Selenium is needed, amongst other things, for:

  • Anti-oxidant, see Thyroid
  • Conversion of T4 to T3, see Thyroid
  • Being an important part of glutathione 

200 mcg per day of selenomethionine usually suffices. I found that, with my mercury toxicity, selenium yeast was very helpful.

Selenium content in foods

Interactions with other minerals



Sulfur (S) protects from selenium toxicity.

Heavy metals and fluorine

It should be noted that selenium does protect tissues from the toxic effects of heavy metals, but excretion of toxic heavy metals are not increased by selenium therapy. Selenium apparently binds these metals, such as mercury and cadmium, rendering them less damaging to cells and tissues.

Fluorine (F) has been shown to counteract the effects of selenosis. This has been found in areas with high levels of both selenium, and fluorine. Selenium was not toxic even with a high body burden when fluorine was also present.


On the basis of TMA studies it is suspected that selenium is antagonistic to magnesium. This is due to the potential sodium raising effect of selenium. Sodium increases the excretion of magnesium. Magnesium is also essential for the synthesis of glutathione, and a deficiency can increase the effects of selenium toxicity.

Zinc and Copper

Antagonism of lead (Pb), tin (Sn), and zinc (Zn) has been sited by Schrauzer. More recent investigations have confirmed the zinc-selenium antagonism. Copper (Cu) has also been shown to be a selenium antagonist.

Iron and Magnanese

The possibility of iron, and manganese antagonism by selenium also exists. Anemia is a consistent finding in animals, and humans with selenium toxicity.

Vitamins A, C, K

Animals suffering from selenosis were found to have decreased levels of vitamin A, and ascorbic acid. Ip, reported that the protective effect of selenium on mammary carcinoma in animals was nullified by high vitamin C supplementation. Selenium toxicity in laboratory animals is associated with a corresponding decrease in the levels of vitamin C, and vitamin K. The nutrients shown in figure 1 and 2, can be antagonized by excessive selenium accumulation. They in turn can inhibit the toxic effects of selenosis.


For clearance see “clearance” below and “Interactions with other minerals” above.
Februari 2014 I overdid the selenium at some point. I was taking a lot of selenium, sometimes as much as 800 mcg daily of the yeast kind. My personal symptoms were:
Itchy eyes, itchy nose (sneezing), very allergy like, but not responsive to anti histamine (ceterizine). Coughing up mucous from lungs. Little hairloss especially during hair washing. Food was not digested properly, I  could recognize some food items in the stool. Lots of air and discomfort in the bowls. Nausea. On and off numbness in extremities: on side of thumbs and under soles of feet. On and off weakness in arms and legs. Edema in whole body, but especially visible in lower legs and face.
I stopped taking selenium. I also started to take about 15 gram of vitamin C daily to help detox pathways. Also, vitamin C is a selenium antagonist. I was already taking folate, B12 and B6.

Once I stopped the selenium, symptoms were gone within a few days.

Handy overview of dangers of selenium toxicity and symptoms:

A thorough overview of selenium:

From: Hazardous Chemicals: Safety Management and Global Regulations


See also “Interactions with other minerals” above: antagonists of selenium can be used to clear selenium from the body or to render the effects of selenium toxicity less damaging in any other way.
Support methylation for clearance (Vitamin B12,B6, and folic acid, betaine or dimethylglycine).
I would take folate in stead of folic acid, because folate can be used as is by the body, where as folic acid has to be converted to folate first. Not everyone does this conversion efficiently.

Taking too much

Taking too much selenium can prevent iodide from being oxidized to iodine, which will impede thyroid hormone production. This is because selenium is a part of glutathione. Glutathione mops up hydrogen peroxide. Hydrogen peroxide is what is used to oxidize iodide to iodine. So taking too much selenium might make you hypothyroid.

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