ALDH2 and alcohol drinking: A number of studies have shown that individuals carrying the ALDH2*2 allele are protected between 66% (heterozygous ALDH2*1/ALDH2*2) and 99% (homozygous ALDH2*2/ALDH2*2) against alcoholism (Harada et al., 1982; Thomasson et al., 1991; Higuchi, 1994; Tu and Israel, 1995; Chen et al., 1999; Luczak et al., 2006; Zintzaras et al., 2006).