From Natural WellBeing
In 1817, selenium was discovered associated with tellurium. It was found to be a byproduct of the production of sulfuric acid. it was also found to be toxic to humans that worked in industry. It was found to be toxic to animals that ate plants high in selenium.
In 1957 it was found to be essential in the functions of selenium in the human body. In the 70's it was found in two sets of enzymes and later in proteins.
Selenium is an essential element in the processes of steel alloying, selenium rectifiers and also in rubber compounding. Selenium is also essential in copier and laser printer drums. It was eventually used primarily for use as a photoconductor in paper copiers. Today organic conductors are the primary use in copiers. Selenium is primarily used in the manufacture of glass and by use in pigments and chemicals. Its use in the electronic industry is declining. Its use in plumbing brass to meet the environmental standards of no lead environments increased in the 90's. To this day its use is increasing at a modest rate.
Modern usage and side effects
Although selenium is toxic if used in excessive dosages, it is essential for animal health. There are some plants that contain toxic dosages of selenium. There are also plants such as locoweed that require large amounts in soil to survive.
The proper function of the thyroid gland is also dependent on selenium. Consequently, every cell that uses the hormone produced by the thyroid will require selenium.
Selenium is found in meat, mushrooms, fish, eggs, nuts and cereal. The richest dietary source is Brazil nuts. Tuna, crab, lobster and kidney are also higher in selenium. The human body has a content of between 13-20mg.
Toxic effects of selenium
Although essential, excess intake is toxic. Selenosis can be caused by exceeding the recommended allowance. In 1992, as study was done that determined the intake of 15mcg of selenium per day was save. It also stated that it is best to keep it lower than 400mcg to avoid toxicity. The study was done in China and it was found that the citizens that had toxicity had been eating corn that was grown in selenium rich soil. 5mg /day can be lethal.
Symptoms of toxicity include hair loss, garlic breath, irritability, fatigue, nerve damage, garlic odor and cirrhosis of the liver if the case is extreme.
The media reported that a group of polo ponies died before a match. It was attributed to the incorrect dosage of an injectable vitamin supplement. While these vitamin and mineral injections are common after a match it is not usual before a match. Selenium is used in very small amounts. The mistake is sometimes made of administering mg instead of mcg. Consequently, the recipient is receiving 1000 times the recommended dosage. It has also been found that excess selenium can cause congenital issues in some birds.
Deficiency is rare except in times of severe malnutrition.
There have been several studies suggest a potential link between deficiency and cancer. The studies have been controversial with some saying yes and others no.