Selenium Benefits For Your Thyroid
Selenium is a micronutrient first described in 1817; its name derives from the Greek “σελήνη—Selene” meaning moon, referring to the bright and grey appearance of this compound when it is melted [1]. Selenium levels in the body are dependent on the population’s characteristics and its diet and geographical area (mainly on the soil composition) [1, 2]. This micronutrient has been studied over the last years, and scientific reports have revealed its crucial role in the maintenance of immune-endocrine function, metabolism, and cellular homeostasis. The thyroid gland is characterized by a high concentration of selenium, which is incorporated into selenoproteins. Some of these selenoproteins have an important antioxidant activity, contributing to the antioxidant defense in the thyroid by removing oxygen free radicals generated during the production of thyroid hormones. Being incorporated into iodothyronine deiodinases, selenium plays also an essential role in the metabolism of thyroid hormones.
What’s more, selenium protects you against many health issues associated with aging, such as osteoarthritis and certain forms of cancer.Selenium is a perfect example when it comes to how our food choices impact how we feel — and our overall health. Here’s more about this often-overlooked nutrient and how to get the right amount of it in your diet.Are your levels of selenium low?
If you’re suffering from the following symptoms, you may have low selenium levels:
- Weakness or pain in the muscles
- Hair or skin discoloration
- Whitening of the fingernail beds
Selenium’s Impact on the Thyroid
In adults, the thyroid is the organ that has the highest concentration of selenium in the body, and this mineral plays a key role in your thyroid gland’s ability to produce thyroid hormone.1 Having an optimal amount of selenium in your diet is vital not just for preventing thyroid disease, but for your overall health.
A selenium deficiency is associated with a variety of thyroid issues, including:2
- Hypothyroidism
- Subclinical hypothyroidism
- Autoimmune Hashimoto’s thyroiditis
- An enlarged thyroid (goiter)
- Thyroid cancer
- Graves’ disease
Iodine—the building block and key ingredient of thyroid hormone—actually requires selenium in order to be synthesized properly into thyroid hormone.
What the Research Shows
A number of research studies have shown key relationships between selenium supplementation and thyroid and immune function. For example:
- Both excessively high and low levels of selenium have been associated in several studies with an increased risk of disease.
- Several studies have shown that supplementing with selenium reduces thyroid peroxidase antibodies (TPO), as well as the severity of hypothyroidism symptoms.2
- Some studies have found that treating patients who have mild to moderate thyroid eye disease (Graves’ orbitopathy) with selenium supplements improved quality of life, as well as outcomes for their eye health, and dramatically slowed progression of symptoms.2 The European Thyroid Association now recommends a six-month trial of selenium supplementation for patients with Graves’ orbitopathy.
- Even for people who don’t have a selenium deficiency, taking selenium supplements has been shown to have a considerable impact on the immune system, increasing the production of activated T-cells and natural killer cell activity, both of which assist in the immune response to disease, tumors, and infection.
- A 2016 study analyzed the impact of selenium supplementation on the thyroid antibody levels of people with Hashimoto’s thyroiditis.3 The study evaluated both thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) antibody levels at three, six, and 12 months of selenium supplementation in two groups of Hashimoto’s patients: one group receiving levothyroxine thyroid hormone replacement treatment, and the other, as newly diagnosed patients, not being treated with thyroid hormone replacement. For those being treated with levothyroxine, selenium supplementation resulted in significantly lower TPOAb levels after three months, which continued to decrease at six months and 12 months. TgAb levels did not decrease until the 12-month point. In the untreated Hashimoto’s group, selenium supplementation resulted in a decrease in TPOAb levels after three months, but not after six or 12 months, while TgAb decreased at three months, but not at six or 12 months.
What role does selenium play in thyroid health?
If you have low levels of selenium, it’s harder for the thyroid to make its hormones and for the body to convert thyroid hormones into the form that’s needed by your cells. That’s because selenium is a fundamental component of various seleno-proteins, molecules essential to the body’s ability to create and use thyroid hormones. Their role includes:
- Regulating thyroid hormone synthesis.
- Supporting the conversion of thyroxine (T4, the hormone produced in greatest quantities by the thyroid) to triiodothyronine (T3, the bioactive thyroid hormone that increases our cells’ basal metabolic rate).
- Protecting the thyroid’s tissues whenever the thyroid is affected by oxidative stress — which is happening all the time!
Selenium isn’t only just important to the production of thyroid hormones — it’s also a key regulator of thyroid hormone levels. A number of enzymes composed around selenium are responsible for making sure that thyroid hormone levels are neither too low nor too high. Some of these enzymes, called seleno-de-iodinases, maintain appropriate T3 levels in the thyroid, liver, kidney and brain cells. Another enzyme, glutathione peroxidase, helps to limit T4 when its levels get too high.
Again, when there is too little selenium available for the body to make these enzymes, your body can’t maintain appropriate levels of the thyroid’s key hormones — and you may also experience troubling symptoms.
How selenium and iodine work together
All of the problems that come with selenium deficiency are compounded by the fact that selenium works in tandem with iodine, another nutrient better known for its role in thyroid health. Selenium is responsible for the properly recycling of iodine in the body, so a person with too little selenium as well as too little iodine is much more likely to develop a significant thyroid imbalance. When iodine deficiency goes hand-in-hand with selenium deficiency, it’s essential to treat both nutrient deficits to restore the thyroid to balance.
Forms and Sources
There are two forms of selenium: organic (selenomethionine and selenocysteine) and inorganic (selenate and selenite). Both forms are good sources, but research has shown that using the organic form of selenium as a supplement may be more effective because your body absorbs more than 90% of organic selenium but only around 50% of the inorganic form.1
Foods that are good sources of selenium include:
- Brazil nuts
- Seafood, such as shrimp, sardines, salmon, halibut, and tuna
- Meats like beef steak, beef liver, ground beef, and ham
- Poultry
- Eggs
- Breads
- Cereals
- Grains
Selenium can be found in supplements either alone or in combination formulas in multivitamins. Due to its overall effects in the body, research is being conducted on whether or not selenium supplementation may affect glucose metabolism, as well as help prevent cancer, thyroid disease, heart disease, and the cognitive decline that occurs as we age.
Are you getting enough selenium?
Selenium is so easy to get through food. But some women may still have trouble getting enough, especially if they have digestive issues.
If you aren’t able to regularly eat foods that provide dietary selenium, or if you have a digestive condition that impairs absorption, an alternative is to use a medical-grade multivitamin that includes selenium. (We don’t generally recommend single-element supplements because a carefully-formulated combination better ensures that selenium is correctly paired with appropriate levels of co-nutrients such as iodine.)
Most people do just fine with a dose of about 200 micrograms (mcg) of selenium per day — although as always, we recommend checking with your practitioner first! It’s especially important to have your practitioner continue monitoring your thyroid hormone levels if you’ve ever been diagnosed with any sort of thyroid disorder, such as Graves’ disease (hyperthyroidism), Hashimoto’s autoimmune thyroiditis, or any other form of hypothyroidism.
Selenium Toxicity
While low levels of selenium are a concern, high levels can result in selenium toxicity over time.1 Symptoms include:
- Garlic smell to the breath
- Metallic taste in the mouth
- Hair and nail loss or brittleness
- Nausea
- Skin rashes
- Diarrhea
- Skin lesions
- Fatigue
- Irritability
- Nervous system abnormalities
In particular, be careful with Brazil nuts; because they contain so much selenium—as much as 90 mcg per nut—you can actually trigger selenium toxicity by eating them too often.
Benefits and Risks
Despite the research, there is still no official recommendation in the international guidelines for treating patients with autoimmune thyroid disease with selenium supplements. For those with thyroid disease and low selenium levels, supplementation can be beneficial, but for those whose selenium levels are normal to high, supplementation could potentially result in toxicity.
A Word From Verywell
Before you consider adding handfuls of Brazil nuts to your diet or taking selenium supplements, you should have your selenium levels evaluated by your healthcare provider. They can then offer guidance on whether you might benefit from increasing your dietary selenium or adding supplements.
Keep in mind that if you choose to supplement with selenium, you should calculate your dietary intake, and be sure to count any selenium in multivitamins and supplements so that your daily intake doesn’t exceed the 400 mcg daily recommended upper intake level.