Selenium (from the Greek word "selene" meaning "moon") was discovered by Jöns Jacob Berzelius in 1817. He reported that tellurium was present in sulphuric acid from a Swedish factory, but in the following year decided that the impurity was not tellurium but another closely related element that he subsequently identified as selenium.

Selenium is essential to mammals and higher plants, but only in small amounts. Selenium is said to stimulate the metabolism. It may help protect against free radical oxidants and against some heavy metals. Livestock grown in areas containing high amounts of selenium in the soil and in which a plant called Astragalus ("loco weed" in USA) is present are poisoned. This is because Astragalus concentrates selenium. On the other hand, sheep grown in areas containing deficient amounts of selenium in the soil develop "white muscle disease."

One of the main activities of this mineral is its anti-aging properties and its ability to help rid the body of free radicals, as well as toxic minerals such as mercury, lead and cadmium. It is helpful in fighting infections since it stimulates increased antibody response to infections, promotes more energy in the body, and while it helps with alleviating menopausal symptoms in women, it assists the male in producing healthy sperm.

In certain cases selenium has also proven effective in helping to fight cold sores and shingles, which are both caused by the herpes virus. Some researchers have shown that in selenium-deficient animals a harmless virus can mutate into a virulent form capable of causing damage and death - this has also been followed up with other studies, which seem to indicate that selenium helps to keep the spread and multiplying of viruses in check.

Selenium is also used against arthritis and multiple sclerosis and if provided in adequate amounts it is thought to help prevent cancer as well. Tissue elasticity and pancreatic function is also dependant on this mineral. In a study it was shown that selenium could be useful in treating certain cancers, and is also helpful in making the blood less "sticky", which is helpful in preventing heart attacks and strokes.

Selenium, once classified as toxic, is now regarded as an essential mineral, needed in small daily amounts. Selenium functions as a component of the enzyme glutathione peroxidase, which accounts for its antioxidant function that protects cell membranes and intracellular structural membranes from lipid peroxidation.

Selenium and vitamin E work together synergistically in that they carry out antioxidant and immunostimulating functions better together than individually; however, their mechanisms of action are probably not the same. Both of these nutrients are part of the "anti-aging" or "longevity" group, which may be directly attributable to their antioxidant functions because tissue oxidation by free radicals may be the contributing factor to degenerative disease.

Because of selenium's immunostimulating function, it's very useful in the treatment of many immunosuppression diseases. With its antioxidant properties, selenium, especially along with vitamin E, may become a routine and powerful nutritional treatment in the medical world. Autoimmune diseases, recurrent illnesses or infections, and other inflammatory problems may be helped by restoring adequate selenium levels in the body. Selenium can help us prevent disease by increasing our resistance. In some cases, selenium promotes more rapid recovery from many basic disease processes. More controlled human studies related to specific illnesses will need to be done to generate greater acceptance by the medical establishment of selenium's important role.

Despite its importance, there is less than 1 mg. of selenium in our body, most of it in the liver, kidneys, and pancreas and, in men, in the testes and seminal vesicles. Men have a greater need for selenium, which may function in sperm production and motility. Some selenium is lost through the sperm as well as through the urine and feces. It is absorbed fairly well from the intestines, with an absorption rate of nearly 60 percent.

Most selenium in foods is lost during processing, such as when making white rice or white flour. Selenium may be present in some drinking water, and it is sometimes even added to drinking water where it is deficient. Mother's milk usually has several times more selenium than cow's milk. Selenium is also used in some shampoos and skin lotions, and it is possible that we absorb small amounts of selenium from these products. Brewer's yeast and wheat germ, both regarded as "health foods," usually contain high concentrations of selenium. Animal sources such as liver, butter, most fish, and lamb have adequate amounts. Many vegetables, whole grains, nuts, and molasses are fairly good selenium foods. Brazil nuts have high amounts; barley, oats, whole wheat, and brown rice are also good sources; and shellfish such as scallops, lobster, shrimp, clams, crab, and oysters are all rich in selenium. Garlic and onions, mushroom, broccoli, tomatoes, radishes, and Swiss chard may be good selenium sources if the soil in which they are grown contains it.