Magnesium stearate in supplements: what is it and is it safe?

Magnesium stearate is one of the most widely used excipients in tablets and capsules. It appears on the labels of countless vitamins and medicines, often as E470b or as an “anti-caking agent”. Online, all kinds of claims circulate: it supposedly blocks absorption, harms the immune system or is a cheap filler. What is true?

On this page you will learn what it is, why manufacturers use it, what the European Food Safety Authority says about its safety and which excipients are in Every Day Better supplements. Want to know how to assess supplement quality further? See our NMN certificates.

Key points

  • Magnesium stearate is the magnesium salt of stearic acid, a saturated fatty acid also found in ordinary food.
  • It is used as a lubricant so powder does not stick to machines.
  • In 2018 EFSA concluded that it poses no safety concern as a food additive at the levels used.
  • Evidence that it noticeably inhibits absorption of active ingredients is limited and comes mainly from laboratory research.
  • Every Day Better capsules and powders contain no magnesium stearate.

What is magnesium stearate?

It is a compound of magnesium and stearic acid. Stearic acid is a saturated fatty acid that occurs naturally in cocoa butter, beef fat and vegetable oils, among others. For supplements it is usually made from plant sources such as palm or coconut oil, so it can also be found in vegan products.

It is a white, greasy powder that does not dissolve in water. In the European Union it is authorised as a food additive under number E470b, in the group “magnesium salts of fatty acids”.

White tablets: magnesium stearate is often used as a lubricant in tablet production
In tablets, a small amount of lubricant helps the powder run smoothly through the machine.

Why is magnesium stearate in supplements?

In tablet and capsule production, powder is pressed or dosed by machines at high speed. Many powders are sticky or clump. A small amount of lubricant, usually less than one to two percent of the weight, ensures the powder flows evenly and does not stick to the punches.

That has a practical benefit for the consumer: each tablet or capsule contains the same amount of active ingredient more accurately. Without an excipient, production can be slower, more expensive and less precise. It is therefore not a filler in the sense of “cheap bulking material”, but a technological processing aid.

Excipient, filler or anti-caking agent?

  • Filler: added to bring a capsule or tablet up to volume, for example microcrystalline cellulose or rice flour.
  • Lubricant: improves powder flow during production, such as magnesium stearate.
  • Anti-caking agent: prevents powder from clumping, such as silicon dioxide.

Is magnesium stearate safe?

In 2018 the EFSA panel on food additives re-evaluated the magnesium salts of fatty acids. The panel concluded that no numerical acceptable daily intake was needed and that the additives pose no safety concern at the levels used. In the gastrointestinal tract, the compound breaks down into magnesium and fatty acids, two substances you also get from food every day.

For comparison: a supplement with a few capsules a day usually provides a few tens of milligrams of this excipient. That is a fraction of the stearic acid in a piece of chocolate or a portion of meat.

The immune system claim

A common claim is that this excipient damages T cells. The claim goes back to a 1990 laboratory study in which mouse cells in a culture dish were exposed to stearic acid. The researchers saw a change in the cell membranes. That is an artificial situation that says nothing about oral intake: there, stearate is simply digested like other dietary fat.

Does it inhibit absorption?

Because the compound is water-repellent, it can in theory slightly delay the dissolution of a tablet. This has been measured in laboratory tests for certain formulations. However, there is no convincing evidence that the small amounts in supplements noticeably reduce absorption in humans. Manufacturers can also test for this with dissolution tests.

Which excipients are in Every Day Better products?

We deliberately chose as few excipients as possible. Our products contain no magnesium stearate:

Product Ingredients according to the label
NMN capsules (250 mg; 60 or 120 capsules) β-nicotinamide mononucleotide (Uthever® NMN), plant-based capsule of hydroxypropyl methylcellulose
NMN powder (30 grams) Nicotinamide mononucleotide (Uthever® NMN)
TMG capsules (500 mg) Trimethylglycine, plant-based capsule of hydroxypropyl methylcellulose
GlyNAC capsules (600 mg) Glycine, N-acetylcysteine, plant-based capsule

That does not mean products with this lubricant are worse or unsafe. It does mean that with us you only take the active ingredient and the capsule shell. Want to know how pure the active ingredient itself is? Read how to check NMN certificates and see the capsules in our shop.

Plant-based capsules without magnesium stearate or other fillers
A capsule can also be filled without a lubricant, provided the powder flows well.

How do you recognise excipients on a label?

A supplement label must list all ingredients in descending order of weight. Look out for these terms:

  • Magnesium stearate, E470b or “magnesium salts of fatty acids”: lubricant.
  • Silicon dioxide, E551: anti-caking agent.
  • Microcrystalline cellulose, E460: filler or binder.
  • Hydroxypropyl methylcellulose (HPMC), E464: plant-based capsule shell.
  • Gelatine: animal-based capsule shell.

A long list of excipients need not be bad, but a short list makes clear what you are taking. Always compare the amount of active ingredient per capsule too. A comparison of NMN brands on purity and composition can be found in our NMN comparison.

Only what belongs in it

Our NMN capsules contain exactly two ingredients: Uthever® NMN and a plant-based capsule shell. Our NMN powder contains only NMN. No magnesium stearate, no fillers:

All variants contain Uthever® NMN, independently tested by Intertek for a purity of 99.5% or higher. View the lab reports.

Frequently asked questions about magnesium stearate

Is magnesium stearate harmful?

According to EFSA, magnesium stearate poses no safety concern at the levels used in food and supplements. In the gut it breaks down into magnesium and fatty acids.

Why is magnesium stearate in vitamins?

It is a lubricant that helps powder flow smoothly through production machines, so each tablet or capsule contains the same dose more accurately.

Is magnesium stearate vegan?

Usually. The stearic acid is generally obtained from vegetable oils, but can also be of animal origin. Only the manufacturer can confirm the source.

Do Every Day Better supplements contain magnesium stearate?

No. Our NMN, TMG and GlyNAC contain only the active ingredient and, for capsules, a plant-based capsule shell.

Does magnesium stearate inhibit supplement absorption?

In laboratory tests it can slightly slow the dissolution of some tablets, but there is no convincing evidence that the small amounts in supplements noticeably reduce absorption in humans.

Conclusion

Magnesium stearate is a widely used excipient that EFSA considers safe, and it makes tablet and capsule production more precise. Claims about damage to the immune system are based on a laboratory study that is not relevant to normal intake. If you still prefer products without excipients, you can check the label. Every Day Better supplements contain no magnesium stearate.

Sources

  • EFSA ANS Panel. Re-evaluation of sodium, potassium and calcium salts of fatty acids (E 470a) and magnesium salts of fatty acids (E 470b) as food additives. EFSA Journal, 2018.
  • Tebbey PW, Buttke TM. Molecular basis for the immunosuppressive action of stearic acid on T cells. Immunology, 1990.
  • Li J, Wu Y. Lubricants in pharmaceutical solid dosage forms. Lubricants, 2014.

This information is for general education and does not replace medical advice.