Essential fatty acids are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. These fatty acids are required for biological processes but does not include the fats that only act as fuel.
Only two fatty acids are known to be essential for humans: alpha-linolenic acid (ALA – an omega-3 fatty acid) and linoleic acid (LA – an omega-6 fatty acid). Some other fatty acids are sometimes classified as “conditionally essential,” meaning that they can become essential under some developmental or disease conditions; examples include docosahexaenoic acid (DHA – an omega-3 fatty acid) and gamma-linolenic acid (GLA – an omega-6 fatty acid).
Omega-9 fatty acids are not essential in humans because they can be synthesized from carbohydrates or other fatty acids.