rs671
Alcohol flush reaction
What this position does
Alcohol becomes acetaldehyde, which ALDH2 then clears. One change disables the enzyme so completely that a single working copy is not enough, and acetaldehyde builds up: flushing, nausea, racing heart.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version GG | No flush reaction expected Two working copies. Acetaldehyde is cleared normally. |
| One copy AG | Flush reaction expected One disabled copy is enough, because the enzyme works as a group of four subunits and one bad subunit spoils the whole assembly. Acetaldehyde is a recognised carcinogen, and people with this genotype who drink have a substantially raised risk of oesophageal cancer. |
| Two copies AA | Strong flush reaction expected Two disabled copies. Almost no acetaldehyde clearance. Most people with this genotype find alcohol genuinely unpleasant and drink very little. |
Worth knowing. This variant is common in East Asia and rare elsewhere. If your file has no call here, that is the expected result for most non-East-Asian ancestries.
How common each version is
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 0.2% | |
| American | 0.3% | |
| East Asian | 17.4% | |
| European | 0.0% | |
| South Asian | 0.0% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
How many people carry each result
| Ancestry group | GG | AG | AA |
|---|---|---|---|
| African | 659 / 661 | 2 / 661 | 0 / 661 |
| European | 503 / 503 | 0 / 503 | 0 / 503 |
| East Asian | 349 / 504 | 135 / 504 | 20 / 504 |
| South Asian | 489 / 489 | 0 / 489 | 0 / 489 |
| American | 345 / 347 | 2 / 347 | 0 / 347 |
Counts of people, not modelled frequencies: every one of the 2,504 individuals sequenced by the 1000 Genomes Project phase 3, tallied by the genotype they carry. Deriving these from allele frequencies instead would assume random mating inside each group and undercount the homozygotes.
How to find out which you have
If you have taken a test with 23andMe, AncestryDNA, MyHeritage, Family Tree DNA, TellMeGen or Living DNA, this position is very likely already in the raw data file they gave you. You do not need another test.
One thing to watch if you look it up by hand: testing companies report some positions from one DNA strand and some from the other, and the file does not say which. Read the letters as they appear and you will get the opposite of the truth for some positions. Sequencings resolves that automatically.
Source
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Trait.
Where this fits
Common questions
What is rs671?
rs671 is a position in the ALDH2 gene on chromosome 12. Alcohol becomes acetaldehyde, which ALDH2 then clears. One change disables the enzyme so completely that a single working copy is not enough, and acetaldehyde builds up: flushing, nausea, racing heart.
What does it mean if I have AA at rs671?
Strong flush reaction expected. Two disabled copies. Almost no acetaldehyde clearance. Most people with this genotype find alcohol genuinely unpleasant and drink very little.
What does it mean if I have GG at rs671?
No flush reaction expected. Two working copies. Acetaldehyde is cleared normally.
How do I find out my rs671 genotype?
If you have taken a home DNA test, this position is very likely in the raw data file you were given. Sequencings reads that file in your browser without uploading it, and resolves which DNA strand each position was reported from, which is the step most manual lookups get wrong.
This is reference information, not medical advice, and not a diagnosis. See the medical disclaimer. Category: Trait.