What you carry at this position in your DNA and what research says about it.
Fatty Acid Metabolism: 8/10 evidence, 16 publications.
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Sample genotype (not yours): C/C
Efficient Omega Synthesis but Higher Cholesterol
Your body is highly efficient at converting plant-based fats into active omega-3 and omega-6 fatty acids. However, this metabolic efficiency is linked to slightly higher LDL cholesterol and fasting glucose levels.
What this genotype means: Highly efficient synthesis of EPA and DHA from plant oils; Slightly higher circulating LDL cholesterol; Slightly higher fasting blood glucose levels.
Sample genotype (not yours): C/T
Typical Omega Synthesis and Lipid Balance
You possess a balanced metabolic profile with moderate efficiency in synthesizing active omega fatty acids. Your cholesterol and blood sugar levels tend to align with typical population averages.
What this genotype means: Moderate synthesis of EPA and DHA from plant precursors; Typical baseline LDL cholesterol levels; Typical fasting blood glucose levels.
Sample genotype (not yours): T/T
Lower Cholesterol but Poor Omega Conversion
Your body has a reduced ability to convert plant-based fats into active omega-3s, making direct dietary sources important. On the positive side, you naturally tend to have lower LDL cholesterol and fasting glucose.
What this genotype means: Inefficient synthesis of EPA and DHA from plant precursors; Slightly lower circulating LDL cholesterol; Slightly lower fasting blood glucose levels.
Gene function and biological role
Gene Function: The FADS1 gene encodes fatty acid desaturase 1, a key enzyme responsible for converting short-chain polyunsaturated fatty acids into biologically active long-chain fatty acids [1]. This enzyme regulates the rate-limiting steps in the synthesis of both omega-3 fatty acids, like eicosapentaenoic acid (EPA), and omega-6 fatty acids, like arachidonic acid (AA) [1] [2]. These lipids are critical components of cell membranes, particularly in the brain and cardiovascular system, and serve as precursors to signaling molecules that regulate inflammation [2]. Variations in this gene heavily influence how efficiently an individual can synthesize these essential fats from plant-based dietary precursors [1].
Variant Impact: The rs174556 variant is an intronic change in the FADS1 gene that strongly influences the expression and enzymatic activity of fatty acid desaturase 1 [1]. Carrying the major C allele is associated with highly efficient enzyme activity, leading to rapid conversion of plant-derived fats into long-chain omega-3 and omega-6 fatty acids [1] [3]. Conversely, the minor T allele reduces enzyme expression, resulting in a lower rate of conversion and lower circulating levels of active EPA and arachidonic acid [3] [4]. This single genetic letter change creates a distinct metabolic trade-off between lipid synthesis efficiency and circulating cholesterol levels [4].
Key Insight: This variant determines whether your body can efficiently convert plant-based omega-3s from flaxseed or chia into the active forms your brain needs, or if you must rely on direct marine sources like fish oil.
Location: FADS1. Chromosome 11 · 11q12.2 · 61.8 Mb
Estimated prevalence by population
Global 56.6%; European 49.5%; African 86.3%; East Asian 21.0%; South Asian 70.0%; Americas 29.1%; Ashkenazi 60.9%; Finnish 36.6%; Middle Eastern 45.8%; Amish 62.7%.
Estimated CC genotype frequency.
Global 34.7%; European 41.7%; African 13.2%; East Asian 49.6%; South Asian 27.3%; Americas 49.7%; Ashkenazi 34.3%; Finnish 47.8%; Middle Eastern 43.7%; Amish 33.0%.
Estimated CT genotype frequency.
Global 8.7%; European 8.8%; African 0.5%; East Asian 29.4%; South Asian 2.7%; Americas 21.3%; Ashkenazi 4.8%; Finnish 15.6%; Middle Eastern 10.4%; Amish 4.3%.
Estimated TT genotype frequency.
Showing effects for C/C genotype
Nutrition & Metabolism
Macronutrient Metabolism
Omega-3 EPA Levels. Evidence: 6/10. Source: PMID 24816252. Highly Efficient.
Arachidonic Acid Levels. Evidence: 4/10. Source: PMID 32682282. Elevated.
Cardiovascular & Metabolic
Lipids & Cholesterol
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Slightly Higher.
Diabetes & Glycemic Traits
Fasting Glucose. Evidence: 5/10. Source: PMID 34951656. Slightly Higher.
Showing effects for C/T genotype
Omega-3 EPA Levels. Evidence: 6/10. Source: PMID 24816252. Moderate Efficiency.
Arachidonic Acid Levels. Evidence: 4/10. Source: PMID 32682282. Typical.
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Typical.
Fasting Glucose. Evidence: 5/10. Source: PMID 34951656. Typical.
Showing effects for T/T genotype
Omega-3 EPA Levels. Evidence: 6/10. Source: PMID 24816252. Low Efficiency.
Arachidonic Acid Levels. Evidence: 4/10. Source: PMID 32682282. Reduced.
LDL Cholesterol. Evidence: 8/10. Source: PMID 39024449. Slightly Lower.
Fasting Glucose. Evidence: 5/10. Source: PMID 34951656. Slightly Lower.
What this genotype means for the people who carry it
Sample genotype: CC (Homozygous)
Inheriting two copies of the C allele ensures that your FADS1 enzyme operates at peak capacity. This allows your body to readily synthesize critical long-chain polyunsaturated fatty acids, such as EPA and arachidonic acid, from shorter plant-derived precursor oils [1] [2]. Because of this efficient conversion, you maintain robust baseline levels of these essential fats even on a vegetarian or vegan diet [1]. However, large-scale genetic studies show that this active metabolic state is also associated with slightly higher circulating LDL cholesterol [3]. Additionally, carriers of this genotype tend to exhibit slightly higher fasting glucose levels compared to those with the T/T genotype [4]. This represents a classic evolutionary trade-off between maximizing essential nutrient synthesis and maintaining lower metabolic biomarkers [1] [3].
Highly efficient synthesis of EPA and DHA from plant oils; Slightly higher circulating LDL cholesterol; Slightly higher fasting blood glucose levels.
Sample genotype: CT (Heterozygous)
Carrying one copy of each allele provides a balanced middle ground in fatty acid desaturase activity. Your body converts plant-based dietary fats into active long-chain omega-3 and omega-6 fatty acids with moderate efficiency [1] [2]. While you can synthesize some EPA and arachidonic acid internally, incorporating direct sources of these fats remains beneficial [1]. Your genetic predisposition for LDL cholesterol and fasting glucose levels is typical, falling between the higher levels of the C/C genotype and the lower levels of the T/T genotype [3] [4]. This intermediate status means you do not experience the extreme metabolic trade-offs associated with either homozygous genotype [1] [3].
Moderate synthesis of EPA and DHA from plant precursors; Typical baseline LDL cholesterol levels; Typical fasting blood glucose levels.
Sample genotype: TT (Homozygous)
Having two copies of the T allele significantly reduces the activity of your FADS1 enzyme. This limitation makes it difficult for your body to convert plant-derived alpha-linolenic acid into the active omega-3 fatty acid EPA [1] [2]. Consequently, relying solely on plant sources like flaxseed may leave you with low circulating omega-3 levels, meaning direct marine sources or supplements are highly beneficial [1]. Interestingly, this reduced enzymatic activity comes with a distinct metabolic advantage [3]. Large-scale cohort data link this genotype to naturally lower circulating LDL cholesterol levels [3]. Furthermore, you are genetically predisposed to lower fasting glucose levels [4]. This genotype represents a unique profile where cardiovascular biomarker benefits are paired with a higher dietary requirement for pre-formed omega-3 fatty acids [1] [3].
Inefficient synthesis of EPA and DHA from plant precursors; Slightly lower circulating LDL cholesterol; Slightly lower fasting blood glucose levels.
Variants with shared genetic architecture
rs174546 · FADS1 Gene · Chr 11 · Fatty Acid Metabolism
rs174554 · FADS1 Gene · Chr 11 · Omega Fat Conversion
rs174545 · FADS1 Gene · Chr 11 · Fatty Acid Metabolism
An atlas of genetic influences on human blood metabolites.
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Multi-ethnic GWAS and fine-mapping of glycaemic traits identify novel loci in the PAGE Study.
Content updated August 2026.
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