While all of the minerals play an important role in the health of individuals, selenium is one of the more important minerals with regards to thyroid health. First of all, selenium is important in the formation of thyroid hormone, as well as the conversion of T4 to T3. Selenium is also important in the synthesis of glutathione. Epidemiological findings link a lowered selenium status to neurodegenerative and cardiovascular diseases as well as to increased cancer risk (1). Selenium is extremely important for optimal immune system health, and a selenium deficiency might make one more susceptible to developing an autoimmune condition such as Graves’ Disease or Hashimoto’s Thyroiditis.
How Does Selenium Enhance Immune Function?
While selenium has many different functions, this blog post will mainly focus on the benefits of selenium with regards to immune system health. But how does selenium enhance immune system function? Selenium can influence immune response by changing the expression of cytokines and their receptors or by making immune cells more resistant to oxidative stress (2). If you’re not familiar with cytokines I would check out my recent blog post entitled “The Role of Cytokines In Autoimmune Thyroid Conditions“. Supplementation with selenium has been shown to stimulate the function of neutrophils, production of antibodies, proliferation of T and B lymphocytes, production of lymphokines, natural killer cell-mediated cytodestruction, delayed-type hypersensitivity reactions and allograft rejection, and the ability of a host to reject transplanted malignant tumors (3).
Selenium is also a cofactor for glutathione. Glutathione is an antioxidant which has numerous functions, and there is evidence that altered glutathione concentrations may play an important role in many autoimmune conditions such as Graves’ Disease and Hashimoto’s Thyroiditis (4). If someone is deficient in selenium then this will affect glutathione production, which is yet another reason why it’s important to correct a selenium deficiency.
Let’s take a look at selenium and how it might play a role in autoimmune conditions such as Hashimoto’s Thyroiditis and Graves’ Disease:
Selenium and Hashimoto’s Thyroiditis
Hashimoto’s Thyroiditis is characterized by an increase in either thyroperoxidase (TPO) and/or thyroglobulin antibodies. While there is no hard evidence that a selenium deficiency can trigger an autoimmune response, there is evidence that selenium can lower thyroperoxidase antibodies (5) (6). As a result, those people with high TPO antibodies might benefit from selenium supplementation, or eating selenium-rich foods such as Brazil nuts.
However, there are also some studies which show that selenium supplementation doesn’t lower TPO antibodies (7). Most of the studies involving selenium and TPO antibodies used 200 mcg of selenium, either in the form of sodium selenite, or selenium yeast. Perhaps giving a higher dose (i.e. 400 mcg) would be more effective for some people? However, one does need to be cautious about taking higher doses of selenium, which I’ll discuss in more detail below. What about those people who have high thyroglobulin antibodies? Most of the studies on selenium and thyroid antibodies focus on thyroid peroxidase antibodies. I did come across one study which showed that selenium helped to lower both thyroperoxidase and thyroglobulin antibodies, although it seems that the thyroperoxidase antibodies are affected to a greater extent by selenium supplementation (8).
Selenium and Graves’ Disease
With regards to Graves’ Disease, a population-based study showed that selenium levels were lower in people with newly diagnosed Graves’ Disease (9). As a result, they postulated that there might be a link between inadequate selenium supply and autoimmune thyroid disease. However, this study alone does not confirm that a selenium deficiency can trigger Graves’ Disease, and more research definitely is needed in this area. Another study showed that there is a possible role of selenium supplementation in improving the course of Graves Disease (10), although it also suggested that further clinical trials are necessary to confirm this.
Should You Supplement With Selenium?
I’m sure many people reading this are aware of the benefits of selenium, and are already eating more selenium-rich foods such as Brazil nuts and sardines, and/or are taking a selenium supplement. Although supplementing with selenium might be beneficial, here are a few things you need to keep in mind:
1) If someone has a selenium deficiency then this might be a factor in one’s autoimmune thyroid condition. However, in most cases this isn’t the only factor. In most cases something else has triggered the autoimmune response, and if you don’t remove this trigger then taking high doses of selenium might not have much of an impact on the thyroid antibodies.
2) Selenium can be toxic at high doses. If you supplement with selenium you need to be cautious. While most people are fine supplementing with 200 mcg per day, taking doses higher than this can cause problems. I’ve had numerous patients take 400 mcg of selenium per day, and some people will be fine taking 600 mcg of selenium for a short period of time. But everyone is different, and so you can’t make the assumption that 400 mcg of selenium is safe to take. When I recommend selenium supplements to my patients I recommend a whole food source, as there is a much greater chance of having a selenium toxicity when taking synthetic selenium supplements. However, if you take too high of a dosage of food based supplements this still can potentially lead to a toxicity.
3) How about eating a couple of Brazil nuts per day? Brazil nuts are a rich source of selenium, and some people can get all of the selenium they need by eating one or two Brazil nuts on a daily basis. This doesn’t mean you should eat a bunch of Brazil nuts if you have a selenium deficiency, as while Brazil nuts are healthy, more isn’t necessarily better, and if someone has gut issues then eating Brazil nuts might not be the best choice. The reason for this is due to the lectins and phytic acid, which can affect digestion. I discussed this more in my blog post entitled “Should People With Thyroid and Autoimmune Thyroid Conditions Avoid Foods With Lectins?” A better option might be a whole food selenium supplement, as I briefly mentioned before. And the reason for this is because while a synthetic selenium supplement will correct a selenium deficiency, selenium (as well as other minerals), works best in the presence of other nutrients and cofactors.
To summarize, if someone has low selenium levels then this might make them more susceptible to developing an autoimmune thyroid condition. However, I think it’s safe to conclude that most cases of Graves’ Disease and Hashimoto’s Thyroiditis are not caused by a selenium deficiency. This doesn’t mean that a selenium deficiency can’t be a factor. Any mineral deficiency should eventually be corrected, and a selenium deficiency can compromise immunity, as well as cause problems with the conversion of T4 to T3, and will also affect the production of glutathione.