Selenium is actually extremely beneficial for the human body! It's an essential mineral that the body needs, though only in small amounts. It helps with bodily operations like regulating metabolism or thyroid functions. Selenium is an antioxidant, meaning that it prevents cell damage in the body. It's also been found that selenium prevents several types of cancers. Dozens of studies have shown that people with high levels of selenium in their bloodstream show less risk of contracting breast, colon, lung, and prostate cancer. Finally, selenium prevents mental decline, such as Alzheimer's. Several studies have shown that people with Alzheimer's generally have lower levels of selenium in their body, and people with higher levels have a fewer risk of contracting it, or other memory related disorders.