selenium supplementation has been shown to reduce a woman’s risk of developing postpartum thyroiditis when she tests positive for TPO antibodies before or during her pregnancy. Supplemental selenium can be started during pregnancy and continued into the postpartum period to reduce this risk.

In the same way, regardless of pregnancy status, adequate and regulated selenium intake can reduce your TPO antibodies if they’re elevated.

As it brings a better balance to your overall thyroid health, supplemental selenium can, in turn, increase your energy, reduce hair loss, stabilize your mood, and increase your menstrual regularity. Those are all common symptoms when you have a hypothyroid condition.

And, here’s the BIG one!

The more you stabilize your thyroid, and you can see how having adequate selenium is a big player in that, the clearer its message is to the rest of your body that you are safe.

When your thyroid is under-functioning or under attack, it can’t effectively support you. It sends out warning signals like fatigue, hair loss, changes in heart rhythms, and irregular menstrual cycles. It’s trying to protect you from overexerting yourself and even from trying to conceive as it sends these signals for you to listen up.

“I can’t even work hard enough to keep you going girlfriend! Now is NOT the time to ask me to care for another precious little life!”

If your reproductive center gets the message that your body isn’t safe, your chances of being able to support another life remain slim. 

Selenium is certainly a mineral that your body and your thyroid can’t do without!


So, Why not “Supplement” with Brazil Nuts?

Here’s where it gets tricky. While selenium is a required nutrient for proper thyroid function, it has a narrow range of effectiveness. It’s kind of a Goldilocks mineral—too much can be toxic, and too little won’t effectively reduce your antibodies. Selenium intake needs to be just right! That’s where Brazil nuts become a problem.

The selenium content in Brazil nuts can vary tremendously, depending on where the nuts were grown, soil nutrients, harvesting conditions, storage, transport, and more. One nut from your bag or bin might have 50 mcg of selenium and the next might contain 500 mcg.

Needless to say, your daily “dose” would vary widely, and unless your specific Brazil nuts were tested for their selenium content (spoiler alert: they weren’t), you can be unknowingly under- or over-dosing yourself. Not a roller coaster your thyroid wants to be on!


How Should I Supplement? 

When it comes to reducing thyroid antibodies, daily supplemental doses of selenium below 200 mcg haven’t been shown to be helpful, and doses above 900 mcg per day were found to be toxic. Depending on the potency of your Brazil nuts, you could be well below or above these levels every day.

For this reason, getting selenium from a standardized supplement is a better option for you and your thyroid. Selenomethionine is the most optimal form of selenium and is most commonly dosed up to 200 micrograms daily. If you’re currently taking a prenatal or multivitamin, check for its selenium content. As with ANY supplement, consult with your health practitioner before adding more selenium or adding any at all if you’re not currently supplementing.

If you’re looking for a comprehensive prenatal vitamin that provides adequate selenium in addition to the whole spectrum of nutrients you need for pre-pregnancy and beyond, I recommend Full Circle Prenatal.

In the meantime, sticking to a regular intake of whole, real, nutrient-dense food is best. A colorful rainbow of vegetables and fruits, well-sourced meats, poultry, and seafood, and heart-healthy fats like olive, avocado, nuts and seeds throughout your day will help support you, your thyroid, and your baby-to-be!


If you want to talk more about getting to the root cause of your hypothyroidism or fertility challenges, you can schedule a time for us to talk here.



Keely, Erin J. Postpartum thyroiditis: an autoimmune thyroid disorder which predicts future thyroid health. Obstet Med. 2011 Mar; 4(1): 7–11.

MacFarquhar, Jennifer K., et al. Acute selenium toxicity associated with a dietary supplement. Arch Intern Med. 2010; 170(3): 256-261.

Negro, Roberto. Selenium and thyroid autoimmunity. Biologics. 2008 Jun; 2(2): 265–273.

Nordio, M. et al. Treatment With Myo-Inositol and Selenium Ensures Euthyroidism in Patients With Autoimmune Thyroiditis. Int J Endocrinol. 2017, 2549491. 2017

Olivieri O, et al. Selenium, zinc, and thyroid hormones in healthy subjects: low T3/T4 ratio in the elderly is related to impaired selenium status. Biol Trace Elem Res. 1996 Jan;51(1): 31-41. 

Zimmermann MB, Köhrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health. Thyroid. 2002 Oct; 12(10): 867-78.

Do you want MORE support for your hormones and fertility?

Subscribe and get great content delivered right to your inbox!
Spam not included!

Your information will never be shared and you can unsubscribe at any time.