ALDH2 rs671 Explained: Alcohol Flush and Drinking Risk

ALDH2 rs671 is one of the most important alcohol-related genetic variants in consumer DNA analysis. It affects how efficiently your body clears acetaldehyde, the toxic byproduct formed after alcohol is broken down [R]. When ALDH2 activity is reduced, acetaldehyde can build up more easily after drinking, which is why this SNP is strongly linked to alcohol flush, low alcohol tolerance, and a different risk profile than people with normal ALDH2 activity [R].

What ALDH2 rs671 actually does

Alcohol metabolism happens in steps. Alcohol is first converted into acetaldehyde, and then ALDH2 helps convert that acetaldehyde into acetate [R]. The key problem with ALDH2 rs671 is that the A allele is the low-activity form, which means acetaldehyde is cleared less efficiently [R]. Both AG and AA genotypes are associated with reduced enzyme activity, while GG is the typical higher-activity genotype [R].

Simple overview of possible genotypes:

• GG is typically linked to more normal ALDH2 activity

• AG is linked to reduced ALDH2 activity

• AA is linked to strongly reduced ALDH2 activity

That is why this variant gets so much attention. Unlike many popular SNPs, ALDH2 rs671 has a direct and biologically meaningful effect that many people can actually notice after drinking.

Why ALDH2 rs671 is linked to alcohol flush

The classic red-face reaction after alcohol is not just a cosmetic quirk. It reflects acetaldehyde accumulation [R]. Research on alcohol flushing in East Asian populations continues to identify ALDH2 rs671 as one of the main genetic drivers of this response [R]. People with reduced ALDH2 activity may experience facial flushing, nausea, palpitations, headache, or dizziness after drinking because acetaldehyde rises more quickly than their body can clear it [R].

This also helps explain why the same SNP is often discussed under names like Asian flush, alcohol flush, or alcohol intolerance. The biology behind those terms overlaps heavily with ALDH2 rs671.

What ALDH2 rs671 may mean for drinking risk

One of the most important points for readers is that feeling bad after alcohol does not mean you are protected if you keep drinking anyway [R]. The uncomfortable reaction is a warning sign of higher acetaldehyde exposure, not a sign that alcohol is somehow safer for you. Studies and reviews link ALDH2 rs671, especially in the context of alcohol intake, to higher risk for certain upper digestive tract cancers, including esophageal cancer in East Asian populations [R, R].

That makes this a very practical SNP to understand. The key message is not fear. It is that reduced ALDH2 activity changes alcohol handling in a meaningful way, and the consequences are more important than a simple “I flush” label suggests [R].

Why this SNP works well in consumer DNA analysis

Because rs671 affects a clear step in alcohol metabolism, it is one of the easier variants to explain in practical terms. For some people, the result lines up closely with noticeable reactions after drinking, such as flushing, nausea, or headache. For readers trying to understand why alcohol affects them differently, rs671 is one of the more useful variants to look at because it changes how efficiently acetaldehyde is cleared.

At GenesUnveiled, you can analyze your DNA and explore research-based interpretations of variants like ALDH2 rs671 in a clearer, more structured way.