What you carry at this position in your DNA and what research says about it.
Omega-3 Metabolism: 9/10 evidence, 17 publications.
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Sample genotype (not yours): C/C
Highly Efficient Omega-3 Synthesis
Highly active desaturase enzymes promote robust conversion of plant-based fats into active omega-3s. This is associated with higher HDL cholesterol and lower triglycerides.
What this genotype means: Highly efficient synthesis of DHA and EPA; Favorable HDL and triglyceride levels; Higher levels of essential fats in breast milk.
Sample genotype (not yours): C/T
Typical Omega-3 Synthesis
Intermediate desaturase enzyme activity results in typical conversion rates of dietary fats. Standard dietary intake of omega-3s is generally sufficient.
What this genotype means: Average conversion of plant-derived fats; Typical baseline blood lipid profile; Standard levels of omega-3s in breast milk.
Sample genotype (not yours): T/T
Reduced Omega-3 Synthesis
Lower desaturase enzyme activity limits the conversion of plant-based fats into active omega-3s. This is linked to higher triglycerides and lower HDL.
What this genotype means: Impaired synthesis of DHA and EPA from plant sources; Elevated triglycerides and lower HDL cholesterol; Reduced levels of essential fats in breast milk.
Gene function and biological role
Gene Function: The FADS2 gene encodes delta-6 desaturase, a critical rate-limiting enzyme in the pathway that converts short-chain plant-derived essential fatty acids into long-chain polyunsaturated fatty acids [1]. This enzyme is responsible for synthesizing crucial lipids like arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid [1]. These fatty acids serve as vital structural components of cell membranes, particularly in the brain and retina [1]. Variations in this gene directly influence how efficiently the body can synthesize these healthy fats from dietary precursors [1]. Consequently, FADS2 activity plays a central role in cardiovascular health, inflammatory responses, and infant neural development [1] [2].
Variant Impact: The rs99780 variant is an intron variant located within the FADS1-FADS2 gene cluster on chromosome 11. This genetic change acts as a major regulator of desaturase enzyme activity, altering the conversion rate of dietary fats [1]. The C allele is strongly linked to highly efficient enzyme function, leading to higher circulating levels of beneficial long-chain omega-3 fatty acids [3]. Conversely, the T allele reduces this conversion efficiency, resulting in lower levels of key polyunsaturated fats [1]. Because of this metabolic shift, the variant has widespread effects on blood lipid profiles and the fatty acid composition of tissues [1] [3].
Key Insight: This variant determines how well your body manufactures its own omega-3 and DHA fats from plant sources like flaxseed, meaning some people require far more pre-formed fish oil to achieve optimal levels.
Location: FADS2. Chromosome 11 · 11q12.2 · 61.8 Mb
Estimated prevalence by population
Global 38.8%; European 43.3%; African 36.9%; East Asian 19.9%; South Asian 66.8%; Americas 21.7%; Ashkenazi 48.7%; Finnish 33.5%; Middle Eastern 35.8%; Amish 54.9%.
Estimated CC genotype frequency.
Global 46.1%; European 45.0%; African 47.7%; East Asian 49.4%; South Asian 29.9%; Americas 49.8%; Ashkenazi 42.2%; Finnish 48.8%; Middle Eastern 48.1%; Amish 38.4%.
Estimated CT genotype frequency.
Global 15.2%; European 11.7%; African 15.4%; East Asian 30.7%; South Asian 3.3%; Americas 28.5%; Ashkenazi 9.1%; Finnish 17.7%; Middle Eastern 16.1%; Amish 6.7%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Nutrition & Metabolism
Macronutrient Metabolism
Omega-3 Fatty Acids. Evidence: 8/10. Source: PMID 34610981. Higher Levels.
Docosahexaenoic Acid. Evidence: 9/10. Source: PMID 34610981. Higher Levels.
Cardiovascular & Metabolic
Lipids & Cholesterol
Triglycerides. Evidence: 9/10. Source: PMID 32154731. Lower Levels.
HDL Cholesterol. Evidence: 8/10. Source: PMID 34610981. Higher Levels.
Endocrine & Reproductive
Female Reproductive Health & Fertility
Breast Milk DHA. Evidence: 3/10. Source: PMID 18936223. Higher Levels.
Showing effects for C/T genotype
Omega-3 Fatty Acids. Evidence: 8/10. Source: PMID 34610981. Typical Levels.
Docosahexaenoic Acid. Evidence: 9/10. Source: PMID 34610981. Typical Levels.
Triglycerides. Evidence: 9/10. Source: PMID 32154731. Typical Levels.
HDL Cholesterol. Evidence: 8/10. Source: PMID 34610981. Typical Levels.
Breast Milk DHA. Evidence: 3/10. Source: PMID 18936223. Typical Levels.
Showing effects for T/T genotype
Omega-3 Fatty Acids. Evidence: 8/10. Source: PMID 34610981. Lower Levels.
Docosahexaenoic Acid. Evidence: 9/10. Source: PMID 34610981. Lower Levels.
Triglycerides. Evidence: 9/10. Source: PMID 32154731. Higher Levels.
HDL Cholesterol. Evidence: 8/10. Source: PMID 34610981. Lower Levels.
Breast Milk DHA. Evidence: 3/10. Source: PMID 18936223. Lower Levels.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Efficient conversion of dietary plant oils into long-chain polyunsaturated fatty acids occurs naturally with this genetic profile [1]. Circulating levels of beneficial docosahexaenoic acid and overall omega-3 fatty acids are significantly elevated compared to other genotypes [2]. This metabolic efficiency helps maintain a favorable blood lipid profile, characterized by higher HDL cholesterol and lower triglycerides [2] [3]. During pregnancy and lactation, women with this genotype secrete higher concentrations of crucial fats like arachidonic acid and DHA into breast milk [1]. These lipids are vital for supporting infant brain development and visual acuity [1]. Consequently, relying on plant-derived alpha-linolenic acid from seeds and nuts is highly effective for meeting daily omega-3 requirements.
Highly efficient synthesis of DHA and EPA; Favorable HDL and triglyceride levels; Higher levels of essential fats in breast milk.
Sample genotype: CT (Heterozygous)
Standard metabolic processing of essential fatty acids is expected with this intermediate genetic profile [1]. The body converts plant-derived alpha-linolenic acid into active omega-3 forms at a moderate, typical rate [1]. Circulating levels of docosahexaenoic acid and eicosapentaenoic acid generally fall within the average population range [2]. Cardiovascular biomarkers, including HDL cholesterol and triglycerides, typically remain at baseline levels without genetic elevation or suppression [2] [3]. For mothers, the transfer of essential fatty acids to breast milk during lactation is average, providing standard support for infant development [1]. Maintaining a balanced diet with a mix of plant-based fats and direct marine sources of omega-3s supports optimal health.
Average conversion of plant-derived fats; Typical baseline blood lipid profile; Standard levels of omega-3s in breast milk.
Sample genotype: TT (Homozygous)
Reduced conversion of dietary plant-derived essential fatty acids into active long-chain polyunsaturated fatty acids is common with this genotype [1]. Circulating levels of beneficial docosahexaenoic acid and overall omega-3s are significantly lower [2]. This metabolic bottleneck is associated with a less favorable lipid profile, including higher triglycerides and lower HDL cholesterol [2] [3]. During pregnancy and lactation, women with this genotype have been shown to secrete lower levels of arachidonic acid and DHA into breast milk [1]. Because the internal synthesis of these vital fats is constrained, relying solely on plant-based precursors like flax or chia seeds may not yield sufficient active omega-3 levels [1]. Direct dietary intake of pre-formed DHA and EPA from marine sources or algae-based supplements is often highly beneficial.
Impaired synthesis of DHA and EPA from plant sources; Elevated triglycerides and lower HDL cholesterol; Reduced levels of essential fats in breast milk.
Variants with shared genetic architecture
rs174570 · FADS2 Gene · Chr 11 · Fatty Acid Metabolism
rs174574 · FADS2 Gene · Chr 11 · Fatty Acid Metabolism
rs1535 · FADS2 Gene · Chr 11 · Fatty Acid Metabolism
Polygenic Hyperlipidemias and Coronary Artery Disease Risk.
Content updated August 2026.
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