What is "alpha-linolenic acid"

n. a polyunsaturated fatty acid with 18 carbon atoms; the only omega-3 fatty acid found in vegetable products; it is most abundant in canola oil; a fatty acid essential for nutrition

α-Linolenic acid (ALA) is an n−3 fatty acid, it is one of two essential fatty acids (the other being linoleic acid), so called because they are necessary for health, and they cannot be produced within the human body. They must be acquired through diet. ALA is an omega-3 fatty acid found in seeds (chia, flaxseed, see also table below), nuts (notably walnuts), and many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is listed by its lipid number, 18:3, and (n−3); its isomer GLA is 18:3 (n−6).

α-Linolenic acid is a carboxylic acid with an 18-carbon chain and three cis double bonds. The first double bond is located at the third carbon from the methyl end of the fatty acid chain, known as the n end. Thus, α-linolenic acid is a polyunsaturated n−3 (omega-3) fatty acid. It is an isomer of gamma-linolenic acid (GLA), a polyunsaturated n−6 (omega-6) fatty acid.