Magnesium stearate is a compound of magnesium salt and stearic acid that supplement manufacturers use to package vitamin capsules and tablets. While the U.S. Food and Drug Administration says that the additive poses no harm, some holistic practitioners in recent years have debated the safety of consuming magnesium stearate along with your vitamins.
Chemical Composition
Magnesium stearate is composed of stearic acid and the essential mineral magnesium. The compound contains between 6.8 and 8.3 percent of magnesium oxide combined with pure stearic acid and palmitic acid. Stearic acid makes up at least 40 percent of the compound, and combined with palmitic acid, makes up at least 90 percent of the substance, according to supplement manufacturer NOW Foods, which uses the substance as a lubricant to fill supplement capsules with dry powdered ingredients and as an ingredient to help tablets hold together and break apart properly.
Controversy
Concern over magnesium stearate as a supplement additive developed after some holistic practitioners began using a 1990 study to sound an alarm against the compound. In an April 2009 article posted on his website, Joseph Mercola, an osteopathic physician who operates a health clinic in Illinois, wrote that stearic acid can suppress your natural killer cells, which are key components of your immune system. He states that if you take "supplements containing magnesium stearate, you actually end up doing the exact opposite as you're consuming large amounts of chalk," Mercola wrote, recommending that people avoid nutritional supplements made with the compound.
Opposing View
However, holistic physician and supplement maker Byron J. Richards refutes these claims. Stearic acid is a common fatty acid found in meat, poultry, fish, grains, eggs, butter and milk products, writes Richards, a certified clinical nutritionist, who offers consultations and products through his Minneapolis-based Wellness Resources Inc. "[T]he amount of stearic acid ingested in a vitamin product is a small percent of a fatty acid that you consume every day as part of your diet, a type of fatty acid that is not problematic in the first place."
Manufacturer's View
Stearic acid is the immediate precursor of oleic acid, which is an important fatty acid found in healthy olive oil and is found in greater quantities in many foods, says Neil E. Levin, a certified clinical nutritionist and the Nutrition Education Manager for NOW Foods. "This science assures us that stearic acid is a safe fatty acid found in healthy foods and that magnesium stearate is a safe analog of stearic acid," Levin writes. "NOW uses them only as necessary for the functionality of a particular dietary supplement in tiny amounts compared to the amount of stearates found in common foods."
Federal View
The U.S. Food and Drug Administration has placed magnesium stearate and stearic acid on its list of substances the agency generally regards as safe for human consumption. There is no evidence that demonstrates or suggests that magnesium stearate or stearic acid presents a hazard to the public when the compound is used by supplement manufacturers, the FDA says.
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