Stearic Acid

Stearic acid, also known as octadecanoic acid, stearophanic acid, stearex beads, stearate, vanicol, n-octadecanoic acid, and pearl stearic, is a saturated fatty acid. Fatty acids are widely distributed in nature as components of animal and vegetable fats. Fatty acids are an important part of the normal daily diet of mammals, birds and invertebrates.

Stearic acid (18:0) is converted to oleic acid (18:1ω9) in brain but cannot be further converted to linoleic acid (18:2ω6). This means that the fatty acids of the ω3 and ω6 series can be obtained only via dietary sources, mainly from plants, and so are termed "essential fatty acids" and have important physiological roles. If the ω3 and ω6 precursors are not available in the diet, then ω9 fatty acids are further chain-elongated and desaturated to form abnormal fatty acids, as a compensatory response of the brain 1.

Together with palmitic acid, stearic acid is one of the most plentiful fatty acids, occurring in practically all animal and plant oils and fats, for example, 34% in cocoa butter, 30% in mutton fat, 18% in beef fat, 5-15% in milk fat. Stearic acid is found in cotton, coconut, palm kernel, corn, palm, castor, rapeseed, soybean, sunflower, herring, and tallow oils, and in several varieties of rice. Stearic acid is thought to be the most poorly absorbed of the common fatty acids. It is used in the manufacture of candles, soaps, detergents, antifoams, pharmaceuticals and cosmetics 6.

Commercial stearic acid does not occur in pure form, but is a mixture of stearic acid and palmitic acid. Purified stearic acid USP is a mixture of same acids that together constitute not less than 96% of the total content.

Purified stearic acid USP is prepared from edible fats and oils by boiling them with soda lye, separating the glycerin, and decomposing the resulting soap with sulfuric or hydrochloric acid. The stearic acid is subsequently separated from any oleic acid by cold expression 2.

Stearic acid is believed to impart a neuroprotective effect against the toxicity of oxygen-glucose deprivation and glutamate in animal brain models 3. Contrary to earlier studies, it does not increase plasma cholesterol level probably because it is easily converted to oleic acid 4. Stearic acid is also reported to cause the reduction of plasma cholesterol by limiting its absorption and enhancing the excretion of endogenous cholesterol 5

  1. Siegel GJ, Agranoff BW, Albers RW, et al., editors. Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition.
  2. Paul Beringer (editor). Remington: The Science And Practice Of Pharmacy
  3. Paul A. Lapchak, John H. Zhang. Translational Stroke Research: From Target Selection to Clinical Trials
  4. Casimir C. Akoh, David B. Min.Food Lipids: Chemistry, Nutrition, and Biotechnology
  5. Effects of the Intake of Natural Cocoa Powder on Some Biochemical and Haematological Indices in the Rat
  6. Walter de Gruyter. Concise Encyclopedia Biochemistry and Molecular Biology. Third Edition.