Essential fatty acids, or EFAs, are fatty acids that cannot be constructed within an organism from other components (generally all references are to humans) by any known chemical pathways; and therefore must be obtained from the diet. The term refers to those involved in biological processes, and not fatty acids which may just play a role as fuel. As many of the compounds created from essential fatty acids can be taken directly in the diet, it is possible that the amounts required in the diet (if any) are overestimated. It is also possible they can be underestimated as organisms can still survive in non-ideal, malnourished conditions.
There are two families of EFAs: ω-3 (or omega-3 or n−3) and ω-6 (omega-6 or n−6). Fats from each of these families are essential, as the body can convert one omega-3 to another omega-3, for example, but cannot create an omega-3 from scratch. They were originally designated as Vitamin F when they were discovered as essential nutrients in 1923. In 1930, work by Burr, Burr and Miller showed that they are better classified with the fats than with the vitamins.
The biological effects of the ω-3 and ω-6 fatty acids are mediated by their mutual interactions. In the body, essential fatty acids serve multiple functions. In each of these, the balance between dietary ω-3 and ω-6 strongly affects function.
They are modified to make:
The classic eicosanoids (affecting inflammation and many other cellular functions).
The endocannabinoids (affecting mood, behavior and inflammation).
The lipoxins from ω-6 EFAs and resolvins from ω-3 (in the presence of aspirin, downregulating inflammation).
The isofurans, neurofurans, isoprostanes, hepoxilins, epoxyeicosatrienoic acids (EETs) and Neuroprotectin D.
They form lipid rafts (affecting cellular signaling).
They act on DNA (activating or inhibiting transcription factors such as NFκB, which is linked to pro-inflammatory cytokine production).
Essential fatty acids play a part in many metabolic processes, and there is evidence to suggest that low levels of essential fatty acids, or the wrong balance of types among the essential fatty acids, may be a factor in a number of illnesses.
References
Burr, G.O., Burr, M.M. and Miller, E. (1930). “On the nature and role of the fatty acids essential in nutrition” (PDF). J. Biol. Chem. 86 (587). View Abstract.
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Skin changes in essential fatty acid deficiency in mice. Nutr.Rev. 1969;27(3):85-88. View Abstract
Is essential fatty acid deficiency part of the syndrome of abetalipoproteinemia? Nutr.Rev. 1980;38(7):244-246. View Abstract
Development of essential fatty acid deficiency in the premature infant given fat-free TPN. Nutr.Rev. 1985;43(1):14-15. View Abstract
ISSFAL Board Statement: recommendations for the essential fatty acid requirement for infant formulas. International Society for the Study of Fatty Acids and Lipids. J.Am.Coll.Nutr. 1995;14(2):213-214. View Abstract
Abdel-Ghaffar, Y. T., Amin, E., Abdel-Rasheed, M., and Fouad, H. H. Essential fatty acid status in infants and children with chronic liver disease. East Mediterr.Health J. 2003;9(1-2):61-69. View Abstract
Abushufa, R., Reed, P., Weinkove, C., Wales, S., and Shaffer, J. Essential fatty acid status in patients on long-term home parenteral nutrition. JPEN J.Parenter.Enteral Nutr. 1995;19(4):286-290. View Abstract
