RogueRose - 22-7-2020 at 10:44
I was looking at the effect of magnesium on the body and a lack of it can cause muscle cramps and constipation and an excess of it is used as a
laxative. The hydroxide is most commonly known as milk of magnesia and I'm guessing it is readily converted into MgCl2 in the stomach, since I think
one of the main digestive enviornment is HCl, but I'm not 100% sure. I'm not sure how the Mg citrate interacts in the stomach though.
I was thinking that the MgCO3 should have the same effect as the Mg(OH)2, IF the effect of the hydroxide is in fact converted into MgCl2, then the
carbonate should be as well with the only possible issue being the production of CO2 which I can't see it being a major issue b/c some people eat Tums
or Roll-aids by the handful and they are usually CaCO3 or even MgCO3 or a mix of the two. The thing is that I don't ever hear of people having a
laxative effect from eating them. I do see some add magnesium stearate as well.
Finally I see Al(OH)3 being used in some antacids which I kind of find hard to believe considering I would think it would make AlCl3 and I thought Al
was supposedly kind of toxic to the body.
So am I correct in how the body converts these hydroxides to chlorides to act as an antacid and if so, would the carbonates (especially MgCO3) work
the same, or work as a laxative in place of Mg(OH)2?
Finally, how exactly does the Mg citrate interact with the stomach acid and does it convert to the MgCl2? I ask b/c I was comparing molar amounts of
Mg in dosages of different products and found some wide variation with the Mg citrate being of lesser amount but having a much more immediate/complete
& pronounced effect.
Herr Haber - 22-7-2020 at 12:30
I dont think Mg by itself is responsible as a laxative.
When you get super high fever, lose a lot of water but not to the point you'll need an IV and hospital you can get prescribed MgCl with an orange
flavour. It's OTC. I'm pretty sure by the taste it is also common in sports / electrolyte drinks.
I sometimes wondered if some came from the Kroll process 
MgSO4 has a laxative effect that's true.
I've seen MgCO3 and "Mg oxides" used as filler material in pills. I'd guess they'd want minimal effects from what is basically a carrier medium.