Summary

Your FADS1 result determines how efficiently you convert plant-based omega-3 (ALA from flaxseed, chia, walnuts) into the forms your brain and cardiovascular system actually use (EPA and DHA) — CC carriers convert poorly and should get their omega-3 directly from fish oil or algae, not rely on plant sources alone.

Genotype spectrum

TT (High conversion)

You get meaningful EPA and DHA from plant omega-3 sources — flaxseed, chia, walnuts, hemp all contribute to your long-chain omega-3 pool. This is a genuine metabolic advantage, particularly if you prefer a plant-based diet.

TC/CT (Intermediate)

You have functional conversion capacity — plant omega-3 sources contribute meaningfully, though not as effectively as in TT carriers. You're in the metabolic middle ground, which gives you flexibility: plant sources help, but direct EPA/DHA sources give you a

CC (Low conversion)

Interventions have outsized impact for you. Direct EPA/DHA supplementation (fish oil or algae oil) bypasses your conversion bottleneck entirely.

Practical takeaway

For CC Carriers (Low Conversion — Direct EPA/DHA Required)

Your core strategy — go direct:
• Fatty fish 2-3x/week: Salmon, mackerel, sardines, herring, anchovies. Each serving provides 500-2000mg combined EPA+DHA. This is your primary dietary omega-3 source.
• Fish oil supplement: If you don't eat fish regularly, supplement with 1000-2000mg combined EPA+DHA daily. Look for supplements listing EPA and DHA individually (not just "fish oil" or "omega-3" on the label — ALA-containing supplements don't help you).
• If vegan/vegetarian: Algae-derived DHA+EPA oil is essential. This is not a lifestyle preference — it's compensating for a genetic limitation. Target 500-1000mg DHA + EPA daily from algae oil.

What NOT to rely on:
• Flaxseed, chia seeds, hemp seeds, walnuts — these contain ALA, which you can't convert efficiently. They're still nutritious foods (fibre, minerals), but they won't build your omega-3 status. Don't count them as omega-3 sources.
• "Omega-3 enriched" eggs or milk — these typically contain ALA, not EPA/DHA, unless specifically stated.

Monitoring:
• Omega-3 index blood test (measures EPA+DHA in red blood cell membranes) is the gold standard. Target: >8% (associated with lowest cardiovascular risk). Most unsupplemented CC carriers sit at 4-6%.
• Retest 3-4 months after starting supplementation (red blood cell turnover takes ~120 days).

What "working" looks like:
• Omega-3 index >8%
• Improved omega-6:omega-3 ratio (<4:1 ideal)
• Reduced inflammatory markers (hs-CRP) if previously elevated
• Potential improvements in joint comfort, skin quality, mood stability

Expected response window: Red blood cell omega-3 index takes 3-4 months to reflect dietary changes. Subjective anti-inflammatory benefits may be noticeable within 4-8 weeks.
For TC Carriers (Intermediate — Mixed Strategy)
• Both sources contribute for you. Fatty fish 2x/week PLUS regular plant omega-3 sources (flaxseed, walnuts) gives you a two-pronged approach.
• Fish oil supplement (500-1000mg EPA+DHA daily) provides reliable insurance, particularly during periods of high demand (intense training, recovery, cognitive stress).
• Plant omega-3 sources are genuinely useful for you — your co

Evidence detail

What This Gene Does

FADS1 encodes delta-5 desaturase, a rate-limiting enzyme in the pathway that converts shorter-chain fatty acids into longer-chain polyunsaturated fatty acids (PUFAs). Specifically, it catalyses the desaturation step that converts dihomo-gamma-linolenic acid (DGLA) to arachidonic acid (AA, omega-6) and eicosatetraenoic acid (ETA) to eicosapentaenoic acid (EPA, omega-3). Without efficient FADS1, the conversion pipeline from plant omega-3 (alpha-linolenic acid, ALA) to the bioactive forms (EPA and DHA) slows to a trickle.

This matters because EPA and DHA are the omega-3 fatty acids that actually do the heavy lifting — reducing inflammation, supporting neuronal membrane fluidity, protecting cardiovascular endothelium, and modulating immune signalling. ALA on its own does very little of this. If your FADS1 is inefficient, eating more flaxseed won't solve the problem. You need the end products directly.

Mechanism

The omega-3 conversion pathway works like this:

1. Alpha-linolenic acid (ALA) — the plant omega-3 from flaxseed, chia, walnuts — enters the conversion pipeline. ALA itself has minimal biological activity for the outcomes people care about (cardiovascular protection, anti-inflammation, brain function).

2. FADS2 (delta-6 desaturase) performs the first desaturation step: ALA → stearidonic acid (SDA). This is also rate-limiting but FADS1 has the larger effect on endpoint EPA/DHA levels.

3. Elongase extends the chain: SDA → eicosatetraenoic acid (ETA).

4. FADS1 (delta-5 desaturase) performs the critical desaturation: ETA → EPA (eicosapentaenoic acid). This is where rs174547 genotype matters most. CC carriers have reduced FADS1 enzyme activity due to lower transcriptional output from the FADS1 promoter.

5. EPA → DHA requires additional elongation and a final desaturation step (via Sprecher's shunt, involving beta-oxidation in peroxisomes). This step is also inefficient, adding another bottleneck.

Why conversion efficiency matters:

In healthy adults, even with fully functional FADS1 (TT genotype), only ~5-10% of ALA converts to EPA and <1% to DHA. CC carriers convert ~30-40% less efficiently than TT — meaning their conversion is closer to 3-6% for EPA and perhaps 0.5% for DHA. At these rates, you'd need to consume unrealistic quantities of flaxseed oil to achieve the EPA/DHA levels associated with cardiovascular protection.

Why direct supplementation bypasses this entirely:

Fish oil and algae oil contain pre-formed EPA and DHA. No conversion needed. The FADS1 bottleneck becomes irrelevant. This is why the practical recommendation for CC carriers is so clear-cut: stop trying to convert, go straight to the end products.

The omega-6 dimension:

FADS1 isn't selective — it desaturates both omega-3 and omega-6 precursors. TT carriers efficiently convert linoleic acid (omega-6, abundant in seed oils) to arachidonic acid (the primary pro-inflammatory omega-6). In a modern high-omega-6 diet, TT carriers may actually produce more inflammatory mediators. The omega-6:omega-3 ratio matters more for TT carriers than for CC carriers.

FADS1 Omega3

Summary

Genotype spectrum

Practical takeaway

Evidence detail

Sources (8)