Introduction

Have you ever wondered what coats your medications and vitamin/dietary/nutritional supplements? Well, it is an additive made from magnesium stearate.

“Magnesium stearate is widely used in the production of dietary supplement and pharmaceutical tablets, capsules and powders as well as many food products, including a variety of confectionery, spices and baking ingredients.” (Hobbs et al., 2017, p.554).

Magnesium stearate is a fine, light white powder that sticks to your skin and is greasy to the touch. It is a simple salt made up of two substances:

• A saturated fat known stearic acid; and
• The mineral magnesium.

Stearic acid can also be found in many foods, including:

• Chicken;
• Eggs;
• Cheese;
• Chocolate;
• Walnuts;
• Salmon;
• Cotton seed oil;
• Palm oil; and
• Coconut oil.

Magnesium stearate is commonly added to many foods, pharmaceuticals, and cosmetics. In medications and vitamins, its primary purpose is to act as a lubricant. It may be derived from plants as well as animal sources.

What is it Used For?

• It has been widely used for many decades in the food industry as an emulsifier, binder and thickener, as well as an anticaking, lubricant, release, and antifoaming agent.
• It is present in many food supplements, confectionery, chewing gum, herbs and spices, and baking ingredients.
• It is also commonly used as an inactive ingredient in the production of pharmaceutical tablets, capsules and powders.
• It is useful because it has lubricating properties, preventing ingredients from sticking to manufacturing equipment during the compression of chemical powders into solid tablets; magnesium stearate is the most commonly used lubricant for tablets.
  • If you would like to understand why lubrication is important in pharmaceutical manufacturing read Lubricants in Pharmaceutical Solid Dosage Forms by Li & Wu (2014).
• However, it might cause lower wettability and slower disintegration of the tablets and slower and even lower dissolution of the drug.
• It can also be used efficiently in dry coating processes.
• In the creation of pressed candies, magnesium stearate acts as a release agent and it is used to bind sugar in hard candies such as mints.
• It is a common ingredient in baby formulas.

It is possible to create capsules without magnesium stearate, but it is more difficult to guarantee the consistency and quality of those capsules.

Other Names

Mangeniusm stearate has number of other names, approximately 45, including:

• Magnesium Distearate.
• Magnesium Octadecanoate.
• Octadecanoic Acid, Magnesium Salt.
• Dibasic Magnesium Stearate.
• Stearic Acid, Magnesium Salt.
• Magnesium Dioctadecanoate.
• Synpro 90.
• Petrac MG 20NF.
• NS-M (Salt).
• SM-P.
• Synpro Magnesium Stearate 90.
• HSDB 713.
• Rashayan Magnesium Stearate.

How is it Manufactured/Made?

• Molecular Formula: C₃₆H₇₀MgO₄ or Mg(C₁₈H₃₅O₂)₂, it exists as a salt containing two stearate anions and a magnesium cation.
  • An anion has more electrons than protons, consequently giving it a net negative charge.
  • A cation has more protons than electrons, consequently giving it a net positive charge.
• Magnesium stearate is produced by:
  • The reaction of sodium stearate (the sodium salt of stearic acid) with magnesium salts; or
  • Treating magnesium oxide with stearic acid.
• Some nutritional supplements specify that the sodium stearate used in manufacturing magnesium stearate is produced from vegetable-derived stearic acid.

Magnesium stearate is a major component of bathtub rings. When produced by soap and hard water, magnesium stearate and calcium stearate both form a white solid insoluble in water, and are collectively known as soap scum.

What Does My Body Do With Magnesium?

• Upon ingestion, magnesium stearate is dissolved into magnesium ion and stearic and palmitic acids.
• Magnesium is absorbed primarily in the small intestine, and to a lesser extent, in the colon.
• Magnesium is an essential mineral, serving as a cofactor for hundreds of enzymatic reactions and is essential for the synthesis of carbohydrates, lipids, nucleic acids and proteins, as well as neuromuscular and cardiovascular function.
• The majority of magnesium content in the body is stored in bone and muscle.
• A small amount (~1%) is present in serum and interstitial body fluid, mostly existing as a free cation while the remainder is bound to protein or exists as anion complexes.
• The kidney is largely responsible for magnesium homeostasis and maintenance of serum concentration.
• Excretion occurs primarily via the urine, but also occurs in sweat and breast milk.
• Stearic and palmitic acids are products of the metabolism of edible oils and fats for which the metabolic fate has been well established.
• These fatty acids undergo ß-oxidation to yield 2-carbon units which enter the tricarboxylic acid cycle (aka Krebs cycle and citric acid cycle, the second stage of cellular respiration) and the metabolic products are utilised and excreted.

How Much Can I Consume and What are the Risks?

• The US Food and Drug Administration (FDA) has approved magnesium stearate for use as an additive in food and supplements, being classified (in the US) as generally recognised as safe (GRAS).
• In the European Union (EU) and European Free Trade Agreement (EFTA) it is listed as food additive E470b.
• In 1979, the FDA’s Subcommittee on GRAS Substances (SCOGS) reported, “There is no evidence in the available information on … magnesium stearate … that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current and in the manner now practiced, or which might reasonably be expected in the future.”
• It is generally considered to have a “safe toxicity profile”. (Hobbs et al., 2017, p.554).
• According to PubChem (a part of the The National Library of Medicine’s National Centre for Biotechnology Information), it is considered safe for consumption at amounts below 2,500 milligrams (mg) per kilogram per day. For a 150-pound (68 kg) adult, that equals 170,000 mg per day.
• Capsule manufacturers typically use only small amounts of magnesium stearate in their products. When you take their products at the recommended dose, they do not contain enough magnesium stearate to cause negative side effects.

“Stearic acid typically ranges between 0.5-10 percent of the tablet weight while magnesium stearate typically represents 0.25-1.5 percent of the tablet weight. Therefore, in a 500 mg tablet, the amount of stearic acid would probably be about 25 mg, and magnesium stearate about 5 mg.” (Bruno, 2013, p.53).

What are the Health Risks of Magnesium Stearate?

• Toxicology data from animal studies relevant to evaluation of magnesium stearate are lacking (e.g. doses that will not lead to a dietary imbalance, known composition of material tested, appropriate administration route, etc.).
• There are also no human data related to magnesium stearate toxicity.
• It has been noted that infants are particularly sensitive to the sedative effects of magnesium salts and that individuals with chronic renal impairment retained 15-30% of administered magnesium, which may cause toxicity.
• Moreover, diarrhoea and other gastrointestinal effects have been observed with excessive magnesium intake resulting from use of various magnesium salts for pharmacological/medicinal purposes.
• Many magnesium-containing food additives have been evaluated individually, but not collectively, for laxative effects.
• With this in mind, it is important to understand what effect cumulative exposure to magnesium via food additives may have, although studies indicate a lack of genotoxic risk posed specifically by magnesium stearate consumed at current estimated dietary exposures.
• PubChem also notes that it can be an irritant which may cause skin, eye, and respiratory irritation, as well as potentially causing long lasting harmful effects to aquatic life (although relates to the powder form and not capsule form).
• Some people report having negative reactions to magnesium stearate and feel much better when they eliminate it. These people might have a sensitivity to it. It is possible to be allergic to magnesium stearate, and it can be difficult to avoid this food additive.

Alleged Health Risks Not Borne Out by the Science

• Some people (mainly on the internet) claim that magnesium stearate suppresses your immune T-cell function and causes the cell membrane integrity in your helper T cells to collapse.
  • However, there is no scientific evidence to support those claims.
  • Generally, these claims have been made based on a single mouse study that was related to stearic acid, not magnesium stearate (Tebbey & Buttke, 1990).
  • Mice lack an enzyme in their T cells that humans have. This makes stearic acid safe for us to ingest. Human T-cells have the delta-9 desaturase enzyme required to convert stearic acid into oleic acid to avoid a toxic build-up.
  • Another factor to consider is that the study was conducted by bathing the mouse T-cells in stearic acid.
  • It is impossible to consume stearic acid in such humongous amounts through supplements.
• Some people have also claimed that magnesium stearate might interfere with your body’s ability to absorb the contents of medication capsules.
  • Studies have found that although magnesium stearate may slow down dissolution and absorption in some cases, it does not affect the overall bioavailability of nutrients.
• Gene Bruno (MS, MHS), writing in Vitamin Retailer in March 2013, gives a good outline on why the above two points are not borne out by the science.
• Another claim is that magnesium stearate can form a biofilm in the intestines just as soaps containing calcium and magnesium stearates form soap scum in sinks and bathtubs.
  • The Human gut environment is completely different to that of a bathroom.
  • Human intestines have acids and enzymes that do not allow soap scum to accumulate.
  • And, soap scum is nothing like a biofilm – If anything, magnesium stearate can actually prevent the formation of biofilms.

What are the Alternatives to Magnesium Stearate?

Magnesium stearate and stearic acid are the most common lubricants used in pharmaceutical processes. However, there are other lubricants, including fatty acid esters, inorganic materials, and polymers.

• Metallic Salts of Fatty Acids:
  • They are still the most dominant class of lubricants.
  • Magnesium stearate, calcium stearate, and zinc stearate are the three common metallic salts of fatty acids used.
  • Of these three lubricants, magnesium stearate is one of the most frequently used.
• Fatty Acids:
  • These are also common lubricants, with stearic acid being the most popular one.
  • Chemically, stearic acid is a straight-chain saturated monobasic acid found in animal fats and in varying degrees in cotton seed, corn, and coco.
  • The commercial material of stearic acid has other minor fatty acid constituents such as myistic acid and palmitic acid.
• Fatty Acid Esters:
  • Fatty acid esters, including glyceride esters (glyceryl monostearate, glyceryl tribehenate, and glyceryl dibehenate) and sugar esters (sorbitan monostearate and sucrose monopalmitate), are often used as lubricants in the preparation of solid dosage forms.
  • In particular, Compritol^® 888 ATO is an effective lubricant to replace magnesium stearate when the latter causes delay of dissolution and other compatibility issues.
• Inorganic Materials and Polymers:
  • Are used as lubricants when magnesium stearate is not appropriate.
  • In terms of inorganic materials, talc (a hydrated magnesium silicate (Mg₃Si₄O₁₀(OH)₂)), is often used as a lubricant or a glidant in formulations.
  • Similarly, polymers, such as PEG 4000, are occasionally used as lubricants in solid dosage forms when the use of magnesium stearate displays compression and chemical incompatibility issues.

Besides the conventional lubricants, manufacturers are also using natural-based lubricants (such as rice extract) or excipient premixes (such as cellulose/rice extract/oil/wax).

Summary

The benefits of using magnesium stearate in supplements far outweigh the potential risks. And, apart from ensuring a homogenous mixture of active ingredients and accurate, consistent dosage, magnesium stearate has several health benefits of its own. As an essential mineral, magnesium is crucial for more than 300 enzyme reactions occurring in the human body. Stearic acid is known to lower LDL cholesterol and improve heart function.

References and Further Reading

• Bruno, G. (2013) Stearic Acid & Magnesium Stearate: Examing the Facts. Vitamnin Retailer. March 2013, pp.52-56. Available from World Wide Web: https://www.huhs.edu/sites/default/files/files/Stearic%20acid%20and%20Magnesium%20sterate%20article.pdf. [Accessed: 03 April, 2022].
• Hobbs, C.A., Saigo, K., Koyanagi, M. & Hayashi, S-M. (2017) Magnesium Stearate, A Widely-Used Food Additive, Exhibits a Lack of In Vitro and In Vivo Genotoxic Potential. Toxicology Reports. 4, pp.554-559. doi: 10.1016/j.toxrep.2017.10.003.
• Li, J. & Wu, Y. (2014) Lubricants in Pharmaceutical Sold Dosage Forms. Lubricants. 2, pp.21-43. doi:10.3390/lubricants2010021.
• PubChem (National Library of Medicine’s National Centre for Biotechnology Information): https://pubchem.ncbi.nlm.nih.gov/compound/magnesium_stearate.
• Tebbey, P.W. & Buttke, T.M. (1990) Molecular Basis for the Immunosuppressive Action of Stearic Acid on T Cells. Immunology. 70, pp.379-384.