FADS1 & FADS2
The genes that determine your ability to convert essential fatty acids.
Omega-6 and FADS1/FADS2 genotyping: why your ability to convert linoleic acid is not universal.
Each major family of fatty acids begins with an essential fatty acid that the human body cannot manufacture and must obtain from the diet. For omega-6, this is linoleic acid. For omega-3, it is alpha-linolenic acid. These two fatty acids were once collectively called vitamin F.
From these starting points, the body produces, through a series of alternating enzymatic transformations, increasingly complex and active molecules. The sequence is: desaturase, elongase, desaturase, elongase, desaturase. Omega-3 and omega-6 share exactly the same enzymes, FADS2 (delta-6 desaturase) and FADS1 (delta-5 desaturase). This competition for the same enzymatic tools explains why the dietary omega-6/omega-3 ratio has direct consequences on the composition of our cells.
The FADS1 and FADS2 genes exist in different versions called polymorphisms. Depending on the inherited version, the enzymes work more or less efficiently. Around one third of the population is thought to be strongly homozygous on both genes: their enzymes quickly convert linoleic acid all the way to arachidonic acid. For these people, an excess of dietary omega-6 can fuel inflammatory processes. The usual warning fully applies to them.
For everyone else, demonising all omega-6 is a mistake. Cutting out linoleic acid also means cutting out GLA and DGLA, the beneficial links of the chain, which are virtually impossible to obtain through other dietary routes. GLA plays a recognised role in premenstrual syndrome, skin health and inflammation regulation. DGLA produces anti-inflammatory series-1 prostaglandins.
A genetically poor converter will not benefit more from plant-based omega-3 either, because the same impaired enzymes also handle that conversion. This profile needs EPA and DHA directly in their preformed state, from fish oil or microalgae.
There is no universal omega-6 protocol. Only FADS1/FADS2 genotyping combined with an erythrocyte fatty acid panel allows for a personalised approach. Talk to your therapist.
Scientific references: Chilton FH et al. Frontiers in Nutrition 2021 https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2021.808054/full Batista LD et al. Metabolites 2025 https://pmc.ncbi.nlm.nih.gov/articles/PMC12735183/ Martinelli N et al. Am J Clin Nutr 2008 https://pubmed.ncbi.nlm.nih.gov/18842780/ Molto-Puigmarti C et al. J Nutr 2010 https://pubmed.ncbi.nlm.nih.gov/18936223/ OCL Journal 2021 https://www.ocl-journal.org/articles/ocl/full_html/2021/01/ocl210018/ocl210018.html