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  • Mythbuster: Debunking the Most Commonly Propagated Myths About Magnesium Stearate

Magnesium stearate is one of the most commonly used additives in supplement manufacturing and it is synthesized by combining stearic acid with magnesium. It is favored by manufacturers because it is cheap, improves production efficiency, and helps boost profits. There’s absolutely nothing wrong with any of that as long as it is also safe for consumers, and that’s where the arguments in favor of magnesium stearate start to wear a little thin.

Over the years, manufacturers have provided a laundry list of reasons in defense of their decision to use magnesium stearate (or stearic acid) in supplements. The reasons have ranged from “it’s from a vegetable source, so it is natural” to “it ensures product quality” to “it is inactive and, therefore, irrelevant to the purchasing decision” and, our personal favorite, “it is present in such a small amount that it doesn’t really matter whether it is good or bad for consumers.” Many of these claims are based on questionable science, defy logic, and are easily debunked by just common sense.

We compiled the 8 most frequently cited myths in defense of magnesium stearate and stearic acid in supplements and debunked them using common sense. Is there any truth to the myths? Is our response to the dubious merits of magnesium stearate and stearic acid justified? You be the judge!

The truth about magnesium stearate infographic

Addressing The Myths

Myth #1: Magnesium stearate is safe to use in supplements because it is synthesized from stearic acid, a saturated fatty acid found in many foods and oils.

While it is accurate that magnesium stearate is synthesized using vegetable sources, that does not automatically mean it is natural, non-GMO, or safe, and any claims to the contrary without adequate evidence should be viewed with some skepticism. Vegetarian sources of stearic acid include cottonseed oil, canola oil, and palm oil, and there are drawbacks to using any of these sources:

  • Cottonseed oil - Cottonseed oil is from cotton, a high risk GM crop and one of the most heavily sprayed crops with high levels of residual pesticides.
  • Canola oil - Also known as rapeseed oil, canola oil is also from a high risk GM crop.
  • Palm oil - In addition to sustainability concerns, palm oil contains high levels of palmitic acid, a saturated fatty acid which, the World Health Organization, has identified as a significant contributor to the risk of cardiovascular disease.
  • While stearic acid may be a naturally-occurring fatty acid in many oils, the form that is used in supplements is refined, deodorized, and bleached, a form that can hardly be described as “natural.”

Myth #2: Because stearic acid is naturally present in many foods (e.g. roasted chicken, milk chocolate), criticizing the use of stearic acid in supplements is illogical.

Stearic acid may occur naturally in many foods, but it does not occur in the synthetic, fractionated, bleached, deodorized form of commercial stearic acid. Further, stearic acid does not occur in nature in isolation—it is usually present with other fatty acids, at least some of which may affect how stearic acid is metabolized in the body. So, it is illogical to rely on the benefits of naturally-occurring stearic acid to defend the synthetic, bleached, fractionated form used as a lubricant in dietary supplement manufacturing.

Myth #3: Magnesium stearate is NOT harmful because it is used in amounts that are too insignificant to worry about.

It is true that magnesium stearate is used in relatively small amounts in each capsule or tablet, but most people consume more than 1 capsule or tablet a day, in which case, these small amounts can add up pretty fast. Regardless, the fact that it is used in small amounts cannot be used as the basis for arguing that it is not worth worrying about. Know what else is present in small amounts in every household, and yet carries warnings about poisoning risk and toxicity? Lead. The risks to human health from consuming magnesium stearate and stearic acid may not yet be fully known or understood, but it would be dangerous to equate the absence of conclusive evidence of its toxicity as definitive proof of its safety.

Myth #4: Magnesium Stearate does NOT impact the bioavailability or absorption of the nutrients it is formulated with.

Even the most passionate supporters of magnesium stearate will agree that magnesium stearate has been clinically shown to delay the dissolution of the active ingredients that it is mixed with during production. This delay can impact the bioavailability of the active ingredient to the body and, consequently, undermine the active ingredients' therapeutic benefits. 

Myth #5: Even though stearic acid is a saturated fat, studies have suggested that it has no negative effect on blood cholesterol levels since such a high proportion is converted to oleic acid. In fact, some research even indicates that stearic acid actually lowers LDL cholesterol. So stearic acid [as a lubricant] in supplements can actually be a good thing.

If we understand this correctly, the reason manufacturers use stearic acid [or magnesium stearate] is not because it is cheap and helps them make more money, but because it is in the best interests of the consumer. And which consumer would say no to a little “value-added” fatty acid in every capsule, right? Even putting aside the sarcasm, there is no denying the absurdity of this myth:

  • While it is true that dietary stearic acid is primarily converted into oleic acid, which offers some health benefits, the study (Emken, 1994) that is often cited to support this examined the metabolism of dietary stearic acid or the stearic acid that naturally occurs in certain foods (e.g. milk, grapeseed oil, olive oil). Results or conclusions from that study cannot and should not be extrapolated to stearic acid that has been refined, bleached, and deodorized into a form that looks nothing like how stearic acid occurs in nature.
  • Stearic acid rarely occurs by itself in nature. It is always in the presence of other fatty acids (e.g. palmitic acid, palmitoleic acid) - and we do not know if, and to what extent, the presence of these other fatty acids influences the metabolism of oleic acid in the body.
  • The reason why dietary stearic acid, despite being a saturated fat, does not have an effect on blood cholesterol levels is NOT because a high proportion of it gets converted in the body to oleic acid, but because it is preferentially utilized for phospholipid [membrane] synthesis in the liver. So, claiming that using isolated, refined, bleached, and deodorized stearic acid is a good thing because it is converted to oleic acid and, therefore, helps lower LDL cholesterol is ignorant, at best, and irresponsible, at worst.
Stacked tablets - Magnesium Stearate is commonly used to manufacture tablets

Myth #6: After Magnesium stearate is broken back down into its component parts (magnesium + stearic acid) in the body, its fat is essentially the same as that of stearic acid, except the magnesium part of it can be used to supply the body with this essential mineral.

There is no pharmacological evidence to support the idea that the body efficiently breaks magnesium stearate into magnesium and stearic acid. But, let’s put it to the common sense test anyway to see if it holds up.

Let’s assume that magnesium stearate is present in capsules and tablets at about 5%. So, in a 500 mg formulation, that would be equal to about 25 mg of magnesium stearate. Given that magnesium stearate is synthetic, let's assume that its bioavailability and rate of absorption is about 10%. Ten percent of 25 mg is 2.5 mg of magnesium stearate. So, if myth #6 were true and the body efficiently breaks down magnesium stearate into magnesium and stearic acid, 25 mg of magnesium stearate would provide the body with about 1 to 2 mg of elemental magnesium, which is approximately 0.5% of the daily recommended dietary intake.

Either magnesium stearate is present in amounts too small to be significant OR it is present in amounts large enough to be a therapeutically beneficial source of elemental magnesium. Somebody needs to tell supporters of magnesium stearate that they can’t have it both ways.

Myth #7: Magnesium stearate’s possible impact on the immune system is based on an “in-vitro” study — a study that was done in a petri dish or test tube, not on animals or humans.

We are not defending the “in-vitro” study or its methodology because it is true that the conditions within the human body cannot be simulated or recreated in a test tube or petri dish perfectly. However, dismissing a study because it was done in a “petri dish” instead of in animals and/or humans is illogical, and perhaps a little self-serving, when we consider the fact that most clinical investigations are first done in test tubes and petri dishes before they are done on animals and/or humans.

Moreover, even though bodily conditions can never be perfectly recreated in test tubes and petri dishes, it is worth noting that disintegration and dissolution tests are routinely done in solutions that mimic stomach acids AND embryos are fertilized in petri dishes even though the conditions in the petri dish are nothing like the uterus, where fertilization normally takes place.

The in-vitro study may not be enough on its own to reject the use of magnesium stearate and stearic acid in supplements, but it adds some value when considered together with ALL the other reasons why these additives have no place in products intended to support health.

The use of magnesium stearate is a highly controversial topic in the nutraceutical and pharmaceutical industries

Myth #8: Negative claims about magnesium stearate constitute fraudulent marketing and are perpetrated by companies that are irresponsible and sell inferior quality products.

You know the saying, “offense is the best defense”? Well, companies that use stearic acid and magnesium stearate appear to have that defense perfected to an art form.

  • Claiming magnesium stearate may not be good for health is NOT fraudulent marketing—it is a reasonable claim based on the fact that it is a synthetic additive made using partially hydrogenated oils sourced from high-risk GMO ingredients that are known to have high pesticide residues.
  • Rejecting the use of magnesium stearate based on inconclusive scientific evidence is NOT irresponsible—if anything, finding non-toxic, food-grade, hypoallergenic, non-GMO alternatives to magnesium stearate, even though it can present additional challenges during manufacturing and add significantly production costs, is THE MOST responsible thing a company can do.
  • Companies that educate consumers about the possible ill-effects of magnesium stearate are NOT the ones who sell inferior quality products. Companies that use magnesium stearate in their products solely because it is a cheap additive that helps boost profits, even though safer alternatives are available, are the ones making inferior quality products.
NutriGold product group of Bacopa, Amla, Magnesium, Ginkgo Biloba, and St John's Wort

Why We Don't Use Magnesium Stearate

At NutriGold, we don’t know if the scientific evidence supports or rejects the use of magnesium stearate and stearic acid in supplements. Our reasons for not using them are simple, straightforward, based on common sense, and consistent with our guiding principle to "do no harm." And in the spirit of transparency, we have provided below our common sense reasons for not using magnesium stearate and stearic acid (frequently listed as ‘vegetable lubricant’ on product labels) in our products:

  1. Because the liver metabolizes almost everything that we eat, put on our skin, or inhale, nothing that we take should be considered inactive or inert. Adding chemically processed additives can burden the liver, tax the body, and diminish the benefits of the supplements themselves.
  2. Magnesium stearate and stearic acid are synthetically processed and, as far as we know, the body does not have a mechanism in place for utilizing it. This increases the risk that the body may treat it as a foreign body and target it for removal, which could produce unintended, unexpected, and potentially harmful effects.
  3. The potential risks of these additives aside, we know that neither magnesium stearate nor stearic acid confer any health benefits in their refined, bleached, and deodorized form, and certainly not in the amounts they are included for manufacturing expediency.
  4. Magnesium stearate is not the only silver bullet that can ensure product integrity and overall quality. Plant-sourced, food-grade, hypoallergenic options are available that can perform the same functions without the risk of adverse side effects.
  5. Until we know for sure how magnesium stearate and stearic acid affect the body when consumed over the long term, the ethical thing to do is to avoid using them altogether.
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