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We know that body needs a certain amount of magnesium. Why are magnesium supplements in the form of magnesium oxide, magnesium citrate, etc?

asmani
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  • Note that this is true for all the trace metals; your body uses magnesium ions, not elemental magnesium. The free metal is not found naturally, it's far too reactive. – Bryan Krause Oct 14 '17 at 15:52
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    Elementary Mg isn't available normally in the environment, only when it's chemically reduced in the lab and stored in the absence of oxygen or other oxidative sources. – AliceD Oct 14 '17 at 17:49
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    I would think pure magnesium would react with the stomach's hydrochloric acid, producing magnesium chloride and hydrogen gas. Probably not a good idea to perform the experiment on yourself, though. – jamesqf Oct 14 '17 at 17:53

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Because like a lot of material we need the ion not the pure form. Pure sodium is explosive metal and pure chlorine is horribly toxic gas but change them into their ionic form and they are essential nutrients, sodium chloride, table salt.

In the case of magnesium however the problems one of reactivity and absorption. If you swallowed a solid lump of magnesium, not much will happen, the molarity of stomach acid is fairly low, it reacts too slowly to get significant amount of magnesium (or hydrogen) out of it before it passes. Your body just is not equipped to break down solid magnesium since it does not occur naturally often. We can only absorb it in it's ionized state.

More importantly we take in some ion combinations better than others, this is called bio-availability and is influenced by a number of factors. Magnesium oxide for instance has very low absorption rates and basically just passes through without doing much, while magnesium glycinate has a fantastic absorption rate, some combinations can actually be mildly toxic like magnesium sulfate. This is a reoccurring issue with dietary supplements many do not contain bioavailable forms of the mineral they list, which is how people can end up with deficiencies even while taking supplements for that mineral.

John
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  • Thank you so much! I've heard magnesium is good for IBS. The question is, which form of it. You said magnesium glycinate has a fantastic absorption rate, so it seems like the perfect choice? – asmani Oct 16 '17 at 20:07
  • once it is absorbed it is basically all the same, but different compounds are absorbed at different rates. – John Oct 17 '17 at 04:17
  • you said magnesium sulfate could be mildly toxic. I'm wondering if different combinations have different mechanism of action? – asmani Oct 19 '17 at 14:22
  • Magnesium sulfate is a fairly powerful laxative, that is what I was referring too. – John Oct 19 '17 at 22:03