if you need a good magnesium suppliment why not try topical magnesium chloride,its the best way to absorb magnesium ive found , it got rid of my muscle cramps and twitches, i make my own because the commercial stuff is way to expensive . just find some nigari(magnesium chloride) either online or sometimes asian markets have it because its used to make tofu.
just do some research on it its really interesting stuff
heres a forum with a bunch of ppl who've have good results with it