Selenium is an important mineral to the human body. Commoin foods containing Selenium are Brazil nuts, tuna, oysters, whole grain bread, rye grain, sunflower seeds, lean lamb or beef steaks, chicken, turkey, pork and Crimini mushrooms. If you consume these foods often, you are probably getting an adequate amount of Selenium for the average person. 

One of the main benefits of Selenium is that it is an excellent antioxidant. Antioxidants are important for a healthy immune system. Another benefit of Selenium is that it positively affects the thyroid to produce more T3, a significant hormone. Research has shown that Selenium can help to prevent prostate and breast cancer, and a supplement of a 200 mcg capsule or pill will be daily support for the average adult.

According to the National Health and Nutrition Study, the risk of selenium deficiency in the U.S. is very low, but if you are deficient in both Selenium and iodine, another common mineral, this could lead to a deficiency in the thyroid.