Essential fatty acids (EFAs) are those fatty acids which are necessary for normal nutrition and which cannot be synthesized by the body from other substances. Linoleic (C:18:2 - an Omega-6 fatty acid) and linolenic (C180:3 - an Omega-3 fatty acid) are essential fatty acids; both are polyunsaturated and serve as precursors to prostaglandins, thromboxanes and leukotrienes (which are collectively known as eicosanoids), which produce a variety of physiological effects on blood aggregation, vasodilation and vasoconstriction.

Arachidonic acid (AA) is sometimes classified as essential but it can be synthesized from linoleic acid. An ethanolamide of AA is anandamide which has demonstrated analgesic qualities along with PAEA (Palmitylethanolamide), an aceylethanolamide found in neural and non-neural tissues which acts to inhibit mast-cell activation and reduces inflammatory responses by a mechanism that may involve binding to CB2 receptors (endogenous cannabinoids). Thus, PAEA manifests analgesic qualities outside the central nervous system, and has some part to play in the regulation of pain in cutaneous tissue. Interestingly, recent research finds support for the possibility that endogenous cannabinoids may participate in buffering emerging pain signals at sites of tissue injury along with PEA.

Omega-3 fatty acids, (the major EFAs in fish oils) such as eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA), are especially abundant in brain phospholipids and are essential for the development and function of brain and retina cells, as well as sperm formation. Omega-3's have a number of beneficial effects being promoted as antithrombotic, anti-inflammatory and acting as vasodilators. Omega-6 fatty acids such as linoleic, alpha linolenic and gamma-linolenic acid (GLA) are found more prevalent in plants (eg. Evening Primrose, Borage, phytoplankton, mosses and ferns wheat and walnuts). The Omega-6's are critically important in acting as prostaglandin precursors as well as for many other eicosanoids. GLA in particular, as precursor to prostaglandins, is critical to the working of the Sodium-Potassium Pump throughout the body, and GLA is also known to allow blood to be "slippery," preventing the type of clots prevalent in heart attacks. In cerebral grey matter, DHA is about 30% of the fatty acid in phosphatidylserine and ethanolamine.

Without sufficient quantities and varieties of EFA's, normal cerebral development can be retarded causing neurological deficiencies and difficulties including ADD/ADHD, MS, MD and other dysfunctions.It is estimated that adults need as much as 1%-2% of their daily caloric intake to be of Omega-6's, and 12%-14% for optimal health (40% of dietary fat). Optimal ratios have been suggested by researchers: Omega-3 to Omega-6 fatty acid ingestion should be in the ratio of 10:4. It is believed that higher ratios of Omega-6 to Omega-3 could lead to depletion of the latter in the phospholipid of vital organs as well as the following symptoms: Omega-6 deficiencies include growth retardation, sparse hair growth, a bran-like desquamation of the skin of the trunk, poor wound healing, and increased susceptibility to infection, especially in infants. In adults, Omega-6 deficiencies also include dry, flaky skin, scaling, eczematoid dermatosis, usually starting on the nasolabial folds and eyebrows and spreading across the face an neck; anemia and enlarged fatty liver also have been reported. Omega-3 deficiencies are more neurological in content including paresthesias, weakness, inability to walk, pain in the legs, blurred vision, and subtle neurological symptomology such as ADD/ADHD, minor depression, dyslexia, aphasia, etc. Omega-6 fatty acids are generally supplied in vegetable based oils, whereas Omega-3s are primarily found in fish oils. Other Omega-6 fatty acids include Palmitic (C16:0), Oleic (C18:1), Ecicosatrienoic Acid (C20:3).

Other fatty acids, although not listed as "essential" are nonetheless critical short chain fats such as Capric Acid, Caproic Acid (C6:0), Caprylic Acid, medium chain triglycerides (C8-C10), Lauric acid (C12:0), Myristic acid (C14:0), Palmitoleic acid (C16:1), Stearic acid (C18:1), Arachidic Acid, and Decosanoic Acid (C12:0).An additional function of EFAs has recently been found to associated with healthy skin. A unique form of linoleic acid becomes bound to ceramides in the skin, forming a unique esterified interstial lipid in man which renders the skin impermeable to water and retains moisture. EFAs play numerous vital roles as substrates for regulatory signals and as structural elements in cell membranes and other barriers in the body. Polyunsaturated fatty acids are also required in the esterification of plasma cholesterol, necessary for its uptake as low density lipoprotein core material (LDL) and the normal excretion of sterols and bile acids. Interestingly, it has been shown that without EFAs in the diet, cholesterol and levels and triglycerides generally rise. So essential are the EFAs that some are now speaking about them as a class of vitamins, known as "VItamin F."