What is selenium deficiency?

Selenium is an important mineral. It’s necessary for many processes, such as:

  • thyroid hormone metabolism
  • DNA synthesis
  • reproduction
  • protection from infection

Selenium deficiency refers to not having enough selenium in your system. This can cause several health problems.

The amount of selenium in food sources is largely determined by the quality of the soil used to grow them. Rainfall, evaporation, and pH levels all affect selenium concentration in soil. This makes selenium deficiency more common in certain parts of the world. In the United States, selenium deficiency is rare. However, an estimated 1 billion people around the world are affected by selenium deficiency, according to a 2017 review.

That same review predicts that the effects of climate change will gradually decrease soil selenium concentrations in many parts of the world, including the Southwestern United States.

Selenium is a particularly important mineral because it supports the function of several systems. These include the endocrine, immune, and cardiovascular systems. The thyroid, part of the endocrine system, is the organ with the highest concentration of selenium per weight of organ tissue.

A 2011 review suggests that there may even be a link between selenium deficiency and certain types of cancer. However, more research is needed to make any firm conclusions.

Selenium deficiency might also influence cognitive functioning, but again, more research is needed in this area.

Selenium deficiency can produce a range of symptoms. The most common ones are:

In addition to living in an area with soil low in selenium, the following things can also increase your risk of selenium deficiency, regardless of where you live:

Each of these things can affect your body’s absorption of selenium, even if you’re getting enough selenium through your diet.

Who is adequate selenium especially important for?

Adequate selenium is especially important for some groups, such as people who:

Selenium deficiency can be hard for doctors to diagnose. This is because there isn’t a widely available test for it. In some cases, your doctor can measure your levels of glutathione peroxidase. This is an enzyme that requires selenium to function. If your level is low, you may not have enough selenium.

The first-line treatment for selenium deficiency is to try to eat more foods that are high in selenium. Selenium-rich foods include:

  • Brazil nuts
  • yellowfin tuna
  • rice
  • beans
  • whole-wheat bread

The National Institutes of Health recommends that people over the age of 14 try to get 55 micrograms (mcg) of selenium per day. For women who are pregnant or lactating, this increases to 70 mcg. Anything over 900 mcg per day can be toxic. Signs of too much selenium include a garlic-like odor on your breath and a metallic taste in your mouth.

When foods high in selenium aren’t an option, selenium supplements can also help. Many multivitamins contain selenium, but you can also find it as a standalone product. Selenium supplements usually come in the form of either selenomethionine or selenite. Selenomethionine tends to be easier for your body to absorb, so it may be a better option for more severe deficiency cases.

The U.S. Food and Drug Administration doesn’t monitor the purity or quality of supplements like they do for drugs. Talk to your doctor before you begin taking a selenium supplement.

Although selenium deficiency is rare, it’s important to make sure you’re getting enough of it and absorbing it properly. If you think you may have a selenium deficiency, work with your doctor to rule out other possible causes of your symptoms.