The conditional nature of the dietary need for polyunsaturates: a proposal to reclassify “essential fatty acids” as “conditionally indispensable” or “conditionally-despensable” fatty acids.
The conditional nature of the dietary need for polyunsaturates: a proposal to reclassify “essential fatty acids” as “conditionally indispensable” or “conditionally-despensable” fatty acids.
Year: 2000
Authors: S C Cunnane.
Publication Name: Brit J Nutr.
Publication Details: Volume 84; Page 803.
Abstract:
The aim of the present review article is two fold: first, to review the anomalies and inconsistencies surrounding the term “essential fatty acid” (EFA), and second, to suggest the reclassification of polyunsaturated fatty acids as either “conditionally-indispensable” or “conditionally-dispensable”. The author states that the term “EFA” has outlived its usefulness and no longer clearly identifies the fatty acids it was originally used to describe. Currently, the term EFA describes two related families of long-chain fatty acids, the n-6 and n-3 PUFAs which were discovered 70 years ago by Burr and Burr. Of these families, only the parent PUFAs are referred to as essential; linoleic acid (LA) of the n-6 family, and a-linolenic acid (ALA) of the n-3 family. Through a series of elongase and desaturase steps each of these parent PUFAs are converted into a number of important longer chain PUFAs that have commonly been referred to as “conditionally essential” or “non-essential” fatty acids. Examples include gamma-linolenic acid (GLA) and arachidonic acid (AA) from the n-6 family, and docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from the n-3 family. However, the author proposes that each long chain PUFAs from each family be analysed separately in terms of their metabolic and nutritional importance and be classified as either “conditionally-indispensable” or “conditionally-dispensable”. According to the author, the concept of “conditionally indispensable-dispensable” has been tested and accepted in the field of amino acids. The amino acid reclassification has helped clarify the changing nature of the dietary need for some amino acids and the unchanging dietary need for others. Overall, the author believes that a reclassification of PUFAs will not result in any one PUFA becoming less important than the other, rather, it will help acknowledge the complexity of the relationship between metabolism, changing nutritional requirements with age, and health implications of each individual PUFA.
