The enzyme aldehyde dehydrogenase 2 (ALDH2) performs an essential step in the normal function of the pathway of ethanol metabolism, by mediating the oxidation of acetaldehyde to acetate in the mitochondria of the liver and other tissues (Bosron and Li, 1986). While very rare in other populations (Li et al., 2009), among East Asian populations a substantial proportion of the populace carries an ALDH2 gene variant rs671 resulting in a Glu504Lys amino acid change (Yoshida, et al., 1984; Li et al., 2009), which codes for an enzyme with greatly diminished oxidative efficacy (Crabb, et al., 2004). Reduced enzyme activity causes build-up of acetaldehyde in tissues after consumption of alcohol (Wall et al., 1997), which produces a number of dysphoric symptoms, including facial flushing, nausea, and headache (Eriksson, 2001). Consequently, it has been repeatedly observed that, relative to those homozygous for the allele producing a fully active enzyme (ALDH2*1), individuals carrying the reduced activity ALDH2 variant (ALDH2*2) drink less (Hendershot et al., 2009), and are less likely to become alcohol dependent (Luczak, et al., 2006).
