The Truth about Magnesium Stearate

What do magnesium stearate, stearic acid, and most other flow agents have in common (other than being flow agents)? It seems that, so far as the nutraceutical industry is concerned, everyone and their mother has a different stance on their overall safety and efficacy.  What’s more, if we turn to the web (which happens to be inundated with studies, articles, and op-ed pieces on the subject) we’re faced with a seemingly endless supply of conflicting information.

What’s a nutraceutical know-it-all seeking knowledge to do?

In an effort to shed some light on the matter, we’ve decided to take a magnifying glass to some of the most popular claims and data concerning magnesium stearate and stearic acid.

Magnesium Stearate Claim #1: Both magnesium stearate and stearic acid are bad for you and you should avoid them at all costs.

Choosing to pursue a diet that’s free of magnesium stearate and stearic acid is a choice that every individual is free to make. For those who are currently considering this dietary option, it’s worth noting that along with many of the pills and supplements in your medicine cabinet you’ll also want to eliminate foods like cocoa, flaxseed, chicken, sweet potatoes, and a myriad of veggies and meats from your diet because they’ve all been shown to contain naturally occurring amounts of magnesium stearate and stearic acid, which either meet or exceed the trace amounts that regulations allow in dietary supplements.1-3

Magnesium Stearate Claim #2: Magnesium stearate interferes with the body’s ability to absorb nutrients from tablets.

In greater detail, this claim is often supported by the notion that magnesium stearate promotes the growth of gastrointestinal bacterial colonies, which, in turn, create a biofilm (a thin, slimy, and adhesive film of bacteria) that can prevent the absorption of nutrients. The primary issue with this claim? Currently, there’s no research proving that biofilms occur in humans who have ingested magnesium stearate. In fact, one laboratory study found that stearic acid actually inhibited the formation of biofilms – which contradicts this claim outright.2

Magnesium Stearate Claim #3: Magnesium stearate and stearic acid have negative effects on immune responses.

“Molecular Basis for the Immunosuppressive Action of Stearic Acid on T Cells”3 is one of the most frequently cited scientific studies concerning stearic acid. Conducted in 1990, the primary experiment consisted of a line of T cells (vital immune cells) in a petri dish that were exposed to stearic acid. As a result, the scientists discovered that exposure to stearic acid had impaired the cells’ ability to perform their immune functions.

While these seem like sound findings, currently, there are a few scientifically backed holes in the story.  The first: Research has shown that T cells are incapable of metabolizing stearic acid,4 which is why it shouldn’t have come as much of a surprise that the tested T cells were unable to function properly after being immersed in the stearic acid.

Now, you may be thinking: “Even if the T cells’ inability to process stearic acid was already known, the fact that after being exposed to stearic acid the T cells weren’t able to function properly is bad, isn’t it?” And you would be entirely right to think that if there were any way for us to guarantee that the experiment was held under realistic conditions that the body could replicate – which brings us to red flag number two!

Red flag number two has to do with the amount of stearic acid that the T cells were exposed to. According to research, the total concentration of free fatty acids (which would include stearic acid)  found in the bloodstream of a healthy adult is about 100 times less than the concentration used in the experiment.5 Taking this research into account, it seems highly unlikely that the body would even be able to come close to replicating the conditions found in the experiment, making a situation where T cells are impaired by the presence of stearic acid seriously unlikely.

Magnesium Stearate Claim #4: Studies have shown that lab rats become sick after eating diets that included magnesium stearate.

One of the most frequently cited rat-based studies required that the rats be put on diets that consisted of 5% magnesium stearate and diets that consisted of 10-20% magnesium stearate.6  While no negative effects were observed in the 5% group, illness and other complications were observed in the 10-20% groups.

Now, let’s take a moment to break these numbers down a little further…

In the 5% group, where no negative effects were observed, the parameters of the diet meant that each rat had to consume 2500mg of magnesium stearate for every 2.2lbs of body weight, daily. To translate that into human terms, if a person weighing 180lbs were to adopt this diet he would have to consume approximately 204 grams (or just under a half pound) of magnesium stearate per day. If he were to follow the 10-20% diet where harmful side effects were observed, that same 180lb human would have to consume anywhere from one to nearly two pounds of magnesium stearate per day. Even the most avid of supplement takers would be hard pressed to ingest that much magnesium stearate.

The Data is Out There…

And the decision is yours to make. Despite the overwhelmingly negative reputation magnesium stearate and stearic acid have earned themselves, we’ve found that there’s an incredible amount of data out there suggesting that some of the more popular inflammatory claims may be less than credible.


  1. Steinberg FM, Bearden MM, Keen CL. Cocoa and chocolate flavonoids: implications for cardiovascular health. J Am Diet Assoc 2003;103(2):215-23.
  2. Babu US, Bunning VK, Wiesenfeld P, Raybourne RB, O’Donnell M. Effect of dietary flaxseed on fatty acid composition, superoxide, nitric oxide generation and antilisterial activity of peritoneal macrophages from female Sprague-Dawley rats. Life Sci 1997;60(8):545-54.
  3. Whitney EN, Rolfes SR. Understanding Nutrition, 9th ed. Belmont, CA: Wadsworth/Thomson Learning; 2002.
  4. Soni KA, Jesudhasan P, Cepeda M, et al. Identification of ground beef-derived fatty acid inhibitors of autoinducer-2-based cell signaling. J Food Prot. 2008 Jan;71(1):134-8.
  5. Tebbey PW, Buttke TM. Molecular basis for the immunosuppressive action of stearic acid on T cells. Immunology 1990 70 379-384.
  6. Buttke TM, Van Cleave S, Steelman L, McCubrey JA. Absence of unsaturated fatty acid synthesis in murine T lymphocytes. Proc Natl Acad Sci USA 1989; 86(16):6133–6137.
  7. Leaf A. Plasma Nonesterified Fatty Acid Concentration as a Risk Factor for Sudden Cardiac Death: The Paris Prospective Study. Circulation 2001;104:744.
  8. Søndergaard D, Meyer O, Würtzen G. Magnesium stearate given perorally to rats. A short term study. Toxicology. 1980;17(1):51-5.
2017-05-31T11:26:58+00:00 April 13th, 2016|

About the Author:

Melissa DellaBartolomea is NutraScience Labs' resident Content Marketing Specialist. Driven by a passion for the world of written, visual, and digital media, she's dedicated herself to keeping up with all things nutraceutical. From ingredient insights to the latest in contract manufacturing regulations and trends, her mission is to provide our readers (like you) with the stories and knowledge they need to fuel long-term growth and nutraceutical industry success.

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