Selenium
One of the primary functions of selenium is as a component of some of the essential antioxidant enzymes. Therefore, it is also responsible for protecting the body against oxidative damage. Selenium is also necessary for the use of iodine in thyroid hormone production, reproductive functions, and immune system function.
The selenium deficiency condition is known as Keshan disease. It is a heart condition that affects children and women of child-bearing years where soils are deficient of selenium. It is essential to understand that excess selenium is exceedingly toxic. The symptoms of selenosis include brittle nails and hair, skin lesions, garlic odour on the breath, and weak immune system.