Selenium is a mineral not often spoken about. Selenium has been shown to cut certain cancers by up to 83%.
Selenium seems to be the main health factor in the Mediterranean diet as well, it chelates heavy metals out of the body including lead, mercury and cadmium, etc.
Selenium is a wonderful mineral that is deficient in most soils in the world. When it is introduced into diets cancer goes down.
Toxicity can happen with over consumption so be wise when taking it.
Here is a great interview with Dr Schrauze, who is an expert on selenium.