You may not realize it, but your thyroid gland plays a huge role in your overall health.  Your thyroid is a small, butterfly-shaped organ located at the base of neck, and it produces hormones that are responsible for maintaining most of your body’s natural processes.  These hormones are called triiodothyronine (T3) and thyroxine (T4).  T3 and T4 are essential in order for your body’s metabolism to function efficiently, and also lend a hand in controlling your cholesterol levels, monitoring your breathing and heart rate, normalizing your body temperature, and more.  Without your thyroid, your entire endocrine system would fall apart.

There are a number of minerals that help keep your thyroid running smoothly, and one of the most important ones is selenium.  Keep reading to discover more about how selenium specifically aids thyroid function and why it is one of the dietary minerals we just can’t do without!

What Happens When Your Thyroid Isn’t Working Properly?

Thyroid conditions are much more common than most people realize; in the U.S. alone, over 20 million people are affected, with the vast majority being women.  Statistically, one man will be diagnosed with a thyroid condition for every 5-8 women who receive the same diagnosis.  Your body requires very precise levels of thyroid hormones, so anything that sets off that balance in going to cause a problem.  The most common form of thyroid dysfunctions are hypothyroidism and hyperthyroidism[i].

Hyperthyroidism is when your body produces too much T3 and T4.  Typical symptoms of hyperthyroidism include sensitivity to heat/ feeling too warm all the day, high levels of stress and anxiety, heart palpitations, thinning skin and hair, weakened muscles, insomnia, and menstrual irregularities.  The most common causes behind this condition are autoimmune disorders like Graves’ Disease, thyroiditis (usually a temporary inflammation caused by a viral infection), or nodules growing on the thyroid.  Occasionally, hyperthyroidism can also be caused by taking too much of a thyroid hormone in tablet form[ii].

Hypothyroidism is the opposite problem; this is when your body produces too little T3/T4 hormones.  People who are hypothyroid usually report feeling cold, insomnia, having difficulty losing weight, cognitive dysfunction (i.e. trouble remembering, etc.), chronic fatigue, and more.  Hypothyroidism can be caused by a genetic predisposition but may also be caused by external factors such as thyroid cancer, chemotherapy treatments, certain medications, and autoimmune disease.  Because the symptoms of both hypothyroidism and hyperthyroidism are myriad, they can be difficult to identify.  But once you or your doctor suspect that your thyroid is the source of your health troubles, both conditions are easily diagnosed with a simple blood test[iii].

How Does Selenium Support the Thyroid?

Selenium is a mineral that is essential to our nutrition and can be found in many foods (or taken in tablet form as a dietary supplement).  Selenium is mostly stored in our skeletal muscles; it helps our bodies defend against cancer, boosts immunity and fertility, improves cardiovascular health, and also helps regulate our thyroid function[iv].

Multiple studies, like this one done at the Centro Hospitalar e Universitário de Coimbra in Portugal in 2016[v], have confirmed selenium’s role in maintaining thyroid function.  Our thyroids actually contain more selenium by weight than any other organ in our body.  All of that selenium acts as a component of the enzyme that helps to remove iodine molecules from the hormone T4, which is biologically inactive in the body; this converts that hormone into T3, which is biologically active and can be used for the body’s various metabolic processes.  Without any selenium, we would not be capable of converting T4 into T3 on our own.  That can very swiftly lead to major health problems, including hypothyroidism or conditions like Hashimoto’s Disease[vi].

It is prudent to note that it is possible to consume too much selenium, so it is not advisable to seek out selenium dietary supplements until you first consult your doctor.  High levels of selenium (anything above 400 micrograms, or mcg, per day) can lead to symptoms such as irritability, bad breath, digestive upset, brittle hair/ nails, discolored teeth, and even occasionally nervous system problems.  Extremely high levels of selenium can produce more severe problems such as respiratory difficulty and kidney or heart failure.  However, the level of selenium required to be at risk for those outcomes is exceptionally high and would require an excessive consumption of the mineral over a period of some time[vii].

Ordinarily, we can consume adequate levels of selenium (around 55 mcg per day for adults) with a diet that has a good balance of natural proteins (seafood, meat/poultry, eggs, dairy, etc.) and grains.  People who suffer from Celiac Disease/ gluten intolerance, or who stick to a vegetarian or vegan diet, may require additional selenium supplements to replace these other natural sources of the mineral.

Whether you’re perfectly healthy or suffering from a condition like hyper- or hypothyroidism, it is essential to make sure that you are consistently getting good levels of selenium into your body so that your thyroid can keep doing its job.  Luckily, that is relatively easy most of the time, and is easily accomplished with a well-balanced diet.  If you have any concerns about your thyroid function or your ability to get enough selenium on a regular basis, consult your doctor right away.  And of course, never begin a supplement or medication regimen without talking to your doctor first.








thyroid gland inside human body. 3d illustration

Iodine is one of the main elements your body needs to produce thyroid hormones.

Your body is unable to produce enough iodine to do this on its own which is why it is an imperative part of any diet.

Iodine can be consumed through many foods (see Table 1). If you do not have enough iodine in your body, then your body will not be able to make enough thyroid hormones.

As such, you can end up with iodine deficiencies.

These deficiencies can cause your thyroid to enlarge, or cause hypothyroidism and mental retardation in unborn babies whose mothers have iodine deficiencies while pregnant.

Prior to the 1920’s iodine deficiencies were common in communities throughout the Great Lakes region, the Appalachian region, the Northwest parts of the United States, and parts of Canada.

Treatment for this deficiency was introduced through iodized salt.

This has actually helped to eliminate most of the issue in areas like this. In the meantime though, other parts of the world have not yet adopted the same treatment.

Without iodized salt readily available in diets throughout these areas, iodine deficiencies continue to present public health issues.

In fact, 40% of the population around the world is at risk for such a deficiency.

Sources of Iodine

Iodine is found inside seawater and soil naturally. There are different levels of iodine in food around the world. In the United States, people can get adequate iodine levels in their diet if they just replace salt in their food with iodized salt.

Eating foods which are high in iodine, like seafood and dairy, or taking a multivitamin with iodine in it can help provide an adequate level of iodine.

Below is a table that shows you just a handful of the foods in the United States that give you iodine necessary to prevent such thyroid issues.


  • Cheese
  • Milk from cows
  • Eggs
  • Frozen Yogurt
  • Ice Cream
  • Iodine-containing multivitamins
  • Iodized table salt
  • Saltwater fish
  • Seaweed such as nori and kelp
  • Shellfish
  • Soy milk
  • Soy sauce
  • Yogurt

Symptoms of Iodine Deficiencies:

The symptoms one would experience for iodine deficiencies are all similar especially with regard to their effect:


If you do not have proper amounts of iodine, then your thyroid gets bigger and bigger, developing a goiter.

This happens when it attempts to keep up with your body’s demand for thyroid hormones. Around the world this deficiency is most common cause of enlarged thyroids.

Within the goiter, nodules sometimes develop. People who have a large goiter might have problems breathing, swallowing, or even choking when they are lying down.


When levels of iodine in the body fall, hypothyroidism can develop especially because iodine is imperative for the production of the thyroid hormone.

This is somewhat uncommon in the United States but around the world this iodine deficiency is actually quite prevalent (see Hypothyroidism brochure).

Pregnancy-Related Issues:

Iodine deficiencies are even more important in women who are currently pregnant or nursing, since they are essentially supplying this mineral to two people.

Severe deficiencies in pregnant women has been linked to congenital abnormalities in birthed babies as well as miscarriages, preterm deliveries, and stillbirths. Children whose mothers had severe deficiencies during pregnancy sometimes face issues of mental retardation, and additional issues with speech, hearing, and growth.

If this condition persists for some time, underactive thyroids can even result in cretinism, a medical condition, due to maternal hypothyroidism, that results in much slower mental and physical developments. This, again, is not a common issue in the United States, but is common in other parts of the world.

Congenital hypothyroidism, the result of a deficiency in pregnant woman is one of the more treatable causes of mental retardation across the globe. Even a mild deficiency in a pregnant woman can result in low intelligence in children, but can be prevented.

Causes of Iodine Deficiencies

The body is unable to produce the amount of iodine necessary for the production of thyroid hormones, as mentioned.

It is because of this that you have to help supplement the iodine levels in your body with iodine in things like vitamins or food.

Now, around the world there are different levels of availability for iodine in different foods.

As mentioned, the table above (table 1) includes a generic list of iodine foods in the United States, but more specific food lists vary based on country and what foods are available in that country.

People in the United States can maintain healthy levels of iodine in their body, enough to properly produce thyroid hormones, by simple restricting the salt they consume and replacing any consuming salt with iodized salt. It is also beneficial to consume foods high in iodine like meat, eggs, seafood, and some breads.

People can complement this by consuming multivitamins daily which contain iodine.

Note that the list in Table 1 is incomplete.’s Iodine Deficiency Brochure has more information on this topic and a pretty good list of foods rich in Iodine.

Diagnosing Deficiencies

Iodine deficiencies can be diagnosed better across whole populations rather than in individual’s Iodine is released by your body by way of urine.

Therefore the best way to figure out iodine deficiencies in a large group of people is to measure the levels of iodine found in their urine samples.

Having an iodine deficiency is when you have an average concentration of iodine in the urine which is less than 50 μg/L in a population (see Table 2). Throughout the United States, the levels of iodine in the population has remained about the same for the same two decades.

Levels dropped by roughly half during the beginning the 1970’s and then through the 1990’s. In other parts of the world through, particularly Europe, Asia, and Africa still face this as a large issue.

Below is a table that shows the median population values for iodine and iodine nutrition.


50-99 75-149 MILD DEFICIENCY
100-199 150-299 OPTIMAL
200-299 300-449 MORE THAN ADEQUATE
[From WHO, UNICEF and ICCIDD 2001 Assessment of the Iodine Deficiency Disorders and monitoring their elimination. A guide for programme managers. WHO publ., Geneva. WHO/NHD/01.1]


How to Prevent Iodine Deficiency

As is the case with many diseases, one of the best ways to handle an iodine deficiency is to prevent the problem rather have to treat it.

The World Health Organization has worked hard to eliminate iodine deficiencies around the world. Iodized salt in fact has been used around the world to treat iodine deficiencies, especially around the United States.

In some areas of the world injections of iodized oil are used where iodized salt is not possible. In certain places around the world iodination of water supplies has been used as a main treatment for deficiencies.

Across the United States, the National Institute of Medicine has stated that there is a recommended daily allowance for iodine. For men and women that allowance is set at 150 μg per day.

Individuals who can add tablet salt to the foods they eat are better off using iodized salt for their foods. The reason being, one teaspoon of iodized salt has 400 μg of iodine. There are many iodine filled multivitamins on the market here too which have on average 150 μg of iodine in them, but you have to be careful when seeking out vitamins.

Not every multi vitamin has iodine in it. Roughly half of those on the market have iodine in them, which is why you need to check before you begin taking them to ensure you are taking the right ones.

Pregnant women should be consuming 220 μg of iodine each day. Women who are breastfeeding should take 290 μg iodine. Women who are pregnant and breastfeeding are the ones who stand the highest risk of iodine deficiency.

Therefore, the American Thyroid Association recommends that any pregnant or breastfeeding woman in Canada and the United States take one prenatal multivitamin each day which contains 150 μg of iodine.

Taking Too Much Iodine

If you take too much iodine, it can cause problems.

This is especially the case in individuals who already have issues with their thyroid like autoimmune thyroid disease, hyperthyroidism, or nodules. Administering large quantities of iodine by way of medications, radiology procedures, or dietary excess can cause issues like hypothyroidism or hyperthyroidism.

It can also worsen existing conditions. Moreover, people who move from iodine-deficient regions to areas with adequate iodine intake can also develop thyroid issues because their thyroids have been trained to take up and use only small amounts of iodine. People facing this issue could develop iodine-induced hyperthyroidism.

For this reason, it is important to speak with a doctor or healthcare professional about ways to regulate intake and measure the amount of iodine in the foods, salts, or vitamins you might be taking. Combining all three might give you the right amount of iodine for your body or it might be slightly too much for the body. Chances are your body will help you to regulate naturally, and anything that goes beyond what is needed will be filtered out through the urine.

Overall, iodine is actually imperative for your body. Even people who have thyroid diseases need to consume iodine and regulate their consumption in order to help with their disease.