If your face turns red when you drink, you should never drink it (Asian Flush).

Symptoms of redness after drinking are common in Korea, China, and Japan, and about 36% of the population in these Asian countries develop this symptom.

When alcohol breaks down in humans, two types of enzymes are needed.

1. In the liver and stomach, an enzyme called [Alcoholderogenase (ADH)] is converted from ethanol to acetaldehyde.

2. In cell an mitochondria, an enzyme called acetaldehyde [Aldehyde (ALDH)] converts acetaldehyde into acetate. It is a derivative of vinegar (acetic acid).

Acetaldehyde is an intermediate substance that comes from the decomposition of alcohol and is a carcinogen.

It is a very poor carcinogen classified as Group 1 by the International Institute of Cancer (IARC).

Alcohol is not associated with cancer because of ethanol itself, but thanks to acetaldehyde, an intermediate substance. 

There are seven genes in charge of ADH, and one of them is the gene ADH1B, which Northeast Asians have a modified trait called [ADH1B*2] at a high rate.

Decompose ethanol into acetaldehyde eight times faster than [ADH1B*1].

Moving on to the gene ALDH2, which is responsible for ALDH, [ALDH2*2] in about 30-50% of the total population is made free of ALDH enzymes that should be present in mitochondria. If you have two of these traits, the symptoms become more serious.

In conclusion, Northeast Asians decompose alcohol (ethanol) into acetaldehyde with tremendously high efficiency, and 30 to 50 percent of the total population was born with a lack of enzymes that decompose the carcinogen acetaldehyde.

When you drink alcohol, you don't get drunk, but acetaldehyde builds up.

When acetaldehyde accumulates in the body, the body and face turn red in the short term, causing increased heart rate (tachycardia), dizziness, vomiting, and headache.

In the long run, as you know, the probability of developing various cancers increases.

It is not yet clear exactly why such genetic modifications were advantageous for survival in the Northeast Asian population.

It is said that acetaldehyde accumulation may have had the effect of killing parasites in the past.

Populations with a variant of ADH or ALDH2 have a significantly lower risk of alcoholism, which is probably due to avoiding alcohol because they don't feel very good even when they drink.

However, as people with this modified gene trait drink a lot in a social atmosphere, the rate of alcoholism has increased more than before, and in this case, the probability of developing cancer will be very high.

If you turn red every day when you drink two glasses of beer (i.e., with a variant of ALDH2), the probability of developing esophageal cancer is as high as 6-10 times that of the existing population.