Is magnesium stearate safe to use as a supplement excipient?

There is much debate among supplement manufacturers, practitioners and the general public on the use of magnesium stearate and other excipients. Many say that it is not toxic and fine for use in foods and food supplements, while others say the opposite.

We firmly believe that excipients such as magnesium stearate should not be in food supplements due to toxicity and reduced bioavailability. Please don't just accept this, take a look for yourself . . . but before you do lets take a scientific look at precisely what magnesium stearate is.

What is magnesium stearate?

Magnesium stearate is a lubricant, a salt containing two equivalents of stearate (the negatively charged anion of stearic acid) and one positively charged magnesium cation (Mg2⁺). Magnesium stearate is also called octadecanoic acid and magnesium salt. Magnesium stearate is not soluble in water and has hydrophobic properties, meaning that it is water-repelling. Its chemical formula is Mg(C₁₈H₃₅O₂)₂ and it is a very fine white powder with a soapy texture.

What is magnesium stearate used for?

The main use of magnesium stearate is in the manufacture of tablet, capsule and powder supplements. It is added to formulations to improve the flow properties of the powder, this also helps to compress the tablet without sticking to the mold and machinery parts whilst improving clean down time. Magnesium stearate is typically used in a concentration range of 0.25% to 2% but we have heard of it being used up to 5%. High values can result in decreased absorption of the product; in the pharma industry it is widely known that magnesium stearate prolongs disintegration.

What is magnesium stearate derived from?

Magnesium stearate is made from bovine and vegetable sources. The vegetable source is made by hydrogenating cottonseed or palm oil. Cotton crops are heavily sprayed and have the highest content of pesticide residues of all commercial oils. In the hydrogenation process, hydrogen gas is forced into the oil at high pressures in the presence of a metal catalyst for a few hours. Hydrogenated vegetable fats contain altered molecules derived from fatty acids (trans fat) and many scientists believe these carry serious health risks.

Discussion

Is magnesium stearate safe? The information in the above paragraphs certainly flags up the need for caution in using magnesium stearate. To reiterate:

• Toxicity; cotton crops are heavily sprayed and have the highest content of pesticide residues of all commercial oils.
• Hydrogenation; hydrogenated vegetable fats contain altered molecules derived from fatty acids (trans fat) that have serious health risks.
• Reduced bioavailability; decreased absorption of the product.

Increasingly health conscious people are aware of the problems with pesticide toxicity and usage of hydrogenated oils, but few are aware of the issues involving supplement excipients such as magnesium stearate. A component of magnesium stearate is stearic acid. Research shows stearic acid suppresses the body's natural killer cells, a type of lymphocyte (a white blood cell) and a component of the innate immune system. It produces a reaction in the gut to form a film or lining that works as a barrier that stops or limits the absorption of nutrients.* Stearic acid may prevent absorption by individuals with compromised digestive systems. Magnesium stearate and stearic acid also present the problem that delivery of the active ingredient may be considerably further down the intestinal tract than the site originally intended. This may result in the nutrient being delivered away from its optimal absorption site. Not only can this impede absorption, in some cases it might be harmful to the liver.** The addition of palmitate or stearate to cultured cells led to activation of a death program with a morphology resembling that of apoptosis. Palmitates and stearates caused cardiac and other types of cells to undergo programmed cell death.***

To achieve the correct flow properties magnesium stearate has to be thoroughly mixed with the active ingredients and in doing so magnesium stearate coats a good percentage of the molecules of the ingredients. This then requires digestive enzymes to first break down the magnesium stearate coating before being able to assimilate the nutrients, which has a negative impact for people suffering with digestion problems, the sick and elderly.