Essential Fatty Acids

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them.^[1]

The term "essential fatty acid" refers to fatty acids required for biological processes, and not those that only act as fuel.

Only two EFAs are known for humans: alpha-linolenic acid (an omega-3 fatty acid) and 

linoleic acid (an omega-6 fatty acid).^[2][3][4]

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)^[7]
• They act on DNA (activating or inhibiting transcription factors such as NF-κB, which is linked to pro-inflammatorycytokine production)^[8]

Essential fatty acids play an important role in the life and death of cardiac cells.^{[14][15][16][17]}

Research suggests that high intakes of fish and omega-3 fatty acids are linked to decreased rates of major depression. Omega-3 fatty acids, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are important for enzymatic pathways required to metabolize long-chain polyunsaturated fatty acids (PUFAs). Low plasma concentrations of DHA predict low concentrations of cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA). It is found that low concentrations of 5-HIAA in the brain is associated with depression and suicide.^[19]

Other fatty acids that are only "conditionally essential" include gamma-linolenic acid (an omega-6 fatty acid), lauric acid (a saturated fatty acid), and palmitoleic acid (a monounsaturated fatty acid).^[5]

When the two EFAs were first discovered in 1923, they were designated Vitamin F. 

In 1930, work by Burr, Burr and Miller on rats showed that the two EFAs are better classified with the fats than with the vitamins.^[6]