What Is Selenium? - Benefits, Foods & Deficiency Symptoms

Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

Explore selenium: discover how the human body uses this element, and find out whether it is wise to include this as a supplement to your diet. Find facts pertaining to selenium's discovery, and learn about its industry uses as well.

What is Selenium?

Selenium comes under the nutritional category of micro-nutrients, meaning that it is needed in smaller amounts than those of macro-nutrients, such as protein. Selenium is found in the soil, where it is taken up by plant roots. The amount of selenium a plant contains is determined by the amount found in the soil where the plant is grown. We generally obtain the mineral by consuming animals that have eaten plants, or by eating the plants themselves. While plants do not need selenium, they do need sulfur. If the ground they are rooted in does not contain sulfur, they will use selenium as they would sulfur.

Selenium is a non-metal element, closely linked to sulfur, number 34 on the periodic chart. Selenium rarely occurs by itself in nature. Most commonly, it is found combined with other elements like sulfur or copper.

Selenium is the 34th element on the periodic table.
periodic table selenium

Selenium was identified in 1817 after some sulfur was burned, leaving behind a red substance. Selenium comes from the Greek word 'Selene,' which means 'moon goddess.' Selenium is used in the glass industry, in solar cells, and in anti-dandruff shampoos. Most of the selenium used today is produced in Germany, while China uses the most.


The human body requires selenium for a variety of enzyme activities in metabolic processes such as reproduction and thyroid function. Enzymes work as catalysts to enable or speed up chemical reactions within the body. For example, if you were to fry an egg, without the addition of heat, you would just have a runny egg. Heat would be the catalyst in this example. Selenium is considered an antioxidant because it is able to repair DNA and prevent oxidative stress. Research is being conducted to see if selenium might be useful in the prevention and treatment of cancer, heart disease, dementia, and thyroid diseases.


We cannot manufacture selenium within our bodies, so we must eat foods that contain it. Many foods are excellent sources, such as nuts (especially Brazil nuts), seafood, meats, grains, and dairy products. Poultry and eggs are also good sources, though fruits and vegetables don't generally contain much selenium. The average daily intake is 120 mcg, with the upper safety limit being 400 mcg. Unprocessed foods are the best source, since selenium may be destroyed during processing.

Brazil nuts contain very high levels of selenium.
brazil nuts

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