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Magnesium Stearate: In Search of The Truth

An interview with  Dr. Dana Myatt, N.M.D.

Dr. Myatt is a graduate of the National College of Naturopathic Medicine and has been in multi-disciplinary, full-scope family practice for 23 years. In addition to her nationwide family practice, she frequently speaks at medical and lay conferences across the country on topics in holistic medicine.  She is the founder and CEO of  Dr. Myatt Nutritionals, her own line of nutritional supplements since 1994.

Dr. Myatt is author of "A Physician’s Diary" (A.R.E. Press, 1994) and the upcoming "Ketone Zone Diet" .  She is a member of  The American Association of Naturopathic Physicians, the Arizona Naturopathic Medical Association, the American Academy of Anti-Aging Medicine and the American Society for Reproductive Medicine.  She is also a certified Advanced Hazmat Life Support provider and instructor.

Magnesium stearate, a common ingredient in many nutritional supplements, has gotten a bad rap from several nutritional supplement companies and online physicians.  One doctor has gone so far as to claim that it forms a deadly “biofilm” in the intestines and suppresses the immune system.  Since magnesium stearate is so widely used in the nutritional industry, we felt it important to carefully examine these claims.


After watching this thorough and completely scientifically referenced video by Dr. Dana Myatt on the subject, a nutritional supplement industry reporter named Jill requested an interview to learn the truth about magnesium stearate.

Here is that interview.

Jill: Dr. Myatt, what exactly is magnesium stearate and what is its role in nutritional supplements?

Dr. Myatt:  Magnesium stearate is a simple salt of two common substances, the mineral magnesium and the saturated fat stearic acid.  It is used as a “flow agent” in many nutritional supplements and pharmaceuticals.

Jill: Could you explain a bit more about magnesium stearate?

Dr. Myatt:  Magnesium stearate is a salt that contains two common ingredients, a fatty acid called stearic acid and the mineral magnesium. Together they form magnesium stearate.

Magnesium stearate contains two molecules of stearic acid and one molecule of magnesium.  The molecule is held together by ionic bonds --- the definition of a salt --- that break apart easily in acid, the condition found in the human stomach.  Though the name may make it sound like a synthetic, space-age molecule, both magnesium and stearic acid are abundantly available in many foods in our diet.  In order to really understand magnesium stearate, let’s look at its two components.

Magnesium is an essential mineral, the major mineral most likely to be deficient in the American diet. (1)  I don’t think anyone would argue the safety of magnesium.

Stearic acid is a saturated fatty acid found in many foods including eggs, chicken, grass-fed beef, coconut oil, walnuts, cheese, chocolate , salmon and human breast milk to name just a few. (2)

Both magnesium and stearic acid are not only safe, they are beneficial to human health. Magnesium stearate is simply a salt that combines both of these molecules.

Jill: What is a “flow agent” and why is it used?

Dr. Myatt:  Flow agents help ensure a consistent dose of product in each capsule. Magnesium stearate does this by preventing individual ingredients from sticking to each other and from sticking to the encapsulating machines.  It allows manufacturers to create a consistently homogenous mix, so the amount of active ingredients is the same from capsule to capsule or tablet to tablet.  In other words, the use of magnesium stearate and other flow agents helps ensure consistency and quality control.

Jill: Some companies claim to fame is that they do not use flow agents or other “inert ingredients.” Is that a good thing?

Dr. Myatt: This might sound good to consumers who do not understand the nuances of good supplement manufacturing practices,  so some companies use it as a selling point.

The truth, however, is that companies who don't use flow agents are more likely to have inconsistent doses of ingredients in each capsule or tablet. This aspect of quality control is so important that the FDA is said to be considering the issue as part of their new GMP (Good Manufacturing Practices) guidelines.  If flow agents are added to the GMP’s, all manufacturers may be required to use flow agents to ensure consistency. Flow agents are that important for quality control.

Jill: Do most drugs, vitamins and supplements contain more than just the active ingredient? Can they be made without them?

Dr. Myatt:  Almost all drugs and supplements contain inactive ingredients. These “inactives” serve multiple purposes.  Flow agents, as we discussed, help ensure consistent dosing in each tablet or capsule. Some products contain fillers like cellulose which acts as a binder in tablets and helps fill out the size of tablets or capsules.

Herbs can be encapsulated and additional herb used as filler, so these products may contain only “actives.”

So yes, it is possible to make capsules or tablets without inactive ingredients, but quality control becomes more difficult.  Manufacturing without minute amounts of inactives is possible but drives the price of the supplement up unnecessarily.  There is no proven benefit to manufacturing without magnesium stearate except as a marketing angle.

Jill: One doctor claims that magnesium stearate suppresses immune t-cell function and causes the collapse of cell membrane integrity in helper t-cells.  Is there any scientific support for this?

Dr. Myatt: (laughing) Not unless you’re a mouse. This claim amuses me the most, because the doctor who promotes the idea that magnesium stearate is dangerous also promotes and sells a lot of foods that are high in steric acid, claiming it to be a healthy fat, which it is.

The entire argument is based on the gross misrepresentation of a single mouse study. Here’s the “Cliff notes”:

The entire claim is based on a single study---- that’s right, one study --- performed in 1990, using mouse T-cells in a Petrie dish. When mouse T-cells were incubated (read that: “soaked” or bathed) with stearic acid --- not magnesium stearate, but stearic acid --- there was indeed a collapse of the cell membrane and a loss of T-cell function. (3) This study was never repeated.

But here’s the factoid that magnesium stearate naysayers conveniently “forget” to mention.  Mouse t-cells are known to lack the delta-9 desaturase enzyme that converts stearic acid into oleic acid. This was mentioned right in the same mouse-cell study.  Mouse T-cells can apparently become toxic from high levels of stearic acid, at least in a Petrie dish and at levels far above what could ordinarily be achieved from diet.

Human t-cells have the delta-9 desaturase enzyme that converts stearic acid to oleic acid, so human T-cells don't develop this same toxic build-up when exposed to stearic acid. (4)

Bottom line: Mice lack an enzyme in their T-calls that humans have, so stearic acid is toxic to mouse T-calls and not to human T-cells. Stated another way: humans are not mice.

Jill: So… stearic acid isn’t bad for humans? What’s the difference between stearic acid and stearate?

Dr. Myatt: Stearic acid is a saturated fatty acid and one of the most common saturated fatty acids found in nature.(5) The term “stearate” is used when steric acid is part of a salt (as when stearic acid combines with magnesium to form magnesium stearate). The terms steric acid and stearate can be used interchangeably.

Jill:  But isn’t stearic acid or stearate toxic at some dose?

Dr. Myatt:  Water is toxic if the dose is high enough.

Anybody concerned about the minute amount of stearic acid in supplements should know the following:

  • The daily adult intake of stearic acid from food (US adult) averages about 7,000 mg/day.(6)
  • A person taking 20 vitamin capsules weighing 500 mg each and containing 1% magnesium stearate would take in less than 96 mg of stearic acid per day. Manufacturers typically use 0.25% - 5% magnesium stearate in nutritional formulations.
  • The amount of stearic acid from supplements in the above scenario is 1.3% of the total daily adult intake.
  • Magnesium stearate is considered safe for human consumption at levels below 2,500 mg/kg per day. This equates to 170,000 mg per day as a safe dose for a 150-pound adult.(7) That’s almost 6 ounces of pure magnesium stearate.

Jill: Got it. Magnesium stearate is magnesium plus stearic acid, correct?  Is there something about the two molecules that, once combined, makes it behave differently than the two separate molecules? In other words, is magnesium stearate actually different than magnesium and steric acid?

Dr. Myatt:  No, there is nothing special or different about magnesium stearate. It is a simple salt of magnesium and stearic acid. Here is the chemical “short course”:

Magnesium Stearate = 2 stearic acid + 1 magnesium

This salt disassociates (comes apart) readily in the acidic medium of the human digestive tract.

One claim I’ve seen is that the addition of magnesium stearate to supplements decreases bioavailability. What the studies actually show is that absorption might be slowed somewhat but overall absorption is not decreased. (8,9)

Jill:  Another claim is that magnesium stearate a chalklike substance that gums up your intestines and prevents absorption of your nutrients.  Fact or fiction?

Dr. Myatt: Fiction.

Magnesium stearate is definitely not a chalk. Chalks are soft, stone-like minerals, including things like gypsum (calcium sulfate) CaCO3 (calcium carbonate) and CaO (calcium oxide).  Remember that magnesium stearate is a salt, containing approximately 96% stearic acid, which is a saturated fat. The other 4% is magnesium. Chalks are combinations of minerals, but magnesium stearate is mostly saturated fat.

How could a fat be a chalk? It isn’t, not by any known scientific definition of a chalk.

Even if it were a chalk, you shouldn’t be worried about it gumming up your intestines or “caking the lining.” Why? Because if you did eat chalk, like calcium carbonate, which is a form of calcium used in many nutritional supplements, your digestive system would break it down to its mineral components. Human digestion is truly amazing.

By the way, I used to perform quite a few endoscopies in clinic. This is where you examine the lining of the large intestine with a special scope, looking for polyps. I never once saw anyone with a “caking of the lining” of their intestinal tract.  Tenacious, dry stool sometimes, yes. But “caking” with a chalk-like substance? Never. If this story about “caking the lining” is told by a doctor, it must be one who has never actually visualized the inside of the large intestine.

Jill: OK. No T-cell collapse in humans, no “caking of the lining” of intestines. How about the claim that magnesium stearate stimulates the gut to form a biofilm? And is a biofilm a sludge that would act as a barrier to the absorption of nutrients?

Dr. Myatt: There is not one single scientific reference or study to support this claim.  In fact, if you know what a biofilm is --- and I’m going to tell you in just a minute --- you’ll see that this entire argument is completely preposterous. It has no basis in any known science.

To clarify for those readers who haven’t seen it, this internet legend, promoted by a well-known doctor, says that a biofilm is basically like the “sludge in your toilet tank,” and that magnesium stearate causes this sludge and prevents nutrient absorption. Just as there is a big difference between a chalk and a fat, a biofilm is not akin to sludge, a.k.a. “soap scum” that you might find in your toilet tank.  By the way, I don’t have soap scum in my toilet tank. But I digress.

A toilet tank film or bathtub ring occurs when hard water, containing calcium or magnesium, reacts with fatty acid in soap to form a so-called "soap scum." If you live in a hard-water area, you’ll see this as an annoying white film on your shower curtain.

Humans get significant amounts of magnesium, calcium and fatty acids --- the ingredients in soap scum ---from diet. But we don't form soap scums in our bodies because of our digestive enzymes and acids. Further, soap scum is not biofilm --- not even close.

We learned that soap scum is a mineral (usually calcium or magnesium) plus fatty acids. Humans eat both all day, every day and do not develop a “scum” in their intestines.

Biofilms are layers of bacteria or yeast embedded in the gel-like substance they secrete. They tend to be highly antibiotic-resistant and often fatal.  As to the claim that stearic acid causes biofilms, this is completely without any scientific evidence. In fact, several studies have shown just the opposite --- stearic acid actually helps prevent the formation of biofilms. (10,11)

Jill:  Next claim.  Magnesium stearate made from contaminated oils from genetically engineered crops. True?

Dr. Myatt:  OK, let’s talk dirty. Magnesium stearate is most commonly sourced from cottonseed oil or palm oil and it’s true that cotton can be a GMO crop and is typically high in pesticides. But even if the starting cottonseed oil is contaminated, the finished product, stearic acid, is so highly purified that contamination really isn't an issue. Cottonseed-derived stearic acid is so purified and the final molecule so far-removed from the original source, it doesn’t carry any pesticide residue. We might as well worry about the food-grade additive cellulose, which is also obtained either from wood waste (we call that “sawdust” out here in Arizona) or cotton waste (known as “gin trash,” --- the waste cotton remaining in the cotton gin). (12)

Just like taking dirty water and purifying it into something clean and drinkable, purifying cottonseed oil to obtain stearic acid delivers a pure finished product.

And by the way, stearic acid can also be derived from palm oil, which many manufacturers, myself included, use as the source of their stearic acid.

Jill:   Is magnesium stearate often contaminated during processing, as one doctor claims?

Dr. Myatt:  Contamination during the manufacture of supplements or pharmaceuticals can occur anywhere along the entire manufacturing process.   That is why quality supplement manufacturers test raw materials before purchase; after purchase when they are received; after mixing and after encapsulating. Raw materials can occasionally become cross contaminated, and that's why quality manufacturers employ so many tests and inspections all along the process.

Now, is magnesium stearate one of the substances more likely to be contaminated? Absolutely not. There is one reported instance of a raw materials manufacturer notifying the World Health Organization that several batches of magnesium stearate had been cross contaminated with zeolite (sodium aluminum silicate), calcium hydroxide, and several other substances. The contamination was determined to be due to incomplete cleaning of air milling equipment. This was traced to a single raw materials manufacturer and was an isolated event.  Moreover, WHO found the contaminating substances to be present in such minute amounts that they posed no health risk.  And this was self-reported by the manufacturer of the raw material before it was used in product.(13)

Jill:  Is magnesium stearate going to be removed from supplements by the Codex Committee on Food Additives?

Dr. Myatt:  No. The Codex Committee considered removing magnesium stearate from the acceptable food list, not because of any danger, but because they didn't see the use for it in food. They were simply trying to trim up their list of allowed food additives.  When food manufacturers pointed out that magnesium stearate is an important and safe anti-caking agent, it was reinstated.  Removing magnesium stearate from Codex for use in nutritional supplements has never been considered as far as I can determine.

Magnesium stearate is currently approved by FDA regulations for use in food and supplements. (14,15)

Jill: Is there room for disagreement in the supplement industry on what is safe and effective?

Dr. Myatt:  (laughing) Is the Pope Catholic?

I don't always agree with my colleagues in the nutritional supplement industry. Some ingredients and doses based on the scientific literature are arguable. With most issues in medicine, there is no black and white. There is instead, “ten thousand shades of gray.” In many instances, there is evidence on both sides of the question.

But the evidence is not "mixed" on the safety of magnesium stearate. The evidence says that magnesium stearate, a simple salt of magnesium and stearic acid, is a safe and effective flow agent that helps maintain dose consistency, and there really isn’t any evidence to the contrary.  At least I haven’t found any, and I’ve looked long and hard at these claims because I, too, manufacture nutritional supplements and use magnesium stearate as a flow agent.  So I had to know if any of these claims had even a shred of basis in fact. They don’t.

That’s not to say that new evidence won’t emerge, but right now, the damning claims for magnesium stearate are completely without scientific verification or substantiation.

Jill:  Dr. Myatt, you have completely dismantled the “danger claims” of magnesium stearate, all supported with verifiable references.  Why would some companies and doctors make these claims if they have no basis in fact?

Dr. Myatt: There is a lot of competition in the nutritional industry today. Everybody and their brother is selling supplements, or so it seems. Companies must distinguish themselves in order to get a toe-hold in the industry. Think about it.

If 537 other companies are selling a calcium supplement, why should you buy mine? Everybody is looking for a unique selling angle.  “More bioavailable,” “72% more absorbable,” “nano-technology,” and on and on. Some of these claims have merit, but many are just marketing hype.

One “angle” is to claim that magnesium stearate is dangerous, bad, or evil --- never mind the proof aspect. To paraphrase the movies, “We don’t need no stinking proof”!  And since the majority of manufactures who use magnesium stearatedo so because it is one of the absolute safest and best flow agents, claiming that it is bad and then making a supplement without it is a marketing strategy, nothing else.  Considering how few people do their “homework” on such claims --- witness how these many unsubstantiated claims about magnesium stearate are now accepted “facts” in the minds of many --- the technique is probably  fairly effective as a marketing tool.  But in my opinion this is not simply “misrepresentation.” Someone is telling outright lies.

Jill: (laughing) Wow --- don’t hold back, Dr. Myatt. Why don’t you tell us what you really think?! Do you have any parting thoughts for our readers?

Dr. Myatt: Don’t believe something just because you read it, heard it or learned it at the University of Google. Check references. See if there is known science or studies to support claims.  Blind sheep can easily be led off a cliff.

Also, use supplements from manufacturers that you have researched and trust.  There are a number of quality manufacturers who are just as concerned with providing pure and health-giving products as they are with their bottom line and who believe that quality is the best way to stay in business.

Jill: Thank you Dr. Myatt for this most informative and, dare I say, entertaining Q & A.

Dr. Myatt: It’s always a pleasure to help set the scientific record straight.


1.) National Institutes of Health, Office of Dietary Supplements: Magnesium.
2.) USDA National Nutrient Database for Standard Reference, Release 24
3.) Tebbey PW, Buttke TM. Molecular basis for the immunosuppressive action of stearic acid on T cells. Immunology. 1990 Jul;70(3):379-84.  Full Text article:
4.) Anel A, Naval J, González B, Uriel J, Piñeiro A. Fatty acid metabolism in human lymphocytes. II. Activation of fatty acid desaturase-elongase systems during blastic transformation. Biochim Biophys Acta. 1990 Jun 14;1044(3):332-9.
5.) Dietary Supplement Fact Sheet. Office of Dietary Supplements, National Institutes of Health.
6.) U.S. Department of Agriculture, Agricultural Research Service. What we eat in America,
NHANES 2001-2002, individuals 2 years and over (excluding breast-fed children), page 5. Accessed 06/28/12
7.) Søndergaard D, Meyer O, Würtzen G. Magnesium stearate given perorally to rats. A short term study.Toxicology. 1980;17(1):51-5.
8.) Alija Uzunović, Edina Vranić; "Effect Of Magnesium Stearate Concentration On Dissolution Properties Of Ranitidine Hydrochloride Coated Tablets"; Bosnian Journal Of Basic Medical Sciences, 2007, 7(3): 279-283
9.)  Natalie D. Eddington, Muhammad Ashraf, Larry L. Augsburger, James L. Leslie, Michael J. Fossler, Lawrence J. Lesko, Vinod P. Shah, Gurvinder Singh Rekhi; "Identification of Formulation and Manufacturing Variables That Influence In Vitro Dissolution and In Vivo Bioavailability of Propranolol Hydrochloride Tablets"; Pharmaceutical Development and Technology, Volume 3, Issue 4 November 1998 , pages 535–547
10.) Soni KA, Jesudhasan P, Cepeda M, Widmer K, Jayaprakasha GK, Patil BS, Hume ME, Pillai SD. Identification of ground beef-derived fatty acid inhibitors of autoinducer-2-based cell signaling. J Food Prot. 2008 Jan;71(1):134-8.
11.) Liaw SJ, Lai HC, Wang WB. Modulation of swarming and virulence by fatty acids through the RsbA protein in Proteus mirabilis. Infect Immun. 2004 Dec;72(12):6836-45.
12.) USDA. Cellulose.
13.) World Health Organization Quality of Medicines for Everyone, Contaminated magnesium stearate VG EP excipient manufactured by Ferro, supplied by Signet and used in finished pharmaceutical products, December 22, 2011.
14.) Food and Drug Administration, CFR - Code of Federal Regulations Title 21, accessed Sept. 10, 2012.
15.) Food and Drug Administration, Select Committee on GRAS Substances (SCOGS) Opinion: Magnesium stearate, accessed Sept. 10, 2012

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