I want to concur about it being possible to get too much Se. For me 200 mcg was too much. I took it on the days that I took Io and also when I didn't. Started to get this weird symptom, hard to describe - felt like my lungs were in my throat. Then I read Trapper's post listing the excess Se symptoms, many of them were bronchial/respiratory related. I stopped it, then things returned to normal. I've since eaten lots of brazil nuts w/out a problem. (I took Solaray - "as Organically Bound Selenium Yeast," whatever that means.)