rs174547 — FADS1

Omega-3 fatty acid conversion efficiency - affects ability to make EPA/DHA from plant sources

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FADS1 — Your Omega-3 Conversion Ability

FADS1 (Fatty Acid Desaturase 1) encodes the delta-5 desaturase enzyme that converts short-chain omega-3 fatty acids11 ALA (alpha-linolenic acid) is the plant-derived omega-3 found in flax, chia, and walnuts into the longer-chain EPA and DHA22 EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the biologically active omega-3s essential for brain function and inflammation control that your brain and body actually use.

The Mechanism

The rs174547 variant sits in intron 9 of FADS1. The C allele (minor allele in most populations) is associated with lower delta-5 desaturase activity, meaning reduced ability to convert plant-derived ALA into the active EPA and DHA forms. Carriers of the C allele have higher levels of the omega-6 precursor linoleic acid and lower levels of arachidonic acid, EPA, and DHA.

Notably, the C allele frequency varies dramatically across populations — from just 6% in Africans to 46% in East Asians — reflecting different evolutionary pressures related to diet.

The Evidence

A landmark GWAS by Tanaka et al.33 landmark GWAS by Tanaka et al.
Tanaka et al. Genome-wide association study of plasma polyunsaturated fatty acids in the InCHIANTI Study. PLoS Genet, 2009 in 1,075 participants identified the FADS1 locus as the strongest genetic determinant of plasma PUFA levels, explaining 18.6% of variance in arachidonic acid levels.

A meta-analysis by Chen et al.44 meta-analysis by Chen et al.
Chen et al. Association between FADS1 rs174547 and levels of long-chain PUFA: a meta-analysis. Br J Nutr, 2021 confirmed that C allele carriers have significantly lower levels of long-chain PUFAs across multiple populations.

Why This Matters

Not everyone converts plant omega-3s efficiently. If you're a poor converter (CC genotype), eating flax seeds won't meaningfully raise your EPA/DHA levels. You need to get these directly from fish or supplements.

This is especially relevant for vegetarians and vegans55 Algae-based EPA/DHA supplements offer a plant-based alternative to fish oil for poor converters who rely on plant sources for omega-3s.

Interactions

FADS1 function interacts with dietary patterns. If you also carry TCF7L2 risk alleles (rs7903146), getting adequate omega-3s from direct sources (fish, supplements) becomes even more important for cardiovascular protection.

Nutrient Interactions

alpha-linolenic acid (ALA) impaired_conversion
EPA increased_need
DHA increased_need

Genotype Interpretations

What each possible genotype means for this variant.

TT Efficient Converter Normal

Normal omega-3 converter

You efficiently convert plant-based omega-3s (ALA from flax, chia, walnuts) into the active EPA and DHA forms your body uses. About 30% of Europeans share this genotype, though it is much more common (~88%) in people of African descent.

This means you can get meaningful omega-3 benefits from plant sources, though fish still provides the most efficient EPA/DHA.

CT Intermediate Converter Intermediate

Intermediate omega-3 converter

You have moderate efficiency at converting plant ALA to active EPA and DHA, shared by about 50% of Europeans. You'll benefit from both plant and direct marine omega-3 sources, but relying solely on plant sources may leave your EPA/DHA levels suboptimal.

CC Poor Converter Poor Converter

Poor omega-3 converter - need direct EPA/DHA

You have reduced ability to convert plant omega-3s (ALA) to the active EPA and DHA forms. About 20% of Europeans share this genotype, but it is much more common (~21%) in East Asians. Eating flax seeds or walnuts won't efficiently raise your omega-3 status.

You need to get EPA and DHA directly from fish or supplements.