Selenium is a mineral1 naturally found in soil and certain foods2. While our body doesn’t produce it, it plays an important role in our health, especially when it comes to our thyroid. It is found in foods like chicken, eggs, kidneys, liver, tuna, shellfish and Brazil nuts. Our small intestine absorbs it from our food and it’s transported to the liver before being disposed of through the urine and faeces.3
Research has shown that selenium is an antioxidant4 and, while it is believed that too much can be toxic, it plays a major role in maintaining our health, including:5
This enzyme is also responsible for getting rid of hydrogen peroxide, a byproduct of thyroid hormone production. When selenium is low, a buildup of hydrogen peroxide may destroy thyroid cells over time.7
Until 2000 researchers believed that selenium deficiency contributed to thyroid conditions only when iodine levels were also low. However, a study published in the Biological Trace Element Research journal of that year presented a case of hypothyroidism caused entirely by lack of selenium.8 Another study9 noted a decrease in selenium levels in patients with autoimmune conditions, which could lead to or worsen inflammation. According to the study, getting enough selenium seems to help manage complications of autoimmune conditions and even improve symptoms, perhaps due to its anti-inflammatory effects.
Being deficient often comes down to three connecting factors: diet, geographical location and soil composition. In North America, for example, the soil is rich in selenium which means that crops have higher levels of it too. That’s why researchers believe most North Americans get enough selenium through their diet.
In her study, The importance of selenium to human health,7 Margaret Raymond found that the opposite was happening in the UK, where dietary consumption of selenium had dropped by 50% over two decades. This correlated to a reduction in imports of selenium-rich North American wheat in favour of European wheat.
Selenium deficiency is known to cause problems for many systems of the body including the cardiovascular system, the immune system and the endocrine system. Many of the symptoms are therefore the same as those of an underactive thyroid:10,11
People at risk of a deficiency are those living in regions where soil or crops are selenium-deficient, those undergoing kidney dialysis and people living with HIV. Testing selenium levels alone can be difficult, especially in the UK where it’s not typically offered. However, you can request a blood test that looks at the amount in the serum/plasma of the blood.13
Order private blood tests, including selenium and other nutritional markers, from Thyroid UK’s partners.
When treating a selenium deficiency the NHS recommends 0.060mg (60 mcg) a day for women (19-64 years) and 0.075mg (75 mcg) a day for men (19-64 years).2 However, healthcare practitioners often treat with higher doses to allow for an optimal level.
Side effects of too much selenium can include hair loss or alopecia, damage to fingernails, nausea, change in bowel movements and problems to the nervous system.12
Experts agree that you should be able to get enough selenium from your diet alone. A single Brazil nut, for example, provides about 80 mcg.
Research has shown that supplementing can have a positive effect on plasma cholesterol and triglycerides levels.13 However, before supplementing, it’s a good idea to speak with your GP or a nutritionist if you suspect a deficiency.
HealthyButSmart.com has a good article “Do Selenium Supplements Have Benefits? 19 Research Papers Examined” if you want to read further about selenium.
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http://www.healthunlocked.com/thyroiduk
Date updated: 17.08.21(V1.3)
Review date: 07.02.22
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