Magnesium Stearate Fact Sheet

Magnesium Stearate Fact Sheet

Key Points

1.    Magnesium stearate holds GRAS status affirming its safe use in foods and supplements.

2.    Magnesium stearate, in proper amounts, results in a more uniform finished product with optimal dissolution.

3.    Magnesium stearate is made with ingredients commonly found in supplements and foods.

4.    Evidence is lacking to indicate that adding the proper amount of magnesium stearate reduces the absorption of nutrients in a supplement.

5.    Americans consume about 7 grams per day of stearic acid from foods; a typical daily supplement contains 10 to 30 milligrams, a much smaller amount.

6.    Unlike other saturated fats, stearic acid has no adverse effect on blood cholesterol.

7.    Evidence is lacking to indicate magnesium stearate forms harmful “biofilms” in the digestive tract.

1.     Magnesium stearate holds GRAS status affirming its safe use in foods and supplements.

For over three decades, the FDA has affirmed the safety of magnesium stearate for use in foods and supplements. It continues to hold GRAS (Generally Recognized As Safe) status as an ingredient that can be safely added to foods and dietary supplements for a variety of important functions, including the following:

  •  Lubricant and release agent added to food contact surfaces to prevent ingredients and finished products from sticking to them.
  • Processing aid used as a manufacturing aid to enhance the appeal or use of a food or food component.
  • Nutrient supplement necessary for the body's nutritional and metabolic processes.

2.     Magnesium stearate, in proper amounts, results in a more uniform finished product with optimal dissolution.

The ability of magnesium stearate to promote the optimal flow of a powdered blend during the manufacturing process is critical to ensure the finished product has a uniform composition (e.g., all finished capsules or tablets consistently provide the effective amount of active ingredients).

Add too little magnesium stearate to a powdered blend, and it has little or no effect. Add too much, and it can over lubricate, which may slow down the rate of dissolution. Add a precise amount of magnesium stearate, however, and the finished product not only has a more uniform composition, but also optimal dissolution. Optimal dissolution allows more of the active ingredient(s) to be released from a finished product and be available for absorption by the body.

The “sweet spot” is the addition of about 1% magnesium stearate, which results in a finished product with both uniform composition and high dissolution. Experienced formulators of high-quality supplements understand the precision required for this important technical step and formulate products accordingly.

Separately, drug research investigating the most effective amount of magnesium stearate for drug delivery confirms that adding about 1% magnesium stearate to a formula not only results in a finished product that is more uniform in composition, but also has an optimal rate of release of the active ingredient (e.g., an optimal dissolution rate).[i]

The ability of magnesium stearate to help reduce variation in the composition of finished products is an important function that helps ensure finished products are safe and effective. This is especially true for complex formulas with many active ingredients. Without it, a finished product has the potential to have drastically different compositions, which are ineffective at best and harmful at worst.

Thus, the addition of a precise amount of an effective flow agent such as magnesium stearate during the manufacturing process helps ensure all active ingredients will be uniformly present in the finished product while maintaining an optimal dissolution rate. The result is a finished product that is not only effective, but safe.

3.     Magnesium stearate is made with ingredients commonly found in supplements and foods.

Magnesium stearate used in dietary supplements is typically made by combining a magnesium salt (e.g., magnesium oxide, magnesium hydroxide or magnesium carbonate) with a fatty acid (stearic acid).

Both magnesium salts and stearic acid are common ingredients. In addition to being a building block for magnesium stearate, magnesium salts are also bioavailable sources of elemental magnesium, an essential mineral for human health. The Daily Value for magnesium is 250 mg for children under 4 years of age; 400 mg for adults and children age 4 and over; and, 450 mg for women who are pregnant or nursing.

The stearic acid used in the production of magnesium stearate is a fatty acid that naturally occurs in both animal- and plant-based foods. For products designed to be free of animal products, palm oil is often used as the food source of stearic acid.

4.     Evidence is lacking to indicate that adding the proper amount of magnesium stearate reduces the absorption of nutrients in a supplement.

In a video demonstration, JJ Virgin, a triple-board certified nutrition and fitness expert, states that magnesium stearate… “could impact [nutrient] absorption by as much as 60%.” She also states, “… as little as 1% of magnesium stearate can potentially affect the absorption of nutrients in your supplements.”[ii]

The spokesperson, however, fails to provide any competent and reliable  evidence to substantiate her statements that adding proper amounts of magnesium stearate (e.g., about 1%) to a product formula adversely affects nutrient absorption in the body. This requires a specific type of study (e.g., a pharmacokinetic study) to measure just how the body absorbs and metabolizes a given nutrient in a product taken by mouth. The only evidence provided in the video is a “glass of water” test described below.

By contrast, a MEDLINE search of the peer-reviewed published scientific literature (www.pubmed.gov) fails to reveal any research showing the addition of magnesium stearate, in proper amounts, to a supplement formula reduces the absorption of nutrients in the body.

Separately, at least one study[iii] has been published demonstrating adding 1% magnesium stearate to a drug formula improves the quality of the finished product while maintaining a high rate of dissolution. These findings indicate that the addition of 1% magnesium stearate had no adverse effect on the release of the active ingredient in this formula and its availability for absorption by the body.

In the same video, Mario Roxas, N.D., a naturopathic doctor and medical liaison for Thorne Research, completes a demonstration in which he mixes two vitamin C products — with and without magnesium stearate — in glasses of water. He remarks on how the one with magnesium stearate “didn’t go into solution as quickly as the other one did” and suggests that this is evidence that magnesium stearate is “a potential barrier” to absorption. However, Dr. Roxas stops short of restating the unsubstantiated “60% claim” and appears mindful to qualify his claims in all instances with “potential” (e.g., “potential effect,” “potential barrier”).

Of course, any doubt of “potential” actions can be eliminated by testing finished products using validated analytical testing procedures, which are routinely used by manufacturers of high-quality supplements (see details below).

While the results of Dr. Roxas’ demonstration would be expected, they are not relevant to how nutrients in dietary supplements are digested and absorbed by the body. Vitamin C (a water-soluble compound) would be expected to mix well in a glass of water. Adding magnesium stearate (a fat-soluble compound) would slow down this effect in a glass of water. In the body, however, magnesium stearate is readily digested in the same way the fat in food is digested.

A more accurate measure of the dissolution rate of a product requires well-established analytical methods as defined in the U.S. Pharmacopeia. Using these more sophisticated analytical methods, products containing a proper amount of magnesium stearate regularly meet or exceed the dissolution rate required for optimal absorption in the body.

Indeed, manufacturers of high-quality supplements routinely include validated dissolution testing as part of their quality control procedures to confirm proper dissolution, which eliminates any speculation of other “potential” actions.

5.     Americans consume about 7 grams per day of stearic acid from foods; a typical daily supplement contains 10 to 30 milligrams.

The typical American diet provides, on average, about 7 grams of stearic acid per day from commonly consumed foods, based on national survey data.[iv] Especially rich food sources include cocoa butter, meat, solid fats such as butter, lard and beef tallow, and, to a lesser extent, vegetable oils (see Table 1).[v] By comparison, a high quality supplement contains about 1% magnesium stearate resulting in an intake of only a few milligrams per day, typically in the range of 10 to 30 milligrams per day.

Table 1. Stearic Acid Content of Select Foods

1 ounce of  Dark Chocolate (70-85% solids) contains 3.9 g

1 medium Pork chop contains 3.1 g 

1 tablespoon of Beef tallow contains 2.4 g 

6 ounce of beef steak contains 1.9 g 

1 tablespoon of Lard contains 1.7 g

1 tablespoon of Butter contains 1.4 g

1 tablespoon of Palm oil contains 0.6 g

1 tablespoon of Coconut Oil contains 0.4 g

Source: USDA Nutrient Database ( http://ndb.nal.usda.gov/ndb/)

6.     Unlike other saturated fats, stearic acid has no adverse effect on blood cholesterol.

Stearic acid is a saturated fatty acid found in a wide variety of foods. Yet, unlike other long-chain saturated fatty acids, stearic acid does not raise blood cholesterol.[vi]

7.     Evidence is lacking to indicate magnesium stearate forms harmful “biofilms” in the digestive tract.

Competent and reliable research fails to support the claim that magnesium stearate has the ability to promote biofilm formation in the digestive tract that can interfere with nutrient absorption. A biofilm occurs when bacteria or other microorganisms multiply, stick together and adhere to a surface, including the intestinal lining. Preliminary laboratory research suggests that magnesium stearate may inhibit — rather than promote — biofilm formation. In one study,[vii] stearic acid has been shown to play a role in inhibiting biofilm formation.

[i]. Nelson D, Wu R, Wymbs K. Effects of magnesium stearate on tablet properties. Rutgers University, July 23, 2009. Available at: http://www.soe.rutgers.edu/sites/default/files/gset/PharmaDC.pdf.

[ii]. Thorne Research Magnesium Stearate Demo. Available at: http://www.youtube.com/watch?v=Hv391hhfSOM.

[iii]. Nelson D, Wu R, Wymbs K. Effects of magnesium stearate on tablet properties. Rutgers University, July 23, 2009. Available at: http://www.soe.rutgers.edu/sites/default/files/gset/PharmaDC.pdf.

[iv]. USDA Agricultural Research Service. What We Eat in America, NHANES 2001-2002, Individuals 2 Years and Over (Excluding Breast-Fed Children). Nutrient Intakes: Mean Amount Consumed Per Individual, One Day. Available at: http://www.ars.usda.gov/SP2UserFiles/Place/12355000/pdf/0102/Table_2_BIA.pdf

[v]. Kris-Etherton PM, Mustad VA. Chocolate feeding studies: a novel approach for evaluating the plasma lipid effects of stearic acid. Am J Clin Nutr. 1994;60(6 Suppl):1029S-1036S. PMID: 7977145.

[vi]. Mensink RP. Effects of stearic acid on plasma lipid and lipoproteins in humans. Lipids. 2005;40(12):1201-1205. PMID: 16477803.

[vii]. Soni KA, Jesudhasan P, Cepeda M, et al. Identification of ground beef-derived fatty acid inhibitors of autoinducer-2-based cell signaling. J Food Prot. 2008;71(1):134-138. PMID: 18236673.

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