T Nation

Magnesium Stearate Bioavailability?


I know Magnesium Stearate for a filler in pills. However, I am interested if Magnesium Stearate could serve as a source of magnesium in one's diet? Google does not seem to hold the answer, or maybe I am not asking the right question....


The amount of magnesium stearate that is often included as a lubricant (not really as a filler, though this is often said) isn't sufficient to be an important dietary source of magnesium.

I'd strongly expect that magnesium has good bioavailability when taken this way, but it would be quite inefficient as the great majority of the weight is the stearate, not the magnesium.

Magnesium citrate or various other forms are more efficient choices.


Thanks for the response Bill. I can't believe I didn't look at its molecular formula or weight haha.

For anyone that is interested:
591.27 g/mol
24.3MW of Magnesium

Magnesium is 4.1% mass of Magnesium stearate. Again, thanks Bill.


Bill is there going to be much difference between magnesium citrate or an amino acid chelate for the cost difference?


Well, it really depends on whether the money involved in the cost difference is something substantial to the individual or something that is not so much, and how much they value using what is to the best current knowledge the most optimal approach versus using a good approach. So whether it's "worth it" will depend so much on those individual factors.

Magnesium citrate can be completely effective. It can be dosage sensitive with regard to producing loose stools for many at doses only slightly higher than what may be the best daily dose for the individual, at least if dosing is only 1x/day.

Magnesium glycinate is showing interesting properties with regard to mood (or likely more broadly, in positive effect on the brain) and may be preferable to other forms in this regard. The dosing also doesn't seem to have to be on the edge of causing loose stools for most, if for any.

Magnesium citrate can get the job done if money is tight. I wouldn't recommend suffering significantly in other areas of life, due to a money situation, for the sake of the form of magnesium.


Hey Bill, I heard that magnesium stearate could lower the absorption of other nutrients due to it forming a film in the intestine and coating the inside of the digestive tract. Any truth to this?


No. It dissociates to the magnesium and stearate ions in the GI tract: and you get the stearate ion also from hydrolysis of ordinary fats, so it's something that's ordinarily present in the GI tract. And neither the magnesium ion nor the stearate ion would make a film coating the digestive tract.


Bill Roberts, so you say magnesium stearate dissociates in GI, but i read that magnesium stearate is not soluble in water, so what i'm asking is, will magnesium stearate in water dissociate in into magnesium and stearate ions? since it does dissociate in the GI, or does it dissociate in the GI because the GI is acid breaks it down?


The solubility is very low in water, because stearate ions are not very well solubulized.

The process is assisted in the GI tract because fats and bile acids, acting as emulsifiers, are present. So the stearate ions don't have to have their entire chains in aqueous phase: most of them probably have the long carbon chain, which is hydrophobic, incorporated into a micelle while the polar head group is in aqueous phase.


Bill Roberts so if i put magnesium strearate in water and stir it, will it dissociate into seperate magnesium ions and stearate ions?


If the amount of magnesium stearate were very small, then all of it could dissolve and all or virtually of it would be dissociated.

But an amount containing any dietarily-significant amount of magnesium would not anything like fully dissolve in any reasonable quantity of water.

I don't know of a specific numeric value for magnesium stearate's water solubility, but the term "insoluble," which is used for magnesium stearate's solublity in water, isn't properly used unless the solubility is less than 1 part in 10,000.

So if a glass had 500 mL of water -- a pretty big glass -- it should be the case that the amount of magnesium stearate that would dissolve would be less than 50 mg. It might be much less. But it would be something, and that which dissolved would be dissociated into ions, as you say.


I must say, seeing Bill discuss nutritional chemistry is akin to listening to a movement of Beethoven in concert; I may not understand what the fuck I am listening to or just how complex it really is, but it sounds fascinating. /Bill nut hugging.


Well, I see I wasn't as clear as I should have been.

Phillybadboy was referring to the fact that some molecules "dissociate" when they dissolve. What this means is, in some cases rather than a molecule dissolving (going into water solution, so that it is surrounded entirely by water) intact and staying in the same form, it breaks into parts. One or more of these will be positively charged, and one or more of them will be negatively charged.

So for example when table salt (NaCl) dissolves into water, rather than having NaCl molecules remain intact in water, "floating" as NaCl and surrounded by water molecules, instead the molecule breaks into positive Na (sodium) and negativel Cl (chloride) ions, which each are surrounded by their own group of water molecules.

That is what will happen with molecules of magnesium stearate.

In the GI tract, the magnesium ions will be quite independent, "floating" entirely disconnected, or dissociated, from the stearate ions.


Bill, or anyone else for that matter, have you heard of transdermal magnesium?

Regular magnesium supplements always give me loose stools and I've heard that magnesium needs to stay in the intestines for 12 hours or so for proper absorption....seems like transdermal delivery would help this problem, but also seems like overkill.


If I may add, Magnesium Oxide is usually used for that coating effect (for instance in harsh pain killers)


I've never seen (I have looked fairly extensively) any evidence at all substantiating, from any type of measurement, that significant transdermal delivery of magnesium has occurred.

Transdermal delivery of compounds with low lipid solubility is very poor. If we had a drug with the properties of magnesium citrate or magnesium stearate, it would be a major problem in my opinion to deliver even just a few mg of it.

Transdermal delivery can be predicted fairly accurately from physical properties -- lipid solubility, water solubility, and molecular weight. So this is something that can be estimated.

Delivering hundreds of grams of magnesium, and therefore thousands of milligrams of a magnesium compound such as a chelate or the stearate, is not going to happen, from the physical properties of the compounds.

On the loose stools problem, it's true that doses of 250 mg or more (for some individuals, even 200 mg) of many forms are likely to cause loose stools.

The glycinate form definitely seems to cause less problem here. This is why the Elite Pro Minerals is able to provide 400 mg/day of magnesium without dividing the dose, as ordinarily would be done. For example personally I absolutely could not take an amount of magnesium citrate delivering 400 mg of magnesium at one time, but I have no problem with a corresponding amount of magnesium glycinate.

You are more sensitive to this problem than I am, but it could well be the case that an amount of magnesium glycinate delivering 200 mg of magnesium at a time would be fine for you, or almost certainly, for example, 114 mg at a time, 3x/day.

This would work, whereas transdermal would not.


I've read that magnesium sulfate (epsom salts) can substantially boost measured magnesium levels in the blood.


If taken orally, undoubtedly.

Transdermally, where's the measurement? Wherever I have seen something like this, it has unfortunately always been assertions with no backup of any kind.