I recently have been trying the Magnesium L-Threonate as a new form of magnesium By Life Extension, and it is supposed to give greater mental focus. I noticed that my heart would race at night and seemed to have a difficult time pumping. So I have decided to stop taking them. I also took all 3 at nite time so that may have been too many at once, but heck I'd rather not have thumping heart problems from a Magnesium supplement. Xoxo
