Magnesium stearate is a commonly used ingredient in supplements, but its use has become controversial in recent years. In this blog post, we will explore what magnesium stearate really is (you may be surprised!), its purpose in supplements, what ‘fillers’ are and the arguments for and against them. We will then give our honest opinion on whether magnesium stearate is a health concern and what We Know Health uses in its supplements.

What is Magnesium Stearate really?

Commercial magnesium stearate is a synthetic salt that is formed by chemically combining magnesium salts with fatty acids, including stearic acid and palmitic acid.

In fact, the definition of magnesium stearate consists of:

  • 4-5% magnesium by dry weight
  • At least 40% stearic acid
  • The fatty acid fraction comprises >= 90% stearic and palmitic acids (1)

So crazily enough, magnesium STEARATE may actually not contain that much stearate! Additionally, it may have significant amounts of palmitic acid and up to 10% of other fatty acids in that fraction. Some commercially available magnesium stearates we looked at used ratios of stearic acid:palmitic acid of approximately 65:35, but this varies a lot by brand.

I find this more than slightly misleading!

Also, don’t think you are getting a significant extra source of magnesium from magnesium stearate because the magnesium content by weight is very low.

What is its purpose in supplements?

Magnesium stearate is a white, powdery substance that is commonly used as an anti-caking agent and lubricant in supplement manufacturing (agents like this in the final formulation are called ‘excipients’). What this means in reality is that it helps reduce the ingredients sticking together OR sticking to the machinery. This increases the efficiency of mass production and improves the homogeneity (consistency) of what the consumer receives. 

What about supplements with ‘no fillers’?

A filler is used to bulk up a capsule or help form the structure of a tablet. Just because a supplement contains agents like magnesium stearate doesn’t mean they are necessarily being used as fillers. As mentioned, these agents serve an important role in creating a smooth manufacturing process and only the smallest amount needed to get that job done should be used.

It is technically possible to create supplements with none of these agents, but the issue is what you receive may be quite varied per capsule and therefore the label claims of active ingredients may be incorrect. Not what you want! In particular, the more active ingredients you have that need to be mixed together, the more important it is to use agents that help with the consistency of that process. Secondly, the manufacturing process would be quite inefficient.

So, these agents play an important role. The real question is, do we need to use magnesium stearate to do this job? 

Let’s talk about stearic acid first.

Where does Stearic Acid come from and are there concerns?

Stearic acid is a type of fatty acid mostly derived from saturated animal fat, predominantly pigs. Red flag for those on plant-based diets!

Luckily, these days, most stearic acid (and palmitic acid) in supplements is derived from plant-based sources. However, these are less than desirable. They include palm oil (mainly), cottonseed oil and canola oil. Cottonseed is highly sprayed with pesticides, canola and cottonseed are genetically modified and palm oil is an unhealthy oil with sustainability concerns. It is becoming more clear the terrible environmental impact the palm oil industry is having: deforestation, destroying peat lands, climate change and destruction of wildlife habitats.

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We do consume naturally occurring stearic acid in our diets in higher quantities than in a few supplement capsules, but it’s not that simple. We do not consume it in this highly processed form and we do not know the health effects of consuming many supplements per day (becoming more common) over the long term containing these processed magnesium stearates. That is not to say it is definitely harmful, but the evidence is lacking to say it is appropriate for all individuals in increasingly large quantities.

Arguments For Magnesium Stearate Use in Supplements

  • Safe and effective: Proponents of magnesium stearate use in supplements argue that it is a safe and effective ingredient that is necessary for the manufacturing process. They point out that magnesium stearate is generally recognized as safe by the FDA and has been used in supplements for decades without any reported negative side effects. The issue is that it can be very difficult to separate side effects of the supplement or medicine from the excipients used.
  • Required ingredient: Additionally, they argue that magnesium stearate is an essential ingredient for ensuring the consistency and quality of supplements. Without magnesium stearate, the ingredients in supplements may clump together or not mix evenly, which could lead to inconsistent dosing and reduced efficacy. This is a valid point but there are alternatives.
  • Cost effective: Furthermore, magnesium stearate is a cost-effective ingredient that allows supplement manufacturers to produce large quantities of supplements at a reasonable price. This cost savings can be passed on to consumers, making supplements more affordable and accessible. This is true, it is cheap and readily available.

Arguments Against Magnesium Stearate Use in Supplements

  • Impaired nutrient absorption: Critics of magnesium stearate use in supplements argue that it can have negative effects on the absorption and bioavailability of nutrients. They claim that the coating of magnesium stearate on particles can prevent proper dissolution and absorption of the nutrients in the supplement. I do think this is a valid argument and, in fact, a more recent study in 2020 concluded “solubility studies showed that for the majority of cases, the presence of MgSt significantly decreased drug apparent solubility due to its hydrophobic nature” (2). They also identified a number of variables that would affect solubility between brands, such as the crystallinity and ratio of different fatty acids. Another study also demonstrated the solubility issue with ranitidine tablets containing different amounts of magnesium stearate (3). Tablets are known to dissolve more slowly than capsules. This is a complex area and also depends on the drug or nutrient in question. In vivo (inside your body), everyone has different gastrointestinal systems and it is quite different to lab testing of solubility, so the impact of this will vary amongst individuals.
  • Immune system suppression: I cannot find any proper evidence to support this issue. 
  • Allergy and intolerances: Many consumers have reported concern about allergic reactions or intolerances linked to magnesium stearate, but there haven’t been any systematic trials to assess this and it can be hard to discern the cause of the allergic reaction without actually doing proper skin prick testing. In my research I have seen many reports from consumers of quite varied responses and side effects to different brands of the same active ingredient. There can be many reasons for this, but I cannot exclude excipients used in the different brands based on what we have learned so far about the variability of magnesium stearate and the amount used by different companies.
  • Sourcing: The source of stearate may be animal based or originate from genetically modified crops, which is of concern to many. It’s hard to ignore this point.
  • Cholesterol: Palmitic acid is a saturated fat that can potentially raise cholesterol and is a major component of magnesium stearate. It doesn’t appear to be well known to consumers about how much palmitic acid in fact is in magnesium stearate. These two articles discuss its effect on cholesterol, in particular LDL cholesterol (4)(5). In reality, most people will unlikely consume enough to have a meaningful effect on their cholesterol.
  • Alternatives available: Additionally, critics argue that magnesium stearate is not a necessary ingredient and can be replaced with alternative anti-caking agents and lubricants that do not have the same potentially negative effects.

What alternatives are there to Magnesium Stearate in supplements?

The argument that magnesium stearate must be used in the manufacturing process no longer rings true as there are many other options, admittedly with varying physical properties that may not be as suited to lubrication as magnesium stearate, that can be considered.

  • Silicon dioxide: Also known as silica, this is a naturally occurring mineral that is often used as a flow agent in supplements. It is considered safe and has been shown to have no negative effects on nutrient absorption or bioavailability. In fact, a number of people consume silica supplements for hair, nail and skin support.
  • Microcrystalline Cellulose: This is a plant-derived fiber that is often used as a bulking agent in supplements. It can also be used as a flow agent or lubricant and is considered safe.
  • L-leucine: This is an amino acid that is sometimes used as a lubricant in supplements. It has been shown to be safe and effective, and may even have some health benefits.
  • Rice flour: This is a finely ground powder made from rice grains. It can be used as a flow agent or filler in supplements and is considered safe. 
  • Others: ascorbyl palmitate and proprietary rice blends.

rice plantation magnesium stearate alternative
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Discussion and conclusion

So, is Magnesium Stearate bad for you?

For the vast majority of people, consuming small amounts of magnesium stearate in supplements or medicines will likely have no major adverse effect. Read on for a more nuanced reality!

However, there are multiple reports of adverse effects from consumers and a growing concern in some parts of the wellness community. Those who are known to have sensitivity, are consuming large amounts of supplements or who are concerned about the origin or process required to make magnesium stearate should consider avoiding it.

The adverse effect on solubility and nutrient absorption is a real concern and is why excessive amounts of magnesium stearate should not be used. However, exactly how the reduced solubility impacts on different nutrient absorptions in different individuals has not been clearly studied.

Additionally, we are exposed to small amounts of toxins, heavy metals or suboptimal ingredients in food products every day. It is impossible and not necessary to avoid them all. That being said, you should expect your supplement supplier to minimize the use of magnesium stearate for ‘filling’ out tablets or capsules. In my experience, unfortunately, this is often not the case or not possible. Cheap supplements or medicines have low active ingredients and bulk out the product with magnesium stearate. It may also be the case that the active ingredient should only be used in a small dose, such as a vitamin B12 (dosed in micrograms) supplement. In this case, the smallest possible tablet or capsule should be used to avoid using a large amount of filler, but expect to still be ingesting a lot.

Finally, there are many things in our lifetimes that have been regarded as safe and have later been found to be carcinogenic or cause other issues. I don’t think we can necessarily say that about magnesium stearate, but if it can be substituted with something like a rice blend with known commonly used food ingredients, why not do it?

What does We Know Health use in its supplements?

We do NOT use magnesium stearate or stearic acid in any of our supplements. Whilst we believe the evidence of harm is mixed or non-existent, we choose alternatives for the following reasons:

  • We only use plant-based ingredients in our products, so animal-based stearic acid is not acceptable.
  • The plant-based sources of stearic acid may use GMO crops or may be heavily pesticide sprayed. We only use non-GMO ingredients in our products.
  • We are highly concerned about the environmental impact of the palm oil industry and you should be too! Stearic + palmitic acid are often derived from palm oil.
  • Some people have reported adverse effects they put down to magnesium stearate and we want all those who could benefit to enjoy our supplements without this concern.
  • We want our active ingredients to be quickly absorbed so you can enjoy their benefits.
  • As people begin using more and more supplements in their healthy lifestyles, we believe it is important to be transparent and cautious of additive long-term effects.

Our approach

We substitute magnesium stearate with a natural non-GMO rice extract blend and combine with a small amount of other safe agents such as microcrystalline cellulose.


Excipients are not used as ‘fillers’ at We Know Health because our products contain a large amount of active ingredients and we do not use tablet form. Instead, they are used to facilitate a smooth and consistent manufacturing process. We want to ensure what you receive meets strict Good Manufacturing Practice active ingredient consistency aims across capsules.

It may be harder and more expensive to convince manufacturers to utilize alternatives, but we feel obliged to provide the best for you and your families. Out with magnesium stearate!


April 16, 2023 — Steven Musca
Tags: #supplements


We Know Health said:

Hi Gordon, Magnesium Chelates in themselves are fine but most manufacturers will still use fillers or other excipients. Here is a list of other ingredients from the TGA website for a common brand of Magnesium Chelate in Australia. Note this is not displayed on the bottle.

hydrogenated vegetable oil
magnesium stearate
microcrystalline cellulose
sodium lauryl sulfate

Gordon warwick said:

Is chelate magnesium ok for consumption or does it have the same fillers as Stearate cheers

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