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Magnesium Stearate: 6 Supposed Dangers That Need Attention to Determine if It Is Harmful or Harmless


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Reviewed by Laura Beth Schoenfeld, RD, MPH

One of the benefits of ancestral eating is that you avoid potentially harmful food additives like artificial colors, monosodium glutamate (MSG), and artificial sweeteners.

magnesium stearate
Magnesium stearate is commonly used in supplement manufacturing. iStock/PeopleImages

However, even on a Paleo diet, it can be hard to avoid some fillers, thickeners, and additives. In fact, many common Paleo foods contain more additives than their Neolithic counterparts. For instance, commercial nut milks and coconut milk often contain thickeners like gums or carrageenan, while your run-of-the-mill grocery store whole cow’s milk is additive-free.

In this series, I’ll review the science on some of the most common additives and let you know whether you should be concerned about consuming them. First up—magnesium stearate.

Is magnesium stearate a harmless additive or a dangerous chemical? Check out this article to find out. #magnesium #magnesiumstereate #foodadditives

What Is Magnesium Stearate?

Magnesium stearate is a salt that is produced when a magnesium ion bonds with two stearate molecules. Stearate is just the anion form of stearic acid. Stearic acid is a long-chain saturated fat that is abundant in beef, cocoa butter, coconut oil, and other natural foods. As I mentioned in my red meat article, it’s also the only long-chain saturated fat that scientists and medical practitioners agree doesn’t raise cholesterol levels, and doesn’t increase the risk of heart disease.

Uses and Function

Magnesium stearate is most commonly used in supplement manufacturing as a “flow agent,” which helps ensure that the equipment runs smoothly and the ingredients stay blended together in the correct proportions. It can also be found in some cosmetics.

Given the seemingly benign components of this additive, it’s a little surprising how controversial it is. There are a lot of misconceptions and inaccurate statements about it floating around the internet, and while I wouldn’t recommend consuming vats of the stuff (not that you’d want to), I think the concern over magnesium stearate is largely overblown.

What Are the Supposed Side Effects and Dangers, and Are They a Cause for Concern?

1. Effect on Immune Cells

One study that many people have used as evidence against magnesium stearate is a 1990 experiment entitled “Molecular basis for the immunosuppressive action of stearic acid on T cells.” This baffles me, and I suspect that anyone using this study to indict magnesium stearate hasn’t actually read it.

In the experiment, scientists isolated T cells and B cells from mice, put them in a Petri dish, and bathed them in a solution containing stearic acid (along with some other components). They observed that the T cells incorporated the stearic acid into their cell membrane, eventually destabilizing the membrane enough that the cell died.

First of all, this study has nothing to do with magnesium stearate. They just used the plain old stearic acid that you’d find in your beef, chocolate, or coconut oil, so this study could just as easily be used against those foods. If you’re going to be concerned about this study (which you shouldn’t be), you’d have much bigger sources of stearic acid to worry about than the magnesium stearate in your supplements.

Second, the study has nothing to do with stearic acid consumed in the diet. Under normal conditions, your T cells are not bathed in stearic acid, even if you consume superhuman amounts of coconut oil, tallow, and cocoa butter.

Finally, the researchers used T cells from mice, and in this case, the results cannot be applied to humans. The mouse cells incorporated stearic acid into their membranes because they lacked the ability to desaturate fatty acids. However, human T cells do have the ability to desaturate fatty acids, so even if you did bathe your T cells in stearic acid, they would be able to maintain their membrane function. (1)

In case you got lost, here’s a summary: this study has no relevance whatsoever to human consumption of magnesium stearate, I have no idea why the study is being referenced in this manner, and you shouldn’t be concerned about it.

2. Concerns about Pesticides and Genetically Modified Organisms (GMOs)

Another criticism is that because stearate is often derived from cottonseed oil, it can be contaminated with pesticides. Keep in mind that magnesium stearate is a highly purified substance, and goes through an intensive refining process before appearing in your supplements. So far, I haven’t come across any reports indicating that magnesium stearate retains substantial amounts of pesticide residue.

As for the concern that cottonseed oil is often genetically modified, the source of crude fat shouldn’t make a difference in the final form of the stearate. Stearic acid is an 18-carbon molecule with a specific chemical structure that will be the same whether the stearic acid is from a genetically modified cotton plant, a bar of Hershey’s chocolate, or a grass-fed rib eye steak.

3. Effect on Nutrient and Drug Absorption

Another criticism is that magnesium stearate might inhibit nutrient absorption. One in vitro study conducted in 2007 found that tablets containing magnesium stearate dissolved more slowly than tablets without magnesium stearate when placed in artificial gastric juice. (2) The study authors concluded that in vivo studies are needed to determine whether this finding has any practical significance. However, an earlier study found that although magnesium stearate increased the time it took for a drug to dissolve, it had no effect on overall bioavailability, as evidenced by blood levels of the drug in test subjects. (3) Further, another study found that levels of magnesium stearate didn’t affect tablet dissolution at all. (4)

All of this information indicates that although magnesium stearate might affect the rate of tablet dissolution in some circumstances, it doesn’t affect the overall bioavailability of the drug or supplement.

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4. Biofilms

I’ve seen this claim pop up in a few places around the internet, so I’ll address it briefly. Some critics of magnesium stearate claim that it can induce formation of harmful biofilms in the intestine. (Biofilms are immobile communities of bacteria that form when bacteria adhere to a surface and generate a polysaccharide matrix.) This assertion appears to be based on the fact that soap scum contains magnesium and calcium stearate, so they insist that just as soap scum creates film on your sink or shower, magnesium stearate creates film on your intestines.

It should be pretty obvious that the intestinal lumen is a vastly different environment from a shower door, but some people still seem to be concerned. Rest assured, there is no conceivable reason why this would take place, and I haven’t seen a single scientific article that even hints at this possibility.

5. Magnesium Stearate Allergy

A 2012 study entitled “Magnesium stearate: an underestimated allergen” reported on a 28-year-old woman who had an allergic reaction to magnesium stearate, resulting in hives. I’m very curious about this result, because an allergy to either magnesium or stearate seems highly unlikely, but unfortunately, I don’t have full-text access to that study. But, needless to say, if you develop hives (or another allergic response) after consuming magnesium stearate, you should probably avoid it in the future.

6. Magnesium Stearate in Cosmetics

Magnesium stearate has several uses in the cosmetics industry: it’s an anti-caking agent, a bulking agent, a colorant, and more. In the Environmental Working Group’s Skin Deep Cosmetics Database, magnesium stearate is marked as “low hazard,” although it’s noted that limited data are available on this ingredient.

So, Is Magnesium Stearate Safe or Bad for You?

As a final note, a rat study determined that you’d have to take 2,500 mg of magnesium stearate per kilogram of body weight per day to start seeing toxic effects. (5) That means a 150-pound person would have to consume 170,000 mg per day, which is so far beyond any amount you would encounter in supplements that it’s a non-issue.

Overall, I haven’t found scientific evidence to substantiate the claims against magnesium stearate, and the small amounts found in supplements shouldn’t be a problem for the majority of the population.


Join the conversation

  1. Hello, I believe it was the magnesium stearate in two medications that caused debilitating joint point for about a year. I woke up in the middle of the night feeling like I had slammed a car door on my hands, the pain was so bad. I would have to get in the shower under hot water to relieve the pain a few times a night and several times a day to get the pain to a manageable level. I could barely climb a flight of stairs. At the age of 32, I felt very old. I could not so much as stand up long enough to blow dry my hair. I had to sit down. My joints could not support me. My inflammation was so high, my CRP level measured 38 (with anything above 3 indicating serious disease activity). I stopped taking the meds when I went out of town and forgot them, and my arthritic pain vanished. I could walk upright! Make a fist! Climb stairs. These medications are completely unrelated (Nuvigil, a stimulant I used for narcolepsy, and Trazadone, which I used to aid my sleep).
    Here is another funny thing. My doctor put me on Low Dose Naltrexone, which is supposed to aid T cell activity. This drug was amazing. I had lived with widespread muscle pain for about 12 years and suddenly, it was all gone. Like something out of an infomercial, gone.
    I stopped taking the Low Dose Naltrexone in favor of another drug for Narcolepsy; the two do not mix well. My pain/inflammation has slowly crept back up, so my doctor put me on Tramadol. After about a month on this drug, which was great for the muscle pain, I started to get that pesky arthritic pain again. Guess what’s in Tramadol? Magnesium stearate.
    I am no doctor or scientist; this is all speculation. But I will add that I take two other medications regularly, and they do not hurt my joints. They do not contain magnesium stearate.

    • Just a new trick for Arthritis sufferers,who like me cannot tolerate magnesium stearate.I drink a tea blend that’s main ingredient is kava.This REALLY works,no snakeoil herb-crap.

  2. Ironically, the one supplement I take that contains MS is bioperine — a substance used to increase absorption of nutrients! Do you still feel it is safe to take 3-4 of these daily?

    • If the magenesium stearate will eventually form a biofilm in your guts, you’ll have a much more problematic issue regarding absorption than if you avoided the substance altogether.

      • Weird that you would make a claim that directly contradicts what Chris wrote in his article. I trust Chris for evidence based advice. Wher is your evidence?

        “I’ve seen this claim pop up in a few places around the internet, so I’ll address it briefly. Some critics of magnesium stearate claim that it can induce formation of harmful biofilms in the intestine. This assertion appears to be based on the fact that soap scum contains magnesium and calcium stearate, so they insist that just as soap scum creates films on your sink or shower, magnesium stearate creates films on your intestines.

        It should be pretty obvious that the intestinal lumen is a vastly different environment from a shower door, but some people still seem to be concerned. Rest assured, there is no conceivable reason why this would take place, and I haven’t seen a single scientific article that even hints at this possibility.”

    • LR, Garden of Life and a few other better supplements have no additives,especially magnesium stearate.Better Health and many other non- additive,non- gmo stores are not too hard to find now,thankfully.If you live in a rural area,you can order online.Garden of Life bioperine is 95% pure perine abstract.PS…It is reasonably priced,and should be paired with a PURE cleansing mud,since your skin is probably spotty from your body trying to remove the MS.Good Luck

  3. I found an article by Dr. Mercola discussing sketchy ingredients in supplements. He claims previous research indicates magnesium stearate suppresses natural killer cells (your immune system) and over time will create a sludgy biofilm in your intestines that will block nutrient absorption. I don’t believe I have any particular sensitivity to magnesium stearate, however since eliminating all supplements containing the ingredient I feel notably better.

  4. I have Alpha-gal allergy. For those who are unfamiliar, it is a fatal allergy to mammalian meat & byproducts. It is caused by a tick bite and causes delayed severe anaphylaxis after consuming any mammal products. I am extremely sensitive to the point that I cannot consume anything that has stearate, stearic acid, magnesium stearate, or gelatin that was derived from an animal. If so, I go into anaphylactic shock within a few hours and earn myself a flight to the ER. These substances are found in so many medications! Not everyone is as sensitive to these substances, some simply break out in hives or have digestive upset. I would be curious if those who experience these symptoms also test positive for Alpha-Gal.

    • I also have Alpha Gal and have been experiencing negative reactions to magnesium stearate. Nice to know I’m not alone…

  5. I was getting hives on my back and pins and needles in my face and found the only common factor was magnesium stearate in medication I was taking. When I stopped, the reaction stopped. Any time it came back I checked any pills I had taken that day and found it in the excipients. When I checked ingredients and avoided it I no longer got the reaction. I was diagnosed with a hypersensitivity to magnesium stearate, as such miniscule amounts (tiny pills, tiny amount of binder in each pill) caused the worsening reaction. Now, years later I am getting it back again, and it seems to be caused by products with stearic acid or other stearates (definitely a progesterone cream with stearates in), so I have no idea what that all means for me.

    • I found this article only because my son had a fixed drug reaction two Falls ago and they never figured out what it was. This Fall, it happened again and they immediately determined it was a fixed drug reaction. It was a drug he had taken on and off all his life, but since turning 13, we had switched from the liquid to the pill. So his doctor said it must be an additive in the pill. This week, the same reaction is starting, again. I compared the additives in the pill he reacted to to a new vitamin he was taking. The only common ingredient is magnesium stearate. So I’m researching now to see what to avoid, etc. His reaction was horrific two falls ago. The next Fall, we stopped taking the pill and it went away after two weeks. Hopefully, we stopped ingestion even earlier so maybe he won’t react as long. Thanks for the info. Now I wonder if I should do a gentle colon cleanse or something to flush it out. It seemed to build up pretty badly the first time.

      • Hi Celeste
        I was going along ok having cut out magnesium stearate from my life, and then suddenly I got the exact same reaction……. to eggs! It took a while to work out it was eggs as I ate them every day and love them so much and they are in everything! So the reaction was the same, got to be worse than I had with the ms, but the same reaction. So I cut out eggs and I havent got it anymore, but now I am wondering what next. It was about 6 years from the ms reaction to the egg one. I have looked up mast cell activation disease (MCAD) so thought I would just alert you to that. Hope your son is ok.

    • Hey,Hay(couldn’t resist)check the other products you eat and wear,kiss most cosmetics and prepared foods goodbye.Added vitamins such as in milk(it actually has no natural vitamin D)and cereals,etc…Eliminate additives,including the horrid titanium dioxide,a bleaching agent used in everything from tap water to flour.Antiperspirant is so full of toxic chemicals,how can the FDA allow them to direct us to put it on our lymph glands?My point is check everything,especially processing and its resultant affect on you.Your body is sending you signals that are being ignored.I was originally diagnosed as “hypersensitive”And as I’d cut out one additive ,I’d react to a different one,sound like what you’re experiencing?It’ll take awhile to make changes,but I think you know what your body is trying to save you from.Let’s make Americans healthy again!

      • Hi Di (heh)
        Well, I am now reacting to eggs, and the only conclusion I can draw is that I have a mast cell issue (MCAD). I have been ill with an auto inflammatory illness for 20 yrs and so this makes sense. Horrible depressing sense.

        • Nice riposte Hey,rather laugh than cry eh!Some people are raised in a kill or cure environment,and could probably never believe or understand the issues we face.Like Giselle and I, keep getting the word out and you will save others from the struggles we face.A lot of smaller American companies are offering products of the highest purity levels,so it isn’t that bleak anymore.15 years ago it was,word of mouth and articles like this are helping.Research and buying internationally will help you live a more normal life .Thanks for the shout back.PS:Thanks to Chris and others who provide these forums.

    • Sorry to hear about your allergic reaction! I had my first reaction during my pregnancy in the hospital. They had me hooked up with magnesium sulfate through IV and my face felt hot and flushed. They were very surprised because it’s rare to be allergic to this and quickly stopped.
      My next reaction was when I took over the counter probiotics, my face felt weird like a numbing feeling and my throats felt like someone was chocking me. I was having a hard time breathing and someone gave me Benadryl which help while I drove to the ER. There they gave me medicine to help with the swelling in the throats and to relieve the allergic reaction.

  6. I sometimes deal with the side effects mentioned, like panic attacks, asthma, joint pain, etc., and have not tested if stopping all magnesium stearate would help with that.

    That said, I take Gabapentin (brand name Neurontin) as a mood stabilizer, which is rendered inactive by magnesium, so I have to be very careful not consume anything with magnesium within two hours before or after I take the Gabapentin. Every time I have found myself having mood swings even though I was consistently taking the Gabapentin, I have been able to identify a vitamin or supplement source of magnesium causing the problem, including whatever tiny amounts are in Calcium supplements, pro-biotics, etc. I either stop taking the supplement or make sure I only take it at least 2 hours separate from the Gabapentin, and then everything goes back to working as normal. I’ve been through this routine with Triple-Flex (for joint pain), calcium supplements, pro-biotics, fish oil, multivitamins, you name it. I will now try eliminating all magnesium stearate and see how I feel. Thank you Dr. Kresser and everyone else for your feedback.