FADS1: are you a poor converter of plant omega-3s?
Flax and chia hand you ALA. Your body still has to convert it into the omega-3s that work, and this gene sets how well that goes.
The omega-3s your body actually uses are EPA and DHA. Flax, chia, walnuts: none of those hand you EPA or DHA. They give you ALA, and your body has to convert it into the active forms, which is the job FADS1 does. A common variant at rs174546 reduces that desaturase activity. Conversion of ALA into EPA and DHA is already inefficient in most people, so if your whole omega-3 plan is plants, preformed EPA and DHA is the more dependable way to actually hit your targets.
What FADS1 does
Slow converter? The simplest fix is to get EPA and DHA ready-made, from oily fish or a fish-oil or algae supplement. That skips the conversion step your genes are bad at entirely.
This matters most if you rarely eat fish. Without it, you're leaning on exactly the conversion your genotype drags its feet on.
Your variants, decoded
The T allele tracks with reduced FADS1 (delta-5 desaturase) activity, the step that builds longer-chain fats like arachidonic acid, EPA and DHA from shorter ones. The effect is clearest on arachidonic acid; the shift in EPA and DHA is real but smaller and varies between studies.
| CC | Typical desaturase activity. |
| CT | Somewhat lower activity. |
| TT | Lowest of the three. If your omega-3s come mostly from plant ALA, preformed EPA and DHA is the more dependable bet. |
We show genotypes on the forward strand and ignore letter order. Your own export may print the complementary letters. Same result either way.
What the research suggests
Your FADS1 rs174546 T allele tracks with lower delta-5 desaturase activity, so you build less long-chain omega-3 (EPA and DHA) from plant ALA than a CC converter. The effect is clearest on arachidonic acid, with the EPA/DHA shift real but smaller. Since ALA-to-EPA/DHA conversion is inefficient in people generally, taking EPA and DHA preformed is the dependable way to hit your targets.
PubMed 39021601 · Rabehl et al., Front Nutr 2024. In carriers of the rs174546 minor allele, blood arachidonic acid (n-6) was significantly lower, consistent with reduced FADS1 desaturase activity; the EPA and DHA (n-3) difference trended the same way but was not statistically significant in this 85-person cohort, so the conversion effect is real with a modest measured EPA/DHA magnitude.
Educational only, not medical advice. “General evidence” means the finding is real, but the benefit isn’t specific to your genotype.
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Questions
Does FADS1 mean flax oil won't work for me?
Flax gives you ALA, and FADS1 is what turns that into EPA and DHA. With a slow-conversion variant you wring less active omega-3 out of the same flax, so getting EPA and DHA preformed is the more dependable bet. Flax oil isn't useless. It just isn't your best omega-3 source.