Acetaldehyde is a toxic intermediate, and systemic buildup of acetaldehyde results in unpleasant feelings such as dizziness, nausea, and tachycardia. Individuals carrying even a single copy of the ALDH2*504K (ALDH2*2 allele; rs671) display the “Asian flushing reaction” when they consume even small amounts of alcohol; this includes prominent facial flushing, tachycardia, and nausea, and deters most individuals from excessive consumption of ethanol, although some can drink large quantities and become alcoholic despite this. ALDH2*504K is relatively common in East Asia, where up to 30-40% of Han Chinese and Japanese carry at least one copy; however, it is extremely rare outside Asia. Nearly no individuals of European or African descent carry this allele21-23. The mechanism by which the ALDH2*504K allele works is known. The replacement of a glutamate residue in position 504 of the ALDH2 enzyme with lysine severely inhibits the enzyme activity20, 24, 25. Most of the ALDH2 enzyme, which functions as a tetramer, is inactivated and degraded when a person carries even a single ALDH2*504K allele25. This leads to a major buildup of acetaldehyde in the circulation. It is
