What you carry at this position in your DNA and what research says about it.
Alcohol Tolerance and Flushing: 10/10 evidence, 44 publications.
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Sample genotype (not yours): G/G
Typical Alcohol Tolerance with Higher Cardiovascular Risks
You possess the fully active version of the alcohol-clearing enzyme, allowing normal breakdown of acetaldehyde. However, this typical metabolic profile is linked to higher baseline risks for high blood pressure and gout.
What this genotype means: Typical alcohol tolerance; Higher baseline blood pressure; Increased risk of gout.
Sample genotype (not yours): A/A
Severe Alcohol Intolerance and Altered Drug Response
Carrying two copies of the variant results in a near-complete inability to break down acetaldehyde. This causes immediate, severe physical distress upon drinking alcohol, but offers strong protection against cardiovascular issues.
What this genotype means: Extreme alcohol intolerance; Inability to use nitroglycerin effectively; Lowest risk of high blood pressure and gout.
Sample genotype (not yours): G/A
Moderate Alcohol Flushing and Elevated Esophageal Risk
Carrying one copy of the variant significantly slows down your ability to clear toxic acetaldehyde after drinking. This leads to facial flushing, nausea, and a highly elevated risk of esophageal cancer if alcohol is consumed.
What this genotype means: Facial flushing and nausea from alcohol; Highly elevated esophageal cancer risk if drinking; Lower risk of high blood pressure.
Gene function and biological role
Gene Function: The ALDH2 gene encodes mitochondrial aldehyde dehydrogenase, a critical liver enzyme responsible for breaking down acetaldehyde into acetate [1]. Acetaldehyde is a highly toxic byproduct of alcohol metabolism and a known carcinogen [2]. When this enzyme is fully functional, it rapidly clears acetaldehyde to prevent cellular damage and toxicity [1]. However, specific genetic variations can severely compromise the enzyme's structural integrity, leading to a dramatic loss of its clearance capacity [3]. This gene also plays a vital role in metabolizing other aldehydes and activating certain cardiovascular medications like nitroglycerin [4].
Variant Impact: The rs671 variant, often called the ALDH2*2 allele, is a missense mutation that changes the amino acid glutamate to lysine at position 504 of the protein [3]. This single structural change acts in a dominant-negative manner, meaning even a single copy of the variant allele drastically reduces the overall enzyme activity [5]. Individuals with one copy of the variant retain only a fraction of normal enzyme function, while those with two copies have virtually no active enzyme [5] [6]. Consequently, toxic acetaldehyde accumulates rapidly in the body after alcohol consumption, triggering an intense physical reaction [2]. This variant is highly prevalent in East Asian populations but remains exceptionally rare in other ancestries [7].
Read on the Alcohol Flush page
Key Insight: A single copy of this variant reduces alcohol-clearing enzyme activity by up to 60 percent, while carrying two copies reduces it by over 99 percent, making even tiny amounts of alcohol highly toxic.
Location: ALDH2. Chromosome 12 · 12q24.12 · 111.8 Mb
Origin Story: This variant is estimated to have originated among Han Chinese populations thousands of years ago, potentially spreading due to agricultural changes or protection against certain infectious pathogens.
Estimated prevalence by population
Global 98.5%; European 100.0%; African > 99.9%; East Asian 60.1%; South Asian 99.8%; Americas 99.8%; Ashkenazi 100.0%; Middle Eastern 100.0%; Amish 100.0%.
Estimated GG genotype frequency.
Global 1.3%; European 0.0%; African < 0.1%; East Asian 34.9%; South Asian 0.2%; Americas 0.2%; Ashkenazi 0.0%; Middle Eastern 0.0%; Amish 0.0%.
Estimated GA genotype frequency.
Global 0.2%; European 0.0%; African < 0.1%; East Asian 5.1%; South Asian < 0.1%; Americas < 0.1%; Ashkenazi 0.0%; Middle Eastern 0.0%; Amish 0.0%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Nutrition & Metabolism
Alcohol Metabolism
Alcohol Flush Reaction. Evidence: 6/10. Source: PMID 19698717. Typical Tolerance.
Cancer & Oncology
Gastrointestinal Cancers
Esophageal Cancer. Evidence: 6/10. Source: PMID 19698717. Typical Risk.
Pharmacogenomics
Cardiovascular Drug Response
Nitroglycerin Response. Evidence: 8/10. Source: PMID 31250045. Normal Response.
Cardiovascular & Metabolic
Gout & Uric Acid
Gout. Evidence: 10/10. Source: PMID 31289104. Higher Risk.
Hypertension
Hypertension. Evidence: 8/10. Source: PMID 32709000. ~1.3x Higher Risk.
Heart Rhythm & Conduction
Atrial Fibrillation. Evidence: 10/10. Source: PMID 40050429. ~1.26x Higher Risk.
Showing effects for A/A genotype
Alcohol Flush Reaction. Evidence: 6/10. Source: PMID 19698717. Extreme Intolerance.
Esophageal Cancer. Evidence: 6/10. Source: PMID 19698717. Highly Elevated Risk.
Nitroglycerin Response. Evidence: 8/10. Source: PMID 31250045. Poor Response.
Gout. Evidence: 10/10. Source: PMID 31289104. Lowest Risk.
Hypertension. Evidence: 8/10. Source: PMID 32709000. Lowest Risk.
Atrial Fibrillation. Evidence: 10/10. Source: PMID 40050429. Lowest Risk.
Showing effects for G/A genotype
Alcohol Flush Reaction. Evidence: 6/10. Source: PMID 19698717. Severe Flushing.
Esophageal Cancer. Evidence: 6/10. Source: PMID 19698717. ~1.67x Higher Risk.
Nitroglycerin Response. Evidence: 8/10. Source: PMID 31250045. Reduced Response.
Gout. Evidence: 10/10. Source: PMID 31289104. Lower Risk.
Hypertension. Evidence: 8/10. Source: PMID 32709000. Lower Risk.
Atrial Fibrillation. Evidence: 10/10. Source: PMID 40050429. Lower Risk.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Having two copies of the G allele means your liver produces fully functional ALDH2 enzymes to rapidly clear toxic acetaldehyde [1]. Because you do not experience the immediate, unpleasant flushing response, you are statistically more likely to consume alcohol regularly, which drives up certain behavioral risks [2]. This typical metabolic state is strongly associated with higher blood pressure and an increased risk of developing hypertension [3]. Furthermore, you have a higher baseline level of serum uric acid, which elevates your susceptibility to gout [4]. Your cardiovascular profile also shows a slightly higher risk for atrial fibrillation and ischemic stroke compared to variant carriers [5]. On the positive side, you respond normally to standard heart medications like nitroglycerin [6].
Typical alcohol tolerance; Higher baseline blood pressure; Increased risk of gout.
Sample genotype: AA (Homozygous)
Having two copies of the A allele means your body produces virtually no active ALDH2 enzyme [1]. Even minimal exposure to alcohol triggers immediate, severe toxicity, characterized by intense facial flushing, nausea, dizziness, and physical distress [2]. Because of this extreme intolerance, individuals with this genotype almost always avoid alcohol entirely, which virtually eliminates the risk of alcohol-related cancers [2]. This lifelong avoidance of alcohol contributes to significantly lower blood pressure and a highly reduced risk of hypertension [3]. You also have a much lower risk of developing gout due to lower serum uric acid levels [4]. However, you are classified as a poor responder to nitroglycerin, meaning this standard chest pain medication may not work effectively for you in a medical emergency [5].
Extreme alcohol intolerance; Inability to use nitroglycerin effectively; Lowest risk of high blood pressure and gout.
Sample genotype: GA (Heterozygous)
Inheriting one copy of the A allele reduces your ALDH2 enzyme activity by more than half due to a dominant-negative structural effect [1]. When you drink alcohol, toxic acetaldehyde builds up rapidly in your bloodstream, causing facial flushing, a rapid heart rate, and headaches [2]. If you regularly consume alcohol despite this flushing response, your risk of developing esophageal cancer rises dramatically [2]. However, because this physical discomfort naturally deters heavy drinking, carriers statistically have lower rates of alcohol use disorder [3]. This reduced alcohol intake also correlates with lower blood pressure and a decreased risk of gout [4]. Additionally, you may experience a significantly reduced response to nitroglycerin, a common emergency medication used for chest pain [5].
Facial flushing and nausea from alcohol; Highly elevated esophageal cancer risk if drinking; Lower risk of high blood pressure.
Variants with shared genetic architecture
rs4646776 · ALDH2 Gene · Chr 12 · Esophageal Cancer Risk
rs10733682 · LMX1B Gene · Chr 9 · Body Mass Index
rs10096633 · LPL Gene · Chr 8 · Triglycerides and Heart Health
Structural mutation in a major human aldehyde dehydrogenase gene results in loss of enzyme activity.
The aldehyde dehydrogenase ALDH2*2 allele exhibits dominance over ALDH2*1 in transduced HeLa cells.
Determination of genotypes of human aldehyde dehydrogenase ALDH2 locus.
A cross-population atlas of genetic associations for 220 human phenotypes.
Content updated August 2026.
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