Inflammation underlies many common conditions and diseases. Fatty acids can influence inflammation through a variety of mechanisms, including acting via cell surface and intracellular receptors/sensors that control inflammatory cell signalling and gene expression patterns. Some effects of fatty acids on inflammatory cells appear to be mediated by, or at least are associated with, changes in fatty acid composition of cell membranes.

Changes in these compositions can modify membrane fluidity, lipid raft formation, cell signalling leading to altered gene expression, and the pattern of lipid and peptide mediator production. Cells involved in the inflammatory response are typically rich in the n-6 fatty acid arachidonic acid, but the contents of arachidonic acid and of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can be altered through oral administration of EPA and DHA.

Eicosanoids produced from arachidonic acid have roles in inflammation. EPA also gives rise to eicosanoids and these may have differing properties from those of arachidonic acid-derived eicosanoids. EPA and DHA give rise to resolvins which are anti-inflammatory and inflammation resolving.

Thus, fatty acid exposure and the fatty acid composition of human inflammatory cells influences their function. As a result of their anti-inflammatory actions marine n-3 fatty acids have therapeutic efficacy in rheumatoid arthritis, although benefits in other inflammatory diseases and conditions have not been unequivocally demonstrated. The anti-inflammatory effects of marine n-3 fatty acids may contribute to their protective actions towards atherosclerosis, plaque rupture and cardiovascular mortality.
The therapeutic dose of n-3 fatty acids is not clear.