The hydrolysis products-monoglycerides and free fatty acids-are then incorporated into bile-salt– containing micelles and absorbed into enterocytes, largely by passive diffusion. Īfter ingestion, dietary lipids are hydrolyzed in the intestinal lumen. When fish consume phytoplankton that consumed microalgae, they accumulate the omega-3s in their tissues. DHA and EPA are present in fish, fish oils, and krill oils, but they are originally synthesized by microalgae, not by the fish. Therefore, consuming EPA and DHA directly from foods and/or dietary supplements is the only practical way to increase levels of these fatty acids in the body.ĪLA is present in plant oils, such as flaxseed, soybean, and canola oils. ALA can be converted into EPA and then to DHA, but the conversion (which occurs primarily in the liver) is very limited, with reported rates of less than 15%. Therefore, ALA and linoleic acid are considered essential fatty acids, meaning that they must be obtained from the diet. The human body can only form carbon–carbon double bonds after the 9th carbon from the methyl end of a fatty acid. Linoleic acid (C18:2n-6) and arachidonic acid (C20:4n-6) are two of the major omega-6s. Omega-6 fatty acids (omega-6s) have a carbon–carbon double bond that is six carbons away from the methyl end of the fatty acid chain. Similarly, EPA is known as C20:5n-3 and DHA as C22:6n-3.

ALA, for example, is known as C18:3n-3 because it has 18 carbons and 3 double bonds and is an n-3, or omega-3, fatty acid. PUFAs are frequently designated by their number of carbon atoms and double bonds. ALA contains 18 carbon atoms, whereas EPA and DHA are considered 'long-chain' (LC) omega-3s because EPA contains 20 carbons and DHA contains 22. Several different omega-3s exist, but the majority of scientific research focuses on three: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Omega-3s, sometimes referred to as 'n-3s,' are present in certain foods such as flaxseed and fish, as well as dietary supplements such as fish oil. Omega-3 fatty acids (omega-3s) have a carbon–carbon double bond located three carbons from the methyl end of the chain. PUFAs are distinguished from saturated and monounsaturated fatty acids by the presence of two or more double bonds between carbons within the fatty acid chain. Like all fatty acids, PUFAs consist of long chains of carbon atoms with a carboxyl group at one end of the chain and a methyl group at the other. The two major classes of polyunsaturated fatty acids (PUFAs) are the omega-3 and omega-6 fatty acids.

For a reader-friendly overview of Omega-3 Fatty Acids, see our consumer fact sheet on Omega-3 Fatty Acids. This is a fact sheet intended for health professionals.

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