The first two links are to studies indicating the reduced sodium was HELPFUL!
"These data showed that oral magnesium supplementation may reduce the blood pressure, which can be partially explained by the decrease in intracellular sodium and augment in intracellular magnesium."
" It appears that magnesium suppresses circulating Na+,K(+)-ATPase inhibitory activity to attenuate vascular tone, and thereby reduces blood pressure in EH."
I did not read the studies but these groups of people with high blood pressure might have had high sodium. They were not studies of people with adrenal insufficiency.
If a person has a cluster of symptoms that is associated with low magnesium (Mg) or symptoms that tend to respond somewhat to Mg supplementation it is quite reasonable to take some extra Mg, especially those who eat a "Western" diet that tends to be deficient in Mg.
Of course people can overdose on anything. Mg tends to be one of the safer supplements. Also the ligand attached to the Magnesium can also be beneficial--citrate, glycinate, sulfate, malate, etc.
I'm not disregarding the potential need for calcium, sodium, maybe potassium in some people. I take modest doses of all of those.
Also I realize that some people will have difficulty balancing their minerals, etc.
I've heard many reports from chemically sensitive people who prefer the more subtle effect of an Epsom Salt (Mg sulfate) foot bath.
In contrast a female friend with a long history of PTSD but who does not have MCS loves the full Epsom Salt bath.
Hopefully people will do their homework and or work with a medical professional when selecting supplements and reasonable doses. It is also wise to be aware of commonly reported symptoms of taking too much.