Docosahexanoic acid (C22:6, DHA) is a highly unsaturated omega-3 fatty acid that forms part of the central nervous and visual system structures. DHA is synthesized in the body from its precursor, alpha-linolenic acid that can be obtained from vegetable and seed oils.
DHA is also available from fish oils. The vegetarian/vegan form of DHA is derived from the oceanic algae Schizochytrium sp., a marine micro-algae rich in docosahexaenoic acid. DHA can be converted from alpha-linolenic acid within the body. ALA is first converted into eicosapentaenoic acid (EPA) via the enzyme delta-6 desaturase. This can then go on to form DHA through further enzymatic reactions including elongase and peroxisomal oxidation.
Over-heating through cooking can destroy DHA in foods. Frying is the worst method as the extremely high heat of the oil accelerates free radical oxidation, destroying the DHA. The DHA may also be leeched out of the food and lost. DHA is a very unstable oil which can easy react with oxygen. Oxygenation of the oil will turn it rancid through free radical production. Products containing unstable oils should be nitrogen flushed to prevent air in the packaging oxygenating and damaging the oil. Alternatively, antioxidants should be added.