What you carry at this position in your DNA and what research says about it.
Cholesterol and Gut Health: 8/10 evidence, 26 publications.
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Sample genotype (not yours): A/A
Typical Cholesterol and Lower Digestive Risks
Standard vitamin B12 levels and a lower risk of elevated cholesterol characterize this profile. It also correlates with a reduced likelihood of gallstones and peptic ulcers.
What this genotype means: Typical vitamin B12 levels; Lower risk of elevated cholesterol; Lower risk of gallstones.
Sample genotype (not yours): A/G
Typical Nutrient and Standard Health Risks
Typical vitamin B12 levels and average baseline risks for cholesterol and digestive issues are expected. It represents a common, intermediate genetic profile.
What this genotype means: Typical vitamin B12 levels; Standard cholesterol levels; Average risk of gallstones.
Sample genotype (not yours): G/G
Higher Vitamin B12 but Elevated Cholesterol Risk
Higher circulating vitamin B12 levels, particularly in women, are characteristic of this profile. However, it also increases the risk of elevated cholesterol, gallstones, and peptic ulcers.
What this genotype means: Higher circulating vitamin B12; Increased risk of high cholesterol; Higher risk of gallstones.
Gene function and biological role
Gene Function: The FUT2 gene encodes fucosyltransferase 2, an enzyme responsible for secreting ABO blood group antigens into bodily fluids like saliva and gastrointestinal mucus [1]. People who produce these soluble antigens are known as secretors, whereas those with inactive enzymes are non-secretors [1]. Secretor status plays a pivotal role in shaping the gut microbiome by providing fucose sugars that feed beneficial bacteria [2]. It also influences susceptibility to various pathogens, including norovirus and Helicobacter pylori [1]. Additionally, FUT2 activity is closely linked to the absorption and transport of essential nutrients like vitamin B12 [3].
Variant Impact: Identified as a single-nucleotide change in the FUT2 gene, rs492602 does not alter the encoded amino acid sequence but serves as a strong genetic marker for secretor status [1]. It is in tight linkage disequilibrium with functional nonsense mutations that deactivate the FUT2 enzyme [1]. The G allele is strongly associated with the non-secretor phenotype, which leads to a lack of blood group antigens in bodily secretions [1]. This molecular shift alters how the body interacts with gut microbes and absorbs nutrients, resulting in higher circulating vitamin B12 levels [3]. However, the same genetic change is also linked to elevated blood lipids and increased susceptibility to certain digestive conditions [4].
Key Insight: Although the G allele increases the risk for high cholesterol and gallstones, it actually boosts circulating vitamin B12 levels by altering how the gut absorbs nutrients.
Location: FUT2. Chromosome 19 · 19q13.33 · 48.7 Mb
Origin Story: The non-secretor phenotype of FUT2, strongly linked to the G allele of this variant, has been maintained in human populations due to natural selection. Non-secretors lack the specific sugar molecules on mucosal surfaces that many pathogens, such as noroviruses, use to attach and infect host cells, providing a survival advantage against major historical epidemics.
Estimated prevalence by population
Global 32.2%; European 27.3%; African 25.2%; East Asian 99.2%; South Asian 49.8%; Americas 39.9%; Ashkenazi 31.0%; Finnish 40.0%; Middle Eastern 21.1%; Amish 42.2%.
Estimated AA genotype frequency.
Global 47.3%; European 49.9%; African 50.0%; East Asian 0.8%; South Asian 41.5%; Americas 46.5%; Ashkenazi 49.4%; Finnish 46.5%; Middle Eastern 49.7%; Amish 45.5%.
Estimated AG genotype frequency.
Global 20.4%; European 22.8%; African 24.8%; East Asian < 0.1%; South Asian 8.7%; Americas 13.5%; Ashkenazi 19.6%; Finnish 13.5%; Middle Eastern 29.2%; Amish 12.3%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Nutrition & Metabolism
Vitamin & Mineral Metabolism
Vitamin B12 Levels. Evidence: 6/10. Source: PMID 18776911. Typical.
Cardiovascular & Metabolic
Lipids & Cholesterol
Total Cholesterol. Evidence: 8/10. Source: PMID 20686565. Typical.
Organ Systems
Digestive & Gut Disorders
Gallstones. Evidence: 8/10. Source: PMID 39789286. Typical.
Peptic Ulcer. Evidence: 6/10. Source: PMID 39024449. Typical.
Neurology & Mental Health
Addiction & Reward
Alcohol Use Disorder. Evidence: 7/10. Source: PMID 30336701. Typical.
Showing effects for A/G genotype
Total Cholesterol. Evidence: 8/10. Source: PMID 20686565. Slightly Higher.
Showing effects for G/G genotype
Vitamin B12 Levels. Evidence: 6/10. Source: PMID 18776911. Higher.
Total Cholesterol. Evidence: 8/10. Source: PMID 20686565. Higher.
Gallstones. Evidence: 8/10. Source: PMID 39789286. Increased Risk.
Peptic Ulcer. Evidence: 6/10. Source: PMID 39024449. Increased Risk.
Alcohol Use Disorder. Evidence: 7/10. Source: PMID 30336701. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Standard FUT2 enzyme activity is maintained with this genotype, supporting normal secretor status where blood group antigens are present in bodily secretions [1]. This active secretion helps maintain a balanced gut microbiome and typical nutrient absorption pathways [1]. Circulating vitamin B12 levels remain within the normal baseline range [2]. Crucially, this profile is associated with lower levels of total cholesterol, LDL cholesterol, and triglycerides compared to carriers of the G allele [3]. The risk of developing gallstones or peptic ulcer disease is also significantly lower [4]. Additionally, studies show a lower susceptibility to alcohol use disorder in those with this genetic makeup [5]. Overall, this combination represents a favorable baseline for cardiovascular and digestive health.
Typical vitamin B12 levels; Lower risk of elevated cholesterol; Lower risk of gallstones; Lower risk of peptic ulcers.
Sample genotype: AG (Heterozygous)
Possessing one copy of each allele typically results in intermediate FUT2 enzyme activity and standard secretor status [1]. Circulating vitamin B12 levels generally remain within the normal, healthy baseline range [2]. Blood lipid markers, including total cholesterol and LDL cholesterol, are typically close to population averages [3]. The risk of developing digestive conditions like gallstones or peptic ulcers is not significantly elevated [4]. Similarly, the likelihood of experiencing alcohol use disorder remains at the standard baseline [5]. Because this profile does not strongly lean toward extreme high or low risks, standard dietary and lifestyle guidelines are sufficient to maintain wellness. It represents a balanced genetic baseline across both metabolic and digestive traits.
Typical vitamin B12 levels; Standard cholesterol levels; Average risk of gallstones; Average risk of peptic ulcers.
Sample genotype: GG (Homozygous)
A strong association exists between this genotype and the non-secretor phenotype, which reduces FUT2 enzyme activity in mucosal linings [1]. This reduction is linked to significantly higher circulating levels of vitamin B12, especially in women, likely due to altered gut absorption dynamics [2]. However, this metabolic shift is accompanied by an increased risk of elevated total cholesterol, LDL cholesterol, and triglycerides [3]. There is also a higher statistical likelihood of developing gallstones and peptic ulcer disease [4]. Furthermore, genetic studies have connected this profile to an increased risk of alcohol use disorder [5]. While the boost in B12 levels is a positive biomarker, the overall profile warrants closer attention to cardiovascular and digestive health.
Higher circulating vitamin B12; Increased risk of high cholesterol; Higher risk of gallstones; Higher risk of peptic ulcers.
Variants with shared genetic architecture
rs516246 · FUT2 Gene · Chr 19 · Gut Health and Immunity
rs602662 · FUT2 Gene · Chr 19 · Vitamin B12 and Gut Health
rs1047781 · FUT2 Gene · Chr 19 · Norovirus and Gut Health
Common variants of FUT2 are associated with plasma vitamin B12 levels.
A large electronic-health-record-based genome-wide study of serum lipids.
A scalable variational inference approach for increased mixed-model association power.
Content updated August 2026.
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