Stearic acid is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is C18H36O2, or CH3(CH2)16COOH. Its name comes from the Greek word stear, which means tallow. The salts and esters of stearic acid are called stearates.
Stearic acid is prepared by treating animal fat with water at a high pressure and temperature, leading to the hydrolysis of triglycerides. It can also be obtained from the hydrogenation of some unsaturated vegetable oils. Common stearic acid is actually a mix of stearic acid and palmitic acid, although purified stearic acid is available separately.
An isotope labeling study in humans concluded that the fraction of dietary stearic acid oxidatively desaturated to oleic acid was 2.4 times higher than the fraction of palmitic acid analogously converted to palmitoleic acid. Also, stearic acid was less likely to be incorporated into cholesterol esters. In epidemiologic and clinical studies stearic acid was associated with lowered LDL cholesterol in comparison with other saturated fatty acids. These findings may indicate that stearic acid is less unhealthy than other saturated fatty acids.
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