Magnesium stearate is a compound that is formed chemically by combining stearic acid — a naturally occurring waxy substance in vegetable oil or animal fat — with a magnesium ion, which is an electron which has lost or gained an electric charge. This causes the magnesium stearate to precipitate out, or condense, to form a magnesium salt. This salt is granular and has a white color, unlike uncombined stearic acid, also termed octadecanoic acid, which is a colorless clear liquid.
Widely used, magnesium stearate is a key ingredient in the production of medicines, food supplements, and health products such as vitamins. It has been approved by the Food and Drug Administration (FDA) of the US Government for use as a food additive, supplement tablet additive, and also for use as a coating in medical capsules and medical tablets. It is in high demand by food and drug manufacturers because it is such an effective lubricant.
Magnesium stearate has gained such wide usage due, in part, to the FDA certification of its essentially harmless chemical composition. Principal sources today include palm oil, coconut oil, or cottonseed oil, allowing certifications that indicate that supplements using the compound are acceptable for ingestion by vegetarians. There is some concern, however, that cottonseed oil contains a high degree of pesticide contamination, making it unsuitable for use in food supplements. Labels of supplement powders simply tend to list magnesium stearate as an inert ingredient that does not react with other active ingredients and will not impede their desired effects.
Magnesium stearate is also highly used as a tablet lubricant for prescribed medicine, since it not only helps prevent tablets from sticking together in the bottle, but its coating helps make tablets easier to swallow. The addition of this compound to solid tablets and capsules also helps them to break apart easier once they are swallowed, and it helps to more predictably release the active ingredients of the tablet or capsule. An ability to predict the release time is an important factor in prescribing medicine for medical conditions, since, for a medication to be effective, it needs to be capable of producing desired results within a predetermined time period.
Although magnesium stearate has been accepted as a relatively innocuous food additive in itself, some debate has arisen regarding the unknown toxic accumulative effects of such widespread usage of this substance — which, according to some reports, is present in about 95% of food supplements. Concerns have also appeared regarding the as yet unknown interactions that may develop from its increasingly widespread usage in ingested products.