[ Essential Fatty Acid, EFA ]
Fatty acids which must come from dietary sources because they are required for good health but cannot be synthesised by the organism in sufficient quantities.
Not be confused with essential oils, which are “essential” in the sense of being a concentrated essence.
Formally, only two fatty acids, alpha-linolenic acid (ALA) and linoleic acid (LA), are considered essential because all of the other required fatty acids can, in theory, be synthesised from these two. Nontheless, synthesis does not produce sufficient quantities to meet the minimum requirement for good nutrition.
It is also argued that all nutrients can only be properly understood when their interactive effects are taken into account. In the case of fatty acids, the ratio of omega-3 to omega-6 fatty acids is at least as important as the recommended consumption. Arguably, the typical modern diet contains toxic levels of LA (omega-6) and insufficient levels of omega-3 fatty acids (EPA and DHA).
Also see: Conditionally‑Essential Fatty Acids, Non‑Essential Fatty Acids.