Is this potentially harmful substance lurking in YOUR nutritional supplements?


If you are taking any supplements right now, I have a mini assignment for you.

Step away from the computer for a moment, check the ingredients, and see whether you see “magnesium stearate” (also known as “stearic acid”) listed.

If you take anything other than the very highest quality, most natural supplements, chances are that this substance – contained in over 90% of supplements and in most pharmaceutical drugs – will feature on the label/s.

You may have seen it there before and, like me, not batted an eyelid, assuming it was a supplemental form of magnesium, and therefore no cause for concern.

But magnesium stearate is not a substance added for your nutrition, nor for any health benefits whatsoever.

It’s machine lube.

No, I’m not kidding, but I wish I was.

Magnesium stearate is a flow enhancer, added so that production machinery will run at maximum speeds, and require minimal cleaning, thereby maximising profits.

In other words, it is an excipient; a synthetic substance added to enable supplement manufacturers to mass-produce their wares more easily and cheaply. Other common excipients are titanium dioxide and talcum powder, or talc.

Where magnesium stearate is used in the supplements industry it is only used in tiny quantities. (Or rather it should be – the industry is grossly under-regulated.)

Still – if you’re taking 5-10 or more capsules every day containing this substance, as many health seekers do, it adds up.

Magnesium stearate is generally manufactured by hydrogenating cottonseed or palm oil. During the hydrogenation process, the oil is subjected to high heat and pressure.

Hydrogenated fats contain highly altered toxic molecules, and cottonseed oil additionally has an extremely high level of pesticide residues, due to the fact that cotton crops are heavily sprayed.

The company ScienceLab produces chemicals and laboratory equipment. Its Material Safety Data Sheet for magnesium stearate contains the following information:

“Potential Acute Health Effects:

Hazardous in case of ingestion.

Potential Chronic Health Effects:

CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Not available. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available. The substance may be toxic to liver, skin. Repeated or prolonged exposure to the substance can produce target organs damage.”

In other words, we simply don’t know the full effects of magnesium stearate on the body.

Magnesium stearate is a grossly under-tested substance, given its ubiquity in pills manufactured by both the pharmaceutical and nutritional supplement industries.

Some point out that there isn’t research that conclusively proves that magnesium stearate is harmful to humans.

And maybe it’s not. But let’s not forget that the same was once said about cigarettes, and is still vehemently argued about aspartame, mercury fillings, vaccines and many other synthetic substances – most often by the parties who profit from their sale.

And those who assure us that magnesium stearate is a safe substance to consume generally fall into that very same category.

Some of these further contend that magnesium stearate has been unjustly maligned by sellers of natural supplements who want to create false alarm in order to boost sales of their own products.

The argument is uncannily similar to the argument that, “there’s nothing wrong with conventional (or even genetically modified) food and organic food isn’t better for you – that’s just what the organic farmers want you to think”.

Others argue that they, or others they know, have been consuming handfuls of magnesium stearate containing pills for decades, and it hasn’t affected them.

This is missing the point.

There are numerous manmade substances in our air, water and food supply, the full effects of which on human health – as they silently accumulate, year on year – are not known.

We can’t avoid exposure to all of these substances, but we can choose to avoid synthetic substances whenever possible, so as to lighten our toxic load.

Don’t get me wrong. I’m not advocating neuroticism about any of this.

I’m passionate about eating wholesome real food…and I eat rubbish sometimes.

I do my best to source natural and eco versions of everything I use…but where those haven’t worked for me (foundation, conditioner, wall paint, to name three) I compromise.

When it comes to supplements, it’s an easy decision as far as I’m concerned.

Most contain a synthetic flow agent – magnesium stearate – whose full effects in the human body are unknown.

But not all do. It’s becoming easier and easier to source excipient-free supplements, and these tend to be lines that contain the highest-quality (often whole-food) ingredients, produced by companies that really care about purity and ethics.

My go-to brand is Viridian Nutrition (and no, I’m not on commission). All their products contain 100% active ingredients – no synthetic nasties of any kind – and 40% of the range is certified organic. Find out more here.

June 2015 addendum

Every now and then, someone writes in regarding this article to point out that stearic acid, of which magnesium stearate is one form, occurs naturally in certain foods, and is therefore safe.

It sounds like a convincing argument, but it’s actually just like saying that sugar occurs naturally in foods so therefore sugar must be fine – including the refined white variety. The magnesium stearate that supplement manufacturers buy to add to their products is another highly processed white powder which is about as far removed as it’s possible to get from anything that occurs naturally in food. Here’s a picture of it. Any further questions? 🙂

Magnesium stearate


  • I’ve just finished reading this article.

    I’ve started taking a supplement in preparation for pregnancy and now see that it contains stearic acid.

    I believed it was a high quality supplement (Lamberts StrongStart) bought from a local health store. The supplement was not cheap – I was working on the basis that you get what you pay for!

    I’m at a loss to know where to start looking for a replacement. Can you recommend a company known for their high quality supplements – I appreciate you can’t recommend a specific supplement.

    Thanks again for the article and bringing these matters into the public domain.

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  • Hi Sarah, glad to get another pithy report from you. yes, I assumed magenesium stearate was a useful source of magnesium!
    Is it permitted in organic supplements? And if so, does being organic, and therefore relatively pesticide-free, reduce its toxicity?

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    • More great questions! I’m not sure whether it’s permitted in organic supplements – I’ll see if I can find out. I’m not even sure whether there is such a thing as organic magnesium stearate – and sadly the word “organic” on a supplement label often means nothing more than that it contains some organic ingredients… Yes, the organic version would be less toxic, but would still have the other negatiives. I’d see this as analagous to the difference between, say, regular refined white sugar and organic refined white sugar.

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      • Yes of course there is organic magnesium stearate. It’s made from non-GM, organic palm or coconut oil that has not been modified or hydrogenated.

        If you eat wholesome foods you probably consume thousands of grams, GRAMS, not milligrams, of magnesium stearate per day in your diet.

        As with anything under the sun known to be good for a human body, that all depends on the dose of that substance. Water as we all know is essential to life, but you’d have to drink gallons a day before you’d die of that dangerous chemical. H2O kills people all the time. There is not a day when I don’t hear of someone drowning.

        You’d have to eat, or breathe, or inject, an impossibly large dose of magnesium stearate to experience the quick onset of death water can bring, provided you’re a healthy individual to begin with.

        But to eat enough to kill you would be a impossible feat. Yet to eat enough to make you feel unwell is easy. You’ve probably done that many times over at your family Thanksgiving dinner.

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        • Hi Truthseeker,

          This article is specifically about the synthetic, lab-produced magnesium stearate that supplement companies add to their products as a flow agent.

          You’re quite right that the magnesium stearate that occurs naturally in food is a very different animal.

          While magnesium stearate is an extremely common ingredient in supplements, I have never seen a supplement that claims to contain organic magnesium stearate. That’s not to say it’s not out there, but if it is, it’s a rare thing.

          The purer and more whole-food based a supplement is, the less likely it is to contain an additive like magnesium stearate.

          Also, this article is not about “death by magnesium stearate”. 🙂 The point is simply that we all need to reduce our exposure to synthetic additives (and other manmade chemicals) as much as we possibly can, so if you’re taking multiple supplements daily and can make those supplements that are free of this one, do!

          Sarah xo

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  • Thank you for that important info.

    Checked my Vitamin Ester C ( Sisu) it contains magnesium stearate

    also my Vitamin B-50 magnesium stearate.

    Am so dissapointed–been taking theses for years. Into the dumpster with these products.

    Will be more careful and read labels in future.

    Gracias thank you..keep up the good work.

    Will also email both these companies!

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  • Oh my, stearic adic is in my moisturising cream. I have CFS and use this cream for body and face, could that contribute to my health? Thank you, wonderful article.

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    • And another great question… I haven’t looked into the effects of stearic acid when absorbed through the skin, but here are my thoughts. Less of it will get into the body this way. I once read that around 60% of anything on our skin gets into our blood – but of course this must depend on the substance itself. BUT as this route bypasses the stomach and liver, more of the substance gets into the bloodstream than if the amount *absorbed* (not applied) were taken orally.

      As you’re using it on body as well as your face, this could be adding up – though *how* much depends on what percentage of the product is stearic acid. I would personally change to another moisturiser, one that is 100% pure and organic.

      But please don’t worry about it. I personally don’t believe that any ONE thing like this is going to make a noticeable difference to our health. The point is that if we don’t eliminate those “one” things when we become aware of them, we’re going to really add to our toxic load over our lifetime. Because those things are everywhere and in everything (mainstream). We can’t avoid them completely, the human organism can take a lot, and worrying is bad for us too! It’s just wise to avoid them *where possible* – hope that helps.

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  • Great article, it’s rare to see someone who blogs about health that actually realises that magnesium stearate is a flowing agent. I always buy my supplements from Metabolics Limited ( They don’t use magnesium stearate at all.

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  • Karen Eiles asked: “I’ve started taking a supplement in preparation for pregnancy and now see that it contains stearic acid. I’m at a loss to know where to start looking for a replacement. Can you recommend a company known for their high quality supplements?”

    Many of the higher end supplement manufacturers, whose products are higher quality than average, with the prices to match, do sadly use magnesium stearate.

    I would first say that if you are taking just one pill a day containing stearic acid/magnesium stearate, the benefits may outweigh that downside. My main concern is with those who take several such pills, day in, day out. I know of a doctor who regularly prescribes patients 5 to 10 – and in some cases even more – of his magnesium stearate containing pills a day.

    Should you wish to completely avoid magnesium stearate and other synthetic flow agents, fillers and binders, go for natural supplements made from whole foods. In your case I would recommend The Synergy Company. You might want to look into their Organic Vita*Min*Herb for Women:

    This product has been around for some years, it’s quite well known in holistic health circles and used to be called Vita Synergy for Women.

    I don’t know whether there are specific nutrients you wanted from your supplement, but for example this one contains 100% of the recommended daily amount of folate, the natural form of folic acid – among much else.

    I note that Lamberts Strongstart also includes a daily fish oil supplement. That doesn’t appear to contain magnesium stearate. If you’re concerned about getting enough long-chain omega-3 fatty acids, you might want to continue taking that, but if you’re looking for another brand, the one I’ve heard best things about is Eskimo BrainSharp:

    Hope this helps.

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  • Sarah,

    Thank you very much for such a comprehensive response to my comment and the very useful links which I’m going to follow up.

    Adam, thank you for sharing the details of Metabolics Ltd. Another very helpful resource.

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  • This is a response from Swanson Vitamins who are rated #1 by Consumer Labs. I have read the Mercola article, however, it is good to seek out more information.

    We do appreciate your opinion, and we would be happy to forward your comments to the appropriate department for further consideration. However, we do wish to point out the following, as customer satisfaction is our highest priority and that the article that you provided us is over twenty years old. We commissioned a report on this matter from an independent expert toxicologist. When reading about the “dangers” of magnesium stearate, please consider the following:
    • Magnesium Stearate is the magnesium salt of stearic acid, a long-chain saturated fatty acid unique in that it is the only saturated fatty acid that does not increase blood cholesterol or LDL.
    • Stearic acid is found naturally in meat, poultry, fish, grains, cocoa butter and milk products.
    o While some supplements may contain up to 20 mg of stearic acid (as mag stearate), consider that this is a very low amount compared to the 5 grams (5,000 mg) that can be found in a single common chocolate bar.
    o Furthermore, in rat model studies, magnesium stearate has been shown to have no effect at levels up to 2,500 mg per kg of body weight.
    ‚Ä¢ Recently, claims have been made that magnesium stearate causes formation of biofilms that may affect different parts of the body, including the immune system. According to the independent toxicology report: “Claims that magnesium stearate can facilitate or form biofilms have no basis in the scientific literature and in fact, current scientific data indicate that stearic acid actually inhibits biofilm formation.”
    • Stearic acid is the most poorly absorbed of the common dietary fatty acids and therefore is less likely to interfere with food uptake in the GI tract. Furthermore, the primary route of uptake is via the lymphatic system, indicating that stearic acid would not interfere with gut absorption of other materials as most nutrients are typically absorbed through the gut wall and are not transported via the lymphatic system.
    • Magnesium stearate is an important ingredient in the manufacture of dietary supplements. It serves as a filler, diluent and flow agent that helps producers maintain ingredients in a proper form for handling and prevents material from adhering to manufacturing equipment. There are few, if any, acceptable substitutes in most cases. Swanson Health Products feels confident in the quality and safety of our supplements produced with magnesium stearate.

    For more information about magnesium stearate, please visit the following link:

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    • As I said in my article, those who try to assure us that magnesium stearate is safe are generally parties who have a vested interest in our believing that 🙂 My only other comment on what was written would be that to claim that the magnesium stearate in supplements is the same as the naturally occurring stearic acid in foods is like claiming that we shouldn’t be worried about consuming refined white sugar as it’s “just the same as the natural sugar in fruits”… The magnesium stearate in supplements is another synthetic, highly processed white powder, far removed from anything found in natural foods. In view of that, and the fact that little research has been done into its effects in the body, I stand by my statement that it’s best avoided.

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      • Most supplement companies use plant-derived magnesium stearate so not sure what you’re talking about when you say “synethetic magnesium stearate”. It’s literally the same thing that’s in a ton of foods already, only it’s like less than 1mg per capsule whereas it’s 1000mg+ in certain foods.

        The overwhelming evidence suggests it’s completely safe. The only parties who try to tell us magnesium stearate is harmful are the companies who sell supplements without magnesium stearate. It’s a marketing ploy.

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  • This is a helpful post indeed! I also found out that Magnesium stearate is a salt that is produced when a magnesium ion bonds with two stearate molecules. Stearic acid is a long-chain saturated fat that is abundant in beef, cocoa butter, coconut oil, and other natural foods.

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  • Fascinating information from all sides. Karen, is “vegetable-grade magnesium stearate the same thing as commercial grade?

    I am taking a magnesium Bis-Glycinate product by CanPrev


    Each capsule contains

    Magnesium (elemental magnesium bisglycinate) 200mg
    Non-medicinal ingredients: Vegetable-grade magnesium stearate (1%), vegetable capsule.

    Thanks for the feedback.

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