Chris Kresser: Serum is okay for selenium. Actually toenail selenium is the best marker for selenium status. Hair selenium is pretty good too. Serum is not quite as accurate. Red blood cell selenium is also another marker that’s on the Quicksilver blood metals panel or the Doctor’s Data essential elements panel, and that has some validity. So it’s a little bit of a, it’s a piecemeal kind of thing. There are several different markers for selenium. Probably putting them together is best, but is that really practical in a clinical setting? That’s something I’m still looking into because, as we discussed I think at that point, supplementing with selenium in a patient that already has sufficient selenium stores, especially over the long term, could be problematic.
So at present I think that the best option is to just stick with food-based sources of selenium in most cases, unless there is pronounced selenium deficiency that’s evident through hair and serum or red blood cell levels.