Selenium and iodine make a strong team but are you getting enough?

The way in which selenium and iodine interact is determining for the thyroid gland and the metabolism. A deficiency of one or both nutrients coupled with exposure to environmental toxins may have grave consequences and contribute to some of the most commonly occurring metabolic disorders.

Selenium and iodine make a strong team but are you getting enough? The rate of metabolic disorders has increased exponentially on a global scale. Most of these disorders fly under the radar so to speak and remain undiagnosed. At the same time, up to 20 per percent of those people who are diagnosed and get medical treatment for their condition do not improve. We need to focus much more on selenium and iodine - partly because these essential trace elements work as a team in regulating thyroid hormones, and partly because modern diets and exposure to environmental toxins increase the risk for deficiencies and imbalances.

How iodine and selenium regulate thyroid hormones

The thyroid gland that is located on the front side of the throat produces two different thyroid hormones. T4 is the passive hormone that contains four iodine atoms, while T3, the active hormone, contains three iodine atoms. In order to activate the metabolism in the different tissues and cells of the body, selenium-containing enzymes remove an iodine atom from the T4 hormone, thereby converting it to active T3. This conversion is regulated in accordance with the body's specific needs. As expected, it requires sufficient amounts of selenium and iodine for this to take place, but is there enough or do we have a shortage?

Low selenium intake in Europe and disagreements about the actual requirements

An estimated 20% of the European population fails to get the recommended amount of selenium, which is around 55 micrograms per day. Vegetarians, vegans, and those who do not consume fish are at increased risk of a selenium shortage.
The selenium intake in Europe is substantially lower than in other parts of the world such as the United States and Japan. This is a result of soil conditions and eating habits. Experts are still not able to reach an agreement on how much selenium we humans really need.

Mercury and other heavy metals increase the need for selenium

Selenium atoms bind to mercury atoms and form mercury selenide, a non-toxic compound which the body can excrete. Once selenium atoms are bound in this form, however, they are unable to be incorporated in the many selenoproteins that control our metabolism, immune defense, and other vital functions. Because of this, exposure to mercury and other heavy metals increases the need for selenium.


100-200 micrograms of selenium daily tested on metabolic disorders

Two Danish research projects are planned to investigate selenium's effect on two common metabolic disorders. One is named Hashimoto's Disease and involves low metabolism (hypothyroidism), while the other is known as Graves' Disease and is characterized by an overactive thyroid gland (hyperthyroidism). Both are so-called autoimmune diseases where antibodies attack the thyroid gland. In the two Danish studies, daily supplements of organic selenium yeast (100 micrograms) will be given as treatment.
Earlier (international) studies have shown that supplementation with 200 micrograms of selenium improves quality of life, reduces the amount of antibodies and improves the structure of the thyroid gland in both of the above mentioned autoimmune diseases.

Iodine enrichment of salt - but still signs of iodine deficiency

In year 2000, mandatory iodine enrichment of salt was introduced in Denmark because the iodine intake among Danes was lower than international recommendations. However, even though the iodine intake has slightly increased it is still too low, particularly among pregnant women. Also, other factors contribute to the body's iodine status.

Did you know that sea salt contains less iodine than regular, iodine-enriched table salt?

Selenium deficiency and poor utilization may be a result of various factors such as:

  • Poor diets without fish and shellfish
  • Lack of selenium and an imbalance between iodine and selenium
  • High consumption of goitrogens like soy beans (edamame beans, tofu, soy milk etc.), peanuts, and cruciferous vegetables like broccoli and other types of cabbage - especially raw or fermented
  • Pregnancy
  • Smoking
  • Fluoride compounds in toothpaste, mouth rinses, and contaminated groundwater. Also dirt- and water-repellent PFCs that are found in Teflon, parchment paper, pizza trays, impregnation etc.
  • Chlorine in chlorinated water and cleaning agents
  • Bromium in pesticides, certain processed foods, some types of plastic, coloring etc. Bromium is also found in polluted fish
  • Lithium that is commonly used in the treatment of bipolar disorders. 40-50% of this type of patients suffer from goiter.

Did you know that fluoride compounds in the body can damage your metabolism and increase the risk of cancer?

An iodine deficiency has serious health implications

Iodine deficiencies may cause goiter (enlarged thyroid gland), hypothyroidism (low metabolism) and hyperthyroidism (increased metabolism). Children may be affected by dwarfism and mental retardation.

Recommended daily allowance for iodine

Adults: 11 years of age and older:  150 micrograms
Children: 1-10 years of age:    70 micrograms
Pregnant and lactating women:  175 and 200 micrograms respectively

Increased need: Pregnant women, growing children, older people, vegetarians and vegans. In the case of poisoning with chlorine, fluoride, and bromium, there is an increased need for iodine.

Did you know that iodine helps the body get rid of environmental toxins - especially halogens such as bromium, fluoride, and chlorine - and this may increase your need for iodine to regulate thyroid hormones?

Iodine sources, overdosing, and side effects

Iodine is found in fish and shellfish, fish sauce, eggs, and sea salt. Seaweed is a particularly good source of iodine. We humans can tolerate rather large amounts of iodine. However, prolonged intake of iodine may inhibit the production of thyroid hormone and cause hyper- and/or hypothyroidism (too high or too low metabolism). Radioactive iodine may accumulate in the thyroid gland and cause hypothyroidism plus other types of damage and cancer.

Iodine supplementation in thyroid disease also requires selenium

It is controversial to give iodine supplements to people with thyroid disorders like Hashimoto's disease that causes low metabolism. Some get worse and show sudden signs of elevated antibody production that can attack the thyroid gland. Others who take iodine supplements show clear signs of improvement with lower antibody levels. There is increasing evidence that simultaneous intake of selenium supplements contributes to an improved balance between the two trace elements, both of which are important for regulating thyroid hormones but also help detoxify the body when it gets exposed to mercury, fluoride, chlorine, and bromium. In addition, selenium is a powerful antioxidant that protects the thyroid gland against free radicals and the type of inflammation that is usually seen with autoimmune thyroid diseases like Hashimoto's and Graves'. People who suffer from these two conditions may benefit from reading about the importance of iodine and selenium supplementation and discussing this with a knowledgeable physician.


Anne Krejbjerg. Den Danske Jod - genundersøgelse af befolkningen efter jodberigelsen. Thyreoidea Landsforeningen 2014
Pernille Lund: Har du problemer med stofskiftet? 2015
Janie Bowenthorpe. Stop stofskiftevanviddet. 2014
Dansk jordbrugsforskning. Selenanvendelse i dansk landbrug. 2006.
The chronic autoimmune thyroiditis quantity of life serum trial (CATALYST): Study protocol for a randomized controlled trial
Selenium supplementation for patients with Graves' hyperthyroidism (the GRASS trial): study protocol for a randomized controlled trial