Functional polymorphisms of genes for the alcohol metabolizing enzymes ADH and ALDH2, and differences in the prevalence of the polymorphic alleles in different ethnic populations, have resulted in several studies examining racial and ethnic differences in alcohol metabolism and the influence of ADH1B, ADH1C, and ALDH2 genotypes. In general, the ADH1B*2 polymorphism has been associated with an increase in alcohol metabolic rates. This has been most clearly seen in populations of Jewish ancestry, reflecting a more direct genetic effect (174). The effect is less clear in Asian ancestry populations that carry the ADH1B*2 variation, as a significant proportion also carry the ALDH2*2 polymorphism, which has a more profound effect on alcohol (and acetaldehyde) metabolic rates (discussed further below) (112, 175). Studies of the effect of ADH1B*3 polymorphism have been less consistent. An early study in individuals of Black/African American ancestry showed a higher alcohol disappearance rate (mg%/hr) for ADH1B*3 allele carriers (176), although a separate study, also conducted in an African American sample, did not replicate this effect (177).
