ALDH2 rs671: Understanding the Alcohol Flushing Variant
The ALDH2 rs671 variant is a common genetic change that significantly reduces the activity of the ALDH2 enzyme, which is responsible for breaking down toxic acetaldehyde. This variant is strongly associated with alcohol-induced facial flushing and altered alcohol consumption behaviors.
What each genotype means
Normal enzyme activity
This genotype represents the fully functional version of the ALDH2 enzyme, which efficiently breaks down acetaldehyde, a toxic byproduct of alcohol metabolism. Individuals with this genotype typically do not experience alcohol-induced facial flushing or rapid heart rate associated with acetaldehyde accumulation. Please discuss any concerns regarding alcohol metabolism or medication responses with your clinician or pharmacist.
This is the most common genotype globally, though it is less frequent in East Asian populations where the A allele is prevalent.
Reduced enzyme activity
This genotype, often referred to as ALDH2*1/*2, results in significantly reduced ALDH2 enzyme activity, typically less than 20% of normal levels. You may experience facial flushing, nausea, or increased heart rate after consuming alcohol due to the slower clearance of acetaldehyde. Please discuss your alcohol sensitivity and any potential impacts on medication metabolism with your clinician or pharmacist.
This genotype is common in East Asian populations, where it is carried by a significant portion of the population, but it is rare in individuals of European ancestry.
Deficient enzyme activity
This genotype, often referred to as ALDH2*2/*2, results in a near-total loss of ALDH2 enzyme activity, leading to a severely diminished ability to detoxify acetaldehyde. Individuals with this genotype are highly likely to experience intense physical reactions to alcohol, such as flushing and tachycardia, and may have an increased risk for certain alcohol-associated cancers. Please discuss your metabolic profile and any necessary health precautions with your clinician or pharmacist.
This genotype is found in approximately 3% of East Asian populations and is extremely rare in other global populations.
What is the rs671 Variant?
The rs671 variant is a single-nucleotide polymorphism (SNP) located within the ALDH2 gene. Specifically, it involves a G to A nucleotide substitution that results in a change from glutamic acid to lysine at position 504 of the ALDH2 protein, often referred to as the E504K mutation. This change is a dominant-negative substitution, meaning that even a single copy of the variant allele can interfere with the function of the normal enzyme. Because the ALDH2 enzyme functions as a tetramer, the presence of the variant protein can disrupt the formation of a fully active enzyme complex, leading to a substantial loss of enzymatic activity. This variant is widely studied in pharmacogenomics because it fundamentally alters how the body metabolizes ethanol and other aldehydes.
The Role of the ALDH2 Gene
The ALDH2 gene provides instructions for making the aldehyde dehydrogenase 2 enzyme, which is primarily found in the mitochondria of cells throughout the body, including the liver. This enzyme plays a critical role in the second step of alcohol metabolism. When you consume alcohol, it is first converted into acetaldehyde, a toxic substance that can cause cellular damage. ALDH2 is responsible for rapidly converting this acetaldehyde into acetate, a harmless substance that the body can easily process. Beyond alcohol metabolism, ALDH2 also helps detoxify other aldehydes produced by oxidative stress within the body. When ALDH2 activity is impaired, acetaldehyde accumulates in the bloodstream, leading to the physiological symptoms often associated with the rs671 variant, such as facial flushing, nausea, and rapid heart rate.
Research Associations and Evidence
Research has consistently linked the rs671 variant to a range of physiological and behavioral traits. The most well-documented association is the 'alcohol flushing response,' where individuals experience redness of the face, neck, and chest after consuming even small amounts of alcohol. Because of the discomfort caused by acetaldehyde accumulation, carriers of the A allele often report lower habitual alcohol consumption. Beyond behavioral traits, the variant has been investigated for its role in cardiovascular health and other metabolic conditions. Some studies suggest that reduced ALDH2 activity may be linked to an increased risk of certain cardiovascular issues, though the evidence remains complex and is often influenced by lifestyle factors. It is important to note that while these associations are statistically significant in large population studies, they do not predict individual health outcomes with certainty.
Population Frequency
The frequency of the rs671 variant varies dramatically across different global populations. It is highly prevalent in East Asian populations, including Chinese, Japanese, and Korean groups, where the A allele frequency is estimated to be between 30% and 50%. In contrast, the A allele is rare in populations of European or African ancestry, typically appearing at a frequency of less than 5%. This distribution makes rs671 a classic example of an ancestry-specific genetic variant. Because of this high prevalence in East Asia, much of the research regarding the physiological impacts of ALDH2 deficiency has been conducted within these specific cohorts. Understanding these frequency differences is essential for interpreting genetic data in a global context and highlights the importance of diversity in genomic research.
What You Can Do With This Information
Knowing your genotype for rs671 can provide insight into how your body processes alcohol and why you might experience certain physical reactions after drinking. However, this information should not be used to diagnose any medical condition or to make definitive health decisions. If you are concerned about how your genetics might influence your response to alcohol or specific medications, the most appropriate step is to consult with a healthcare professional or a pharmacist. They can provide personalized guidance based on your full medical history and current health status. Never use genetic information to self-prescribe or alter your lifestyle without professional medical advice. Genetic testing results are just one piece of a much larger puzzle that includes your environment, diet, and overall health.
How common is this variant?
The A allele is rare (<0.1%) globally outside East Asia, where the frequency of the variant reaches 30-50%.
Frequently asked questions
Does the rs671 variant mean I am allergic to alcohol?
No, the rs671 variant is not an allergy. It is a genetic difference that impairs your body's ability to break down acetaldehyde, a toxic byproduct of alcohol metabolism, leading to physical symptoms like flushing.
Can I change my ALDH2 activity level?
Currently, there is no medically approved way to change your genetic ALDH2 activity level. The best approach for those with the variant is to be aware of their sensitivity to alcohol and manage their intake accordingly.
Is the rs671 variant linked to cancer risk?
Some research suggests that the accumulation of acetaldehyde in individuals with reduced ALDH2 activity may be associated with an increased risk of certain cancers, particularly esophageal cancer, when combined with heavy alcohol consumption. You should discuss your specific risk factors with a doctor.
Should I get tested for the ALDH2 rs671 variant?
Genetic testing for rs671 is generally not required for routine medical care. If you are curious about your genotype, you may choose to do so, but you should discuss the results with a healthcare provider to understand what they mean for your health.
Sources & further reading
Educational information only, last refreshed 10/26/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Regulatory upstream polymorphism in linkage disequilibrium with the classic ALDH2*2 allele modulating alcohol-induced facial flushing and peak acetaldehyde accumulation.
A missense variant (Glu504Lys) in ALDH2 that results in a loss of enzymatic activity, leading to the accumulation of acetaldehyde and the characteristic alcohol flushing response.