I have noticed that after taking calcium tablets or sea kelp for a couple of weeks ( which contains a lot of calcium among other things ) I end up feeling really depressed and anxious . I am inclined that way anyway and been taking magnesium which has brought great relief, I have read that an antagonism exists between magnesium and calcium ions and calcium can lower magnesium levels and I wonder if this has anything to do with me having felt so low after taking calcium tablets.