Stearidonic acid (18:4n-3):: Metabolism, nutritional importance, medical uses and natural sources

Stearidonic acid (SA, 18:4n-3) is a polyunsaturated fatty acid (PUFA) that constitutes the first metabolite of alpha-linolenic acid (ALA, 18:3n-3) in the metabolic pathway leading to C20-22 PUFA, such as eicosapentaenoic acid (EPA, 20:5n-3), and docosahexaenoic acid (DHA, 22:6n-3), which recently have received much attention because of their various physiological functions in the human body. Recently, several studies indicated that dietary SA increased EPA more efficiently than ALA. Thus, vegetable oils containing SA may become a dietary source of n-3 fatty acids that is more effective in increasing tissue n-3 PUFA concentrations than the current ALA-containing vegetable oils. Nevertheless, few SA sources occur in nature, although there are still a large number of species untested to date. SA has been detected in variable amounts in several species of algae, fungi and animals tissues, but the seeds of some plant families seem to be better sources of SA, especially Echium (Boraginaceae) species. This work reviews the nutritional significance, medical uses and natural occurrence of SA.