Q. What is stearic acid and why is it used?
A. Stearic acid is an essential saturated fatty acid that is found in all vegetable, seed, nut, and animal oils. Although stearic acid can be from several sources, the most common source in better quality nutritional supplements is vegetable stearic acid.
Tablet manufacturing requires certain substances like stearic acid to help powders flow smoothly through the tableting machines and help the tablets hold their shape. Stearic acid is ideal because of its natural source and inactive state-so it doesn't interfere with the proper utilization or absorption of the active ingredients in the tablet.
Q. Does stearic acid interfere with the absorption of vitamins and minerals?
A. No. There is no evidence that stearic acid, in the miniscule levels used in tablet manufacturing, interferes with or blocks breakdown and absorption of nutrients. The amount of stearic acid in a typical tablet is much less than what you'll find in a salad with olive oil and vinegar dressing. (Olive oil is a source of stearic acid.)
Q. I noticed that some Poliquin products contain stearic acid. I was reading a report that magnesium stearate suppresses the immune system through T cell suppression. Is this true and should I be worried?
A. Stearic acid is a naturally occurring fat that is present in all of our bodies. Some nutritional supplement manufacturers, however, would like you to believe that stearic acid (or its salt, magnesium stearate) is a bad thing. They've focused on one small ingredient and created widespread misconceptions about its use and its effects on health. Most formulations—whether in tablet or capsule form—require some added ingredients to assist in manufacture. A manufacturer of high quality nutritional supplements will ensure that excipients, binders, or dilutents are derived from natural sources.
Stearic acid, for example, may be of a vegetable origin. Stearic acid enables providers to manufacture tablets of uniform size, weight, texture, and shape that help to ensure a pure, safe, and effective product. Both the Federal Drug Administration (FDA) and the United States Pharmacopeia (USP) recommend the use of stearic acid and magnesium stearate in the production of high quality nutritional and pharmaceutical products. According to Vitkova and Chalabala, "Magnesium stearate is the lubricant of choice in the production, found in up to 80% of all industrially produced tablets."1 It is important to note that the levels of stearic acid found in Poliquin products are very low—much lower than the levels used in human studies surrounding stearic acid.
Your question regarding magnesium stearate and immune dysfunction comes up a lot. While stearic acid is not considered a "beneficial" fat (such as those found in cold-water fish and flaxseed), it has not been shown to contribute to immune dysfunction in humans. In fact, most research documents show just the opposite effect:
1. Stearic acid is a normal constituent of the body and immune system, including lymphocytes (a type of white blood cell) and red blood cells.
"Lecithin of leukemic lymphocytes contained more palmitinic acid and oleic acid and a lower level of stearic acid than the same fraction in normal lymphocytes."
Bleiber R, Kunze D, Reichmann G, et al. Leukocyte lipids in mature cell leukemia. Acta Haematol 1976;55(2):81-88.
"The fatty acid compositions of 1,2-diacylglycerol and polyphosphoinositides have been determined in human erythrocyte membranes [red blood cells]…it appears that these plasma-membrane polyphosphoinositides and their derived diacylglycerols are rich in stearic acid and arachidonic acid."
Allan D, Cockcroft S. The fatty acid composition of 1,2-diacylglycerol and polyphosphoinositides from human erythrocyte membranes. Biochem J 1983;213(2):555-57.
2. Stearic acid seems to activate components of the immune system (i.e., neutrophils) instead of suppress it.
"…the polyunsaturated fatty acid arachidonic acid, the triglycerides tricaproin, tricaprylin, and trilaurin as well as the fatty acids lauric acid, palmitic acid, stearic acid, and arachidic acid all induced oxygen radical production in neutrophils…"
Wanten GJ, Janssen FP, Naber AH. Saturated triglycerides and fatty acids activate neutrophils depending on carbon chain-length. Eur J Clin Invest 2002;32(4):285-89.
Vitkova M, Chalabala M. The use of some hydrophobic substances in tablet technology. Acta Pharm Hung 1998;68(6):336-44.