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 meta-analysis by Chen et al.33 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 vegans44 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.