Selenium and Your Thyroid

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What is Selenium?

Selenium is an essential mineral and is critical to human health. Present in many everyday foods; selenium is also available as a food supplement. It can be found in many common foods such as fish, seafood, beef, chicken, and grains. It plays a vital role in many processes in the body including reproduction, thyroid hormone metabolism and DNA synthesis. For this discussion, we will focus on the effects of selenium on the thyroid.

The Thyroid

It is best to recognize what the thyroid does in order to gain an understanding of how selenium can affect thyroid functioning.

The thyroid is a small gland that sits toward the front of your neck just below your Adam’s apple. This small gland carries out the function of manufacturing and distributing vital hormones to the whole body. These hormones help manage several critical systems in your body including:

  • Breathing
  • Heart rate
  • Central and peripheral nervous systems
  • Body weight/metabolism
  • Muscle strength
  • Menstrual cycles
  • Body temperature
  • Cholesterol levels

It is amazing to think that such a small little gland can have such a great impact on your body’s life providing functions.

The easiest way to describe how your thyroid works is that it converts iodine into the two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). These hormones are then carried throughout the body where they mainly control metabolism. I am remembering this lecture that I had in high school biology but was not that interested in it 40 some years ago. It is interesting today.

The pituitary gland produces Thyroid Stimulating Hormone (TSH). When the levels of the thyroid hormones T4 and T3 are low, the pituitary gland sends out TSH to tell the thyroid to make more T4 and T3. And the reverse is also true. If the pituitary gland senses the levels of T4 and T3 are too high, it slows down the production of TSH.

For most of us, these glands work together like a fine-tuned machine. But for many the thyroid just does not work efficiently. The T4 and T3 levels may be almost nonexistent (hypothyroid) or the thyroid may be overactive and produce too much (hyperthyroid). And when the fine-tuned machine is off balance, the body is off balance and you can be more prone to several diseases.

Here are some symptoms if your thyroid is out of balance.

Hypothyroid (under working)Hyperthyroid (overworking)
Trouble sleepingAnxiety
Tiredness and fatigueIrritability
Difficulty concentratingNervousness
Dry skin and hairSensitivity to high temperatures
DepressionHands trembling
Sensitivity to cold temperaturesHair loss
Frequent, heavy periodMissed menstrual periods
Joint and muscle pain



So where does selenium come in? Interesting fact, the thyroid contains more selenium than any other organ. Selenium helps with hormone production. The thyroid cells make a protein called thyroglobulin. This protein assists iodine in making the hormone T4. During the formation of the T4 hormone, free radicals are produced. To counteract the free radicals the thyroid cells make two enzymes called glutathione peroxidase and thioredoxin to act as antioxidants and fight off the free radicals. Selenium is a key ingredient in making these enzymes. In fact, your body makes over 25 of these special enzymes from selenium. These enzymes are called selenoproteins. Each enzyme has a specific purpose. A 2012 study, Composition, and evolution of vertebrate and mammalian selenoproteins, has provided crucial evidence on how these proteins work in the body.  Three of the enzymes actually activate the T4 hormone because it is not biologically active. The enzymes work to turn it on and off as the body needs it. One enzyme turns T4 into T3 which is essential for metabolism management. The enzymes also help keep your brain functioning.

Our bodies also use selenium for detoxification and immunity. A number of vital organs utilize selenium such as the liver and kidneys. A poor health trend will set off a call for more selenium in your body and it is quickly depleting, which aggravates the sickness and health issues of the individual.

As you can see, the thyroid is a very complex little gland that basically controls everything that goes on in our bodies and selenium is one of the minerals we need for the thyroid to function properly. No wonder selenium is so crucial along with the thyroid it fuels.

Symptoms Associated with Selenium Deficiency

Of important note, people living in the United States and Canada are not prone to selenium deficiency as a whole. That being said, there are individuals that definitely suffer from deficiency. Since selenium is essential to thyroid function it is no wonder that the symptoms of selenium deficiency symptoms of selenium deficiency are so close to symptoms of thyroid disease, especially hypothyroidism. Take a look and see:

  • Fatigue
  • Low immunity
  • Poor concentration (brain fog)
  • Hair loss and fingernail discoloration
  • Fertility/reproductive issues
  • Heart problems

There are certain groups of people that are more susceptible to selenium deficiency.

  • China and some European countries where vegan diets prevail. Low selenium in the soil does not produce enough in the plants they eat. A study conducted in 2015, Low Population Selenium Status Is Associated With Increased Prevalence of Thyroid Disease, showed that the risk of thyroid disease was as much as 69% higher for people who lived in low-selenium areas compared to those who live in adequate-selenium areas.
  • People who live with digestive conditions such as Crohn’s Disease, ulcerative colitis, and short bowel syndrome are unable to absorb sufficient amounts of selenium
  • People needing kidney dialysis – the treatment of dialysis actually removes selenium from the blood; typically these folks are also deficient in nutrition and on dietary restrictions so they do not get enough selenium through their diet
  • People living with HIV – deficient intakes, excessive loss through diarrhea and malabsorption are all culprits

A severe deficiency can lead to two specific diseases: Keshan disease and Kashin-Beck disease.

Keshan disease is a condition of the heart, cardiomyopathy, which is a disease of the heart muscle. It was first discovered in China in 1935. In 2012 a study, An original discovery: selenium deficiency and Keshan disease (an endemic heart disease), found that food sources grown on selenium-depleted soil were a direct cause of Keshan. While other factors could not be ruled out, selenium deficiency is a key cause. This disease is mostly contained in China but has also been found in New Zealand and Finland. Bear in mind, this disease is not contagious my any means, it is a selenium deficiency. The symptoms of Keshan disease are many: cancer, cardiovascular disease, hypertension, strokes, eczema, psoriasis, arthritis, cataracts, alcoholism, and infections.

Kashin-Beck disease (KBD) is a crippling, degenerative disease of the joints and spine. This disease is predominantly found in North Korea, Siberia, Tibet, and China. Several causes for KBD have been researched with inconclusive results. However, of the suspect causes selenium was one of them and it could not be ruled out. In fact, a study conducted in 2009, Selenium for preventing Kashin-Beck osteoarthropathy in children: a meta-analysis, showed selenium to actually lower the risk of the disease for children living in the identified areas.

Fortunately, these diseases are rare and research is continuing to understand selenium and all of its effects on the human body.

Selenium Benefits

Selenium has great antioxidant properties; when combined with vitamin E the effects are even better. Selenium fights off free radicals that damage the cells and play a part in aging and contribute to a list of health issues. Antioxidants counteract free radicals and prevent cell damage.

Selenium can also boost your immune system and in fact, actually helps your immune system to work more efficiently. Several other benefits are listed below.

  • Antioxidant and defends against oxidative stress
  • Improves blood flow
  • Lowers chance of heart disease
  • Boosts immunity
  • Increases longevity
  • Help reduce asthma symptoms
  • Regulates thyroid function
  • Can help boost fertility
  • Cancer-fighting

A note about cancer-fighting properties, in 1996 a landmark study conducted by Dr. Larry Clark and others saw dramatic results concerning selenium and fighting cancer. In this study participants took 200mcg of selenium yeast; the results showed a reduction in cancer deaths of 53% and the incidence of cancer by 37%.

Selenium has also been prescribed for people with a variety of other ailments but no proof exists as to whether it helps or not. Many tests have been conducted over the years to test the assumption that selenium helps these conditions, but the tests continue to come back inconclusive. Here is a list of these ailments:

  • Acne
  • Anxiety
  • Arthritis
  • Cataracts
  • Celiac disease – A 2010 study, Selenium status and over-expression of interleukin-15 in celiac disease and autoimmune thyroid diseases, has shown that selenium deficiency is a key factor in thyroid disease.
  • Cervical dysplasia
  • Depression
  • Fibromyalgia
  • Gout
  • Multiple sclerosis
  • Osteoarthritis
  • Psoriasis
  • Ulcers

Selenium Interactions

Along with its benefits, there are also some negative interactions for those taking certain medications. Selenium has a thinning effect on the blood; those taking Coumadin need to be extra cautious as you blood may become too thin and lead to greater chance of bleeding and bruising. Also, those taking anticoagulants such as aspirin, heparin, Plavix, and others – beware. Selenium also effects clotting. Utilizing selenium along with vitamins C and E may adversely affect those taking statins by decreasing the effectiveness of the statin medication. Finally, taking selenium with sedatives may slow down how the body breaks down the sedative which may increase the effects of the sedative.


Many tests have been conducted by various agencies and they have no conclusion on the amount of selenium that is optimum for thyroid function. The accepted amount by western doctors is 55mcg-100mcg. Nutritionists and naturopathic doctors feel that 200mcg-300mcg is a much better dosage. One study conducted in 2010, Establishing Optimal Selenium Status, proved that levels between 1600mcg and 3200mcg had no toxic or adverse reactions. However, the accepted ceiling for the dosage amount is 400 mcg.

There are supplements that you can take if you can’t seem to get enough selenium through your diet. Selenite is inorganic and some tests have shown it to be more difficult to absorb. Two organic types are selenomethionine and high-selenium yeast. Tests conducted have returned inconclusive as to which type is absorbed easier. Certain multivitamins contain selenium; Centrum® and One-A-Day® have vitamins that contain selenium.

The US Institute of Medicine recommends the following dosages which include dietary and supplements together:

  • Infants
    • 0-6 months: 45 mcg
    • 7-12 months: 60 mcg
  • Children
    • 1-3 years: 90 mcg
    • 4-8 years: 150 mcg
    • 9-13 years: 280 mcg
  • Males and Females
    • 14 years and older: 400 mcg
  • Pregnant or Nursing Women: 400 mcg

There are also some side effects of taking too much selenium. These side effects are simple things like bad breath, fever, nausea; but can also be life-threatening conditions with lungs, kidneys, and heart. Furthermore, selenium overdose has been linked to skin cancer, prostate cancer, and diabetes. This mineral is nothing to fool around with. I will caution you to work with your doctor if you feel you have a selenium deficiency so you don’t go overboard and develop a toxic level of selenium.

Best Ways of Getting Selenium in Your Diet

The best sources of selenium are found in our diet. The selenium content in our foods is dependent on the selenium in the soils where it was grown. Through millenniums of farming the soils have been depleted of many essential trace minerals including selenium. It turns out Brazil nuts have a high concentration of selenium; one ounce will give you 544mcg of selenium or 777% of your daily requirement. I think we should all start eating Brazil nuts! Selenium is found in many other foods as well but in much lower doses.

  • Meats & Fish: Shrimp, sardines, salmon, tuna, cod, turkey, chicken breast, beef chuck roast and ground beef
  • Grains & Bread: Bagel, fortified instant oatmeal, whole-wheat bread, white bread, long-grain brown and white rice, enriched egg noodles and macaroni
  • Nuts & Seeds: Brazil nuts, sunflower seeds, black walnuts
  • Dairy & Eggs: Hard-boiled egg, low-fat cottage cheese, and cheddar cheese

Final Thoughts

We have reviewed quite a lot of information on selenium and its functions, benefits, interactions, and dosages. It has been proven that selenium is crucial to optimal thyroid function. Without selenium, we would suffer a great number of health issues. The benefits, on the other hand, are remarkable. Its antioxidant properties, cancer-fighting characteristics, and immune system boost prove it is a necessary supplement.

We need to be cognizant that testing is still underway. While many advances have been made in the study of selenium, there is still much more to find out. There is no consensus on optimal dosage, although a healthy range has been identified. The levels need to be extremely high for it to be toxic. People in certain regions of the world who are battling specific medical conditions are more susceptible to selenium deficiencies. Always see your doctor before starting a new supplement. Particular minerals and herbs have been known to interact with certain medicines.

Fortunately, there are a lot of foods that contain this super-mineral. They are every day, regular food – the kind we always hear about – fruits, vegetables, protein, whole grains, eggs, and dairy. The bottom line is it would be worth our while to make sure we eat selenium-rich foods on a regular basis. If we can’t eat the suggested foods, try adding Brazil nuts to your daily routine; 1 or 2 nuts could do the trick. Thyroid supplements may also help in this regard as many of them contain selenium. Here’s to your health!



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