Hi Donna!
I have no idea. BUT, the best source of selenium is Brazil nuts, so I eat ONE organic Brazil nut almost every day. I keep a month + supply in the refrig next to my SuperFood etc.
Since my Mom, Dad and sister all died of lung cancer in the last two years, I feel comforted by keeping my selenium level higher. And I'm not in love with Brazil nuts. So amazing as it may sound, I can eat just one! LOL