Two working copies of Aldehyde Dehydrogenase (ALDH2) mean you won't turn bright red when you drink alcohol, unlike most Asians. After your body turns alcohol into the dangerous acetaldehyde, this gene quickly turns the acetaldehyde into vinegar. It also stops the acetaldehyde in cigarettes from causing Esophageal Cancer. It reduces hangovers compared to Asians, but less hangovers and flushing obviously increases the risk of alcoholism. Alcoholism can be treated effectively with the drug Disulfiram (Antabuse) which would stop this gene from working and cause the Asian flush in non-Asians.
PMC2659709 "AALDH2-deficient individuals are at much higher risk of esophageal cancer (specifically squamous cell carcinoma) from alcohol consumption than individuals with fully active ALDH2. This is particularly unfortunate as esophageal cancer is one of the deadliest cancers worldwide, with five-year survival rates of 15.6% in the United States, 12.3% in Europe, and 31.6% in Japan"