The two aldehyde dehydrogenase (ALDH) genes involved in alcohol metabolism are ALDH1A, located on chromosome 9q21.13, and ALDH2, located on chromosome 12q24.2. The ALDH2 enzyme is the primary enzyme responsible for acetaldehyde metabolism, and a mutation in ALDH2 (commonly referred to as the ALDH2*2 allele) produces a largely inactive aldehyde dehydrogenase enzyme that leads to elevated acetaldehyde levels when alcohol is consumed. This ALDH2*2 allele has been shown to produce an aversive flushing reaction and an increased level of response to alcohol that is associated with lower rates of alcohol use and alcoholism in Japanese and Chinese samples demonstrating its protective effect against the development of alcoholism [46]. Nonetheless, this allele does not appear to be present in Native American populations [49].
