Selenium: Deficiency & Toxicity Symptoms

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Magnesium Deficiency & Toxicity Symptoms

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Selenium
  • 1:58 Sources
  • 2:19 Deficiency
  • 4:23 Toxicity
  • 5:37 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed
Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Selenium is a trace mineral needed for proper thyroid function and other processes. Learn about conditions linked to selenium deficiency, such as Keshan disease and Kashin-Beck disease, as well as toxicity symptoms, such as hair and nail loss, in this lesson.


If you post something to the Internet, it's possible that post could go viral and end up being dispersed to a number of different locations. It might end up in blog posts, tweets or broadcast out in emails that reach across the world. In a way, this is what we see with minerals, which are inorganic compounds needed for your body to function properly. They all come from the same source: the earth.

These minerals then find their way into plants that grow in the earth's soil. Animals then pick up the minerals from the plants they eat, while other minerals get washed into the oceans where they are picked up by sea plants and critters. Eventually these plants, animal products and seafoods find their way to your neighborhood grocery store and when you eat them, the minerals that started in the ground end up inside of you. This is a good thing because your body needs a variety of minerals to carry out many vital functions.

One of these minerals, selenium, is a trace mineral that works as an antioxidant and is needed for the synthesis of thyroid hormones. Selenium, like all minerals, comes from the ground, but concentrations of selenium vary greatly between different regions of the world. Now, if you live somewhere like the United States, where we import foods from a number of different geographical areas, then you likely meet your selenium intake with little difficulty. However, there are groups of people in the world that eat a diet that consists of foods grown or obtained only from local sources.

So, what happens if that local soil is too low or too high in selenium? Could this varying concentration of selenium affect the health of the people in that area? These are the questions we'll explore in this lesson.


A few of the better food sources of selenium include seafood, organ meats, such as kidney and liver, and eggs. And, depending on the selenium content of the soil in which certain plant foods are grown, we see that sources of selenium can also include grains, nuts and seeds.


Having a selenium deficiency is not a major concern for otherwise healthy citizens of the U.S. because the foods we eat come from many different areas, so the foods that come from soils with a low selenium concentration are offset by the high selenium content foods from other areas. The same cannot be said for groups of people living in regions of China, where the diet consists mainly of locally obtained foods grown in soils with low selenium levels.

In these areas, symptoms of selenium deficiency may present as muscular weakness and fatigue, which might be tied to the role selenium plays in proper thyroid gland health as the thyroid gland regulates your metabolism and gives you pep. Selenium deficiency, in combination with an infection, can lead to Keshan disease, which is a form of heart disease that occurs in parts of China. In fact, the disease was named after Keshan County, which is located in Northeast China and the site of the first reported symptoms.

Too little selenium may also play a role in Kashin-Beck disease, which is a disorder of the bones and joints that occurs in low-selenium areas of China, Tibet and Siberia. This disorder causes stiff and deformed joints mainly in children. People from the regions affected by Kashin-Beck disease have given it the nickname 'Big Bone disease,' which likely comes from the enlargement of the joints. It might help you to recall that this disorder affects the bones and joints if you remember that the shin is a bone in the lower leg, and we see the word 'shin' hidden in the word Ka'shin.'

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account