Selenium

Selenium is a semi-metallic mineral, closely related to sulphur.
The importance of Selenium was only discovered in 1973 when it was found to be an integral part of the enzyme glutathione peroxidase and is a very potent antioxidant protecting the body from damage due to oxidation by free radicals. Selenium is a trace element or micronutrient as the amount needed for human health is measured in micrograms (millionths of a gram). In excess, selenium can be toxic.
Selenium works with vitamin E and other antioxidants to protect cells from damage caused by oxidation by free radicals. Selenium helps synthesize antibodies. Selenium helps synthesize co-enzyme Q10. Selenium helps transport ions across cell membranes.
Gross deficiency in selenium can cause: Heart disease (Keshan Disease); osteoarthritis (Kashin-Beck disease)
Mild deficiency in selenium can cause: Weakened immune system; increased risk of some cancers, heart disease, ageing and other illnesses associated with a weakened immune
Best sources of selenium in the diet are: Brazil nuts, wheatgerm, molasses, sunflower seeds, wholewheat bread, dairy foods.
The Selenium content of foods is related to the Selenium content in the soil in which the foods are grown. Some countries have been shown to contain soil which has become severely deficient in selenium - these include China, Finland, New Zealand, some areas in the United States as well as central and eastern Canada, and some part sof Europe. In these areas it is therefore advisable to take a nutritional supplement containing 60-70 mcg of selenium.
Selenium supplements vary greatly in efficiency of absorption. The simplest, and furthest away from the form found in foods, are as usual the worst absorbed. Sodium selenite (the inorganic form) is commonly found in the lower-quality supplements; the two best forms are high-selenium yeast and selenomethionine (in which the sulphur atom in methiinine is replaced with selenium). Of these, the better is probably selenomethionine, as quite a lot of people are slightly allergic to yeast.