I must take Selenium to boost up my immune system. 5 years ago I went to the hospital for a couple of weeks with the physicians unable to diagnose my problem. After the first week, they realized I had deficiency of potassium and selenium, as soon as they gave me one of each, I came back to reality. Until the end, the doctors couldn't detect what exactly was wrong with me, finally, they discharged me with Pneumonia diagnose. Since then, I haven't been seriously ill and of course, I do not have the level of stress I experienced during the "great financial catastrophe of 2008" when I became so ill. I took charge of my health and stopped making the hospitals and doctors richer. I realized our food, if not organic, does not provide the necessary nutrients for a healthy life. Even with organic -no NATURAL FOODS- products, pollution and stress contribute to deteriorate our health. We must take some vitamins and mineral supplements to prevent costly diseases. NOW Selenium is a great product at a good price