Discovered by a Swedish chemist in 1817, selenium became an area of scientific interest during the 1950s and is now recognized as an essential trace element to the human body. Trace elements are minerals present in small amounts in living tissues with various important functions. There are a total of 14 known trace elements, including iron, zinc, iodine, copper, manganese, aluminum, lead, and fluoride.
Selenium can be obtained only through diet or supplementation intake. Acting as a powerful antioxidant, it benefits the human body by protecting against harmful free radicals, thus providing protective immune functions.
Selenium exists in two forms: inorganic and organic. Inorganic compounds are known as “selenate” and “selenite” while organic compounds are known as “selenomethionine” and “selenocysteine”. Typically, plants contain the inorganic form, which is converted to selenocysteine and can be utilized by the human body.
The human body absorbs the mineral easiest when in the presence of fat-soluble vitamins such as A, D, and E.
Other foods such as cereals, dairy grains, and eggs also contain adequate amounts of selenium.
The best intake of selenium is through a balanced diet. However, it can be appropriate to supplement with a selenium vitamin when necessary levels cannot be met via a proper diet. While supplemental selenium comes in both organic or non-organic forms, research has shown that the organic form can be more readily absorbed.
When one does not consume adequate amounts of selenium, the following signs and symptoms may be present.
Those with impaired digestion are at risk for malabsorption and an increased risk for deficiency.
Recommended intake depends on a person’s age and sex, but generally, the daily allowance for an adult is 55 mcg daily and for a child is 20 mcg daily. While many experts feel this is too low and is simply the minimal — not optimal — amount, side effects can occur when selenium is taken in excess.
When selenium is taken in multivitamins or in a supplement form as directed, it is safe. Taking more than what is recommended on a supplement label, however, may cause side effects to occur, including anemia, hair loss, and bone stiffness. Other common symptoms of toxicity include metallic taste in the mouth, diarrhea, nausea, mental status changes, and peripheral neuropathy.