What you carry at this position in your DNA and what research says about it.
Fatty Acid Metabolism: 8/10 evidence, 28 publications.
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Sample genotype (not yours): A/A
Enhanced Breastfeeding IQ Benefit and Higher LDL
This genotype is linked to a significant cognitive benefit from breastfeeding in infancy, but also correlates with higher baseline LDL cholesterol levels.
What this genotype means: Enhanced cognitive response to breastfeeding; Higher circulating LDL cholesterol; Slightly elevated asthma susceptibility.
Sample genotype (not yours): A/G
Enhanced Breastfeeding IQ Benefit and Balanced Lipids
This genotype retains the cognitive advantages associated with breastfeeding while maintaining intermediate metabolic and cholesterol profiles.
What this genotype means: Enhanced cognitive response to breastfeeding; Intermediate LDL cholesterol levels; Typical metabolic risk profile.
Sample genotype (not yours): G/G
Typical Breastfeeding IQ Benefit and Higher Metabolic Risk
This genotype shows a standard cognitive trajectory regardless of infant feeding method, alongside lower LDL cholesterol but higher metabolic syndrome risk.
What this genotype means: Standard cognitive response to feeding type; Lower circulating LDL cholesterol; Increased risk of metabolic syndrome.
Gene function and biological role
Gene Function: The FADS2 gene encodes delta-6 desaturase, a key rate-limiting enzyme responsible for converting dietary fatty acids into long-chain polyunsaturated fatty acids like DHA and arachidonic acid [1]. These fats are critical structural components of cell membranes, particularly in the brain and nervous system [2]. Because humans cannot synthesize these essential fats from scratch, the efficiency of this enzyme dictates how well the body processes plant-based precursors into active forms [3]. Genetic variations in this gene heavily influence circulating lipid levels and modify how the body responds to dietary fat intake [4].
Variant Impact: The rs1535 variant is an intron variant located within the FADS2 gene that influences the expression and efficiency of fatty acid desaturase enzymes. This genetic change alters the baseline levels of circulating polyunsaturated fatty acids and lipid metabolites in the bloodstream [5]. It is highly studied for its role in modifying how dietary fats, such as those found in breast milk or vegetable oils, impact cognitive development and metabolic health [1]. The major A allele is associated with higher levels of certain blood cholesterols, while the minor G allele shifts the lipid profile toward higher triglycerides and metabolic risk [6].
Key Insight: This variant acts as a genetic bridge between infant diet and cognitive development, determining whether breast milk provides a measurable boost in early childhood IQ.
Location: FADS2. Chromosome 11 · 11q12.2 · 61.8 Mb
Estimated prevalence by population
Global 49.0%; European 43.7%; African 71.8%; East Asian 19.9%; South Asian 67.0%; Americas 24.9%; Ashkenazi 51.1%; Finnish 33.6%; Middle Eastern 40.9%; Amish 59.1%.
Estimated AA genotype frequency.
Global 39.9%; European 44.8%; African 25.9%; East Asian 49.4%; South Asian 29.7%; Americas 50.0%; Ashkenazi 40.8%; Finnish 48.7%; Middle Eastern 46.1%; Amish 35.6%.
Estimated AG genotype frequency.
Global 11.1%; European 11.5%; African 2.3%; East Asian 30.6%; South Asian 3.3%; Americas 25.1%; Ashkenazi 8.1%; Finnish 17.7%; Middle Eastern 13.0%; Amish 5.3%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Neurology & Mental Health
Neurodevelopmental Traits
Breastfeeding and Cognition. Evidence: 4/10. Source: PMID 17984066. Enhanced Benefit.
Cardiovascular & Metabolic
Lipids & Cholesterol
LDL Cholesterol. Evidence: 8/10. Source: PMID 28334899. Increased Levels.
Metabolic Syndrome & Insulin Resistance
Metabolic Syndrome. Evidence: 8/10. Source: PMID 20694148. Typical Risk.
Organ Systems
Respiratory Health
Asthma. Evidence: 6/10. Source: PMID 32296059. ~1.1x Higher Risk.
Showing effects for A/G genotype
LDL Cholesterol. Evidence: 8/10. Source: PMID 28334899. Slightly Increased.
Metabolic Syndrome. Evidence: 8/10. Source: PMID 20694148. Slightly Increased.
Asthma. Evidence: 6/10. Source: PMID 32296059. ~1.05x Higher Risk.
Showing effects for G/G genotype
Breastfeeding and Cognition. Evidence: 4/10. Source: PMID 17984066. Typical Benefit.
LDL Cholesterol. Evidence: 8/10. Source: PMID 28334899. Typical Levels.
Metabolic Syndrome. Evidence: 8/10. Source: PMID 20694148. Increased Risk.
Asthma. Evidence: 6/10. Source: PMID 32296059. Typical Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Carrying two copies of the A allele is historically associated with a distinct cognitive advantage in children who were breastfed compared to those who were formula-fed [1]. This interaction suggests that the A allele allows for highly efficient processing of the long-chain polyunsaturated fatty acids naturally abundant in breast milk [2]. However, this efficient processing pathway also correlates with elevated levels of circulating LDL and total cholesterol in adulthood [3]. Additionally, genome-wide association studies have linked this genotype to a slightly increased risk of developing asthma [4] and colorectal cancer [5]. While metabolic syndrome risk remains typical, managing dietary saturated fats is often recommended to balance the cholesterol-elevating tendencies of this genetic profile.
Enhanced cognitive response to breastfeeding; Higher circulating LDL cholesterol; Slightly elevated asthma susceptibility.
Sample genotype: AG (Heterozygous)
Having one copy of each allele represents a balanced genetic middle ground for fatty acid metabolism. Children with this genotype show a clear positive association between breastfeeding and childhood intelligence scores, similar to those with the AA genotype [1]. This suggests that even a single A allele is sufficient to facilitate the beneficial processing of breast milk fatty acids [2]. In terms of cardiovascular health, this heterozygous state results in intermediate levels of LDL cholesterol and a moderate, typical risk profile for metabolic syndrome [3]. While there is a minor increase in asthma risk compared to the GG genotype, it is less pronounced than in AA homozygotes [4]. Overall, this profile represents a common, highly adaptable metabolic state.
Enhanced cognitive response to breastfeeding; Intermediate LDL cholesterol levels; Typical metabolic risk profile.
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele is associated with a metabolic profile that does not show an extra cognitive boost from breastfeeding [1]. Studies suggest that individuals with this genotype process dietary fatty acids differently, meaning their early cognitive development is less sensitive to the specific lipid composition of breast milk versus formula [2]. In adulthood, this metabolic pathway leads to lower circulating levels of LDL and total cholesterol [3]. However, this benefit is offset by a significantly higher risk of developing metabolic syndrome and elevated triglycerides [4]. Because this genotype alters how the body processes polyunsaturated fats, maintaining a diet rich in direct sources of omega-3 fatty acids may be beneficial for long-term metabolic health.
Standard cognitive response to feeding type; Lower circulating LDL cholesterol; Increased risk of metabolic syndrome.
Variants with shared genetic architecture
rs174570 · FADS2 Gene · Chr 11 · Fatty Acid Metabolism
rs174574 · FADS2 Gene · Chr 11 · Fatty Acid Metabolism
rs99780 · FADS2 Gene · Chr 11 · Omega-3 Metabolism
Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism.
Novel Common Genetic Susceptibility Loci for Colorectal Cancer.
Genome-Wide Association Study of the Metabolic Syndrome in UK Biobank.
Content updated August 2026.
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