ALDH2 (Aldehyde Dehydrogenase 2)

Overview

ALDH2 encodes an enzyme that converts toxic acetaldehyde (from alcohol) into harmless acetic acid. The Glu504Lys variant (*2 allele) results in severely reduced enzyme activity and causes the “Asian Flush” syndrome.

📍 Chromosomal Position

12q24.12 (Chromosome 12)

🧬 Gene Category

Detoxification

🔬 Inheritance

Autosomal dominant (Flush)

📊 Prevalence

~40% in East Asia, rare in Europe

Function & Significance

ALDH2 is the second step in alcohol metabolism:

Alcohol → Acetaldehyde (by ADH enzymes)
Acetaldehyde → Acetic Acid (by ALDH2) ⚠️
Acetic Acid → CO₂ + H₂O (harmless)

⚠️ Acetaldehyde is highly toxic!

Acetaldehyde is:

Carcinogenic: Group 1 carcinogen (IARC)
DNA-damaging: Causes mutations
Toxic: 10-30x more toxic than alcohol
Responsible for Hangovers: Headaches, nausea

In cases of defective ALDH2, acetaldehyde accumulates in the body!

🧬 Relevant SNPs

The Glu504Lys variant (rs671):

rs671
12:111803962

Allele 1

Allele 2

Significance: Glu504Lys (ALDH2*2)

• GG (*1/*1): Normal ALDH2 activity, normal alcohol metabolism

• GA (*1/*2): Reduced activity (~6%), Asian Flush, increased cancer risk

• AA (*2/*2): No activity, severe flush, very high cancer risk

🚨 Asian Flush – Symptoms

Upon alcohol consumption with the *2 allele (GA or AA):

Facial Flushing: Within minutes
Tachycardia: Increased heart rate
Nausea: Strong discomfort
Headaches: Immediately after alcohol
Lower Blood Pressure: Dizziness

Cause: Acetaldehyde accumulation (up to 20x higher than normal!)

☠️ EXTREMELY HIGH CANCER RISK!

ALDH2*2 carriers who still drink alcohol:

Esophageal Carcinoma: 10-100 fold increased risk!
Head and Neck Tumors: Severely increased risk
Stomach Cancer: Increased risk
Liver Cancer: Increased risk

URGENT: *2 carriers should NOT drink alcohol! Even small amounts are dangerous.

✅ Positive Aspect

ALDH2*2 as natural protection:

Lower Alcoholism Rate: Unpleasant symptoms protect against addiction
Warning Signal: The body immediately shows that alcohol is harmful
Healthier Lifestyle: Many *2 carriers avoid alcohol entirely

Recommendation: Use this genetic “advantage” and abstain from alcohol!

📚 Data Sources

The information on this page is based on the following scientific sources:

OMIM: #100650 – Online Mendelian Inheritance in Man
dbSNP: rs671 – SNP Database (NCBI)
ClinVar: Clinical Variant Database (NCBI)
PubMed: ALDH2 and Cancer Risk
IARC: Acetaldehyde Carcinogenicity

Last Update: February 2026

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ALDH2