Background. This is the second of two review parts aiming at describing the major physiological roles of fatty acids, as well as their applications in specific conditions related to human health.Results. The review included the current literature published in Pubmed up to March 2011. In humans, fatty acids are a principle energy substrate and structural components of cell membranes (phospholipids) and second messengers. Fatty acids are also ligands of nuclear receptors affecting gene expression. Longer-chain (LC) polyunsaturated fatty acids (PUFA), including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid are precursors of lipid mediators such as eicosanoids (prostaglandins, leukotrienes, thromboxanes), resolvins and neuroprotectins. Lipid mediators produced by EPA and DHA (LC n-3 PUFA; mainly found in oily fish) are considered as inflammation-resolving, and thus, fish oil has been characterised as antiinflammatory. Recommendations for EPA plus DHA intake from oily fish vary between 250-450 mg/day. Dietary reference values for fat vary between nutrition bodies, but mainly agree on a low total and saturated fat intake. The existing literature supports the protective effects of LC n-3 PUFA (as opposed to n-6 PUFA and saturated fat) in maternal and offspring health, cardiovascular health, insulin sensitivity, the metabolic syndrome, cancer, critically ill patients, and immune system disorders.Conclusion. Fatty acids are involved in multiple pathways and play a major role in health. Further investigation and a nutrigenomics approach to the effects of these biocompounds on health and disease development are imperative and highlight the importance of environmental modifications on disease outcome.humans. Thus, these FA may be characterised as conditionally essential depending on EFA availability. Genetic variation in human desaturase genes affects FA metabolism, plasma lipid profiles, and risk of disease development [5][6][7] . Recommendations for minimum dietary intake of EPA plus DHA vary between 250-450 mg/day 8 , especially for pregnant women and those of reproductive age. Rich sources of LC n-3 PUFA are fish oils and the flesh of oily fish, whereas non-oily (white) fish contain them but in lower amounts.Long-chain PUFA with 18-20 carbon atoms, including EPA and AA, are precursors of eicosanoids (prostaglandins, leucotrienes and thromboxanes), which have a broad scale of regulatory, autocrine and paracrine effects. Long-chain PUFA with 20 and 22 carbon atoms are precursors of autacoids -resolvins (resolution phase interaction products), lipoxins and neuroprotectins 9 . FA are also ligands of nuclear receptors which take part in the subcellular control of metabolic pathways. Covalent modification of proteins by FA acylation enables their incorporation into membranes. Hydroxy FA are activators of some nuclear factors and are responsible for the expression of proinflammatory cytokines (interleukin (IL)-1,
