Omega-3 fatty acids from fish and plants: same family different biological activity

Low intakes of the very long-chain n-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid are common in most individuals living in Western countries. Seafood, especially oily fish, is a natural source of these fatty acids, which are also found in fish oil capsules. Very long-chain n-3 fatty acids are readily incorporated into transport, functional and storage pools. This incorporation is dose-dependent and follows a kinetic pattern that is characteristic for each pool. Once they are incorporated at sufficiently high levels, eicosapentaenoic acid and docosahexaenoic acid influence the physical nature of cell membranes and membrane protein-mediated responses, lipid mediator generation, cell signalling, and gene expression in many different cell types. By acting through these mechanisms, eicosapentaenoic acid and docosahexaenoic acid influence cell and tissue physiology and the way cells and tissues respond to external signals. This appears to result in improvements in disease biomarker profiles or in health-related outcomes. Because of the recognized health improvements brought about by very long-chain n-3 fatty acids, it has been recommended to increase their intake. There is also a plant n-3 fatty acid, ?-linolenic acid. This can be converted to eicosapentaenoic acid, whereas conversion to docosahexaenoic acid appears to be poor in humans. The effects of ?-linolenic acid on human health appear to be due to its conversion to eicosapentaenoic acid. Since this is limited in humans, there may be little health benefit from moderately increased consumption of ?-linolenic acid as compared with increased intake of preformed eicosapentaenoic and docosahexaenoic acids.